Solved 4. The Gatterman-Koch reaction installs aldehyde | Chegg.com
Gattermann reaction - Wikipedia
SOLVED:In the Gatterman-Koch reaction, a formyl group (-CHO) is introduced directly onto a benzene ring. For example, reaction of toluene with CO and \mathrm{HCl} in the presence of mixed \mathrm{CuCl} / \mathrm{AlCl}_{3}