What is the difference between Clemmensen reduction and Wolff Kishner reduction?

Clemmensen reduction and Wolff-Kishner reduction are both chemical reactions used to convert carbonyl compounds (aldehydes or ketones) into their corresponding alkanes. However, they differ in terms of the reagents and conditions used.

Clemmensen Reduction:

Reagent: Zinc (Zn) metal and concentrated hydrochloric acid (HCl).
Conditions: Heat is applied under reflux (boiling with condensation of vapors) conditions.
Mechanism: The carbonyl compound is reduced via a mechanism that involves the formation of an organozinc intermediate followed by protonation to yield the alkane.
Substrate: Clemmensen reduction is effective for both aldehydes and ketones.
Limitations: It cannot be used for carbonyl compounds that are sensitive to acidic conditions.
Wolff-Kishner Reduction:

Reagent: Hydrazine (N2H4) and a strong base such as potassium hydroxide (KOH) or sodium hydroxide (NaOH).
Conditions: The reaction is typically carried out under high temperatures, often in the presence of a solvent like ethylene glycol.
Mechanism: The carbonyl compound reacts with hydrazine to form a hydrazone intermediate, which is then treated with a strong base to eliminate nitrogen gas and yield the alkane.
Substrate: Wolff-Kishner reduction is generally used for ketones and aldehydes that are sensitive to acidic conditions.
Limitations: The reaction conditions can be harsh and may not be suitable for substrates containing acid-sensitive functional groups.
In summary, while both reactions achieve the reduction of carbonyl compounds to alkanes, they utilize different reagents, conditions, and mechanisms. Clemmensen reduction employs zinc metal and hydrochloric acid under heat, while Wolff-Kishner reduction involves hydrazine and a strong base under high-temperature conditions.