Organic Chemistry

834 CHAPTER 19 Carbonyl Compounds III

49. Show how the following compounds could be prepared from cyclohexanone:


50. A carbonyl compound rearranges to a more stable conjugated compound in the presence of either
    acid or base.
    a. Propose a mechanism for the base-catalyzed rearrangement.
    b. Propose a mechanism for the acid-catalyzed rearrangement.


51. There are other condensation reactions similar to the aldol and Claisen condensations:
    a. The Perkin condensationis the condensation of an aromatic aldehyde and acetic anhydride. Give the product obtained from the
    following Perkin condensation:

b. What compound would result if water were added to the product of the Perkin condensation?

c. The Knoevenagel condensationis the condensation of an aldehyde or a ketone that has no and a compound such

as diethyl malonate that has an flanked by two electron-withdrawing groups. Give the product obtained from the

following Knoevenagel condensation:

d. What product would be obtained if the product of the Knoevenagel condensation were heated in an aqueous acidic solution?

52. The Reformatsky reactionis an addition reaction in which an organozinc reagent is used instead of a Grignard reagent to attack the
    carbonyl group of an aldehyde or a ketone. Because the organozinc reagent is less reactive than a Grignard reagent, a nucleophilic
    addition to the ester group does not occur. The organozinc reagent is prepared by treating an a-bromo ester with zinc.

CH 3 CH 2 O−

+ C 2 H 5 OCCH 2 COC 2 H 5

O

CH OO

a-carbon

a-hydrogens

CH 3 CO−

O

+ CH 3 COCCH 3

O

CH O O

H 3 O+ or HO−

OO

an , -unsaturated

carbonyl compound

a , -unsaturated

carbonyl compound

b,g-unsaturated a,b-unsaturated

O

COH CH

O

O

OH

O

CH 2 CH 2 CH 3

CH 2 CH 3

CH 2 COH

CH 2 CCH 3

CH 3

O

O

CCH 2 CH 2 CH 3

O

O

O

O

O

O

O