Question

In crossed cannizzaro reaction between formaldehyde and benzaldehyde the alcohol formed is only benzyl alcohol and not methanol. Give reason.

Answer 1

Crossed Cannizzaro reaction between formaldehyde and benzaldehyde-

$\underset{\left(\text{Benzaldehyde}\right)}{C_6{H}_5-CHO}+\underset{\left(\text{Formaldehyde}\right)}{HCHO}\stackrel{NaOH}{\to }HCOOH+C_6{H}_5-C{H}_2-OH$

As there is no electron donating group on formaldehyde, the initial nucleophilic addition of hydroxide ion is faster on formaldehyde due to which formaldehyde oxidises easily and forms formic acid.

Hence the alcohol formed is only benzyl alcohol and not methanol.