Photochlorination of α - and γ -3, 4, 5, 6-Tetrachlorocyclohexene -Effects of Temperature and Solvents on the Yields of 1, 2, 3, 4, 5, 6-Hexachlorocyclohexane lsomers-

Abstract

The photochlorination of a and r-3, 4, 5, 6-tetrachlorocyclohexene(BTC), which are the intermediates of r-1, 2, 3, 4, 5, 6-hexachlorocyclohexene (r-BHC) in the photochlorination of benzene, was studied i, n carbon tetrachloride, methylene chloride, 1, 2-dichloroethane and acetic anhydride at the temperature of 50. v 40"C. Based on the results summarized in Table 2, 3, and 4, it is concluded that the effect of temperature is small in the chlorinated hydrocarbons. T-BHC is obtained in 16%e yield from ev-BTC in methylene chleride and 1, 2 dichloroethane, while the yield is only 6%e in carbon tetrachloride. The BHC isomer ratios in the photochlorination of r-BTC was near!y the same in methylene chloride and in carbon tetrachloride, but r-BHC content increased in acetic anhydride to about 70%o at 300C, as compared to about 55%e in carbon tetrahloride at 10eC.1-Hydroxycyclohexyl hydreperoxide had little effect on the produced isomer ratio (a-BTC, Table 3).
Stereochemical courses of radical chlorination of a and r-BTC were interpreted in terms of Kanda's rate-controlling factor A, B and C (Fig.1).
It was inferred that the increase of r-BHC in the photochlorination of benzene in the presence of partially chlorinated aliphatic hydrocarbons and acetic anhydride is not due to the eMcient addition of chlorine to ev and r-BTC, but to the increase in ec and especially r-BTC.