When CH2=CHCOOH is reduced with LiAlH4, the compound obtained will be [aieee-2003]a)CH3CH2CH2OHb)CH3CH2CHOc)CH3CH2COOHd)CH2=CH-CH2OHCorrect answer is option 'D'. Can you explain this answer?

Question

When CH2=CHCOOH is reduced with LiAlH4, the compound obtained will be  [aieee-2003]a)CH3CH2CH2OHb)CH3CH2CHOc)CH3CH2COOHd)CH2=CH-CH2OHCorrect answer is option 'D'. Can you explain this answer?

Answer

LiAlH₄ does not affect the olefinic carbon so only the COOH group is reduced to CH₂-OH group and the final product will be option D....

Answer

Answer

Reaction and Mechanism:
The given compound CH2=CHCOOH is an unsaturated carboxylic acid with a double bond between carbon 2 and carbon 3. When it is reduced with LiAlH4, a strong reducing agent, it undergoes a reduction reaction to form a new compound.

The mechanism of the reduction reaction involves the following steps:

1. Formation of an aldehyde intermediate:
- The double bond between carbon 2 and carbon 3 breaks, and the oxygen of the carboxylic acid group becomes protonated by LiAlH4.
- This leads to the formation of an aldehyde intermediate, CH3CH2CHO, with a protonated oxygen atom.

2. Reduction of the aldehyde intermediate:
- The aldehyde intermediate then reacts with LiAlH4 to undergo further reduction.
- LiAlH4 donates a hydride ion (H-) to the carbon atom adjacent to the carbonyl group.
- The hydride ion attacks the carbon atom, breaking the double bond and forming a new bond with the carbon atom.
- Simultaneously, the oxygen atom of the aldehyde group accepts a proton from LiAlH4, leading to the formation of an alcohol group.

Result:
The compound obtained after reduction with LiAlH4 is CH2=CH-CH2OH, which is an alcohol with a single bond between carbon 2 and carbon 3. This corresponds to option 'D' (CH2=CH-CH2OH) as the correct answer.

Summary:
- The given compound CH2=CHCOOH is reduced with LiAlH4 to form a new compound.
- The mechanism involves the formation of an aldehyde intermediate followed by its reduction to an alcohol.
- The final compound obtained after reduction is CH2=CH-CH2OH, which corresponds to option 'D' as the correct answer.

Answer

The correct answer is option D
LiAlH4 can reduce the carboxylic acid group without affecting the double bond because alkene is electron-rich species.

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