GB703202A - Processes for the preparation of polychloro alicyclic compounds - Google Patents

Abstract

Octachlorocyclopentene is prepared by chlorinating tetrachlorocyclopentane or mixtures of C5H6Cl4 and C5H5Cl5 in the liquid phase, by maintaining the reaction mixture constantly saturated with chlorine at a temperature within 20 DEG C. of that at which it refluxes at atmospheric pressure. Preferably the temperature is maintained at 170-275 DEG C. Phosphorus pentachloride or arsenic oxide may be present as a catalyst and the reaction may be carried out under increased chlorine pressure. The octachlorocyclopentene may be converted to hexachlorocyclopentadiene by pyrolysis at 275 DEG C.-500 DEG C. preferably by passing the octachlorocyclopentene through a heated zone at 375 DEG C.-500 DEG C., fractionating the pyrolysed product and returning any unchanged octachlorocyclopentene to the pyrolysis zone. Examples describe the chlorination of tetrachlorocyclopentane according to the invention to give octachlorocyclopentene which is pyrolysed to hexachlorocyclopentadiene. Tetrachlorocyclopentane is prepared by chlorinating a monocyclic, five carbon atom ring, hydrocarbon or a chlorinated derivative thereof containing less than four chlorine atoms in the molecule, in a saturated solution of chlorine at -50 DEG C. to +80 DEG C. Preferably the cyclic five carbon atom hydrocarbon, such as cyclopentadiene, is added to a cold saturated solution of chlorine in a solvent which may suitably be the chlorinated cyclopentane itself.