Blanc chloromethylation

The Blanc chloromethylation is the chemical reaction of aromatic rings with formaldehyde and hydrogen chloride catalyzed by zinc chloride to form chloromethyl arenes. The reaction was discovered by Gustave Louis Blanc (1872-1927) in 1923. The reaction should be performed with care, as (like most chloromethylation reactions) it produces highly carcinogenic bis(chloromethyl) ether as a by-product.