Organic Chemistry

Section 18.6 Reactions of Aldehydes and Ketones with Nitrogen Nucleophiles 751

3-D Molecules:

The N-methylimine of

acetone;

The oxime of acetone;

The hydrazone of acetone;

The semicarbazone of acetone

imines—often called imine derivativesbecause the substituent attached to the imine
nitrogen is not an R group. The imine obtained from the reaction with hydroxylamine
is called an oxime, the imine obtained from the reaction with hydrazine is called
a hydrazone, and the imine obtained from the reaction with semicarbazide is called a
semicarbazone.

Phenyl-substituted hydrazines react with aldehydes and ketones to form phenyl-
hydrazones.

PROBLEM 21

Imines can exist as stereoisomers. The isomers are named by the E,Zsystem of nomencla-

ture. (The lone pair has the lowest priority.)

Draw the structure of each of the following compounds:

a. (E)-benzaldehyde semicarbazone c. cyclohexanone 2,4-dinitrophenylhydrazone

b. (Z)-propiophenone oxime

PROBLEM 22

Semicarbazide has two NH 2 groups. Explain why only one of them forms an imine.

R X

R′

C N

X

N

R

R′

C

CO+

CH 3

H 2 NNH 2

OH+ 2 NNHCNH 2 NNHCNH 2

O O

H 2 O

a hydrazone

NNH 2 + H 2 O

a semicarbazone

+

C

CH 3

hydrazine

semicarbazide

catalytic

H+

catalytic

H+

CH O + H 2 NOH

an oxime

CH NOH + H 2 O

hydroxylamine

catalytic

H+

Tutorial:

Imine and oxime formation

a phenylhydrazone

O + H 2 NNH NNH + H 2 O

a 2,4-dinitrophenylhydrazone

O + H 2 NNH NO 2 CH 3 CH 2 CH

O 2 N O 2 N

CH 3 CH 2 CH NNH NO 2 + H 2 O

phenylhydrazine

2,4-dinitrophenylhydrazine

catalytic

H+

catalytic

H+