(b) Use of chromic oxide (CrO3): Toluene or substituted toluene
is converted to benzylidene diacetate on treating with chromic
oxide in acetic anhydride The benzylidene diacetate can be
hydrolysed to corresponding benzaldehyde with aqueous acid (iii) By Gatterman – Koch reaction
When benzene or its derivative is treated with carbon monoxide
and hydrogen chloride in the presence of anhydrous aluminium
chloride or cuprous chloride, it gives benzaldehyde or substituted
benzaldehyde (ii) By side chain chlorination followed by hydrolysis
Side chain chlorination of toluene gives benzal chloride, which
on hydrolysis gives benzaldehyde