Abstract
γ-Isomer of 1, 2, 3, 4, 5, 6-hexachlorocyclohexane (BHC) showed greater decomposition on γ or UV irradiation of five isomers of BHC in crystalline state or in 2-propanol solution. The α- and δ-isomer of BHC and known 1a, 2a, 3e, 4e, 5e-pentachlorocyclohexane were separated from the irradiation product of crystalline γ-BHC. Four compounds were isolated from the irradiation product of γ-BHC in 2-propanol. Two compounds were tetrachlorocyclohexenes (C6H6Cl4•): γ-isomer (mp 8687°C) and ε-isomer (mp 99100°C). The other two were isomers of pentachlorocyclohexane (C6H7Cl5). One of them (mp 788.5°C) was consistent with known meso-1e, 2a, 3a, 4a, 5e isomer. The molecular structure of the other (mp 75°C) established by X-ray crystal structure analysis was 1α, 2α, 3α, 4β, 5α configuration or 1e 2a 3e 4e 5e conformation of Cl atoms. A reaction mechanism was proposed that included a radical chain reaction and chlorine atom migration.
