Question

Write short notes on the following:
(i) Claisen condensation (ii) Benzoin condensation

Answer 1

(i) Claisen condensation: A base catalysed condensation reaction between an aromatic aldehyde and an aliphatic aldehyde or ketone is called claisen condensation or claisen schmidt condensation.

$C_6{H}_{5}CH=O+H_{2}CHCHO+NaOH\to C_6{H}_{5}CH=CHCHO+H_{2}O$.

(ii) Benzoin condensation: Two molecules of benzaldehyde in presence of alcohol $KCN$ or $NaCN$ condenses to form benzocaine.

$C_6{H}_5-\stackrel{O}{\stackrel{||}{C}}-H+C_6{H}_5\stackrel{O}{\stackrel{||}{C}}-H\underset{KCH}{\overset{alc}{\to }}{C}_2{H}_5-\underset{H}{\underset{|}{\stackrel{OH}{\stackrel{|}{C}}}}-\stackrel{O}{\stackrel{||}{C}}-C_6{H}_5$