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.
$2C{H}_{3}C{H}_2\stackrel{\underset{||}{O}}{C}OC{H}_3\underset{(ii)H^{+}}{\overset{(i)C{H}_3{O}^{-}}{\to }}$
$C{H}_{3}C{H}_2\underset{\beta }{\stackrel{\underset{||}{O}}{C}}\underset{\stackrel{|\alpha }{C}{H}_3}{C}H\stackrel{\underset{||}{O}}{C}OC{H}_3+C{H}_{3}OH$
Mechanism
Step I

Step II

Step III