Question:

In a Claisen condensation reaction (when an ester is treated with a strong base)

Updated On: Apr 26, 2024
  • a proton is removed from the $\alpha$ -carbon to form a resonance stabilised carbanion of the ester
  • carbanion acts as a nucleophile in a nucleophilic acyl substitution reaction with another ester molecule
  • a new $C?C$ bond is formed
  • All of the above statements are correct
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The Correct Option is D

Solution and Explanation

When two molecules of an ester undergo a condensation reaction, the reaction is called as Claisen condensation and product is a $\beta$ - keto ester.
$2CH_3CH_2\overset{\underset{||}{O}}{C}OCH_3 \ce{->[(i)CH_3O^-][(ii)H^+]}$
$CH_3CH_2 \,\underset{\beta}{\overset{\underset{||}{O}}{C}} \underset{\overset{|\alpha}{C}H_3}{C}H\overset{\underset{||}{O}}{C}OCH_3 + CH_3OH$
Mechanism
Step I

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Step II



Step III


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Concepts Used:

Aldehydes, Ketones, and Carboxylic Acids

Aldehydes, Ketones, and Carboxylic Acids are carbonyl compounds that contain a carbon-oxygen double bond. These organic compounds are very important in the field of organic chemistry and also have many industrial applications.

Aldehydes:

Aldehydes are organic compounds that have the functional group -CHO.

Preparation of Aldehydes

Acid chlorides are reduced to aldehydes with hydrogen in the presence of palladium catalyst spread on barium sulfate.

Ketones:

Ketones are organic compounds that have the functional group C=O and the structure R-(C=O)-R’.

Preparation of Ketones

Acid chlorides on reaction with dialkyl cadmium produce ketones. Dialkyl cadmium themselves are prepared from Grignard reagents.

Carboxylic Acid:

Carboxylic acids are organic compounds that contain a (C=O)OH group attached to an R group (where R refers to the remaining part of the molecule).

Preparation of Carboxylic Acids

Primary alcohols are readily oxidized to carboxylic acids with common oxidizing agents such as potassium permanganate in neutral acidic or alkaline media or by potassium dichromate and chromium trioxide in acidic media.