Advices For Studying Organic Chemistry

R 2 CuLi + R' X R R' RCu LiX

Alkyl halide Alkane

++

Lithium dialkylcuprate

i) For the last step to give a good yield of the alkane, the alkyl halide R’–X must

be either a methyl halide, a 1° alkyl halide, or a 2° cycloalkyl halide.

ii) The alkyl groups of the lithium dialkylcuprate may be methyl, 1°, 2°, or 3°.

iii) The two alkyl groups being coupled need not be different.

3) The overall scheme for this alkane synthesis:

AlkyllithiumLithium dialkylcuprate Alkane

RLi CuI R 2 CuLi R'X R R' RCu LiX

R'

R'−

Li/Et 2 O

R X X

An alkyl halide A methyl, 1o alkyl,

or 2o cycloalkyl halide

++

There are organic strating materials. The R− and

groups need not be different.

4) Examples:

H 3 C I

H 3 C CH 2 CH 2 CH 2 CH 2 CH 3

Li CH^3 CH^2 CH^2 CH^2 CH^2 I

Et 2 O CH^3 Li

CuI (CH 3 ) 2 CuLi

Hexane(98 %)

CH 3 CH 2 CH 2 CH 2 Br CH 3 CH 2 CH 2 CH 2 Li (CH 3 CH 2 CH 2 CH 2 ) 2 CuLi

CH 3 CH 2 CH 2 CH 2 CH 2 Br CH

H 3 CH 2 CH 2 CH 2 C 2 CH 2 CH 2 CH 2 CH 3

Nonane

(98 %)

Li

Et 2 O

CuI

2. Lithium dialkylcuprates couple with other organic groups: