 In a related reaction, formyl chloride is implicated in Gattermann-Koch formylation reaction.The reaction of formyl fluoride/BF3 with perdeuteriobenzene (C6D6) exhibits a kinetic isotope effect of 2.68, similar to the isotope effect observed in Friedel-Crafts acetylation of benzene.Formylation of benzene with a mixture of CO and hexafluoroantimonic acid however, exhibits no isotope effect (C6H6 and C6D6 react at the same rate), indicating that this reaction involves a more reactive formylating agent, possibly CHO+.