Separations of a-hexachlorocyclohexane (a-HCH) and pentachlorocyclohexene (PCCH) enantiomers on a cyclodextrin-phase (Cyclodex-B) by HRGC/ECD

The separation of a-hexachlorocyclohexane and of all eight possible pentachlorocyclohexene isomers into their enantiomers by high-resolution gas chromatography and electron capture detection was achieved by using permethylated β-cyclodextrin in DB 1701 (Cyclodex-B, J & W) as chiral stationary phase. The first step in the metabolism of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) is the formation of 1,3,4,5,6-pentachlorocyclohexene-1 (PCCH). Various degradation experiments were carried out with α-, β-, γ-, and δ-HCH. Whereas β-HCH gave no degradation products, the isomers α-, γ-, and δ-HCH degraded into various PCCHs and trichlorobenzenes, when using pyridine as dehydrochlorination reagent in xylene at 60°C. Isomerization into other HCH isomers was observed only for δ-HCH. Enantioselective dehydrochlorination was observed for a- and γ-HCH using the alkaloid (?)-brucine, R-(+)- or S-(?)-a-phenylethylamine as chiral base.