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Reduction of aldehydes and ketones into hydrocarbons using zinc amalgam and conc. HCl is called
A
Cope reduction
B
Dow reduction
C
Wolff-Kishner reduction
D
Clemmensen reduction
Detailed Solution
In the Clemmensen reduction, the carbonyl group of an aldehyde or ketone is reduced to a $CH_2$ group on treatment with zinc amalgam and concentrated hydrochloric acid.
$\gt C=O \xrightarrow{Zn\text{-}Hg,\ conc.\ HCl} \gt CH_2 + H_2O$
For example: $CH_3-CO-CH_3 \xrightarrow{Zn\text{-}Hg,\ conc.\ HCl} CH_3-CH_2-CH_3 + H_2O$
In the Wolff-Kishner reduction the same conversion is done with hydrazine followed by heating with KOH in ethylene glycol, i.e. in a basic medium.
The Dow process is used for the manufacture of phenol from chlorobenzene, and the Cope reaction is an elimination (or rearrangement), not this reduction.
So the reduction with zinc amalgam and conc. HCl is the Clemmensen reduction.
$\gt C=O \xrightarrow{Zn\text{-}Hg,\ conc.\ HCl} \gt CH_2 + H_2O$
For example: $CH_3-CO-CH_3 \xrightarrow{Zn\text{-}Hg,\ conc.\ HCl} CH_3-CH_2-CH_3 + H_2O$
In the Wolff-Kishner reduction the same conversion is done with hydrazine followed by heating with KOH in ethylene glycol, i.e. in a basic medium.
The Dow process is used for the manufacture of phenol from chlorobenzene, and the Cope reaction is an elimination (or rearrangement), not this reduction.
So the reduction with zinc amalgam and conc. HCl is the Clemmensen reduction.