Also found in: Wikipedia.
a method of synthesizing aromatic aldehydes by the action of a mixture of CO and HC1 on aromatic hydrocarbons. The catalyst is aluminum chloride or aluminum bromide, with a small amount of monochloride of copper. The Gattermann-Koch reaction is a particular case of the Friedel-Crafts reaction. It was discovered by the German chemists L. Gattermann and J. Koch in 1897.