2,2-Difluorocyclopropanecarboxylic acid (CAS number 107873-03-0) is a 3-membered ring substituted with two fluorines and a carboxylic acid. The inductive effect introduced by the gem-difluorination enhances the acidity of 2,2-difluorocyclopropanecarboxylic acid, compared to the non-fluorinated species. The carboxylic acid allows 2,2-difluorocyclopropanecarboxylic acid to be attached to molecular scaffolds through esterification. It can also undergo functional group conversion to form acyl halide, isocyanate and amine, for varied reactivities.
An unexpected ring-opening has been discovered while 2,2-difluorocyclopropanecarboxylic acid reacts with arenes in Friedel-Crafts reaction. It is proposed that the formation of the acylium ion destabilizes the strained 3-membered ring leading to the ring-opening reaction.