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Also known as: Huang-Minlon Modification
Discovered by Nikolai Kishner, Ludwig Wolff (1911)
Complete removal of a C=O group, replacing it with CH₂. The ketone/aldehyde is first converted to a hydrazone, then heated with strong base to lose N₂ gas. Basic conditions — complementary to Clemmensen (acidic conditions).
The carbonyl reacts with hydrazine (H₂NNH₂) to form the hydrazone (C=NNH₂) via standard imine formation.
Under strong base and high heat, the hydrazone loses N₂ through a series of proton transfers (tautomerizations) and E1cb elimination.
N₂ is an excellent leaving group (very stable)
The carbanion is protonated by the solvent to give the alkane product.
Net result: C=O → CH₂
Acetophenone
H₂NNH₂, KOH, ethylene glycol, 200°C
Ethylbenzene
Cyclohexanone
H₂NNH₂, KOH, diethylene glycol, reflux
Cyclohexane
Pairs perfectly with FC acylation: ArH → ArCOR (FC) → ArCH₂R (W-K). This is the best route to straight-chain alkylbenzenes.