Abstract This paper describes the transformation of α, ω-bis (trichloromethyl) compounds into perhalogenated diacid chlorides. The general formulae of the starting products are CCl 3(CF 2 CFCl) x CF 2 CCl 3 (I, x) with x= 0, 1, 2 and CCl 3 CF 2 CCl 2 CF 2 ...