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19.6 Structures and Names of Amides
19.7 Hydrolysis of Amides
Chapter 19 Amines and Amides
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In amides, an amino group replaces the –OH group of carboxylic acids.
O O || ||
CH3—C—OH CH3—C—NH2
Amides
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Preparation of Amides Amides are produced by reacting a carboxylic acid
with ammonia or an amine (1° or 2°). O O CH3—C—OH + NH3 CH3—C—NH2 + H2O
O O CH3—C—OH + CH3—NH2 CH3—C—NH—CH3
+ H2O
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Amides are named as alkanamides. In the IUPAC and common names, the –oic acid
or -ic acid endings are replaced by –amide. O Methanamide (IUPAC)H—C—NH2 Formamide (common) O Propanamide (IUPAC)CH3—CH2—C—NH2 Propionamide (common)
Naming Amides
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An alkyl group bonded to the N atom is named as N-alkyl in front of the amide name.
O CH3 —C—NH—CH3 N-methylethanamide (IUPAC)
N-methylacetamide (common) O CH3
CH3—CH2 —C—N—CH3
N,N-dimethylpropanamide N,N-dimethylpropionamide
Naming Amides with N Groups
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Aromatic Amides
The amide of benzene is named benzamide.
C
O
NH2
Benzamide
C
O
NH CH3
N methylbenzamide -
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Classification of Amides Amides are classified according to the number of
carbon atoms bonded to the nitrogen atom. O H || |CH3—C—N—H Primary (1°) amide O H || |CH3—C—N—CH3 Secondary (2°) amide O CH3 || |CH3 —C—N—CH3 Tertiary (3°) amide
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Amides in Health and Medicine
Urea is the end product of protein metabolism.
Saccharin is an artificial sweetener. Some amides such as phenobarbital,
Nembutal and Seconal are barbiturates. Acetaminophen is used to reduce fever and
pain.
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Amides in Health and Medicine
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Physical Properties of Amides
Hydrogen bonds form in primary and secondary amides, but not tertiary amides.
The melting points of primary amides are higher than secondary amides, which have higher melting points than tertiary amides.
All amides can form hydrogen bonds with water. Amides with 1-5 carbon atoms are soluble in
water.
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Hydrogen Bonding of Amides O
||CH3—C—N—H
| H Hydrogen bonding occurs
between primary amides. O ||
CH3—C—N—H |
H
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Amides undergo: Acid hydrolysis to produce a carboxylic acid
and ammonium salt.
Base hydrolysis to produce the salt of a carboxylic acid and an amine or ammonia.
Reactions of Amides
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acid hydrolysis O ||
O CH3—C—OH + NH4+Cl–
|| HCl + H2O CH3—C—NH2
NaOH O ||
CH3—C—O– Na+ + NH3
base hydrolysis
Hydrolysis Reactions