t-BuOK法によるPCBの脱塩素化分解反応機構

抄録

Three mono-chlorobiphenyls (2-chlorobiphenyl, 3-chlorobiphenyl and 4-chlorobiphenyl) were dechlorinated by the reaction with potassium tert-butoxde (t-BuOK). Gas chromatography-mass spectroscopy (GC-MS) techniques were used for identification and quantitative analysis of all reactants and products. The three mono-chlorobiphenyls were compared in terms of the reactivity of their ortho, meta and para chlorine atoms. The dechlorination of 2-chlorobiphenyl was slower than that of 3- or 4-chlorobiphenyl. The low degradation rate of 2-chlorobiphenyl is probably due to the steric hindrance of the ortho chlorine situated between the benzene rings. Biphenyl, t-butoxy-biphenyl, methyl-biphenyl and hydroxy-biphenyl were the products in the reaction. 2-Chlorobiphenyl, 3-chlorobiphenyl and 4-chlorobiphenyl were converted into either of 2- or 3-, 2- or 3- or 4-, and 3- or 4-substituted-biphenyl, respectively. The substitutive groups, OH, CH₃, H and t-BuO, combined to either of the carbon which released a chlorine atom or the adjacent carbon. This shows the dechlorination reaction of mono-chlorobiphenyl with t-BuOK occurred via benzyne intermediate.