a process is disclosed for the preparation of derivatives of perfluoroalkanecarboxylic acids and perfluoroalkanesulphinic acids by reacting a perfluoroalkylhalide having the general formula r f x , in which x represents an atom of chlorine , bromine , or iodine , and r f represents an unbranched or branched perfluorinated chain containing from 2 to 12 carbon atoms ; with co 2 or so 2 in a solvent medium and in the presence of activated or unactivated zinc .