![Clemmensen reduction](https://scienceinfo.com/wp-content/uploads/2022/12/Clemmension-reduction.jpg)
Clemmensen reduction involves the reduction of aldehyde or ketone into alkane.
Aldehyde or ketone reacts with Zn-Hg in the presence of conc. hydrochloric acid to form the corresponding hydrocarbon. This reaction is known as Clemmensen reduction.
![Clemmenson reduction](https://scienceinfo.com/wp-content/uploads/2022/12/image-37.png)
In this reaction, acid supplies proton to the oxygen. At the same time, metal supplies an electron pair to electron-deficient carbonyl carbon to form carbanion.
The carbanion mechanism or the carbenoid mechanism can both be used to carry out this reaction mechanism. The carbanion mechanism entails a direct Zn attack on protonated carbon, whereas the carbenoid mechanism is a radical reaction that involves a reduction at the zinc catalyst surface.
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Mechanism of Clemmensen reduction
The mechanism involves three steps
First step : Formation of carbanion
![Clemmensen reduction](https://scienceinfo.com/wp-content/uploads/2022/12/image-38.png)
Second step : Elimination of water
![Clemmensen reduction](https://scienceinfo.com/wp-content/uploads/2022/12/image-39.png)
Third step: Addition of proton
![Clemmensen reduction](https://scienceinfo.com/wp-content/uploads/2022/12/image-40.png)
Apllications of Clemmensen reduction
- The reduction mechanism is commonly used to convert the carbonyl group to the methyl group.
- It is an important application in preparing polycyclic aromatic compounds containing unbranched side hydrocarbon chains.
- It is commonly used to convert acyl benzene to alkyl benzene.
Some synthetic applications
1. Conversion of acetophenone into ethyl benzene.
![](https://scienceinfo.com/wp-content/uploads/2022/12/image-42.png)
2. Conversion of pyrrole to dihydropyrrole and pyrrolidine
![](https://scienceinfo.com/wp-content/uploads/2022/12/image-43.png)
Limitations
This reaction can not be used for acid senstitive substances. Additionally, this method cannot reduce the -COOH group.
References
- Morrison, R. T., & Boyd, R. N., Organic chemistry, Allyn and Bacon, Inc. 1987.
- March, J., Advanced Organic Chemistry, Wiley Eastern Limited, 1986.
- Skyes, P., A Guide Book to Mechanism in Organic Chemistry, Second edition, Orient Longman Ltd., 1988.