When certain aromatic compounds are treated with formaldehyde, \(\mathrm{CH}_{2} \mathrm{O}\), and \(\mathrm{HCl}\), the \(\mathrm{CH}_{2} \mathrm{Cl}\) group is introduced onto the ring. This reaction is known as chloromethylation.

Q: Explain the chloromethylation reaction when certain aromatic compounds react with formaldehyde and HCl. A: The chloromethylation reaction involves an aromatic compound reacting with formaldehyde and HCl, and proceeds through the following steps: 1. Formation of the chloromethyl cation by the reaction of formaldehyde and HCl. 2. Electrophilic aromatic substitution reaction where the aromatic compound attacks the electrophilic carbon in the chloromethyl cation, adding a CH2Cl group to the ring. 3. Restoring the aromaticity of the ring by a neighboring chloride ion abstracting a proton from the newly formed carbon attached to the ring. The final product is the aromatic compound with a CH2Cl group attached.