The trifluoromethyl group is a functional group that has the formula -CF. The naming of is group is derived from the methyl group (which has the formula -CH), by replacing each hydrogen atom by a fluorine atom. Some common examples are trifluoromethane H–, 1,1,1-trifluoroethane –, and hexafluoroacetone –CO–. Compounds with this group are a subclass of the organofluorines.