Clemmensen Reduction of aldehydes and ketones by Zn(Hg), HCl. Zinc amalgam and concentrated hydrochloric acid ( Zn(Hg) / concentrated HCl ) is used as the reagent for clemmensen reduction. The reaction mechanism of Clemmensen’s reduction is still debatable on certain levels, but a majority of the scientific community accepts the following mechanism. Mechanism of the Clemmensen Reduction. The mechanism for the Clemmensen reduction is not yet fully understood and there are two popular proposals. * There is a net flow of electrons from zinc to the carbonyl compound. * The Clemmensen reduction is complementary to Wolff-Kishner reduction, which may be used to reduce acid sensitive compounds. C=O group of aldehydes and ketones is reduced to -CH 2-group by clemmensen reduction.
The probable mechanism is shown below. Mechanism of Clemmensen Reduction Reaction: The mechanism of this reaction is not completely understood, but there are two proposals; Carbanionic mechanism: The carbanionic mechanism of reaction shows that the zinc attacks directly to the protonated carbon. MECHANISM OF CLEMMENSEN REDUCTION * The Clemmensen reduction occurs over the surface of zinc catalyst. In this reaction, alcohols are not postulated as intermediates, because subjection of the corresponding alcohols to these same reaction conditions does not lead to alkanes. The mechanism of Clemmensen reduction is not fully understood; intermediacy of radicals are implicated. The reduction takes place at the surface of the zinc catalyst. Clemmensen reduction is complementary to Wolff-Kishner reduction, which also converts aldehydes and ketones to hydrocarbons, in that the former is carried out in strongly acidic conditions and the latter in strongly basic conditions. The "Carbanionic mechanism", where the zinc attacks the protonated carbonyl directly, and the "Carbenoid mechanism", which is a radical process and …