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KMID : 1059519940380100719
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Journal of the Korean Chemical Society
1994 Volume.38 No. 10 p.719 ~ p.725
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Kinetics and Mechanism for Substitution of cis-[Co(NH3)4Cl(H2O)]2+ 와 GlyOR (R = C2H5, CH3, H) in Acidic Solution (Ⅰ)
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Lee Il-Bong
Moon Jin-Hee
Park Byung-Kak
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Abstract
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Kinetic studies were carried out for substitution reaction of cis-[Co(NH3)4Cl(H2O)]2+(μ = 0.75) with GlyOR (R = C2H5, CH3, H) in pH 5 buffer solution at 20℃ by UV/Vis-spectrophotometry. We obtained cis-[Co(NH3)4Cl(glyOR]2+ as product. The reaction turns out to be first order for Co(Ⅲ) and GlyOR, respectively. The rate constants are obtained as 9.21, 11.66 and 15.33 l·mol-1·sec-1 for GlyOEt, GlyOMt and GlyOH, respectively. The activation parameters Ea, △H≠ and △S≠ for GlyOEt were obtained as 65.77, 63.35 kJ/mol and -53.51(e.u.), respectively and were obtained as 70.91, 68.50 kJ/mol and -38.42(e.u.) for GlyOMt. In case of GlyOH, respectable values of 79.72, 77.30 kJ/mol and -26.59(e.u.) were obtained. On the basis of kinetic data and the observed activation parameters, we propose that the proper mechanism involves SN2 step.
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