* The Clemmensen reduction is used to conveniently reduce the carbonyl compounds, which are stable to strongly acidic conditions, to alkanes.
* In Clemmensen reduction, the amalgamated zinc in HCl is used as reducing agent.
* The C=O group is converted to CH2 group.
* The Clemmensen reduction is complementary to Wolff-Kishner reduction, which may be used to reduce acid sensitive compounds.
* The Clemmensen reduction occurs over the surface of zinc catalyst. The probable mechanism is shown below.
* There is a net flow of electrons from zinc to the carbonyl compound.
* As there is no formation of alcohol during the reaction, this method is not useful to reduce alcohols to alkanes.
|CH3CHO + 4(H)||----------------->||CH3CH3 + H2O|
3) In the following reaction, along with the reduction of carbonyl group, the -OH group is substituted by the -Cl group (side reaction). However this side reaction can be avoided by employing Wolff-Kishner method.
4) But the phenol group is not affected in Clemmensen reduction. (Why? Ans: Nucleophilic substitution is not easy on sp2 carbon of benzene ring!)
1) Acetophenone when reacted with Zn (Hg) and HCl in ethyl alcohol easily gives ethyl benzene. This is an example of : (KERALA SET 2010)
A) Clemmensen reduction
B) Birch reduction
C) Wolf-Kishner reduction
D) MPV reaction