Clemmensen Reduction Mechanism Animation:

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The reduction of carbonyl groups of aldehydes and ketones to methylene groups with amalgamated zinc and concentrated hydrochloric acid is known as Clemmensen reduction.

The reduction of carbonyl groups of aldehydes and ketones to methylene groups with amalgamated zinc and concentrated hydrochloric acid is known as Clemmensen reduction.

1. The reduction consists in refluxing the carbonyl compounds with amalgamated zinc and excess of concentrated hydrochloric acid.
2. The reduction is useful especially for ketones containing phenolic or carboxylic groups which remain unaffected. Ketones are reducing more often than aldehydes.
3. This reduction is also observed in Wolff-Kishner reduction but Clemmensen reduction is easier to perform.
4. The reduction, however, fails with acid-sensitive and high molecular weight substrates. The α, β-unsaturated ketones undergo reduction of both the olefinic and carbonyl groups.