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Organic Chemistry, 7th Edition
L. G. Wade, Jr.
Chapter 21
Part 1: Structure and Properties of
Carboxylic Acid Derivatives
 2010, Prentice Hall
Acid Derivatives
All the derivatives can be converted to the
carboxylic acid by acidic or basic hydrolysis.
Esters and amides are commonly found in
nature.
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Esters from Carboxylic Acids
Esters can be made from the carboxylic acid
through the Fischer esterification.
Excess alcohol is used to drive the equilibrium
toward the ester.
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Nomenclature of Esters
Esters are named as alkyl carboxylates.
The first word is derived from the alkyl group
of the alcohol, and the second word from the
carboxylate group of the carboxylic acid.
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Cyclic Esters
Reaction of —OH and —COOH on same molecule
produces a cyclic ester called lactone.
To name, add the word lactone to the IUPAC acid
name or replace the -ic acid of common name with
-olactone.
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Amide Structure
Amides are the product of the reaction of a carboxylic
acid with ammonia or an amine.
Not basic because the lone pair on nitrogen is
delocalized by resonance.
The C—N bond has double-bond character.
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Protonation of Amides
Under acidic conditions, the double-bonded
oxygen will get protonated.
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Classes of Amides
3º amide
2º amide
1º amide
1° amide has one C—N bond (two N—H).
2° amide or N-substituted amide has two C—N bonds
(one N—H).
3° amide or N,N-disubstituted amide has three C—N
bonds (no N—H).
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Nomenclature of Amides
O CH3
CH3CHC N CH2CH3
N-ethyl-N-methyl-2-dimethylpropanamide
(N-ethyl-N-methylisobutyramide)
CH3
For 1° amide, drop -ic or -oic acid from the
carboxylic acid name, add -amide.
Alkyl groups bonded to nitrogen are named
with N-alkyl to indicate their attachment to the
nitrogen atom.
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Cyclic Amides
Cyclic amides are called lactams.
To name, add the word lactam to the IUPAC
acid name or replace the -ic acid of common
name with -olactam.
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Nitriles
Nitriles contain the cyano group (—C≡N).
They can be hydrolyzed to carboxylic acids.
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Structures of Acetonitrile and
Propyne
In both compounds, the atoms at the ends of the triple bonds
are sp hybridized, and the bond angles are 180°.
In place of the acetylenic hydrogen atom, the nitrile has a lone
pair of electrons in the sp orbital of nitrogen.
The nonbonding electrons on the nitrogen are not basic.
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Naming Nitriles
CN
CH3 C
N
acetonitrile
CH3
CH2 CH
CH2
COOH
CN
cyclopropanecarbonitrile
3-cyanopentanoic acid
For IUPAC names, add -nitrile to the alkane name.
The Ethyl Octanoate group can also be named as a
substituent, the cyano group.
Common names come from the carboxylic acid.
Replace -ic acid with -onitrile.
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Acid Halides
O
O
R C Cl
R C Br
acid chloride
(acyl chloride)
acid bromide
(acyl bromide)
Also called acyl halides.
These are more reactive than carboxylic acids, so
they are used to synthesize other acid derivatives
such as esters and amides.
Used in the Friedel–Crafts acylation to make
acylbenzenes.
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Acid Halide Nomenclature
O
CH3CH2
C Cl
propanoyl chloride
Br
CH3CHCH2
O
C Br
3-bromobutanoyl bromide
Named by replacing -ic acid with -yl halide.
Acyl chlorides are more common.
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Acid Anhydrides
Two molecules of acid combine with the loss of water
to form the anhydride.
Anhydrides are more reactive than acids, but less
reactive than acid chlorides.
A carboxylate ion is the leaving group in nucleophilic
acyl substitution reactions.
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Anhydride Nomenclature
O
CH3
O
C O C CH3
ethanoic anhydride
(acetic anhydride)
O
CF3
O
O
CH3
C O C CF3
trifluoroethanoic anhydride
(trifluoroacetic anhydride)
O
C O C H
ethanoic methanoic anhydride
(acetic formic anhydride)
The word acid is replaced with anhydride.
For a mixed anhydride, name both acids.
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Multifunctional Compounds
The functional group with the highest priority
determines the parent name.
OH
CH3
CH2
CH
C
N
2-hydroxybutanenitrile
acid > ester > amide > nitrile > aldehyde > ketone >
alcohol > amine > alkene > alkyne
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Boiling Points of Carboxylic Acid Derivatives
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Intermolecular Forces of Amides
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Melting Points
Amides have very high boiling points and melting
points compared to other compounds of similar
weight.
Melting points increase with increasing number of
N—H bonds.
Tertiary amides cannot hydrogen bond, but still have
high boiling points.
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Solubility
Acid chlorides and anhydrides are too
reactive to be used with water or alcohol.
Esters, 3° amides, and nitriles are good
polar aprotic solvents.
Solvents commonly used in organic
reactions:
Ethyl acetate
Dimethylformamide (DMF)
Acetonitrile
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Common Solvents
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IR Spectroscopy
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IR Spectrum of Ethyl Octanoate
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IR Frequencies of Lactones and
Lactams
• Ring strain in lactones and lactams increases
the carbonyl stretching frequency.
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IR Spectrum of Propionic
Anhydride
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Typical 1H–NMR Absorptions
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NMR Spectra of DMF
Chapter 21
13C–NMR
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Spectroscopy
The carbonyl carbons of acid derivatives appear at
shifts around 170 to 180 ppm, slightly more shielded
than the carbonyl carbons of ketones and aldehydes.
The α-carbon atoms absorb around 30 to 40 ppm.
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