Question

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

• A. a proton is removed from the $\alpha$ -carbon to form a resonance stabilised carbanion of the ester
• B. carbanion acts as a nucleophile in a nucleophilic acyl substitution reaction with another ester molecule
• C. a new $C—C$ bond is formed
• D. All of the above statements are correct

Answer 1

Answer: (D)

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

Step II

Step III