Organic Chemistry

822 CHAPTER 19 Carbonyl Compounds III

Carboxylic acids with two substituents bonded to the can be prepared by

carrying out two successive alkylations.

PROBLEM 36

Explain why the following carboxylic acids cannot be prepared by the malonic ester

synthesis:

19.19 The Acetoacetic Ester Synthesis:

Synthesis of Methyl Ketones

The only difference between the acetoacetic ester synthesis and the malonic ester

synthesis is the use of acetoacetic ester rather than malonic ester as the starting material.

The difference in starting material causes the product of the acetoacetic ester synthesis

to be a methyl ketonerather than a carboxylic acid.The carbonyl group of the methyl

ketone and the carbon atoms on either side of it come from acetoacetic ester, and the rest

of the ketone comes from the alkyl halide used in the second step of the reaction.

ethyl 3-oxobutanoate

ethyl acetoacetate

"acetoacetic ester"

acetoacetic ester synthesis

O O

COC 2 H 5

O

CH 3 CCH 2 RCH 2 CCH 3

1. CH 3 CH 2 O−


2. RBr


3. HCl, H 2 O, ∆

from the alkyl halide

from acetoacetic ester

b. CH 2 CHCH 2 COH

O

c. CH 3 CCH 2 COH

CH 3 O

CH 3

a. CH 2 COH

O

a-carbon

a-carbon

−

OO

C 2 H 5 OC CH 2 COC 2 H 5

OO

C 2 H 5 OC CH COC 2 H 5

OO

C 2 H 5 OC CH +

R

COC 2 H 5 Br−

+ 2 CH 3 CH 2 OH

CH 3 CH 2 O−

CH 3 CH 2 O−

∆

RBr

OO

C 2 H 5 OC

+ CO 2

C

R

COC 2 H 5

O

R CH COH

HCl, H 2 O

∆

R′ Br

−

OO

C 2 H 5 OC C

R

R′

COC 2 H 5

R

R′ O O

HOC C COH

R′