A New Isomer of 1, 2, 3, 4, 5-Pentachlorocyclohexane from UV Irradiation Products of α-, β- and δ-Isomers of 1, 2, 3, 4, 5, 6-Hexachlorocyclohexane

Abstract

UV irradiation of α-, β- or δ-isomer of 1, 2, 3, 4, 5, 6-hexachlorocyclohexane (BHC) in 2-propanol resulted in the formation of a new compound. The compound isolated from each irradiation product was found to be an isomer of pentachlorocyclohexane, and the steric orientation for chlorine atoms was determined to be 1a, 2e, 3e, 4e, 5e from X-ray structural analysis. In the case of α-and δ-BHC, the pentachlorocyclohexane may be produced by hydrogen abstraction of the radiation-induced pentachlorocyclohexyl radicals, but migration of an equatorial chlorine atom to the vicinal axial position seems to occur at the intermediate pentachlorocyclohexyl radicals in the case of β-BHC.