Clemmensen reduction is a chemical reaction described as a reduction of ketones (or aldehydes) to alkanes using zinc amalgam and hydrochloric acid. This reaction is named after Erik Christian Clemmensen, a Danish chemist.
The Clemmensen reduction is particularly effective at reducing aryl-alkyl ketones, such as those formed in a Friedel-Crafts acylation. With aliphatic or cyclic ketones, zinc metal reduction is much more effective.
The substrate must be stable in the strongly acidic conditions of the Clemmensen reduction. Acid sensitive substrates should be reacted in the Wolff-Kishner reduction, which utilizes strongly basic conditions; a further, milder method is the Mozingo reduction. The oxygen atom is lost in the form of one molecule of water.
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