Process of preparing bromochlorodifluoromethane by reacting chlorodifluoromethane and bromine

摘要

A brominated product containing a substantial amount of dibromodifluoromethane and/or bromochlorodifluoro methane is obtained by reacting bromine and chlorodifluoromethane at 300-1000 DEG C. in such proportions that for each mol. of chlorodifluoromethane there is provided 0.8 to 1.2 mol. of bromine. When the reaction is carried out at between 550 DEG and 750 DEG C. a mixture of perhalomethanes containing a substantial amount of chlorobromodifluoromethane and of dibromodifluoromethane is obtained. Bromochlorodifluoromethane is the primary product when the reaction is conducted at 300 DEG to 650 DEG C., preferably 550-650 DEG C., whilst at 650-900 DEG C., preferably 650-750 DEG C., the primary product is dibromodifluoromethane. The invention also comprises as a new product bromochlorodifluoromethane having a density (d DEG 4) of substantially 1.917 and a boiling point of substantially -2.5 DEG C. In carrying out the process the chlorodifluoromethane may be passed into a vaporizer containing bromine maintained at about 42 DEG C. and the mixed vapours then passed into a combustion tube maintained at the required temperature, the exhaust gases from the tube being introduced into the bottom of a scrubber wherein they are scrubbed with water or alkali to remove unreacted bromine and hydrogen bromide. The scrubbed gases are then dried and fed through a series of traps cooled to below -20 DEG C. and the condensate fractionated to recover the perhalomethanes produced. The results obtained by operating the furnace at 650 DEG , 725 DEG , 750 DEG and 775 DEG C. are tabulated. Under preferred operating conditions the combined weight of the perhalomethanes is at least 50 per cent of the brominated product. The reaction is usually effected at atmospheric pressure but higher or lower pressures may be used. The chlorobromodifluoro methane produced may be reacted with certain olefins to produce new adducts and any mixture of the perhalomethanes obtained by the process may be used as a fire-fiighting liquid (see Group XXI).