Kinetics of Zinc Incorporation into the Atropisomers of Tetra (o-pivalamidophenyl) porphyrin

概要

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The rates of zinc incorporation into four atropisomers of tetra (o-pivalamidophenyl) porphyrin in dimethylformamide have been measured spectrophotometrically under pseudo-firstorder conditions. The anion species of zinc salts used have substantial effects on the kinetics of the porphyrin metallation. When Zn (OAc)_2 was used as a metal salt, the values of the first-order rate constant were in the order αβαβ>αααβ≃ααββ>αααα, while when Zn (NO_3)_2 was used, the order was αααα>αααβ>αβαβ≃ααββ. Two factors, an"electronic factor"and a "steric factor, "were considered to affect the reaction. The electronic factor is dominant in the former case, while the steric factor is dominant in the latter case. On the basis of the zinc concentration dependence and temperature dependence of the rate constants, the difference in order among the atropisomers could be explained by a hypothetical reaction mechanism involving two alternative rate-determining steps.
社団法人日本薬学会の論文
1984-06-25