Schematic of the Clemmensen reduction. Reagents: aldehyde, ketone, Zn(Hg), HCl. Product: alkane.

The Clemmensen reduction is an organic reaction used to reduce an aldehyde or ketone to an alkane using amalgamated zinc and hydrochloric acid. Price of 374791-02-3 The mechanism for the Clemmensen reduction is not yet fully understood and there are two popular proposals. 2,5-Dihydroxyterephthalic acid site The “Carbanionic mechanism”, where the zinc attacks the protonated carbonyl directly, and the “Carbenoid mechanism”, which is a radical process and the reduction happens on the surface of the zinc metal. [1][2][3]

Mechanism

Mechanism of the Clemmensen reduction. 1. Carbanionic mechanism. 2. Carbenoid mechanism on surface of zinc metal and zinc carbenoid.

References:

1.
Clemmensen, E. Ber. Dtsch. Chem. Ges. 1913, 46, 1837–1843.
2.
Clemmensen, E. Ber. Dtsch. Chem. Ges. 1914, 47, 51–63.
3.
Clemmensen, E. Ber. Dtsch. Chem. Ges. 1914, 47, 681–687.