The Thermal Chlorination of Chloroform

The thermal chlorination of chloroform has been studied in the range 260–320°C, using chloroform to chlorine ratios from 10 down to ⅙. For high partial pressures of chloroform the reaction is independent of the chloroform and unimolecular with respect to chlorine. At lower chloroform pressures there is a small dependence on the chloroform in addition to the first-order dependence on chlorine. A mechanism similar to one postulated for the photochemical chlorination of chloroform is discussed and a comparison with the thermal hydrogen-chlorine mechanism leads to the significant conclusion that the reaction has a chain mechanism initiated by chlorine atoms originating on the walls. Production of the latter is interfered with by chloroform adsorption and possibly also by adsorption of reaction products. The chains are broken principally in the gas phase.