- Ultraviolet Light Induced Dechlorination of Vicinal Polychlorocyclohexanes with Triethylamine
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Photochemical dechlorination of trans- and cis-1,2-dichlorocyclohexanes (t-and c-DCC) in the presence of triethylamine (TEA) results in predominant dechlorination to form cyclohexene, where higher reactivity of the trans isomer over that of the cis (Φt-DCC/Φc-DCC = 4.8) is observed.Four stereoisomers of 1,2,3,4,5,6-hexachlorocyclohexanes, i.e., benzene hexaclorides (BHCs), were similarly dechlorinated to give their stereoselective benzene tetrachlorides (BTC), which mainly lose two adjacent chlorine atoms with a trans configuration to each other among the six chlorines available in BHC.Quantum efficiencies for the dechlorination of the four isomers α-, β-, γ-, and δ-BHC are 0.072, 0.060, 0.19, and 0,11, respectively, which correlate with their reduction potentials, implying that the reaction may be initiated by an electron transfer from TEA to BHC.
- Takagi, Katsuhiko,Ogata, Yoshiro
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p. 1966 - 1970
(2007/10/02)
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- Radiation- and Photo-Induced Degradation of Five Isomers of 1,2,3,4,5,6-Hexachlorocyclohexane
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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 86-87 deg C) and ε-isomer (mp 99-100 deg C).The other two were isomers of pentachlorocyclohexane (C6H7Cl5).One of them (mp 78-8.5 deg C) was consistent with known meso-1e,2a,3a,4a,5e isomer.The molecular structure of the other (mp 75 deg 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.
- Hamada, Masayuki,Kawano, Eiko,Kawamura, Shunichi,Shiro, Motoo
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p. 659 - 666
(2007/10/02)
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