Question

Clemmenson vs. Wolf-Kishner reduction

I know that the Clemmenson reduction is done under acidic conditions and the Wolf-Kishner is done under basic conditions.

If there was an cyclohexane with 2 functional group, one a ketone, and one an aldehyde, why would the clemmenson reduction get rid of all of the oxygen on the functional group whereas the Wolf-Kishner reduction only get rid of the aldyhyde?

Clemmenson reduction use: Zn(Hg), HCl, temperature, H20

Wolff-Kishner reduction use: H2NNH2, KOH, HOC2H4OC2H4OH

Answer 1

A key consideration for the Wolff-Kishner reduction is thermal stability of the substrate. High temperature is required for the classical reaction using hydrazine and KOH, sometimes up to 200C. This can rule out plenty of compounds. The Clemmensen reduction may be fine for the laboratory, but fundamentally many industries wouldn't use it due to scaling up the use of mercury.

In case of clemmenson reduction it goes through hydrogenation process but in wolf kishner reduction it goes through hydragone formation. Being much more reactivity of aldehyde than ketone it will get rid of easily.