[PDF] Hydrolysis of Amides PDF 20_13

Preparation of Amides Amines do not react with carboxylic acids to give amides The reaction that occurs is proton-transfer (acid-base) RCOH O + R'NH 2

equilibrium is closely balanced because carbonyl group of ester and of carboxylic acid are comparably stabilized Acid-Catalyzed Ester Hydrolysis RCOH O

[PDF] Hydrolysis of Amides

Preparation of Amides Amines do not react with carboxylic acids to give amides The reaction that occurs is proton-transfer (acid-base) RCOH O + R'NH 2

[PDF] Lecture 6: Hydrolysis Reactions of Esters and Amides

draw the mechanism of ester hydrolysis under acidic and basic reaction conditions form new esters by base- or acid-catalysed transesterification mechanisms;

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Hydrolysis of nitriles under both acidic and basic conditions involves the formation of an amide, which is then hydrolyzed to a carboxylic acid as we have already

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[PDF] HYDROLYSIS

Hydrolysis reactions are generally enhanced by both acids and bases and three independent reaction mechanisms account for neutral, acid and base

Preparation of Amides

acyl chlorides (Table 20.2) acyl chlorides (Table 20.2) anhydrides (Table 20.3) anhydrides (Table 20.3) esters (Table 20.6) esters (Table 20.6)Preparation of Amides

Preparation of Amides

Amides are prepared from amines by acylation

with: with:

Preparation of Amides

Amines do

Amines do notnotreact with carboxylic acids to givereact with carboxylic acids to give amides. The reaction that occurs is proton amides. The reaction that occurs is proton--transfertransfer (acid (acid--base).base). RCOH RCOHO O +R'R'NNHH22RCO RCOO O +R'R'NNHH33+

If no heat

If no heat--sensitive groups are present, the sensitive groups are present, the resulting ammonium carboxylate salts can be resulting ammonium carboxylate salts can be converted to amides by heating. converted to amides by heating.

Preparation of Amides

Amines do

RCNNHR'HR'O

O +HH22OO

Example

COH COHO O H

H22NN225°C

225°C

+HH22OO (80 (80--84%)84%) CNH CNHO O 20.14
20.14

Lactams

Lactams are cyclic amides. Some are industrial

chemicals, others occur naturally. chemicals, others occur naturally. N NH HO Oe e--Caprolactam*: used toCaprolactam*: used to prepare a type of nylon prepare a type of nylona ab bgg d d e e *Caproic acid is the common name for hexanoic acid. *Caproic acid is the common name for hexanoic acid.

Lactams

Lactams are cyclic amides. Some are industrial

chemicals, others occur naturally. chemicals, others occur naturally.

Penicillin G: a

Penicillin G: a bb--lactam antibioticlactam antibiotica abb CH CH33 CH CH33S S CO

CO22HHO

ON NC

C66HH55CHCH22CNHCNHO

O 20.15
20.15

Imides

Imides have 2 acyl groups attached to the

nitrogen. nitrogen. RC

RCNNCRCRO

OO OR' R'

Imides

The most common examples are cyclic imides.

N NHHO O O O

Phthalimide

N NHHO O O O

Succinimide

Preparation of Imides

Cyclic imides are prepared by heating the

ammonium salts of dicarboxylic acids. ammonium salts of dicarboxylic acids. N NHHO O O

OHOCCH

HOCCH22CHCH22COHCOHO

OO O NH

NH33OCCH

OCCH22CHCH22COCOO

OO O NH NH44+

NHNH44+

+heat heat 20.16
20.16

Hydrolysis of Amides

Hydrolysis of amides is irreversible. In acid

solution the amine product is protonated to solution the amine product is protonated to give an ammonium salt. give an ammonium salt.+ +R'R'NNHH33+ +RCOHRCOHO O RC

RCNNHR'HR'O

O +HH22OOHH++++

Hydrolysis of Amides

In basic solution the carboxylic acid product

is deprotonated to give a carboxylate ion. is deprotonated to give a carboxylate ion. RC

RCNNHR'HR'O

O+ +R'R'NNHH22--RCORCOO O HO

HO++--

Example: Acid Hydrolysis

(88 (88--90%)90%)CH

CH33CHCH22CHCNHCHCNH22O

O CH

CH33CHCH22CHCOHCHCOHO

O H

H22OOH

H22SOSO44

heat heat+ +NHNH44+ +HSOHSO44--

Example: Basic Hydrolysis

(95%) (95%)CH

CH33COKCOKO

O KOH KOHH H22OO heat heat+ +CH

CH33CNHCNHO

O Br BrNH NH22 Br Br Acid Acid--catalyzed amide hydrolysis proceeds viacatalyzed amide hydrolysis proceeds via the customary two stages: the customary two stages: 1)

1)formation of tetrahedral intermediateformation of tetrahedral intermediate

2)dissociation of tetrahedral intermediatedissociation of tetrahedral intermediateMechanism of Acid

Mechanism of Acid--CatalyzedCatalyzed

Amide Hydrolysis

First stage: formation of tetrahedral intermediateFirst stage: First stage: formation of tetrahedral intermediateformation of tetrahedral intermediate RC RCOH OH OH OHN

NHH22+

+HH22OORCRCNNHH22O OH

H++water adds to the

water adds to the carbonyl group of the carbonyl group of the amide amide this stage is this stage is analogous to the acid analogous to the acid-- catalyzed addition of catalyzed addition of water to a ketone water to a ketone

Second stage: cleavage of tetrahedral

intermediateSecond stage: Second stage: cleavage of tetrahedralcleavage of tetrahedral intermediate intermediate +H

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