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When does LiAlH4 reduce double bond? When it is in conjugation with either phenyl or carbonyl or both?

When does LiAlH4 reduce double bond?


When it is in conjugation with either phenyl or carbonyl or both? 

Grade:12

3 Answers

Vikash Kumar
36 Points
10 years ago

 LiAlH4 reduces double bond in case of only when it is conjugation with phenyl ring but ''cinnamic acid'' is an excepection because it has both carbonyl carbon as well as phenyl ring in its conjugation.

figure-

cinnamic acid

 

2316_94652_getStructureImage.gif

Thanks & Regards
Vikash Kumar, 
askIITians Faculty
B.Tech, IIT Delhi

Vikash Kumar
36 Points
10 years ago

 

 LiAlH4 reduces double bond when it is in conjugation with phenyl but not in case of carbonyls. there is an exception to it that is ''cinnamic acid'' but it has both the phenyl ring on one side and carbonyl on the other side.the figure is given below.

 

1283_94652_107587.jpg


Thanks & Regards
Vikash Kumar, 
askIITians Faculty
B.Tech, IIT Delhi

Nitish
15 Points
5 years ago
As the hydroxyl group in the carboxylic acid forms a dative bond with the carbonyl cation it reduces the resonance with the double bond so the double bond remains in reactive

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