Question

Propose a mechanism for both parts of the Wolff-Kishner reduction of cyclohexanone: the formation of the hydrazone, and then the base catalyzed reduction with evolution of nitrogen gas.

Short answer

Cyclohexanone is first converted to hydrazone, which then undergoes base catalyzed reduction to give the cyclohexane.

Step-by-step solution

Wolf-Kishner Reduction

The compound that cannot resist treatment with hot acids can be deoxygenated (loss of oxygen) by using Wolf Kishner reduction. Aldehydes and ketones on being heated with hydrazine $\left({\mathrm{H}}_2\mathrm{N}-{\mathrm{NH}}_2\right)$and a strong base like potassium hydroxide$\left(\mathrm{KOH}\right)$ at the temperature range of$\left(140-200°\mathrm{C}\right)$ form hydrocarbon.

Mechanism of Wolf-Kishner Reduction

The mechanism part is shown below.

Step (a) Formation of hydrazone from cyclohexanone.

Step (b) Base catalyzed reduction of hydrazone to cyclohexane with the evolution of nitrogen gas.