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WOLFF KISHNER REDUCTION

* In Wolff-Kishner reduction, the carbonyl compounds which are stable to strongly basic conditions can be reduced conveniently to alkanes. The C=O group is converted to CH2 group.

The carbonyl compound is first treated with excess of hydrazine to get the corresponding hydrazone which upon heating, in presence of a base, furnishes the hydrocarbon. 

A high-boiling hydroxylic solvent, such as diethylene glycol (DEG), is commonly used to achieve the temperatures needed. 

wolff-kishner reduction general equation

* The Wolff-Kishner reduction is complementary to Clemmensen reduction, which is used to reduce base sensitive compounds.

MECHANISM OF WOLFF KISHNER REDUCTION

mechanism of wolff kishner reduction 

 

ILLUSTRATIONS

1) The Wolff-Kishner reduction of acetone gives propane.

wolff kishner reduction of acetone

2) The cyclohexane is formed upon Wolff-Kishner reduction of cyclohexanone.

wolff kishner reduction of cyclohexanone

3) The Wolff-Kishner reduction is best suited for the reduction of carbonyl compounds containing groups stable to strongly basic conditions. In the following example, the alcohol group is not affected during the reduction. 

wolff kishner reduction of acid sensitive compounds

4) However, the base sensitive groups may be affected during Wolff-Kishner reduction. In the following case, the halogen group undergoes dehydrohalogenation under strongly basic conditions. 

wolff kishner reduction of base sensitive compounds

This side reaction can be avoided by using Clemmensen reduction.

 

<Wittig reaction: Explanation  Table of contents Wurtz reaction >
Author: Aditya vardhan Vutturi