Wolff-Kishner reduction
The carbonyl group of an aldehyde or ketone is converted to CH2 by hydrazine followed by KOH or NaOH in ethylene glycol on heating.
AcetophenoneC₆H₅COCH₃Ketone - Step 1
(i) NH₂NH₂ (ii) KOH or NaOH, ethylene glycol, heat
EthylbenzeneC₆H₅CH₂CH₃Arene
How it works
- The carbonyl compound forms a hydrazone with NH₂NH₂.
- Strong base removes protons and nitrogen is lost as N₂.
- The CH₂ group results.
What it makes
Alkanes from aldehydes and ketones.
Where it fails
The compound must tolerate strong base and heat.
Class 12, Chapter 8 Aldehydes, Ketones and Carboxylic Acids
Wolff-Kishner reduction: quick answers
Why is ethylene glycol used?
It is a high-boiling solvent that allows the high temperature needed.
Which gas is evolved?
Nitrogen.
How does it differ from Clemmensen?
Wolff-Kishner is done in base; Clemmensen in acid.