Organic Chemistry, 7th Edition L. G. Wade, Jr

1. Chapter 21
Copyright © 2010 Pearson Education, Inc.
Organic Chemistry, 7th
Edition
L. G. Wade, Jr.
Part 1: Structure and Properties of
Carboxylic Acid Derivatives

2. Chapter 21 2
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.

3. Chapter 21 3
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.

4. Chapter 21 4
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.

5. Chapter 21 5
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.

6. Chapter 21 6
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.

7. Chapter 21 7
Protonation of Amides
 Under acidic conditions, the double-bonded
oxygen will get protonated.

8. Chapter 21 8
Classes of Amides
 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).
3º amide 2º amide 1º amide

9. Chapter 21 9
Nomenclature of Amides
 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.
N-ethyl-N-methyl-2-dimethylpropanamide
(N-ethyl-N-methylisobutyramide)CH3CHC N
O
CH2CH3
CH3
CH3

10. Chapter 21 10
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.

11. Chapter 21 11
Nitriles
 Nitriles contain the cyano group (—C≡N).
 They can be hydrolyzed to carboxylic acids.

12. Chapter 21 12
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.

13. Chapter 21 13
Naming Nitriles
 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.
CH3 C N
acetonitrile 3-cyanopentanoic acid
CH3 CH2 CH CH2 COOH
CN
CN
cyclopropanecarbonitrile

14. Chapter 21 14
Acid Halides
R C Cl
O
R C Br
O
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.

15. Chapter 21 15
Acid Halide Nomenclature
CH3CH2 C Cl
O
CH3CHCH2 C Br
OBr
propanoyl chloride 3-bromobutanoyl bromide
 Named by replacing -ic acid with -yl halide.
 Acyl chlorides are more common.

16. Chapter 21 16
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.

17. Chapter 21 17
Anhydride Nomenclature
CH3 C O
O
C
O
CH3 CF3 C O
O
C
O
CF3 CH3 C O
O
C
O
H
ethanoic anhydride
(acetic anhydride)
trifluoroethanoic anhydride
(trifluoroacetic anhydride)
ethanoic methanoic anhydride
(acetic formic anhydride)
 The word acid is replaced with anhydride.
 For a mixed anhydride, name both acids.

18. Chapter 21 18
Multifunctional Compounds
 The functional group with the highest priority
determines the parent name.
CH C NCH2CH3
OH
2-hydroxybutanenitrile
acid > ester > amide > nitrile > aldehyde > ketone >
alcohol > amine > alkene > alkyne

19. Chapter 21 19
Boiling Points of Carboxylic Acid Derivatives

20. Chapter 21 20
Intermolecular Forces of Amides

21. Chapter 21 21
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.

22. Chapter 21 22
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

23. Common Solvents
Chapter 21 23

24. Chapter 21 24
IR Spectroscopy

25. Chapter 21 25
IR Spectrum of Ethyl Octanoate

26. Chapter 21 26
IR Frequencies of Lactones and
Lactams
• Ring strain in lactones and lactams increases
the carbonyl stretching frequency.

27. Chapter 21 27
IR Spectrum of Propionic
Anhydride

28. Chapter 21 28
Typical 1
H–NMR Absorptions

29. Chapter 21 29
NMR Spectra of DMF

30. Chapter 21 30
13
C–NMR 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.