Organic Chemistry

Section 20.1 Reduction Reactions 849

In contrast, in aqueous ethanol at in the presence of cerium trichloride

reduces ketones faster than it reduces aldehydes. There are many reducing reagents—

and conditions under which those reagents should be used—available to the synthetic

chemist. We can cover only a fraction of these in this chapter.

PROBLEM 3

Explain why terminal alkynes cannot be reduced by Na in liquid

PROBLEM 4

Give the products of the following reactions:

a. d.

b. e.

c. f.

PROBLEM 5

Can carbon–nitrogen double and triple bonds be reduced by lithium aluminum hydride?

Explain your answer.

PROBLEM 6

Give the products of the following reactions (assume that excess reducing agent is used in d):

a. c.

b. d.

PROBLEM 7 SOLVED

How could you synthesize the following compounds from starting materials containing no

more than four carbons?

a. OH b.

O O

CH 2 COCH 3

1. LiAlH 4


2. H 2 O

O

H 2

Pt

COCH 3

O

O

1. NaBH 4


2. H 2 O

CH 2 COCH 3

O

1. NaBH 4


2. H 2 O

CCH 3

O

CH 3 CH 2 CH 2 COH

1. LiAlH 4
   2. H 3 O+

O

CH 3 CH 2 CCH 2 CH 3

1. NaBH 4
   2. H 3 O+

O

CH 3 CH 2 CNHCH 2 CH 3

1. LiAlH 4


2. H 2 O

O

1. LiAlH 4
   COH 2. H 3 O+

O

1. LiAlH 4

COCH 2 CH (^3) 2. H 3 O+
O

1. LiAlH 4

CNH (^2) 2. H 2 O
NH 3.
O O
H
OH O
H
NaBH 4 , CeCl 3
C 2 H 5 OH/H 2 O
− 15 °C
NaBH 4 - 15 °C
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