G-1
GLOSSARY
Absolute configuration (Section 7.5): The three-dimensional
arrangement of atoms or groups at a stereogenic center.
Acetal (Section 17.8): Product of the reaction of an aldehyde or
a ketone with two moles of an alcohol according to the
equation
Acetoacetic ester synthesis (Section 21.6): A synthetic method
for the preparation of ketones in which alkylation of the
enolate of ethyl acetoacetate
is the key carbon—carbon bond-forming step.
Acetyl coenzyme A (Section 26.1): A thiol ester abbreviated as
that acts as the source of acetyl groups in biosynthetic
processes involving acetate.
Acetylene (Sections 1.18 and 9.1): The simplest alkyne,
HCPCH.
Achiral (Section 7.1): Opposite of chiral. An achiral object is
superimposable on its mirror image.
Acid (Section 4.6): According to the Arrhenius definition, a
substance that ionizes in water to produce protons. Accord-
ing to the Br?nsted—Lowry definition, a substance that do-
nates a proton to some other substance. According to the
Lewis definition, an electron-pair acceptor.
Acid anhydride (Sections 2.3 and 20.1): Compound of the type
Both R groups are usually the same, although they need not
always be.
Acid dissociation constant K
a
(Section 4.6): Equilibrium con-
stant for dissociation of an acid:
K
a
H11005
[H
H11001
][A
H11002
]
[HA]
RCOCR
O
X
O
X
CH
3
CSCoA
O
X
CH
3
CCH
2
COCH
2
CH
3
O
X
O
X
2RH11033OHH11001 H
2
OH11001RCRH11032
O
X
RCRH11032
W
W
ORH11033
ORH11033
H
H11001
Activating substituent (Sections 12.10 and 12.12): A group
that when present in place of a hydrogen causes a particular
reaction to occur faster. Term is most often applied to
substituents that increase the rate of electrophilic aromatic
substitution.
Active site (Section 27.20): The region of an enzyme at which
the substrate is bound.
Acylation (Section 12.7 and Chapter 20): Reaction in which an
acyl group becomes attached to some structural unit in a
molecule. Examples include the Friedel—Crafts acylation
and the conversion of amines to amides.
Acyl chloride (Sections 2.3 and 20.1): Compound of the type
R may be alkyl or aryl.
Acyl group (Sections 12.7 and 20.1): The group
R may be alkyl or aryl.
Acylium ion (Section 12.7): The cation .
Acyl transfer (Section 20.3): A nucleophilic acyl substitution.
A reaction in which one type of carboxylic acid derivative
is converted to another.
Addition (Section 6.1): Reaction in which a reagent X±Y
adds to a multiple bond so that X becomes attached to one
of the carbons of the multiple bond and Y to the other.
1,2 Addition (Section 10.10): Addition of reagents of the type
X±Y to conjugated dienes in which X and Y add to adja-
cent doubly bonded carbons:
1,4 Addition (Section 10.10): Addition of reagents of the type
X±Y to conjugated dienes in which X and Y add to the ter-
mini of the diene system:
Addition—elimination mechanism (Section 23.6): Two-stage
mechanism for nucleophilic aromatic substitution. In the
R
2
C?CH±CH?CR
2
R
2
C±CH?CH±CR
2
W
X
W
Y
X±Y
R
2
C?CH±CH?CR
2
R
2
C±CH±CH?CR
2
W
X
W
Y
X±Y
R±CPO
H11001
RC±
O
X
RCCl
O
X
GLOSSARY G-2
Alkaloid (Section 22.5): Amine that occurs naturally in plants.
The name derives from the fact that such compounds are
weak bases.
Alkane (Section 2.1): Hydrocarbon in which all the bonds are
single bonds. Alkanes have the general formula C
n
H
2nH110012
.
Alkene (Section 2.1): Hydrocarbon that contains a carbon—car-
bon double bond (C?C); also known by the older name
olefin.
Alkoxide ion (Section 5.14): Conjugate base of an alcohol; a
species of the type .
Alkylamine (Section 22.1): Amine in which the organic groups
attached to nitrogen are alkyl groups.
Alkylation (Section 9.6): Reaction in which an alkyl group is
attached to some structural unit in a molecule.
Alkyl group (Section 2.10): Structural unit related to an alkane
by replacing one of the hydrogens by a potential point of at-
tachment to some other atom or group. The general symbol
for an alkyl group is R±.
Alkyl halide (Section 4.1): Compound of the type RX, in which
X is a halogen substituent (F, Cl, Br, I).
Alkyloxonium ion (Section 4.6): Positive ion of the type
ROH
2
H11001
.
Alkyne (Section 2.1): Hydrocarbon that contains a carbon—car-
bon triple bond.
Allene (Section 10.5): The compound CH
2
?C?CH
2
.
Allyl cation (Section 10.2): The carbocation
CH
2
?CHCH
2
H11001
The carbocation is stabilized by delocalization of the H9266
electrons of the double bond, and the positive charge is
shared by the two CH
2
groups. Substituted analogs of allyl
cation are called allylic carbocations.
Allyl group (Sections 5.1, 10.1): The group
CH
2
?CHCH
2
±
Allylic rearrangement (Section 10.2): Functional group trans-
formation in which double-bond migration has converted
one allylic structural unit to another, as in:
Amide (Sections 2.3 and 20.1): Compound of the type
Amine (Chapter 22): Molecule in which a nitrogen-containing
group of the type ±NH
2
, ±NHR, or ±NR
2
is attached to
an alkyl or aryl group.
H9251-Amino acid (Section 27.1): A carboxylic acid that contains
an amino group at the H9251-carbon atom. H9251-Amino acids are
the building blocks of peptides and proteins. An H9251-amino
acid normally exists as a zwitterion.
RCHCO
2
H11002
W
H11001
NH
3
RCNRH11032
2
O
X
R
2
C?CHCH
2
XR
2
CCH?CH
2
W
Y
R±O
H11002
addition stage, the nucleophile adds to the carbon that bears
the leaving group. In the elimination stage, the leaving
group is expelled.
Alcohol (Section 4.2): Compound of the type ROH.
Alcohol dehydrogenase (Section 15.11): Enzyme in the liver
that catalyzes the oxidation of alcohols to aldehydes and ke-
tones.
Aldaric acid (Section 25.19): Carbohydrate in which car-
boxylic acid functions are present at both ends of the chain.
Aldaric acids are typically prepared by oxidation of aldoses
with nitric acid.
Aldehyde (Sections 2.3 and 17.1): Compound of the type
Alditol (Section 25.18): The polyol obtained on reduction of
the carbonyl group of a carbohydrate.
Aldol addition (Section 18.9): Nucleophilic addition of an
aldehyde or ketone enolate to the carbonyl group of an
aldehyde or a ketone. The most typical case involves two
molecules of an aldehyde, and is usually catalyzed by
bases.
Aldol condensation (Sections 18.9—18.10): When an aldol ad-
dition is carried out so that the H9252-hydroxy aldehyde or ke-
tone dehydrates under the conditions of its formation, the
product is described as arising by an aldol condensation.
Aldonic acid (Section 25.19): Carboxylic acid obtained by oxi-
dation of the aldehyde function of an aldose.
Aldose (Section 25.1): Carbohydrate that contains an aldehyde
carbonyl group in its open-chain form.
Alicyclic (Section 2.12): Term describing an aliphatic cyclic
structural unit.
Aliphatic (Section 2.1): Term applied to compounds that do not
contain benzene or benzene-like rings as structural units.
(Historically, aliphatic was used to describe compounds de-
rived from fats and oils.)
Alkadiene (Section 10.5): Hydrocarbon that contains two
carbon—carbon double bonds; commonly referred to as
a diene.
2RCH
2
CH
O
X
RCH
2
CH?CR
W
CH?O
H
2
OH11001
HO
H11002
heat
2RCH
2
CH
O
X
RCH
2
CHCHR
W
OH
W
CH?O
HO
H11002
RCH
O
X
ArCH
O
X
or
X
Y
H11002
addition
H11002X
H11002
elimination
Y X
H11002
Y
G-3 GLOSSARY
L-Amino acid (Section 27.2): A description of the stereochem-
istry at the H9251-carbon atom of a chiral amino acid. The
Fischer projection of an H9251-amino acid has the amino group
on the left when the carbon chain is vertical with the car-
boxyl group at the top.
Amino acid racemization (Section 27.2) A method for dating
archeological samples based on the rate at which the ste-
reochemistry at the H9251 carbon of amino acid components is
randomized. It is useful for samples too old to be reliably
dated by
14
C decay.
Amino acid residues (Section 27.7): Individual amino acid
components of a peptide or protein.
Amino sugar (Section 25.11): Carbohydrate in which one of
the hydroxyl groups has been replaced by an amino group.
Amylopectin (Section 25.15): A polysaccharide present in
starch. Amylopectin is a polymer of H9251(1,4)-linked glucose
units, as is amylose (see amylose). Unlike amylose, amy-
lopectin contains branches of 24—30 glucose units con-
nected to the main chain by an H9251(1,6) linkage.
Amylose (Section 25.15): The water-dispersible component of
starch. It is a polymer of H9251(1,4)-linked glucose units.
Anabolic steroid (Section 26.15): A steroid that promotes mus-
cle growth.
Androgen (Section 26.15): A male sex hormone.
Angle strain (Section 3.4): The strain a molecule possesses be-
cause its bond angles are distorted from their normal values.
Anion (Section 1.2): Negatively charged ion.
Annulene (Section 11.19): Monocyclic hydrocarbon character-
ized by a completely conjugated system of double bonds.
Annulenes may or may not be aromatic.
Anomeric carbon (Section 25.6): The carbon atom in a fura-
nose or pyranose form that is derived from the carbonyl car-
bon of the open-chain form. It is the ring carbon that is
bonded to two oxygens.
Anomeric effect (Section 25.8): The preference for an elec-
tronegative substituent, especially a hydroxyl group, to oc-
cupy an axial orientation when bonded to the anomeric car-
bon in the pyranose form of a carbohydrate.
Anti (Section 3.1): Term describing relative position of two
substituents on adjacent atoms when the angle between
their bonds is on the order of 180°. Atoms X and Y in the
structure shown are anti to each other.
Anti addition (Section 6.3): Addition reaction in which the two
portions of the attacking reagent X±Y add to opposite
faces of the double bond.
X
Y
CO
2
H11002
H
3
NH
R
H11001
Antibonding orbital (Section 1.14): An orbital in a molecule in
which an electron is less stable than when localized on an
isolated atom.
Anticodon (Section 27.28): Sequence of three bases in a mole-
cule of tRNA that is complementary to the codon of mRNA
for a particular amino acid.
Anti-Markovnikov addition (Sections 6.8, 6.11): Addition re-
action for which the regioselectivity is opposite to that pre-
dicted on the basis of Markovnikov’s rule.
Aprotic solvent (Section 8.12): A solvent that does not have
easily exchangeable protons such as those bonded to oxy-
gen of hydroxyl groups.
Ar± (Section 2.2): Symbol for an aryl group.
Arene (Section 2.1): Aromatic hydrocarbon. Often abbreviated
ArH.
Arenium ion (Section 12.2): The carbocation intermediate
formed by attack of an electrophile on an aromatic substrate
in electrophilic aromatic substitution. See cyclohexadienyl
cation.
Aromatic compound (Section 11.3): An electron-delocalized
species that is much more stable than any structure written
for it in which all the electrons are localized either in cova-
lent bonds or as unshared electron pairs.
Aromaticity (Section 11.4): Special stability associated with
aromatic compounds.
Arylamine (Section 22.1): An amine that has an aryl group at-
tached to the amine nitrogen.
Aryne (Section 23.8): A species that contains a triple bond
within an aromatic ring (see benzyne).
Asymmetric (Section 7.1): Lacking all significant symmetry
elements; an asymmetric object does not have a plane, axis,
or center of symmetry.
Asymmetric center (Section 7.2): Obsolete name for a ste-
reogenic center.
Atactic polymer (Section 7.15): Polymer characterized by ran-
dom stereochemistry at its stereogenic centers. An atactic
polymer, unlike an isotactic or a syndiotactic polymer, is
not a stereoregular polymer.
Atomic number (Section 1.1): The number of protons in the
nucleus of a particular atom. The symbol for atomic number
is Z, and each element has a unique atomic number.
Axial bond (Section 3.6): A bond to a carbon in the chair con-
formation of cyclohexane oriented like the six “up-and-
down” bonds in the following:
Azo coupling (Section 22.19): Formation of a compound of the
type ArN?NArH11032 by reaction of an aryl diazonium salt with
an arene. The arene must be strongly activated toward elec-
trophilic aromatic substitution; that is, it must bear a power-
ful electron-releasing substituent such as ±OH or ±NR
2
.
GLOSSARY G-4
Baeyer strain theory (Section 3.4): Incorrect nineteenth-cen-
tury theory that considered the rings of cycloalkanes to be
planar and assessed their stabilities according to how much
the angles of a corresponding regular polygon deviated
from the tetrahedral value of 109.5°.
Baeyer—Villiger oxidation (Section 17.16): Oxidation of an
aldehyde or, more commonly, a ketone with a peroxy acid.
The product of Baeyer—Villiger oxidation of a ketone is an
ester.
Ball-and-stick model (Section 1.10): Type of molecular model
in which balls representing atoms are connected by sticks
representing bonds. Similar to ball-and-spoke models of
Learning By Modeling.
Base (Section 4.6): According to the Arrhenius definition, a
substance that ionizes in water to produce hydroxide ions.
According to the Br?nsted—Lowry definition, a substance
that accepts a proton from some suitable donor. According
to the Lewis definition, an electron-pair donor.
Base pair (Section 27.27): Term given to the purine of a nu-
cleotide and its complementary pyrimidine. Adenine (A) is
complementary to thymine (T), and guanine (G) is comple-
mentary to cytosine (C).
Base peak (Section 13.21): The most intense peak in a mass
spectrum. The base peak is assigned a relative intensity of
100, and the intensities of all other peaks are cited as a per-
centage of the base peak.
Basicity constant K
b
(Section 22.4): A measure of base
strength, especially of amines.
K
b
H11005
Bending vibration (Section 13.19): The regular, repetitive mo-
tion of an atom or a group along an arc the radius of which
is the bond connecting the atom or group to the rest of the
molecule. Bending vibrations are one type of molecular
motion that gives rise to a peak in the infrared spectrum.
Benedict’s reagent (Section 25.19): A solution containing the
citrate complex of CuSO
4
. It is used to test for the presence
of reducing sugars.
Benzene (Section 11.1): The most typical aromatic hydrocar-
bon:
Benzyl group (Section 11.7): The group C
6
H
5
CH
2
±.
H
H
H
H
H
H
[R
3
NH
H11001
][HO
H11002
]
[R
3
N]
RCRH11032
O
X
RCORH11032
O
X
RH11033COOH
O
X
Benzylic carbon (Section 11.10): A carbon directly attached to
a benzene ring. A hydrogen attached to a benzylic carbon is
a benzylic hydrogen. A carbocation in which the benzylic
carbon is positively charged is a benzylic carbocation. A
free radical in which the benzylic carbon bears the unpaired
electron is a benzylic radical.
Benzyne (Section 23.8): The compound
Benzyne is formed as a reactive intermediate in the reaction
of aryl halides with very strong bases such as potassium
amide.
Bile acids (Section 26.13): Steroid derivatives biosynthesized
in the liver that aid digestion by emulsifying fats.
Bimolecular (Section 4.7): A process in which two particles re-
act in the same elementary step.
Biological isoprene unit (Section 26.8): Isopentenyl pyrophos-
phate, the biological precursor to terpenes and steroids:
Birch reduction (Section 11.11): Reduction of an aromatic ring
to a 1,4-cyclohexadiene on treatment with a group I metal
(Li, Na, K) and an alcohol in liquid ammonia.
Boat conformation (Section 3.5): An unstable conformation of
cyclohexane, depicted as
H9266 bond (Section 1.17): In alkenes, a bond formed by overlap of
p orbitals in a side-by-side manner. AH9266 bond is weaker than
a H9268 bond. The carbon—carbon double bond in alkenes con-
sists of two sp
2
-hybridized carbons joined by a H9268 bond and
a H9266 bond.
H9268 bond (Section 1.14): A connection between two atoms in
which the electron probability distribution has rotational
symmetry along the internuclear axis. A cross section per-
pendicular to the internuclear axis is a circle.
Bond dissociation energy (Section 1.3): For a substance A:B,
the energy required to break the bond between A and B so
that each retains one of the electrons in the bond. Table 4.3
(Section 4.17) gives bond dissociation energies for some
representative compounds.
Bonding orbital (Section 1.14): An orbital in a molecule in
which an electron is more stable than when localized on an
isolated atom. All the bonding orbitals are normally doubly
occupied in stable neutral molecules.
OPP
H
H
H
H
G-5 GLOSSARY
Bond-line formula (Section 1.7): Formula in which connec-
tions between carbons are shown but individual carbons
and hydrogens are not. The bond-line formula
represents the compound (CH
3
)
2
CHCH
2
CH
3
.
Boundary surface (Section 1.1): The surface that encloses the
region where the probability of finding an electron is high
(90—95%).
Branched-chain carbohydrate (Section 25.12): Carbohydrate
in which the main carbon chain bears a carbon substituent
in place of a hydrogen or hydroxyl group.
Bromohydrin (Section 6.17): A halohydrin in which the halo-
gen is bromine (see halohydrin).
Bromonium ion (Section 6.16): A halonium ion in which the
halogen is bromine (see halonium ion).
Br?nsted acid See acid.
Br?nsted base See base.
Buckminsterfullerene (Chapter 11, box, “Carbon Clusters,
Fullerenes, and Nanotubes”): Name given to the C
60
cluster
with structure resembling the geodesic domes of R. Buck-
minster Fuller; see front cover.
n-Butane (Section 2.5): Common name for butane
CH
3
CH
2
CH
2
CH
3
.
n-Butyl group (Section 2.10): The group CH
3
CH
2
CH
2
CH
2
±.
sec-Butyl group (Section 2.10): The group
tert-Butyl group (Section 2.10): The group (CH
3
)
3
C±.
Cahn—Ingold—Prelog notation (Section 7.6): System for spec-
ifying absolute configuration as R or S on the basis of the
order in which atoms or groups are attached to a stereogenic
center. Groups are ranked in order of precedence according
to rules based on atomic number.
Carbamate (Section 20.17): An ester of carbamic acid
(H
2
NCO
2
H); a compound of the type H
2
NCO
2
R.
Carbanion (Section 9.5): Anion in which the negative charge is
borne by carbon. An example is acetylide ion.
Carbene (Section 14.13): A neutral species in which one of the
carbon atoms is associated with six valence electrons.
Carbinolamine (Section 17.10): Compound of the type
Carbinolamines are formed by nucleophilic addition of an
amine to a carbonyl group and are intermediates in the for-
mation of imines and enamines.
Carbocation (Section 4.9): Positive ion in which the charge re-
sides on carbon. An example is tert-butyl cation, (CH
3
)
3
C
H11001
.
Carbocations are unstable species that, though they cannot
normally be isolated, are believed to be intermediates in
certain reactions.
W
W
HO±C±NR
2
CH
3
CH
2
CHCH
3
W
Carboxylate ion (Section 19.5): The conjugate base of a car-
boxylic acid, an ion of the type RCO
2
H11002
.
Carboxylation (Section 19.11): In the preparation of a car-
boxylic acid, the reaction of a carbanion with carbon diox-
ide. Typically, the carbanion source is a Grignard reagent.
Carboxylic acid (Sections 2.3 and 19.1): Compound of the type
, also written as RCO
2
H.
Carboxylic acid derivative (Section 20.1): Compound that
yields a carboxylic acid on hydrolysis. Carboxylic acid de-
rivatives include acyl chlorides, anhydrides, esters, and
amides.
Carotenoids (Section 26.16): Naturally occurring tetrater-
penoid plant pigments.
Cation (Section 1.2): Positively charged ion.
Cellobiose (Section 25.14): A disaccharide in which two glu-
cose units are joined by a H9252(1,4) linkage. Cellobiose is ob-
tained by the hydrolysis of cellulose.
Cellulose (Section 25.15): A polysaccharide in which thou-
sands of glucose units are joined by H9252(1,4) linkages.
Center of symmetry (Section 7.3): A point in the center of a
structure located so that a line drawn from it to any element
of the structure, when extended an equal distance in the op-
posite direction, encounters an identical element. Benzene,
for example, has a center of symmetry.
Chain reaction (Section 4.18): Reaction mechanism in which a
sequence of individual steps repeats itself many times, usu-
ally because a reactive intermediate consumed in one step
is regenerated in a subsequent step. The halogenation of
alkanes is a chain reaction proceeding via free-radical
intermediates.
Chair conformation (Section 3.5): The most stable conforma-
tion of cyclohexane:
Chemical shift (Section 13.4): A measure of how shielded the
nucleus of a particular atom is. Nuclei of different atoms
have different chemical shifts, and nuclei of the same atom
have chemical shifts that are sensitive to their molecular
environment. In proton and carbon-13 NMR, chemical
shifts are cited as H9254, or parts per million (ppm), from the hy-
drogens or carbons, respectively, of tetramethylsilane.
Chiral (Section 7.1): Term describing an object that is not su-
perposable on its mirror image.
Chiral carbon atom (Section 7.2): A carbon that is bonded to
four groups, all of which are different from one another.
Also called an asymmetric carbon atom. A more modern
term is stereogenic center.
Chiral center (Section 7.2): See stereogenic center.
Chlorohydrin (Section 6.17): A halohydrin in which the halo-
gen is chlorine (see halohydrin).
RCOH
O
X
RCO
2
HRMgX
1. CO
2
2. H
3
O
H11001
GLOSSARY G-6
Chloronium ion (Section 6.16): A halonium ion in which the
halogen is chlorine (see halonium ion).
Cholesterol (Section 26.11): The most abundant steroid in ani-
mals and the biological precursor to other naturally occur-
ring steroids, including the bile acids, sex hormones, and
corticosteroids.
Chromatography (Section 13.21): A method for separation and
analysis of mixtures based on the different rates at which
different compounds are removed from a stationary phase
by a moving phase.
Chromophore (Section 13.20): The structural unit of a mole-
cule principally responsible for absorption of radiation of a
particular frequency; a term usually applied to ultraviolet-
visible spectroscopy.
Chymotrypsin (Section 27.10): A digestive enzyme that cat-
alyzes the hydrolysis of proteins. Chymotrypsin selectively
catalyzes the cleavage of the peptide bond between the car-
boxyl group of phenylalanine, tyrosine, or tryptophan and
some other amino acid.
cis- (Section 3.12): Stereochemical prefix indicating that two
substituents are on the same side of a ring or double bond.
(Contrast with the prefix trans-.)
Claisen condensation (Section 21.1): Reaction in which a
H9252-keto ester is formed by condensation of two moles of an
ester in base:
Claisen rearrangement (Section 24.13): Thermal conversion
of an allyl phenyl ether to an o-allyl phenol. The rearrange-
ment proceeds via a cyclohexadienone intermediate.
Claisen—Schmidt condensation (Section 18.10): A mixed al-
dol condensation involving a ketone enolate and an aro-
matic aldehyde or ketone.
Clathrate (Section 2.4): A mixture of two substances in which
molecules of the minor component are held by van der
Waals forces within a framework of molecules of the major
component.
Clemmensen reduction (Section 12.8): Method for reducing
the carbonyl group of aldehydes and ketones to a methylene
group (C?O ±￡ CH
2
) by treatment with zinc amalgam
[Zn(Hg)] in concentrated hydrochloric acid.
Closed-shell electron configuration (Sections 1.1 and 11.6):
Stable electron configuration in which all the lowest energy
orbitals of an atom (in the case of the noble gases), an ion
(e.g., Na
H11001
), or a molecule (e.g., benzene) are filled.
13
C NMR (Section 13.14): Nuclear magnetic resonance spec-
troscopy in which the environments of individual carbon
atoms are examined via their mass 13 isotope.
heat
O
CH
2
CH
CH
2
CH
2
CH
OH
CH
2
RCH
2
CORH11032
O
X
RCH
2
CCHCORH11032
O
X
O
X
W
R
RH11032OHH11001
1. NaORH11032
2. H
H11001
Codon (Section 27.28): Set of three successive nucleotides in
mRNA that is unique for a particular amino acid. The 64
codons possible from combinations of A, T, G, and C code
for the 20 amino acids from which proteins are constructed.
Coenzyme (Section 27.21): Molecule that acts in combination
with an enzyme to bring about a reaction.
Coenzyme Q (Section 24.14): Naturally occurring group of re-
lated quinones involved in the chemistry of cellular respira-
tion. Also known as ubiquinone.
Combinatorial chemistry (Section 27.18): A method for carry-
ing out a large number of reactions on a small scale in the
solid phase so as to generate a “library” of related com-
pounds for further study, such as biological testing.
Combustion (Section 2.15): Burning of a substance in the pres-
ence of oxygen. All hydrocarbons yield carbon dioxide and
water when they undergo combustion.
Common nomenclature (Section 2.8): Names given to com-
pounds on some basis other than a comprehensive, system-
atic set of rules.
Concerted reaction (Section 4.7): Reaction that occurs in a sin-
gle elementary step.
Condensation polymer (Section 20.16): Polymer in which the
bonds that connect the monomers are formed by condensa-
tion reactions. Typical condensation polymers include poly-
esters and polyamides.
Condensation reaction (Section 15.7): Reaction in which two
molecules combine to give a product accompanied by the
expulsion of some small stable molecule (such as water).
An example is acid-catalyzed ether formation:
Condensed structural formula (Section 1.7): A standard way
of representing structural formulas in which subscripts are
used to indicate replicated atoms or groups, as in
(CH
3
)
2
CHCH
2
CH
3
.
Conformational analysis (Section 3.1): Study of the conforma-
tions available to a molecule, their relative stability, and the
role they play in defining the properties of the molecule.
Conformations (Section 3.1): Nonidentical representations of
a molecule generated by rotation about single bonds.
Conformers (Section 3.1): Different conformations of a single
molecule.
Conjugate acid (Section 4.6): The species formed from a Br?n-
sted base after it has accepted a proton.
Conjugate addition (Sections 10.10 and 18.12): Addition reac-
tion in which the reagent adds to the termini of the conju-
gated system with migration of the double bond; synony-
mous with 1,4 addition. The most common examples
include conjugate addition to 1,3-dienes and to H9251,H9252-unsatu-
rated carbonyl compounds.
Conjugate base (Section 4.6): The species formed from a
Br?nsted acid after it has donated a proton.
Conjugated diene (Section 10.5): System of the type
C?C±C?C, in which two pairs of doubly bonded car-
bons are joined by a single bond. The H9266 electrons are de-
localized over the unit of four consecutive sp
2
-hybridized
carbons.
ROR H11001 H
2
O2ROH
H
2
SO
4
G-7 GLOSSARY
Connectivity (Section 1.7): Order in which a molecule’s atoms
are connected. Synonymous with constitution.
Constitution (Section 1.7): Order of atomic connections that
defines a molecule.
Constitutional isomers (Section 1.8): Isomers that differ in re-
spect to the order in which the atoms are connected. Butane
(CH
3
CH
2
CH
2
CH
3
) and isobutane [(CH
3
)
3
CH] are constitu-
tional isomers.
Copolymer (Section 10.11): Polymer formed from two or more
different monomers.
Coupling constant J (Section 13.7): A measure of the extent to
which two nuclear spins are coupled. In the simplest cases,
it is equal to the distance between adjacent peaks in a split
NMR signal.
Covalent bond (Section 1.3): Chemical bond between two
atoms that results from their sharing of two electrons.
Cracking (Section 2.13): A key step in petroleum refining in
which high-molecular-weight hydrocarbons are converted
to lower molecular-weight ones by thermal or catalytic car-
bon—carbon bond cleavage.
Critical micelle concentration (Section 19.5): Concentration
above which substances such as salts of fatty acids aggre-
gate to form micelles in aqueous solution.
Crown ether (Section 16.4): A cyclic polyether that, via
ion—dipole attractive forces, forms stable complexes with
metal ions. Such complexes, along with their accompany-
ing anion, are soluble in nonpolar solvents.
C terminus (Section 27.7): The amino acid at the end of a pep-
tide or protein chain that has its carboxyl group intact that
is, in which the carboxyl group is not part of a peptide bond.
Cumulated diene (Section 10.5): Diene of the type C?C?C,
in which a single carbon atom participates in double bonds
with two others.
Cyanohydrin (Section 17.7): Compound of the type
Cyanohydrins are formed by nucleophilic addition of HCN
to the carbonyl group of an aldehyde or a ketone.
Cycloaddition (Section 10.12): Addition, such as the
Diels—Alder reaction, in which a ring is formed via a cyclic
transition state.
Cycloalkane (Section 2.12): An alkane in which a ring of car-
bon atoms is present.
Cycloalkene (Section 5.1): A cyclic hydrocarbon characterized
by a double bond between two of the ring carbons.
Cycloalkyne (Section 9.4): A cyclic hydrocarbon characterized
by a triple bond between two of the ring carbons.
Cyclohexadienyl anion (Section 23.6): The key intermediate in
nucleophilic aromatic substitution by the addition—elimina-
tion mechanism. It is represented by the general structure
shown, where Y is the nucleophile and X is the leaving
group.
RCRH11032
W
W
OH
CPN
Cyclohexadienyl cation (Section 12.2): The key intermediate
in electrophilic aromatic substitution reactions. It is repre-
sented by the general structure
where E is derived from the electrophile that attacks the
ring.
Deactivating substituent (Sections 12.11 and 12.13): A group
that when present in place of a hydrogen substituent causes
a particular reaction to occur more slowly. The term is most
often applied to the effect of substituents on the rate of elec-
trophilic aromatic substitution.
Debye unit (D) (Section 1.5): Unit customarily used for mea-
suring dipole moments:
1 D H11005 1 H11003 10
H1100218
esuH11080cm
Decarboxylation (Section 19.17): Reaction of the type
RCO
2
H ±￡ RH H11001 CO
2
, in which carbon dioxide is lost
from a carboxylic acid. Decarboxylation normally occurs
readily only when the carboxylic acid is a 1,3-dicarboxylic
acid or a H9252-keto acid.
Decoupling (Section 13.17): In NMR spectroscopy, any
process that destroys the coupling of nuclear spins between
two nuclei. Two types of decoupling are employed in
13
C
NMR spectroscopy. Broadband decoupling removes all the
1
H—
13
C couplings; off-resonance decoupling removes all of
1
H—
13
C couplings except those between directly bonded
atoms.
Dehydration (Section 5.9): Removal of H and OH from adja-
cent atoms. The term is most commonly employed in the
preparation of alkenes by heating alcohols in the presence
of an acid catalyst.
Dehydrogenation (Section 5.1): Removal of the elements of
H
2
from adjacent atoms. The term is most commonly en-
countered in the industrial preparation of ethylene from
ethane, propene from propane, 1,3-butadiene from butane,
and styrene from ethylbenzene.
Dehydrohalogenation (Section 5.14): Reaction in which an
alkyl halide, on being treated with a base such as sodium
ethoxide, is converted to an alkene by loss of a proton from
one carbon and the halogen from the adjacent carbon.
Delocalization (Section 1.9): Association of an electron with
more than one atom. The simplest example is the shared
E H
H11001
H
H
H
H
H
Y X
H11002
H
H
H
H
H
GLOSSARY G-8
electron pair (covalent) bond. Delocalization is important in
conjugated H9266 electron systems, where an electron may be
associated with several carbon atoms.
Deoxy sugar (Section 25.10): A carbohydrate in which one of
the hydroxyl groups has been replaced by a hydrogen.
DEPT (Section 13.18): Abbreviation for distortionless enhance-
ment of polarization transfer. DEPT is an NMR technique
that reveals the number of hydrogens directly attached to a
carbon responsible for a particular signal.
Detergents (Section 19.5): Substances that clean by micellar
action. Although the term usually refers to a synthetic de-
tergent, soaps are also detergents.
Diastereomers (Section 7.10): Stereoisomers that are not enan-
tiomers stereoisomers that are not mirror images of one
another.
Diastereotopic (Section 13.6): Describing two atoms or groups
in a molecule that are attached to the same atom but are in
stereochemically different environments that are not mirror
images of each other. The two protons shown in bold in
CH
2
?CHCl, for example, are diastereotopic. One is cis to
chlorine, the other is trans.
1,3-Diaxial repulsion (Section 3.8): Repulsive forces between
axial substituents on the same side of a cyclohexane ring.
Diazonium ion (Sections 22.16—22.17): Ion of the type
. Aryl diazonium ions are formed by treatment
of primary aromatic amines with nitrous acid. They are ex-
tremely useful in the preparation of aryl halides, phenols,
and aryl cyanides.
Diazotization (Section 22.17): The reaction by which a pri-
mary arylamine is converted to the corresponding diazo-
nium ion by nitrosation.
Dieckmann reaction (Section 21.2): An intramolecular version
of the Claisen condensation.
Dielectric constant (Section 8.12): A measure of the ability of a
material to disperse the force of attraction between oppositely
charged particles. The symbol for dielectric constant is H9280.
Diels—Alder reaction (Section 10.12): Conjugate addition of an
alkene to a conjugated diene to give a cyclohexene deriva-
tive. Diels—Alder reactions are extremely useful in synthesis.
Dienophile (Section 10.12): The alkene that adds to the diene
in a Diels—Alder reaction.
H9252-Diketone (Section 18.5): Compound of the type
also referred to as a 1,3-diketone.
Dimer (Section 6.21): Molecule formed by the combination of
two identical molecules.
Dipeptide (Section 27.7): A compound in which two H9251-amino
acids are linked by an amide bond between the amino group
of one and the carboxyl group of the other:
RCHC±NHCHCO
2
H11002
W
H11001
NH
3
W
RH11032
O
X
R
OO
RH11032
R±NPN
H11001
Dipole—dipole attraction (Section 2.14): A force of attraction
between oppositely polarized atoms.
Dipole/induced-dipole attraction (Section 4.5): A force of at-
traction that results when a species with a permanent dipole
induces a complementary dipole in a second species.
Dipole moment (Section 1.5): Product of the attractive force
between two opposite charges and the distance between
them. Dipole moment has the symbol H9262 and is measured in
Debye units (D).
Disaccharide (Sections 25.1 and 25.14): A carbohydrate that
yields two monosaccharide units (which may be the same
or different) on hydrolysis.
Dispersion force (Section 2.14): See induced-dipole/induced-
dipole attraction.
Disubstituted alkene (Section 5.6): Alkene of the type
R
2
C?CH
2
or RCH?CHR. The groups R may be the same
or different, they may be any length, and they may be
branched or unbranched. The significant point is that there
are two carbons directly bonded to the carbons of the dou-
ble bond.
Disulfide bridge (Section 27.7): An S±S bond between the
sulfur atoms of two cysteine residues in a peptide or protein.
DNA (deoxyribonucleic acid) (Section 27.26): A polynu-
cleotide of 2H11032-deoxyribose present in the nuclei of cells that
serves to store and replicate genetic information. Genes are
DNA.
Double bond (Section 1.4): Bond formed by the sharing of
four electrons between two atoms.
Double dehydrohalogenation (Section 9.7): Reaction in
which a geminal dihalide or vicinal dihalide, on being
treated with a very strong base such as sodium amide, is
converted to an alkyne by loss of two protons and the two
halogen substituents.
Double helix (Section 27.27) The form in which DNA nor-
mally occurs in living systems. Two complementary strands
of DNA are associated with each other by hydrogen bonds
between their base pairs, and each DNA strand adopts a
helical shape.
Downfield (Section 13.4): The low-field region of an NMR
spectrum. A signal that is downfield with respect to another
lies to its left on the spectrum.
Eclipsed conformation (Section 3.1): Conformation in which
bonds on adjacent atoms are aligned with one another. For
example, the C±H bonds indicated in the structure shown
are eclipsed.
Edman degradation (Section 27.13): Method for determining
the N-terminal amino acid of a peptide or protein. It in-
volves treating the material with phenyl isothiocyanate
(C
6
H
5
N?C?S), cleaving with acid, and then identifying
the phenylthiohydantoin (PTH derivative) produced.
H
H
G-9 GLOSSARY
Elastomer (Section 10.11): A synthetic polymer that possesses
elasticity.
Electromagnetic radiation (Section 13.1): Various forms of ra-
diation propagated at the speed of light. Electromagnetic
radiation includes (among others) visible light; infrared, ul-
traviolet, and microwave radiation; and radio waves, cos-
mic rays, and X-rays.
Electron affinity (Section 1.2): Energy change associated with
the capture of an electron by an atom.
Electronegativity (Section 1.5): A measure of the ability of an
atom to attract the electrons in a covalent bond toward it-
self. Fluorine is the most electronegative element.
Electronic effect (Section 5.6): An effect on structure or reac-
tivity that is attributed to the change in electron distribution
that a substituent causes in a molecule.
Electron impact (Section 13.21): Method for producing posi-
tive ions in mass spectrometry whereby a molecule is bom-
barded by high-energy electrons.
18-Electron rule (Section 14.14): The number of ligands that
can be attached to a transition metal are such that the sum of
the electrons brought by the ligands plus the valence elec-
trons of the metal equals 18.
Electrophile (Section 4.10): A species (ion or compound) that
can act as a Lewis acid, or electron pair acceptor; an “elec-
tron seeker.” Carbocations are one type of electrophile.
Electrophilic addition (Section 6.4): Mechanism of addition in
which the species that first attacks the multiple bond is an
electrophile (“electron seeker”).
Electrophilic aromatic substitution (Section 12.1): Fundamen-
tal reaction type exhibited by aromatic compounds. An
electrophilic species (E
H11001
) attacks an aromatic ring and re-
places one of the hydrogens.
Electrophoresis (Section 27.3): Method for separating sub-
stances on the basis of their tendency to migrate to a posi-
tively or negatively charged electrode at a particular pH.
Electrostatic attraction (Section 1.2): Force of attraction be-
tween oppositely charged particles.
Electrostatic potential (Section 1.10): The energy of interac-
tion between a point positive charge and the charge field of
a molecule. The electrostatic potential is positive for the in-
teraction between the point positive charge and the mole-
cule’s electrons and negative for the interaction with the
nuclei.
Elementary step (Section 4.7): A step in a reaction mechanism
in which each species shown in the equation for this step
participates in the same transition state. An elementary step
is characterized by a single transition state.
Elements of unsaturation: See index of hydrogen deficiency.
H9252-Elimination (Section 5.8): Reaction in which a double or
triple bond is formed by loss of atoms or groups from adja-
cent atoms. (See dehydration, dehydrogenation, dehydro-
halogenation, and double dehydrohalogenation.)
Elimination—addition mechanism (Section 23.8): Two-stage
mechanism for nucleophilic aromatic substitution. In the
first stage, an aryl halide undergoes elimination to form an
Ar±HE±YH11001 Ar±EH±YH11001
aryne intermediate. In the second stage, nucleophilic addi-
tion to the aryne yields the product of the reaction.
Elimination bimolecular (E2) mechanism (Section 5.15):
Mechanism for elimination of alkyl halides characterized
by a transition state in which the attacking base removes a
proton at the same time that the bond to the halide leaving
group is broken.
Elimination unimolecular (E1) mechanism (Section 5.17):
Mechanism for elimination characterized by the slow for-
mation of a carbocation intermediate followed by rapid loss
of a proton from the carbocation to form the alkene.
Enamine (Section 17.11): Product of the reaction of a sec-
ondary amine and an aldehyde or a ketone. Enamines are
characterized by the general structure
Enantiomeric excess (Section 7.4): Difference between the
percentage of the major enantiomer present in a mixture
and the percentage of its mirror image. An optically pure
material has an enantiomeric excess of 100%. A racemic
mixture has an enantiomeric excess of zero.
Enantiomers (Section 7.1): Stereoisomers that are related as an
object and its nonsuperimposable mirror image.
Enantioselective synthesis (Section 27.4): Reaction that con-
verts an achiral or racemic starting material to a chiral prod-
uct in which one enantiomer is present in excess of the
other.
Enantiotopic (Section 13.6): Describing two atoms or groups
in a molecule whose environments are nonsuperposable
mirror images of each other. The two protons shown in bold
in CH
3
CH
2
Cl, for example, are enantiotopic. Replacement
of first one, then the other, by some arbitrary test group
yields compounds that are enantiomers of each other.
Endothermic (Section 1.2): Term describing a process or reac-
tion that absorbs heat.
Enediyne antibiotics (Section 9.4): A family of tumor-inhibit-
ing substances that is characterized by the presence of a
CPC±C?C±CPC unit as part of a nine- or ten-
membered ring.
Energy of activation (Section 3.2): Minimum energy that a re-
acting system must possess above its most stable state in or-
der to undergo a chemical or structural change.
Enol (Section 9.12): Compound of the type
Enols are in equilibrium with an isomeric aldehyde or ke-
tone, but are normally much less stable than aldehydes and
ketones.
Enolate ion (Section 18.6): The conjugate base of an enol.
Enolate ions are stabilized by electron delocalization.
RC?CR
2
W
O
H11002
RC±CR
2
H11002
O
O
RC?CR
2
W
OH
R
2
C?CR
W
NRH11032
2
GLOSSARY G-10
Enthalpy (Section 2.15): The heat content of a substance; sym-
bol, H.
Envelope (Section 3.10): One of the two most stable confor-
mations of cyclopentane. Four of the carbons in the enve-
lope conformation are coplanar; the fifth carbon lies above
or below this plane.
Enzyme (Section 27.20): A protein that catalyzes a chemical re-
action in a living system.
Epimers (Section 25.21): Diastereomers that differ in configu-
ration at only one of their stereogenic centers.
Epoxidation (Section 6.18): Conversion of an alkene to an
epoxide by treatment with a peroxy acid.
Epoxide (Section 6.18): Compound of the type
Equatorial bond (Section 3.6): A bond to a carbon in the chair
conformation of cyclohexane oriented approximately along
the equator of the molecule.
Erythro (Section 7.11): Term applied to the relative configura-
tion of two stereogenic centers within a molecule. The
erythro stereoisomer has like substituents on the same side
of a Fischer projection.
Essential amino acids (Section 27.1): Amino acids that must be
present in the diet for normal growth and good health.
Essential fatty acids (Section 26.6): Fatty acids that must be
present in the diet for normal growth and good health.
Essential oils (Section 26.7): Pleasant-smelling oils of plants
consisting of mixtures of terpenes, esters, alcohols, and
other volatile organic substances.
Ester (Sections 2.3 and 20.1): Compound of the type
Estrogen (Section 26.15): A female sex hormone.
Ethene (Section 5.1): IUPAC name for CH
2
?CH
2
. The com-
mon name ethylene, however, is used far more often, and
the IUPAC rules permit its use.
Ether (Section 16.1): Molecule that contains a C±O±C unit
such as RORH11032, ROAr, or ArOAr. When the two groups
bonded to oxygen are the same, the ether is described as a
symmetrical ether. When the groups are different, it is
called a mixed ether.
Ethylene (Section 5.1): CH
2
?CH
2
, the simplest alkene and
the most important industrial organic chemical.
Ethyl group (Section 2.10): The group CH
3
CH
2
±.
Exothermic (Section 1.2): Term describing a reaction or
process that gives off heat.
Extinction coefficient: See molar absorptivity.
E—Z notation for alkenes (Section 5.4): System for specifying
double-bond configuration that is an alternative to cis—trans
RCORH11032
O
X
R
2
C
O
CR
2
notation. When higher ranked substituents are on the same
side of the double bond, the configuration is Z. When higher
ranked substituents are on opposite sides, the configuration
is E. Rank is determined by the Cahn—Ingold—Prelog sys-
tem.
Fats and oils (Section 26.2): Triesters of glycerol. Fats are
solids at room temperature, oils are liquids.
Fatty acid (Section 26.2): Carboxylic acids obtained by hydrol-
ysis of fats and oils. Fatty acids typically have unbranched
chains and contain an even number of carbon atoms in the
range of 12—20 carbons. They may include one or more
double bonds.
Fatty acid synthetase (Section 26.3): Complex of enzymes
that catalyzes the biosynthesis of fatty acids from acetate.
Field effect (Section 19.6): An electronic effect in a molecule
that is transmitted from a substituent to a reaction site via
the medium (e.g., solvent).
Fingerprint region (Section 13.19): The region 1400—625
cm
H110021
of an infrared spectrum. This region is less character-
istic of functional groups than others, but varies so much
from one molecule to another that it can be used to deter-
mine whether two substances are identical or not.
Fischer esterification (Sections 15.8 and 19.14): Acid-cat-
alyzed ester formation between an alcohol and a carboxylic
acid:
Fischer projection (Section 7.7): Method for representing
stereochemical relationships. The four bonds to a ste-
reogenic carbon are represented by a cross. The horizontal
bonds are understood to project toward the viewer and the
vertical bonds away from the viewer.
Formal charge (Section 1.6): The charge, either positive or
negative, on an atom calculated by subtracting from the
number of valence electrons in the neutral atom a number
equal to the sum of its unshared electrons plus half the elec-
trons in its covalent bonds.
Fragmentation pattern (Section 13.21): In mass spectrometry,
the ions produced by dissociation of the molecular ion.
Free energy (Section 3.8): The available energy of a system;
symbol, G.
Free radical (Section 4.17): Neutral species in which one of the
electrons in the valence shell of carbon is unpaired. An ex-
ample is methyl radical, .
Frequency (Section 13.1): Number of waves per unit time. Al-
though often expressed in hertz (Hz), or cycles per second,
the SI unit for frequency is s
H110021
.
CH
3
x
wy
z
C
x
z
wy
is represented
in a Fischer
projection as
RH11032OHH11001 H
2
OH11001RCOH
O
X
RCORH11032
O
X
H
H11001
G-11 GLOSSARY
Friedel—Crafts acylation (Section 12.7): An electrophilic aro-
matic substitution in which an aromatic compound reacts
with an acyl chloride or a carboxylic acid anhydride in the
presence of aluminum chloride. An acyl group becomes
bonded to the ring.
Friedel—Crafts alkylation (Section 12.6): An electrophilic aro-
matic substitution in which an aromatic compound reacts
with an alkyl halide in the presence of aluminum chloride.
An alkyl group becomes bonded to the ring.
Fries rearrangement (Section 24.9): Aluminum chloride-pro-
moted rearrangement of an aryl ester to a ring-acylated de-
rivative of phenol.
Frontier orbitals (Section 10.14): Orbitals involved in a chem-
ical reaction, usually the highest-occupied molecular orbital
of one reactant and the lowest-unoccupied molecular orbital
of the other.
Functional class nomenclature (Section 4.1): Type of IUPAC
nomenclature in which compounds are named according to
functional group families. The last word in the name identi-
fies the functional group; the first word designates the alkyl
or aryl group that bears the functional group. Methyl bro-
mide, ethyl alcohol, and diethyl ether are examples of func-
tional class names.
Functional group (Section 2.2): An atom or a group of atoms in
a molecule responsible for its reactivity under a given set of
conditions.
Furanose form (Section 25.6): Five-membered ring arising via
cyclic hemiacetal formation between the carbonyl group
and a hydroxyl group of a carbohydrate.
Gabriel synthesis (Section 22.9): Method for the synthesis of
primary alkylamines in which a key step is the formation of
a carbon—nitrogen bond by alkylation of the potassium salt
of phthalimide.
Gauche (Section 3.1): Term describing the position relative to
each other of two substituents on adjacent atoms when the
RX
O
NK
O
O
N
O
R RNH
2
AlCl
3
OCR
O
OH
O
RC
Ar±HAr±RH11001 R±X
AlCl
3
Ar±HAr±CR
O
X
H11001 RC±Cl
O
X
AlCl
3
angle between their bonds is on the order of 60°. Atoms X
and Y in the structure shown are gauche to each other.
Geminal dihalide (Section 9.7): A dihalide of the form R
2
CX
2
,
in which the two halogen substituents are located on the
same carbon.
Geminal diol (Section 17.6): The hydrate R
2
C(OH)
2
of an
aldehyde or a ketone.
Genome (Section 27.29): The aggregate of all the genes that
determine what an organism becomes.
Globular protein (Section 27.20): An approximately spheri-
cally shaped protein that forms a colloidal dispersion in wa-
ter. Most enzymes are globular proteins.
Glycogen (Section 25.15): A polysaccharide present in animals
that is derived from glucose. Similar in structure to amy-
lopectin.
Glycolysis (Section 25.21): Biochemical process in which glu-
cose is converted to pyruvate with release of energy.
Glycoprotein (Section 25.16): A protein to which carbohydrate
molecules are attached by covalent bonds.
Glycoside (Section 25.13): A carbohydrate derivative in which
the hydroxyl group at the anomeric position has been re-
placed by some other group. An O-glycoside is an ether of
a carbohydrate in which the anomeric position bears an
alkoxy group.
Grain alcohol (Section 4.2): A common name for ethanol
(CH
3
CH
2
OH).
Grignard reagent (Section 14.4): An organomagnesium com-
pound of the type RMgX formed by the reaction of magne-
sium with an alkyl or aryl halide.
Half-chair (Section 3.10): One of the two most stable confor-
mations of cyclopentane. Three consecutive carbons in the
half-chair conformation are coplanar. The fourth and fifth
carbon lie, respectively, above and below the plane.
Haloform reaction (Section 18.7): The formation of CHX
3
(X H11005 Br, Cl, or I) brought about by cleavage of a methyl
ketone on treatment with Br
2
, Cl
2
, or I
2
in aqueous base.
Halogenation (Sections 4.15 and 12.5): Replacement of a hy-
drogen by a halogen. The most frequently encountered ex-
amples are the free-radical halogenation of alkanes and the
halogenation of arenes by electrophilic aromatic substitu-
tion.
Halohydrin (Section 6.17): A compound that contains both a
halogen atom and a hydroxyl group. The term is most often
used for compounds in which the halogen and the hydroxyl
RCCH
3
O
X
CHX
3
RCO
H11002
O
X
H11001
X
2
HO
H11002
X
Y
GLOSSARY G-12
group are on adjacent atoms (vicinal halohydrins). The
most commonly encountered halohydrins are chlorohydrins
and bromohydrins.
Halonium ion (Section 6.16): A species that incorporates a pos-
itively charged halogen. Bridged halonium ions are inter-
mediates in the addition of halogens to the double bond of
an alkene.
Hammond’s postulate (Section 4.12): Principle used to deduce
the approximate structure of a transition state. If two states,
such as a transition state and an unstable intermediate de-
rived from it, are similar in energy, they are believed to be
similar in structure.
Haworth formulas (Section 25.6): Planar representations of
furanose and pyranose forms of carbohydrates.
Heat of combustion (Section 2.15): Heat evolved on combus-
tion of a substance. It is the value of H11002H9004H° for the combus-
tion reaction.
Heat of formation (Section 2.15): The value of H9004H° for for-
mation of a substance from its elements.
Heat of hydrogenation (Section 6.1): Heat evolved on hydro-
genation of a substance. It is the value of H11002H9004H° for the ad-
dition of H
2
to a multiple bond.
H9251 Helix (Section 27.19): One type of protein secondary struc-
ture. It is a right-handed helix characterized by hydrogen
bonds between NH and C?O groups. It contains approxi-
mately 3.6 amino acids per turn.
Hell—Volhard—Zelinsky reaction (Section 19.16): The phos-
phorus trihalide-catalyzed H9251 halogenation of a carboxylic
acid:
Hemiacetal (Section 17.8): Product of nucleophilic addition of
one molecule of an alcohol to an aldehyde or a ketone.
Hemiacetals are compounds of the type
Hemiketal (Section 17.8): An old name for a hemiacetal de-
rived from a ketone.
Henderson—Hasselbalch equation (Section 19.4): An equa-
tion that relates degree of dissociation of an acid at a partic-
ular pH to its pK
a
.
pH H11005 pK
a
H11001 log
Heteroatom (Section 1.7): An atom in an organic molecule
that is neither carbon nor hydrogen.
Heterocyclic compound (Section 3.15): Cyclic compound in
which one or more of the atoms in the ring are elements
other than carbon. Heterocyclic compounds may or may not
be aromatic.
Heterogeneous reaction (Section 6.1): A reaction involving
two or more substances present in different phases. Hydro-
[conjugate base]
[acid]
R
2
C±ORH11032
W
OH
R
2
CHCO
2
HX
2
H11001 HXH11001R
2
CCO
2
H
W
X
P
or PX
3
genation of alkenes is a heterogeneous reaction that takes
place on the surface of an insoluble metal catalyst.
Heterolytic cleavage (Section 4.17): Dissociation of a two-
electron covalent bond in such a way that both electrons are
retained by one of the initially bonded atoms.
Hexose (Section 25.4): A carbohydrate with six carbon atoms.
High-density lipoprotein (HDL) (Section 26.11): A protein that
carries cholesterol from the tissues to the liver where it is
metabolized. HDL is often called “good cholesterol.”
Hofmann elimination (Section 22.14): Conversion of a quater-
nary ammonium hydroxide, especially an alkyltrimethyl-
ammonium hydroxide, to an alkene on heating. Elimination
occurs in the direction that gives the less substituted double
bond.
Hofmann rearrangement (Section 20.17): Reaction in which
an amide reacts with bromine in basic solution to give a pri-
mary amine having one less carbon atom than the amide.
HOMO (Section 10.13): Highest occupied molecular orbital
(the orbital of highest energy that contains at least one of a
molecule’s electrons).
Homologous series (Section 2.6): Group of structurally related
substances in which successive members differ by a CH
2
group.
Homolytic cleavage (Section 4.17): Dissociation of a two-
electron covalent bond in such a way that one electron is re-
tained by each of the initially bonded atoms.
Hückel’s rule (Section 11.19): Completely conjugated planar
monocyclic hydrocarbons possess special stability when the
number of their H9266 electrons H110054n H11001 2, where n is an integer.
Hund’s rule (Section 1.1): When two orbitals are of equal en-
ergy, they are populated by electrons so that each is half-
filled before either one is doubly occupied.
Hybrid orbital (Section 1.15): An atomic orbital represented as
a mixture of various contributions of that atom’s s,p,d, etc.
orbitals.
Hydration (Section 6.10): Addition of the elements of water
(H, OH) to a multiple bond.
Hydride shift (Section 5.13): Migration of a hydrogen with a
pair of electrons from one atom to another. Hydride
shifts are most commonly seen in carbocation rearrange-
ments.
Hydroboration—oxidation (Section 6.11): Reaction sequence
involving a separate hydroboration stage and oxidation
stage. In the hydroboration stage, diborane adds to an
alkene to give an alkylborane. In the oxidation stage, the
alkylborane is oxidized with hydrogen peroxide to give an
alcohol. The reaction product is an alcohol corresponding to
the anti-Markovnikov, syn hydration of an alkene.
(H )
RCNH
2
O
X
RNH
2
Br
2
NaOH, H
2
O
N(CH
3
)
3
H
2
OH11001H11001
heat
R
2
CH±CRH11032
2
HO
H11002
W
H11001
N(CH
3
)
3
R
2
C?CRH11032
2
G-13 GLOSSARY
Hydrocarbon (Section 2.1): A compound that contains only
carbon and hydrogen.
Hydroformylation (Section 17.5): An industrial process for
preparing aldehydes (RCH
2
CH
2
CH?O) by the reaction of
terminal alkenes (RCH?CH
2
) with carbon monoxide.
Hydrogenation (Section 6.1): Addition of H
2
to a multiple
bond.
Hydrogen bonding (Section 4.5): Type of dipole—dipole attrac-
tive force in which a positively polarized hydrogen of one
molecule is weakly bonded to a negatively polarized atom of
an adjacent molecule. Hydrogen bonds typically involve the
hydrogen of one ±OH group and the oxygen of another.
Hydrolysis (Section 6.9): Water-induced cleavage of a bond.
Hydronium ion (Section 4.6): The species H
3
O
H11001
.
Hydrophilic (Section 19.5): Literally, “water-loving”; a term
applied to substances that are soluble in water, usually be-
cause of their ability to form hydrogen bonds with water.
Hydrophobic (Section 19.5): Literally, “water-hating”; a term
applied to substances that are not soluble in water, but are
soluble in nonpolar, hydrocarbon-like media.
Hydroxylation (Section 15.5): Reaction or sequence of reac-
tions in which an alkene is converted to a vicinal diol.
Imide (Section 20.15): Compound of the type
in which two acyl groups are bonded to the same nitrogen.
Imine (Section 17.10): Compound of the type R
2
C?NRH11032
formed by the reaction of an aldehyde or a ketone with a
primary amine (RH11032NH
2
). Imines are sometimes called
Schiff’s bases.
Index of hydrogen deficiency (Section 13.22): A measure of
the total double bonds and rings a molecule contains. It is
determined by comparing the molecular formula C
n
H
x
of
the compound to that of an alkane that has the same number
of carbons according to the equation:
Index of hydrogen deficiency H11005 (C
n
H
2nH110012
H11002 C
n
H
x
)
Induced-dipole/induced-dipole attraction (Section 2.14):
Force of attraction resulting from a mutual and complemen-
tary polarization of one molecule by another. Also referred
to as London forces or dispersion forces.
Inductive effect (Section 4.10): An electronic effect transmit-
ted by successive polarization of the H9268 bonds within a mol-
ecule or an ion.
Infrared (IR) spectroscopy (Section 13.19): Analytical tech-
nique based on energy absorbed by a molecule as it vibrates
by stretching and bending bonds. Infrared spectroscopy is
useful for analyzing the functional groups in a molecule.
Initiation step (Section 4.18): A process which causes a reac-
tion, usually a free-radical reaction, to begin but which by
itself is not the principal source of products. The initiation
step in the halogenation of an alkane is the dissociation of a
halogen molecule to two halogen atoms.
1
2
RN(CRH11032)
2
O
X
Integrated area (Section 13.6): The relative area of a signal in
an NMR spectrum. Areas are proportional to the number of
equivalent protons responsible for the peak.
Intermediate (Section 3.7): Transient species formed during a
chemical reaction. Typically, an intermediate is not stable
under the conditions of its formation and proceeds further
to form the product. Unlike a transition state, which corre-
sponds to a maximum along a potential energy surface, an
intermediate lies at a potential energy minimum.
Intermolecular forces (Section 2.14): Forces, either attractive
or repulsive, between two atoms or groups in separate mol-
ecules.
Intramolecular forces (Section 2.15): Forces, either attractive
or repulsive, between two atoms or groups within the same
molecule.
Inversion of configuration (Section 8.4): Reversal of the
three-dimensional arrangement of the four bonds to sp
3
-
hybridized carbon. The representation shown illustrates in-
version of configuration in a nucleophilic substitution
where LG is the leaving group and Nu is the nucleophile.
Ionic bond (Section 1.2): Chemical bond between oppositely
charged particles that results from the electrostatic attrac-
tion between them.
Ionization energy (Section 1.2): Amount of energy required to
remove an electron from some species.
Isobutane (Section 2.5): The common name for 2-methyl-
propane, (CH
3
)
3
CH.
Isobutyl group (Section 2.10): The group (CH
3
)
2
CHCH
2
±.
Isoelectric point (Section 27.3): pH at which the concentration
of the zwitterionic form of an amino acid is a maximum. At
a pH below the isoelectric point the dominant species is a
cation. At higher pH, an anion predominates. At the isoelec-
tric point the amino acid has no net charge.
Isolated diene (Section 10.5): Diene of the type
C?C±(C)
x
±C?C
in which the two double bonds are separated by one or more
sp
3
-hybridized carbons. Isolated dienes are slightly less sta-
ble than isomeric conjugated dienes.
Isomers (Section 1.8): Different compounds that have the same
molecular formula. Isomers may be either constitutional
isomers or stereoisomers.
Isopentane (Section 2.7): The common name for 2-methylbu-
tane, (CH
3
)
2
CHCH
2
CH
3
.
Isoprene unit (Section 26.7): The characteristic five-carbon
structural unit found in terpenes:
C
x
w
y
LG Nu
w
x
y
C
GLOSSARY G-14
Isopropyl group (Section 2.10): The group (CH
3
)
2
CH±.
Isotactic polymer (Section 7.15): A stereoregular polymer in
which the substituent at each successive stereogenic center
is on the same side of the zigzag carbon chain.
Isotopic cluster (Section 13.21): In mass spectrometry, a group
of peaks that differ in m/z because they incorporate different
isotopes of their component elements.
IUPAC nomenclature (Section 2.8): The most widely used
method of naming organic compounds. It uses a set of rules
proposed and periodically revised by the International
Union of Pure and Applied Chemistry.
Kekulé structure (Section 11.2): Structural formula for an aro-
matic compound that satisfies the customary rules of bond-
ing and is usually characterized by a pattern of alternating
single and double bonds. There are two Kekulé formula-
tions for benzene:
A single Kekulé structure does not completely describe the
actual bonding in the molecule.
Ketal (Section 17.8): An old name for an acetal derived from a
ketone.
Keto—enol tautomerism (Section 18.4): Process by which an
aldehyde or a ketone and its enol equilibrate:
H9252-Keto ester (Section 21.1): A compound of the type
Ketone (Sections 2.3 and 17.1): A member of the family of
compounds in which both atoms attached to a carbonyl
group (C?O) are carbon, as in
Ketose (Section 25.1): A carbohydrate that contains a ketone
carbonyl group in its open-chain form.
Kiliani—Fischer synthesis (Section 25.20): A synthetic method
for carbohydrate chain extension. The new carbon—carbon
bond is formed by converting an aldose to its cyanohydrin.
Reduction of the cyano group to an aldehyde function com-
pletes the synthesis.
Kinetically controlled reaction (Section 10.10): Reaction in
which the major product is the one that is formed at the
fastest rate.
Kolbe—Schmitt reaction (Section 24.10): The high-pressure
reaction of the sodium salt of a phenol with carbon dioxide
to give an o-hydroxybenzoic acid. The Kolbe—Schmitt
RCR
O
X
RCAr
O
X
ArCAr
O
X
RCCH
2
CORH11032
O
X
O
X
RC±CHR
2
O
X
RC?CR
2
W
OH
and
reaction is used to prepare salicylic acid in the synthesis of
aspirin.
Lactam (Section 20.14): A cyclic amide.
Lactone (Section 19.15): A cyclic ester.
Lactose (Section 25.14): Milk sugar; a disaccharide formed by
a H9252-glycosidic linkage between C-4 of glucose and C-1 of
galactose.
LDA (Section 21.10): Abbreviation for lithium diisopropyl-
amide LiN[CH(CH
3
)
2
]. LDA is a strong, sterically hindered
base, used to convert esters to their enolates.
Leaving group (Section 5.15): The group, normally a halide
ion, that is lost from carbon in a nucleophilic substitution or
elimination.
Le Chatelier’s principle (Section 6.10): A reaction at equilib-
rium responds to any stress imposed on it by shifting the
equilibrium in the direction that minimizes the stress.
Lewis acid: See acid.
Lewis base: See base.
Lewis structure (Section 1.3): A chemical formula in which
electrons are represented by dots. Two dots (or a line) be-
tween two atoms represent a covalent bond in a Lewis
structure. Unshared electrons are explicitly shown, and sta-
ble Lewis structures are those in which the octet rule is sat-
isfied.
Lindlar catalyst (Section 9.9): A catalyst for the hydrogenation
of alkynes to cis-alkenes. It is composed of palladium,
which has been “poisoned” with lead(II) acetate and quino-
line, supported on calcium carbonate.
Lipid bilayer (Section 26.4): Arrangement of two layers of
phospholipids that constitutes cell membranes. The polar
termini are located at the inner and outer membrane—water
interfaces, and the lipophilic hydrocarbon tails cluster on
the inside.
Lipids (Section 26.1): Biologically important natural products
characterized by high solubility in nonpolar organic solvents.
Lipophilic (Section 19.5): Literally, “fat-loving”; synonymous
in practice with hydrophobic.
Locant (Section 2.9): In IUPAC nomenclature, a prefix that
designates the atom that is associated with a particular
structural unit. The locant is most often a number, and the
structural unit is usually an attached substituent as in
2-chlorobutane.
London force (Section 2.14): See induced-dipole/induced-
dipole attraction.
Low-density lipopropein (LDL) (Section 26.11): A protein
which carries cholesterol from the liver through the blood
to the tissues. Elevated LDL levels are a risk factor for heart
disease; LDL is often called “bad cholesterol.”
LUMO (Section 10.13): The orbital of lowest energy that con-
tains none of a molecule’s electrons; the lowest unoccupied
molecular orbital.
Magnetic resonance imaging (MRI): (Section 13.18): A diag-
nostic method in medicine in which tissues are examined by
NMR.
G-15 GLOSSARY
Malonic ester synthesis (Section 21.7): Synthetic method for
the preparation of carboxylic acids involving alkylation of
the enolate of diethyl malonate
as the key carbon—carbon bond-forming step.
Maltose (Section 25.14): A disaccharide obtained from starch
in which two glucose units are joined by an H9251(1,4)-glyco-
sidic link.
Markovnikov’s rule (Section 6.5): An unsymmetrical reagent adds
to an unsymmetrical double bond in the direction that places
the positive part of the reagent on the carbon of the double
bond that has the greater number of hydrogens.
Mass spectrometry (Section 13.21): Analytical method in
which a molecule is ionized and the various ions are exam-
ined on the basis of their mass-to-charge ratio.
Mechanism (Section 4.7): The sequence of steps that describes
how a chemical reaction occurs; a description of the inter-
mediates and transition states that are involved during the
transformation of reactants to products.
Mercaptan (Section 15.13): An old name for the class of com-
pounds now known as thiols.
Merrifield method: See solid-phase peptide synthesis.
Meso stereoisomer (Section 7.11): An achiral molecule that
has stereogenic centers. The most common kind of meso
compound is a molecule with two stereogenic centers and a
plane of symmetry.
Messenger RNA (mRNA): (Section 27.28): A polynucleotide of
ribose that “reads” the sequence of bases in DNA and inter-
acts with tRNAs in the ribosomes to promote protein
biosynthesis.
Meta (Section 11.7): Term describing a 1,3 relationship be-
tween substituents on a benzene ring.
Meta director (Section 12.9): A group that when present on a
benzene ring directs an incoming electrophile to a position
meta to itself.
Metallocene (Section 14.14): A transition metal complex that
bears a cyclopentadienyl ligand.
Metalloenzyme (Section 27.20): An enzyme in which a metal
ion at the active site contributes in a chemically significant
way to the catalytic activity.
Methanogen (Section 2.4): An organism that produces
methane.
Methine group (Section 2.5): The group CH.
Methylene group (Section 2.4): The group ±CH
2
±.
Methyl group (Section 1.16): The group CH
3
±.
Mevalonic acid (Section 26.10): An intermediate in the biosyn-
thesis of steroids from acetyl coenzyme A.
Micelle (Section 19.5): A spherical aggregate of species such as
carboxylate salts of fatty acids that contain a lipophilic end
and a hydrophilic end. Micelles containing 50—100 car-
boxylate salts of fatty acids are soaps.
Michael addition (Sections 18.13 and 21.9): The conjugate ad-
dition of a carbanion (usually an enolate) to an H9251,H9252-unsatu-
rated carbonyl compound.
CH
3
CH
2
OCCH
2
COCH
2
CH
3
O
X
O
X
Microscopic reversibility (Section 6.10): The principle that the
intermediates and transition states in the forward and back-
ward stages of a reversible reaction are identical, but are en-
countered in the reverse order.
Molar absorptivity (Section 13.20): A measure of the intensity
of a peak, usually in UV-VIS spectroscopy.
Molecular dipole moment (Section 1.11): The overall mea-
sured dipole moment of a molecule. It can be calculated as
the resultant (or vector sum) of all the individual bond di-
pole moments.
Molecular formula (Section 1.7): Chemical formula in which
subscripts are used to indicate the number of atoms of each
element present in one molecule. In organic compounds,
carbon is cited first, hydrogen second, and the remaining el-
ements in alphabetical order.
Molecular ion (Section 13.21): In mass spectrometry, the
species formed by loss of an electron from a molecule.
Molecular orbital theory (Section 1.14): Theory of chemical
bonding in which electrons are assumed to occupy orbitals
in molecules much as they occupy orbitals in atoms. The
molecular orbitals are described as combinations of the or-
bitals of all of the atoms that make up the molecule.
Monomer (Section 6.21): The simplest stable molecule from
which a particular polymer may be prepared.
Monosaccharide (Section 25.1): A carbohydrate that cannot be
hydrolyzed further to yield a simpler carbohydrate.
Monosubstituted alkene (Section 5.6): An alkene of the type
RCH?CH
2
, in which there is only one carbon directly
bonded to the carbons of the double bond.
Multiplicity (Section 13.7): The number of peaks into which a
signal is split in nuclear magnetic resonance spectroscopy.
Signals are described as singlets, doublets, triplets, and so
on, according to the number of peaks into which they are
split.
Mutarotation (Section 25.8): The change in optical rotation
that occurs when a single form of a carbohydrate is allowed
to equilibrate to a mixture of isomeric hemiacetals.
Nanotube (Section 11.8): A form of elemental carbon com-
posed of a cylindrical cluster of carbon atoms.
Neopentane (Section 2.7): The common name for 2,2-
dimethylpropane, (CH
3
)
4
C.
Neurotransmitter (Section 22.5): Substance, usually a natu-
rally occurring amine, that mediates the transmission of
nerve impulses.
Newman projection (Section 3.1): Method for depicting con-
formations in which one sights down a carbon—carbon
bond and represents the front carbon by a point and the back
carbon by a circle.
GLOSSARY G-16
Nitration (Section 12.3): Replacement of a hydrogen sub-
stituent by an ±NO
2
group. The term is usually used in
connection with electrophilic aromatic substitution.
Nitrile (Sections 2.3 and 20.1): A compound of the type
RCPN. R may be alkyl or aryl. Also known as alkyl or aryl
cyanides.
Nitrosamine See N-nitroso amine.
N-Nitroso amine (Section 22.16): A compound of the type
R
2
N±N?O. R may be alkyl or aryl groups, which may be
the same or different. N-Nitroso amines are formed by ni-
trosation of secondary amines.
Nitrosation (Section 22.16): The reaction of a substance, usually
an amine, with nitrous acid. Primary amines yield diazonium
ions; secondary amines yield N-nitroso amines. Tertiary aro-
matic amines undergo nitrosation of their aromatic ring.
Noble gases (Section 1.1): The elements in group VIIIA of the
periodic table (helium, neon, argon, krypton, xenon, radon).
Also known as the rare gases, they are, with few excep-
tions, chemically inert.
Nodal surface (Section 1.1): A plane drawn through an orbital
where the algebraic sign of a wave function changes. The
probability of finding an electron at a node is zero.
N terminus (Section 27.7): The amino acid at the end of a pep-
tide or protein chain that has its H9251-amino group intact; that
is, the H9251-amino group is not part of a peptide bond.
Nuclear magnetic resonance (NMR) spectroscopy (Section
13.3): A method for structure determination based on the ef-
fect of molecular environment on the energy required to
promote a given nucleus from a lower energy spin state to a
higher energy state.
Nucleic acid (Section 27.26): A polynucleotide present in the
nuclei of cells.
Nucleophile (Section 4.10): An atom that has an unshared elec-
tron pair which can be used to form a bond to carbon. Nu-
cleophiles are Lewis bases.
Nucleophilic acyl substitution (Section 20.3): Nucleophilic
substitution at the carbon atom of an acyl group.
Nucleophilic addition (Section 17.6): The characteristic reac-
tion of an aldehyde or a ketone. An atom possessing an un-
shared electron pair bonds to the carbon of the C?O group,
and some other species (normally hydrogen) bonds to the
oxygen.
Nucleophilic aliphatic substitution (Chapter 8): Reaction in
which a nucleophile replaces a leaving group, usually a
halide ion, from sp
3
-hybridized carbon. Nucleophilic
aliphatic substitution may proceed by either an S
N
1 or an
S
N
2 mechanism.
H±YH11001RCRH11032
O
X
RC±Y
W
W
OH
RH11032
HNO
3
H
2
SO
4
Ar±HAr±NO
2
Nucleophilic aromatic substitution (Chapter 23): A reaction in
which a nucleophile replaces a leaving group as a sub-
stituent on an aromatic ring. Substitution may proceed by
an addition—elimination mechanism or an elimination—ad-
dition mechanism.
Nucleophilicity (Section 8.7): A measure of the reactivity of a
Lewis base in a nucleophilic substitution reaction.
Nucleoside (Section 27.24): The combination of a purine or
pyrimidine base and a carbohydrate, usually ribose or 2-
deoxyribose.
Nucleotide (Section 27.25): The phosphate ester of a nucleoside.
Octane rating (Section 2.13): The capacity of a sample of
gasoline to resist “knocking,” expressed as a number equal
to the percentage of 2,2,4-trimethylpentane (“isooctane”) in
an isooctane—heptane mixture that has the same knocking
characteristics.
Octet rule (Section 1.3): When forming compounds, atoms
gain, lose, or share electrons so that the number of their va-
lence electrons is the same as that of the nearest noble gas.
For the elements carbon, nitrogen, oxygen, and the halo-
gens, this number is 8.
Oligomer (Section 14.15): A molecule composed of too few
monomer units for it to be classified as a polymer, but more
than in a dimer, trimer, tetramer, etc.
Oligosaccharide (Section 25.1): A carbohydrate that gives
three to ten monosaccharides on hydrolysis.
Optical activity (Section 7.4): Ability of a substance to rotate
the plane of polarized light. To be optically active, a sub-
stance must be chiral, and one enantiomer must be present
in excess of the other.
Optically pure (Section 7.4): Describing a chiral substance in
which only a single enantiomer is present.
Orbital (Section 1.1): Strictly speaking, a wave function H9274. It is
convenient, however, to think of an orbital in terms of the
probability H9274
2
of finding an electron at some point relative
to the nucleus, as the volume inside the boundary surface of
an atom, or the region in space where the probability of
finding an electron is high.
H9268 Orbital (Section 1.14): A bonding orbital characterized by
rotational symmetry.
H9268* Orbital (Section 1.14): An antibonding orbital character-
ized by rotational symmetry.
Organometallic compound (Section 14.1): A compound that
contains a carbon-to-metal bond.
Ortho (Section 11.7): Term describing a 1,2 relationship be-
tween substituents on a benzene ring.
Ortho, para director (Section 12.9): A group that when present
on a benzene ring directs an incoming electrophile to the
positions ortho and para to itself.
Oxidation (Section 2.16): A decrease in the number of elec-
trons associated with an atom. In organic chemistry, oxi-
dation of carbon occurs when a bond between carbon and
an atom that is less electronegative than carbon is re-
placed by a bond to an atom that is more electronegative
than carbon.
G-17 GLOSSARY
Oxime (Section 17.10): A compound of the type R
2
C?NOH,
formed by the reaction of hydroxylamine (NH
2
OH) with an
aldehyde or a ketone.
Oxonium ion (Section 4.6): Specific name for the species
H
3
O
H11001
(also called hydronium ion). General name for
species such as alkyloxonium ions ROH
2
H11001
analogous to
H
3
O
H11001
.
Ozonolysis (Section 6.19): Ozone-induced cleavage of a car-
bon—carbon double or triple bond.
Para (Section 11.7): Term describing a 1,4 relationship be-
tween substituents on a benzene ring.
Paraffin hydrocarbons (Section 2.15): An old name for al-
kanes and cycloalkanes.
Partial rate factor (Section 12.10): In electrophilic aromatic
substitution, a number that compares the rate of attack at a
particular ring carbon with the rate of attack at a single po-
sition of benzene.
Pauli exclusion principle (Section 1.1): No two electrons can
have the same set of four quantum numbers. An equivalent
expression is that only two electrons can occupy the same
orbital, and then only when they have opposite spins.
PCC (Section 15.10): Abbreviation for pyridinium chlorochro-
mate C
5
H
5
NH
H11001
ClCrO
3
H11002
. When used in an anhydrous
medium, PCC oxidizes primary alcohols to aldehydes and
secondary alcohols to ketones.
PDC (Section 15.10): Abbreviation for pyridinium dichromate
(C
5
H
5
NH)
2
2H11001
Cr
2
O
7
2H11002
. Used in same manner and for same
purposes as PCC (see preceding entry).
n-Pentane (Section 2.7): The common name for pentane,
CH
3
CH
2
CH
2
CH
2
CH
3
.
Pentose (Section 25.4): A carbohydrate with five carbon
atoms.
Peptide (Section 27.7): Structurally, a molecule composed of
two or more H9251-amino acids joined by peptide bonds.
Peptide bond (Section 27.7): An amide bond between the car-
boxyl group of one H9251-amino acid and the amino group of
another.
(The bond highlighted in yellow is the peptide bond.)
Pericyclic reaction (Section 10.12): A reaction that proceeds
through a cyclic transition state.
Period (Section 1.1): A horizontal row of the periodic table.
Peroxide (Section 6.8): A compound of the type ROOR.
Peroxide effect (Section 6.8): Reversal of regioselectivity ob-
served in the addition of hydrogen bromide to alkenes
brought about by the presence of peroxides in the reaction
mixture.
Phase-transfer catalysis (Section 22.6): Method for increasing
the rate of a chemical reaction by transporting an ionic re-
±±NHCHC±NHCHC±±
W
RH11032
W
R
O
X
O
X
actant from an aqueous phase where it is solvated and less
reactive to an organic phase where it is not solvated and is
more reactive. Typically, the reactant is an anion that is car-
ried to the organic phase as its quaternary ammonium salt.
Phenols (Section 24.1): Family of compounds characterized by
a hydroxyl substituent on an aromatic ring as in ArOH. Phe-
nol is also the name of the parent compound, C
6
H
5
OH.
Phenyl group (Section 11.7): The group
It is often abbreviated C
6
H
5
±.
Phospholipid (Section 26.4): A diacylglycerol bearing a
choline-phosphate “head group.” Also known as phos-
phatidylcholine.
Photochemical reaction (Section 4.19): A chemical reaction
that occurs when light is absorbed by a substance.
Photon (Section 13.1): Term for an individual “bundle” of en-
ergy, or particle, of electromagnetic radiation.
pK
a
(Section 4.6): A measure of acid strength defined as
H11002log K
a
. The stronger the acid, the smaller the value of pK
a
.
Planck’s constant (Section 13.1): Constant of proportionality
(h) in the equation E H11005 hH9263, which relates the energy (E) to
the frequency (H9263) of electromagnetic radiation.
Plane of symmetry (Section 7.3): A plane that bisects an ob-
ject, such as a molecule, into two mirror-image halves; also
called a mirror plane. When a line is drawn from any ele-
ment in the object perpendicular to such a plane and ex-
tended an equal distance in the opposite direction, a dupli-
cate of the element is encountered.
Pleated H9252 sheet (Section 27.19): Type of protein secondary
structure characterized by hydrogen bonds between NH and
C?O groups of adjacent parallel peptide chains. The indi-
vidual chains are in an extended zigzag conformation.
Polar covalent bond (Section 1.5): A shared electron pair bond
in which the electrons are drawn more closely to one of the
bonded atoms than the other.
Polarimeter (Section 7.4): An instrument used to measure opti-
cal activity.
Polarizability (Section 4.5): A measure of the ease of distortion
of the electric field associated with an atom or a group. A
fluorine atom in a molecule, for example, holds its electrons
tightly and is very nonpolarizable. Iodine is very polariz-
able.
Polarized light (Section 7.4): Light in which the electric field
vectors vibrate in a single plane. Polarized light is used in
measuring optical activity.
Polyamide (Section 20.16): A polymer in which individual
structural units are joined by amide bonds. Nylon is a syn-
thetic polyamide; proteins are naturally occurring
polyamides.
HH
HH
H
GLOSSARY G-18
Polyamine (Section 22.5): A compound that contains many
amino groups. The term is usually applied to a group of nat-
urally occurring substances, including spermine, spermi-
dine, and putrescine, that are believed to be involved in cell
differentiation and proliferation.
Polycyclic aromatic hydrocarbon (Section 11.8): An aromatic
hydrocarbon characterized by the presence of two or more
benzene-like rings.
Polycyclic hydrocarbon (Section 3.14): A hydrocarbon in
which two carbons are common to two or more rings.
Polyester (Section 20.16): A polymer in which individual
structural units are joined by ester bonds.
Polyether (Section 16.4): A molecule that contains many ether
linkages. Polyethers occur naturally in a number of antibi-
otic substances.
Polyethylene (Section 6.21): A polymer of ethylene.
Polymer (Section 6.21): Large molecule formed by the repeti-
tive combination of many smaller molecules (monomers).
Polymerization (Section 6.21): Process by which a polymer is
prepared. The principal processes include free-radical,
cationic, coordination, and condensation polymerization.
Polypeptide (Section 27.1): A polymer made up of “many”
(more than eight to ten) amino acid residues.
Polypropylene (Section 6.21): A polymer of propene.
Polysaccharide (Sections 25.1 and 25.15): A carbohydrate that
yields “many” monosaccharide units on hydrolysis.
Potential energy (Section 2.15): The energy a system has ex-
clusive of its kinetic energy.
Potential energy diagram (Section 4.7): Plot of potential en-
ergy versus some arbitrary measure of the degree to which
a reaction has proceeded (the reaction coordinate). The
point of maximum potential energy is the transition state.
Primary alkyl group (Section 2.10): Structural unit of the type
RCH
2
±, in which the point of attachment is to a primary
carbon.
Primary amine (Section 22.1): An amine with a single alkyl or
aryl substituent and two hydrogens: an amine of the type
RNH
2
(primary alkylamine) or ArNH
2
(primary aryl-
amine).
Primary carbon (Section 2.10): A carbon that is directly at-
tached to only one other carbon.
Primary structure (Section 27.8): The sequence of amino acids
in a peptide or protein.
Principal quantum number (Section 1.1): The quantum num-
ber (n) of an electron that describes its energy level. An
electron with n H11005 1 must be an s electron; one with n H11005 2
has s and p states available.
Propagation steps (Section 4.18): Elementary steps that repeat
over and over again in a chain reaction. Almost all of the
products in a chain reaction arise from the propagation steps.
Protecting group (Section 17.9): A temporary alteration in the
nature of a functional group so that it is rendered inert under
the conditions in which reaction occurs somewhere else in
the molecule. To be synthetically useful, a protecting group
must be stable under a prescribed set of reaction conditions,
yet be easily introduced and removed.
Protein (Chapter 27): A naturally occurring polymer that typi-
cally contains 100—300 amino acid residues.
Protein Data Bank (Section 27.20): A central repository in
which crystallographic coordinates for biological mole-
cules, especially proteins, are stored. The data are accessi-
ble via the World-Wide Web and can be transformed into
three-dimensional images with appropriate molecular-
modeling software.
Protic solvent (Section 8.12): A solvent that has easily ex-
changeable protons, especially protons bonded to oxygen as
in hydroxyl groups.
Purine (Section 27.23): The heterocyclic aromatic compound.
Pyranose form (Section 25.7): Six-membered ring arising via
cyclic hemiacetal formation between the carbonyl group
and a hydroxyl group of a carbohydrate.
Pyrimidine (Section 27.23): The heterocyclic aromatic com-
pound.
Quantum (Section 13.1): The energy associated with a photon.
Quaternary ammonium salt (Section 22.1): Salt of the type
R
4
N
H11001
X
H11002
. The positively charged ion contains a nitrogen
with a total of four organic substituents (any combination of
alkyl and aryl groups).
Quaternary carbon (Section 2.10): A carbon that is directly at-
tached to four other carbons.
Quaternary structure (Section 27.22): Description of the way
in which two or more protein chains, not connected by
chemical bonds, are organized in a larger protein.
Quinone (Section 24.14): The product of oxidation of an ortho
or para dihydroxybenzene derivative. Examples of
quinones include
R (Section 2.2): Symbol for an alkyl group.
Racemic mixture (Section 7.4): Mixture containing equal
quantities of enantiomers.
Rate-determining step (Section 4.11): Slowest step of a multi-
step reaction mechanism. The overall rate of a reaction can
be no faster than its slowest step.
O
O
and
O
O
N
N
N
N
N
N
H
G-19 GLOSSARY
Rearrangement (Section 5.13): Intramolecular migration of an
atom, a group, or a bond from one atom to another.
Reducing sugar (Section 25.19): A carbohydrate that can be
oxidized with substances such as Benedict’s reagent. In
general, a carbohydrate with a free hydroxyl group at the
anomeric position.
Reduction (Section 2.16): Gain in the number of electrons as-
sociated with an atom. In organic chemistry, reduction of
carbon occurs when a bond between carbon and an atom
which is more electronegative than carbon is replaced by a
bond to an atom which is less electronegative than carbon.
Reductive amination (Section 22.11): Method for the prepara-
tion of amines in which an aldehyde or a ketone is treated
with ammonia or an amine under conditions of catalytic hy-
drogenation.
Refining (Section 2.13): Conversion of crude oil to useful ma-
terials, especially gasoline.
Reforming (Section 2.13): Step in oil refining in which the pro-
portion of aromatic and branched-chain hydrocarbons in
petroleum is increased so as to improve the octane rating of
gasoline.
Regioselective (Section 5.10): Term describing a reaction that
can produce two (or more) constitutional isomers but gives
one of them in greater amounts than the other. A reaction
that is 100% regioselective is termed regiospecific.
Relative configuration (Section 7.5): Stereochemical configu-
ration on a comparative, rather than an absolute, basis.
Terms such as D, L, erythro, threo, H9251, and H9252 describe relative
configuration.
Resolution (Section 7.14): Separation of a racemic mixture
into its enantiomers.
Resonance (Section 1.9): Method by which electron delocal-
ization may be shown using Lewis structures. The true elec-
tron distribution in a molecule is regarded as a hybrid of the
various Lewis structures that can be written for a molecule.
Resonance energy (Section 10.6): Extent to which a substance
is stabilized by electron delocalization. It is the difference
in energy between the substance and a hypothetical model
in which the electrons are localized.
Restriction enzymes (Section 27.29): Enzymes that catalyze
the cleavage of DNA at specific sites.
Retention of configuration (Section 6.13): Stereochemical
pathway observed when a new bond is made that has the
same spatial orientation as the bond that was broken.
Retrosynthetic analysis (Section 14.9): Technique for syn-
thetic planning based on reasoning backward from the tar-
get molecule to appropriate starting materials. An arrow of
the type designates a retrosynthetic step.
Ring inversion (Section 3.7): Process by which a chair conforma-
tion of cyclohexane is converted to a mirror-image chair. All
of the equatorial substituents become axial, and vice versa.
Also called ring flipping, or chair—chair interconversion.
RNA (ribonucleic acid) (Section 27.26): A polynucleotide of
ribose.
Robinson annulation (Section 18.13): The combination of a
Michael addition and an intramolecular aldol condensation
used as a synthetic method for ring formation.
Rotamer (Section 3.1): Synonymous with conformer.
Sandmeyer reaction (Section 22.18): Reaction of an aryl dia-
zonium ion with CuCl, CuBr, or CuCN to give, respec-
tively, an aryl chloride, aryl bromide, or aryl cyanide (ni-
trile).
Sanger’s reagent (Section 27.11): The compound 1-fluoro-2,4-
dinitrobenzene, used in N-terminal amino acid identifica-
tion.
Saponification (Section 20.10): Hydrolysis of esters in basic
solution. The products are an alcohol and a carboxylate salt.
The term means “soap making” and derives from the
process whereby animal fats were converted to soap by
heating with wood ashes.
Saturated hydrocarbon (Section 6.1): A hydrocarbon in which
there are no multiple bonds.
Sawhorse formula (Section 3.1): A representation of the three-
dimensional arrangement of bonds in a molecule by a draw-
ing of the type shown.
Schiemann reaction (Section 22.18): Preparation of an aryl
fluoride by heating the diazonium fluoroborate formed by
addition of tetrafluoroboric acid (HBF
4
) to a diazonium ion.
Schiff’s base (Section 17.10): Another name for an imine; a
compound of the type R
2
C?NR H11032.
Scientific method (Section 6.6): A systematic aproach to estab-
lishing new knowledge in which observations lead to laws,
laws to theories, theories to testable hypotheses, and hy-
potheses to experiments.
Secondary alkyl group (Section 2.10): Structural unit of the
type R
2
CH±, in which the point of attachment is to a sec-
ondary carbon.
Secondary amine (Section 22.1): An amine with any combina-
tion of two alkyl or aryl substituents and one hydrogen on
nitrogen; an amine of the type
RNHRH11032 or RNHAr or ArNHArH11032.
Secondary carbon (Section 2.10): A carbon that is directly at-
tached to two other carbons.
Secondary structure (Section 27.19): The conformation with
respect to nearest neighbor amino acids in a peptide or pro-
tein. The H9251 helix and the H9252 pleated sheet are examples of
protein secondary structures.
Sequence rule (Section 7.6): Foundation of the Cahn—
Ingold—Prelog system. It is a procedure for ranking sub-
stituents on the basis of atomic number.
Shielding (Section 13.4): Effect of a molecule’s electrons that
decreases the strength of an external magnetic field felt by a
proton or another nucleus.
GLOSSARY G-20
Sigmatropic rearrangement (Section 24.13): Migration of a H9268
bond from one end of a conjugated H9266 electron system to the
other. The Claisen rearrangement is an example.
Simmons—Smith reaction (Section 14.12): Reaction of an
alkene with iodomethylzinc iodide to form a cyclopropane
derivative.
Skew boat (Section 3.5): An unstable conformation of cyclo-
hexane. It is slightly more stable than the boat conformation.
Soaps (Section 19.5): Cleansing substances obtained by the
hydrolysis of fats in aqueous base. Soaps are sodium or
potassium salts of unbranched carboxylic acids having
12—18 carbon atoms.
Solid-phase peptide synthesis (Section 27.18): Method for
peptide synthesis in which the C-terminal amino acid is co-
valently attached to an inert solid support and successive
amino acids are attached via peptide bond formation. At the
completion of the synthesis the polypeptide is removed
from the support.
Solvolysis reaction (Section 8.7): Nucleophilic substitution in
a medium in which the only nucleophiles present are the
solvent and its conjugate base.
Space-filling model (Section 1.9): A type of molecular model
that attempts to represent the volume occupied by the
atoms.
Specific rotation (Section 7.4): Optical activity of a substance
per unit concentration per unit path length:
[H9251] H11005
where H9251 is the observed rotation in degrees, c is the concen-
tration in g/100 mL, and l is the path length in decimeters.
Spectrometer (Section 13.1): Device designed to measure ab-
sorption of electromagnetic radiation by a sample.
Spectrum (Section 13.2): Output, usually in chart form, of a
spectrometer. Analysis of a spectrum provides information
about molecular structure.
sp Hybridization (Section 1.18): Hybridization state adopted
by carbon when it bonds to two other atoms as, for example,
in alkynes. The s orbital and one of the 2p orbitals mix to
form two equivalent sp-hybridized orbitals. A linear geom-
etry is characteristic of sp hybridization.
sp
2
-Hybridization (Section 1.17): A model to describe the
bonding of a carbon attached to three other atoms or groups.
The carbon 2s orbital and the two 2p orbitals are combined
to give a set of three equivalent sp
2
orbitals having 33.3% s
character and 66.7% p character. One p orbital remains un-
hybridized. A trigonal planar geometry is characteristic of
sp
2
hybridization.
sp
3
-Hybridization (Section 1.15): A model to describe the
bonding of a carbon attached to four other atoms or groups.
The carbon 2s orbital and the three 2p orbitals are combined
to give a set of four equivalent orbitals having 25% s char-
acter and 75% p character. These orbitals are directed to-
ward the corners of a tetrahedron.
Spin quantum number (Section 1.1): One of the four quantum
numbers that describe an electron. An electron may have
either of two different spin quantum numbers, H11001 or H11002 .
1
2
1
2
100H9251
cl
Spin—spin coupling (Section 13.7): The communication of nu-
clear spin information between two nuclei.
Spin—spin splitting (Section 13.7): The splitting of NMR sig-
nals caused by the coupling of nuclear spins. Only non-
equivalent nuclei (such as protons with different chemical
shifts) can split one another’s signals.
Spirocyclic hydrocarbon (Section 3.14): A hydrocarbon in
which a single carbon is common to two rings.
Squalene (Section 26.11): A naturally occurring triterpene
from which steroids are biosynthesized.
Staggered conformation (Section 3.1): Conformation of the
type shown, in which the bonds on adjacent carbons are as
far away from one another as possible.
Stereochemistry (Chapter 7): Chemistry in three dimensions;
the relationship of physical and chemical properties to the
spatial arrangement of the atoms in a molecule.
Stereoelectronic effect (Section 5.16): An electronic effect
that depends on the spatial arrangement between the or-
bitals of the electron donor and acceptor.
Stereogenic axis (Section 10.8): Line drawn through a mole-
cule that is analogous to the long axis of a right-handed or
left-handed screw or helix.
Stereogenic center (Section 7.2): An atom that has four non-
equivalent atoms or groups attached to it. At various times
stereogenic centers have been called asymmetric centers or
chiral centers.
Stereoisomers (Section 3.12): Isomers which have the same
constitution but which differ in respect to the arrangement
of their atoms in space. Stereoisomers may be either enan-
tiomers or diastereomers.
Stereoregular polymer (Section 7.15): Polymer containing
stereogenic centers according to a regular repeating pattern.
Syndiotactic and isotactic polymers are stereoregular.
Stereoselective reaction (Sections 5.11 and 6.3): Reaction in
which a single starting material has the capacity to form two
or more stereoisomeric products but forms one of them in
greater amounts than any of its stereoisomers. Terms such as
addition to the less hindered side describe stereoselectivity.
Stereospecific reaction (Section 7.13): Reaction in which
stereoisomeric starting materials give stereoisomeric prod-
ucts. Terms such as syn addition, anti elimination, and in-
version of configuration describe stereospecific reactions.
Steric hindrance (Sections 3.3, 6.3, and 8.6): An effect on
structure or reactivity that depends on van der Waals repul-
sive forces.
Steric strain (Section 3.2): Destabilization of a molecule as a
result of van der Waals repulsion, distorted bond distances,
bond angles, or torsion angles.
G-21 GLOSSARY
Steroid (Section 26.11): Type of lipid present in both plants
and animals characterized by a nucleus of four fused rings
(three are six-membered, one is five-membered). Choles-
terol is the most abundant steroid in animals.
Strecker synthesis (Section 27.4): Method for preparing amino
acids in which the first step is reaction of an aldehyde with
ammonia and hydrogen cyanide to give an amino nitrile,
which is then hydrolyzed.
Stretching vibration (Section 13.19): A regular, repetitive mo-
tion of two atoms or groups along the bond that connects
them.
Structural isomer (Section 1.8): Synonymous with constitu-
tional isomer.
Substitution nucleophilic bimolecular (S
N
2) mechanism
(Sections 4.13 and 8.3): Concerted mechanism for nucle-
ophilic substitution in which the nucleophile attacks carbon
from the side opposite the bond to the leaving group and as-
sists the departure of the leaving group.
Substitution nucleophilic unimolecular (S
N
1) mechanism
(Sections 4.11 and 8.8): Mechanism for nucleophilic substi-
tution characterized by a two-step process. The first step is
rate-determining and is the ionization of an alkyl halide to a
carbocation and a halide ion.
Substitution reaction (Section 4.8): Chemical reaction in
which an atom or a group of a molecule is replaced by a dif-
ferent atom or group.
Substitutive nomenclature (Section 4.1): Type of IUPAC
nomenclature in which a substance is identified by a name
ending in a suffix characteristic of the type of compound.
2-Methylbutanol, 3-pentanone, and 2-phenylpropanoic acid
are examples of substitutive names.
Sucrose (Section 25.14): A disaccharide of glucose and fruc-
tose in which the two monosaccharides are joined at their
anomeric positions.
Sulfide (Section 16.1): A compound of the type RSRH11032. Sulfides
are the sulfur analogs of ethers.
Sulfonation (Section 12.4): Replacement of a hydrogen by an
±SO
3
H group. The term is usually used in connection with
electrophilic aromatic substitution.
Sulfone (Section 16.16): Compound of the type
R±S±R
W
W
O
O
H11002
2H11001
H11002
SO
3
H
2
SO
4
Ar±HAr±SO
3
H
NH
3
HCN
hydrolysis
RCHCPN
W
NH
2
RCHCO
2
H11002
W
H11001
NH
3
RCH
O
X
Sulfoxide (Section 16.16): Compound of the type
Symmetry-allowed reaction (Section 10.14): Concerted reac-
tion in which the orbitals involved overlap in phase at all
stages of the process. The conrotatory ring opening of cy-
clobutene to 1,3-butadiene is a symmetry-allowed reaction.
Symmetry-forbidden reaction (Section 10.14): Concerted re-
action in which the orbitals involved do not overlap in
phase at all stages of the process. The disrotatory ring open-
ing of cyclobutene to 1,3-butadiene is a symmetry-forbid-
den reaction.
Syn addition (Section 6.3): Addition reaction in which the two
portions of the reagent which add to a multiple bond add
from the same side.
Syndiotactic polymer (Section 7.15): Stereoregular polymer in
which the configuration of successive stereogenic centers
alternates along the chain.
Synthon (Section 21.6): A structural unit in a molecule that is
related to a synthetic operation.
Systematic nomenclature (Section 2.8): Names for chemical
compounds that are developed on the basis of a prescribed
set of rules. Usually the IUPAC system is meant when the
term systematic nomenclature is used.
Tautomerism (Sections 9.12 and 18.4): Process by which two
isomers are interconverted by an actual or formal move-
ment of an atom or a group. Enolization is a form of tau-
tomerism.
Terminal alkyne (Section 9.1): Alkyne of the type RCPCH, in
which the triple bond appears at the end of the chain.
Termination steps (Section 4.18): Reactions that halt a chain
reaction. In a free-radical chain reaction, termination steps
consume free radicals without generating new radicals to
continue the chain.
Terpenes (Section 26.7): Compounds that can be analyzed as
clusters of isoprene units. Terpenes with 10 carbons are classi-
fied as monoterpenes, those with 15 are sesquiterpenes, those
with 20 are diterpenes, and those with 30 are triterpenes.
Tertiary alkyl group (Section 2.10): Structural unit of the type
R
3
C±, in which the point of attachment is to a tertiary car-
bon.
Tertiary amine (Section 22.1): Amine of the type R
3
N with any
combination of three alkyl or aryl substituents on nitrogen.
Tertiary carbon (Section 2.10): A carbon that is directly at-
tached to three other carbons.
Tertiary structure (Section 27.20): A description of how a pro-
tein chain is folded.
Tesla (Section 13.3): Sl unit for magnetic field strength.
RC±CHR
2
O
X
RC?CR
2
W
OH
R±S±R
W
O
H11002
H11001
GLOSSARY G-22
Tetrahedral intermediate (Section 19.14 and Chapter 20): The
key intermediate in nucleophilic acyl substitution. Formed
by nucleophilic addition to the carbonyl group of a car-
boxylic acid derivative.
Tetramethylsilane (TMS) (Section 13.4): The molecule
(CH
3
)
4
Si, used as a standard to calibrate proton and carbon-
13 NMR spectra.
Tetrasubstituted alkene (Section 5.6): Alkene of the type
R
2
C?CR
2
, in which there are four carbons directly bonded
to the carbons of the double bond. (The R groups may be
the same or different.)
Tetrose (Section 25.3): A carbohydrate with four carbon atoms.
Thermochemistry (Section 2.15): The study of heat changes
that accompany chemical processes.
Thermodynamically controlled reaction (Section 10.10): Re-
action in which the reaction conditions permit two or more
products to equilibrate, giving a predominance of the most
stable product.
Thioester (Section 20.12): An S-acyl derivative of a thiol; a
compound of the type
Thiol (Section 15.13): Compound of the type RSH or ArSH.
Threo (Section 7.11): Term applied to the relative configuration
of two stereogenic centers within a molecule. The threo
stereoisomer has like substituents on opposite sides of a
Fischer projection.
Torsional strain (Section 3.1): Decreased stability of a mole-
cule that results from the eclipsing of bonds.
trans- (Section 3.12): Stereochemical prefix indicating that two
substituents are on opposite sides of a ring or a double bond.
(Contrast with the prefix cis-.)
Transcription (Section 27.28): Construction of a strand of
mRNA complementary to a DNA template.
Transfer RNA (tRNA) (Section 27.28): A polynucleotide of ri-
bose that is bound at one end to a unique amino acid. This
amino acid is incorporated into a growing peptide chain.
Transition state (Section 3.1): The point of maximum energy
in an elementary step of a reaction mechanism.
Translation (Section 27.28): The “reading” of mRNA by vari-
ous tRNAs, each one of which is unique for a particular
amino acid.
Triacylglycerol (Section 26.2): A derivative of glycerol (1,2,3-
propanetriol) in which the three oxygens bear acyl groups
derived from fatty acids.
Tripeptide (Section 27.1): A compound in which three H9251-amino
acids are linked by peptide bonds.
Triple bond (Section 1.4): Bond formed by the sharing of six
electrons between two atoms.
Trisubstituted alkene (Section 5.6): Alkene of the type
R
2
C?CHR, in which there are three carbons directly
bonded to the carbons of the double bond. (The R groups
may be the same or different.)
Trivial nomenclature (Section 2.8): Term synonymous with
common nomenclature.
RCSRH11032
O
X
Trypsin (Section 27.10): A digestive enzyme that catalyzes the
hydrolysis of proteins. Trypsin selectively catalyzes the
cleavage of the peptide bond between the carboxyl group of
lysine or arginine and some other amino acid.
Twist boat (Section 3.5): Synonymous with skew boat.
Ultraviolet-visible (UV-VIS) spectroscopy (Section 13.20): An-
alytical method based on transitions between electronic en-
ergy states in molecules. Useful in studying conjugated sys-
tems such as polyenes.
Unimolecular (Section 4.11): Describing a step in a reaction
mechanism in which only one particle undergoes a chemi-
cal change at the transition state.
H9251,H9252-Unsaturated aldehyde or ketone (Section 18.11): Alde-
hyde or ketone that bears a double bond between its H9251 and
H9252 carbons as in
Unsaturated hydrocarbon (Section 6.1): A hydrocarbon that
can undergo addition reactions; that is, one that contains
multiple bonds.
Upfield (Section 13.4): The high-field region of an NMR spec-
trum. A signal that is upfield with respect to another lies to
its right on the spectrum.
Urethan (Section 20.17): Another name for a carbamate ester;
a compound of the type (H
2
NCO
2
R).
Uronic acids (Section 25.19): Carbohydrates that have an alde-
hyde function at one end of their carbon chain and a car-
boxylic acid group at the other.
Valence bond theory (Section 1.13): Theory of chemical
bonding based on overlap of half-filled atomic orbitals be-
tween two atoms. Orbital hybridization is an important ele-
ment of valence bond theory.
Valence electrons (Section 1.1): The outermost electrons of an
atom. For second-row elements these are the 2s and 2p elec-
trons.
Valence shell electron-pair repulsion (VSEPR) model (Section
1.10): Method for predicting the shape of a molecule based
on the notion that electron pairs surrounding a central atom
repel one another. Four electron pairs will arrange them-
selves in a tetrahedral geometry, three will assume a trigo-
nal planar geometry, and two electron pairs will adopt a lin-
ear arrangement.
Van der Waals forces (Section 2.15): Intermolecular forces
that do not involve ions (dipole—dipole, dipole/induced-
dipole, and induced-dipole/induced-dipole forces).
Van der Waals radius (Section 2.15): A measure of the effec-
tive size of an atom or a group. The repulsive force between
two atoms increases rapidly when they approach each other
at distances less than the sum of their van der Waals radii.
Van der Waals strain (Section 3.2): Destabilization that results
when two atoms or groups approach each other too closely.
Also known as van der Waals repulsion.
R
2
C?CHCRH11032
O
X
G-23 GLOSSARY
Vicinal (Section 6.14): Describing two substituents that are lo-
cated on adjacent atoms.
Vicinal coupling (Section 13.7): Coupling of the nuclear spins
of atoms X and Y when they are substituents on adjacent
atoms as in X±A±B±Y. Vicinal coupling is the most
common cause of spin—spin splitting in
1
H NMR spec-
troscopy.
Vicinal diol (Section 15.5): Compound that has two hydroxyl
(±OH) groups which are on adjacent sp
3
-hybridized car-
bons.
Vinyl group (Section 5.1): The group CH
2
?CH±.
Vitalism (Introduction): A nineteenth-century theory that di-
vided chemical substances into two main classes, organic
and inorganic, according to whether they originated in liv-
ing (animal or vegetable) or nonliving (mineral) matter, re-
spectively. Vitalist doctrine held that the conversion of inor-
ganic substances to organic ones could be accomplished
only through the action of some “vital force.”
Walden inversion (Section 8.4): Originally, a reaction se-
quence developed by Paul Walden whereby a chiral starting
material was transformed to its enantiomer by a series of
stereospecific reactions. Current usage is more general and
refers to the inversion of configuration that attends any bi-
molecular nucleophilic substitution.
Wave functions (Section 1.1): The solutions to arithmetic ex-
pressions that express the energy of an electron in an atom.
Wavelength (Section 13.1): Distance between two successive
maxima (peaks) or two successive minima (troughs) of a
wave.
Wave numbers (Section 13.19): Conventional units in infrared
spectroscopy that are proportional to frequency. Wave num-
bers are in reciprocal centimeters (cm
H110021
).
Wax (Section 26.5): A mixture of water-repellent substances
that form a protective coating on the leaves of plants, the fur
of animals, and the feathers of birds, among other things. A
principal component of a wax is often an ester in which
both the acyl portion and the alkyl portion are characterized
by long carbon chains.
Williamson ether synthesis (Section 16.6): Method for the
preparation of ethers involving an S
N
2 reaction between an
alkoxide ion and a primary alkyl halide:
RONa RH11032CH
2
BrH11001 NaBrH11001RH11032CH
2
OR
Wittig reaction (Section 17.12): Method for the synthesis of
alkenes by the reaction of an aldehyde or a ketone with a
phosphorus ylide.
Wolff—Kishner reduction (Section 12.8): Method for reducing
the carbonyl group of aldehydes and ketones to a methylene
group (C?O ±￡ CH
2
) by treatment with hydrazine
(H
2
NNH
2
) and base (KOH) in a high-boiling alcohol sol-
vent.
Wood alcohol (Section 4.2): A common name for methanol,
CH
3
OH.
Ylide (Section 17.12): A neutral molecule in which two oppo-
sitely charged atoms, each with an octet of electrons, are di-
rectly bonded to each other. The compound
is an example of an ylide.
Zaitsev’s rule (Section 5.10): When two or more alkenes are
capable of being formed by an elimination reaction, the one
with the more highly substituted double bond (the more sta-
ble alkene) is the major product.
Zwitterion (Section 27.3): The form in which neutral amino
acids actually exist. The amino group is in its protonated
form and the carboxyl group is present as a carboxylate
RCHCO
2
H11002
W
H11001
NH
3
(C
6
H
5
)
3
P±CH
2
H11001H11002
H11001RCRH11032
O
X
(C
6
H
5
)
3
P±CRH11033
2
H11001H11002
H11001C?C
±
±
±
±
RRH11033
RH11032 RH11033
(C
6
H
5
)
3
P±O
H11002
H11001
| 课件名称： | 有机化学（英文原版） |
| 课件分类： | 化学 |
| 课件类型： | 电子图书 |
| 文件大小： | 28.97MB |
| 下载次数： | 7 |
| 评论次数： | 5 |
| 用户评分： | 8.2 |
- 20. 有机化学（英文原版）：Chapt20
- 21. 有机化学（英文原版）：Chapt21
- 22. 有机化学（英文原版）：Chapt22
- 23. 有机化学（英文原版）：Chapt23
- 24. 有机化学（英文原版）：Chapt24
- 25. 有机化学（英文原版）：Chapt25
- 26. 有机化学（英文原版）：Chapt26
- 27. 有机化学（英文原版）：Chapt27
- 28. 有机化学（英文原版）：End of Book
- 29. 有机化学（英文原版）：Glossary
- 30. 有机化学（英文原版）：help
- 31. 有机化学（英文原版）：letter2
- 32. 有机化学（英文原版）：main
- 33. 有机化学（英文原版）：Preface
- 34. 有机化学（英文原版）：SGAppendix
- 35. 有机化学（英文原版）：SGChapt01.PDF
- 36. 有机化学（英文原版）：SGChapt02
- 37. 有机化学（英文原版）：SGChapt03
- 38. 有机化学（英文原版）：SGChapt04
