Question

An alkyl halide is reduced to the corresponding alkane by tributyl stannane `(C_(4)H_(9))_(3)`SnH and by a free radical menchanism in the presence of an initiator, an azo compound

that breaks down to `N_(2)` and a radical. Give the mechanism of the reaction.
A. carbene
B. free radical
C. cationoic
D. anionic

Answer 1

Correct Answer - B
The initiator is an azo compound,
`(CH_(3))_(2)C(CN)-N=N-C(CN)(CH_(3))_(2)`
which breaks down to `N_(2)` and a radical. The carbon radical `(CH_(3))_(2)overset(. )C CN(Rad^(.))` abstracts an `H^(.)` from the tin compound:
`Rad^(.)+(C_(4)H_(9))_(3)SnHrarr(C_(4)H_(9))_(3)Sn^(.)+Rad-H`
The tributylin radical abstracts a halogen atom form the alkyl halide, and the chain is propagated as follows:
`(C_(4)H_(9))_(3)Sn^(.)+R-Xrarr(C_(4)H_(9))_(3)Sn-X+R^(.)`
`R^(.)+(C_(4)H_(9))_(3)Sn-H-R-H+(C_(4)H_(9))_(3)Sn`