Theory & Defination :
E.clemmensem a Danish Chemist in 1913 converted an alkane from carbonyl group hence the name Clemmensen is given.In this reaction a carbonyl compound ( aldehydes or ketones ) converted into their corresponding alkanes using metals and amalgun in concentrated Hydrochloric acid.In short w can say this method of converting carbonyl group to corresponding methylene group is known as Clemmensen reduction.
General Reaction :
The Clemmensen Reduction allows the deoxygenation of aldehyde or ketones, to produce the corresponding hydrocarbon.
Mechanism :
The reduction takes place at the surface of the zinc catalyst. In this reaction, alcohols are not postulated as intermediates, because subjection of the corresponding alcohols to these same reaction conditions does not lead to alkanes.
The following proposal mechanism of the Clemmensen Reduction involving steps will be
a.Carbocation is formed in the presence of organic solvent.
b.Carbanion is formed when electrons starts flowing from zinc to carbonyl carbon.
c.Hydrogen gets added to the carbon during protonation.
d.By the similar way, the second hydrogen also gets added to carbon, so that, alkane is formed from carbonyl compound.
Example and Application :
1) Conversion of Acetophenone to Ethyl benzene
2) The attached phenol or methoxt group in unaffected in Clemensen reduction due to Sp2 carbon
3) The attached -Cl group gets affected
To avoid such side reactions prefer Wolf-Kishner reaction.
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