Organic Chemistry

838 CHAPTER 19 Carbonyl Compounds III

65. What carbonyl compounds are required to prepare a compound with molecular formula whose spectrum is
    shown?


66. Ninhydrin reacts with an amino acid to form a purple-colored compound. Propose a mechanism to account for the formation of the
    colored compound.


67. A carboxylic acid is formed when an reacts with hydroxide ion. This reaction is called a Favorskii reaction. Propose
    a mechanism for the following Favorskii reaction. (Hint:In the first step, removes a proton from the that is not
    bonded to Br; a three-membered ring is formed in the second step; and is a nucleophile in the third step.)


68. Give the products of the following reactions. (Hint:See Problem 67.)


69. An carbonyl compound can be prepared by a reaction known as a selenenylation–oxidation reaction. A selenoxide
    is formed as an intermediate. Propose a mechanism for the reaction.
    
    
    1. LDA/THF
    
    
    2. C 6 H 5 SeBr
    
    
    
    

a selenoxide

3. H 2 O 2

SeC 6 H 5

O−

OOO+

a,b-unsaturated

OCCH 3

O

O O

Br

a. HO− b.

H 2 O

HO−

H 2 O

CH 3 CH 2 CHCO−

O

CH 3

HO−

CH 3 CHCCH 2 CH (^3) H 2 O
Br
O
HO-
HO- a-carbon
a-haloketone

• R
  2 H 2 NCHCO− N
  O


• CO 2


• 3 H 2 O


• RCH
  O
  O
  O
  OH
  OH
  O−
  O
  O
  O
  ninhydrin an amino acid purple-colored
  compound
  catalytic
  H+
  87654 3210
  δ (ppm)
  frequency
  C^1 H NMR
  10 H 10 O