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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 11, Number 4
BKCSDE 11(4)
April 20, 1990 

 
Title
Initial State and Transition State Solvation for the Solvolysis of trans-[Co(N-eten)2Cl2]+ in Binary Aqueous Mixtures: Excess Free Energy, Free Energy Cycle and Reacton Mechanism
Author
Yu Chul Park*, Young Je Cho
Keywords
Abstract
The rates of solvolysis of trans-[Co(N-eten)2Cl2)+ (N-eten; N-ethylethylenediamine) have been investigated using spectrophotometric method in binary aqueous mixtures containing methyl alcohol, isopropyl alcohol, t-butyl alcohol, ethylene glycol and glycerol. The values of ΔH≠ and ΔS≠ obtained from temperature effect on the rate constants were 80~84 kJmol-1 and - 28~ - 45 JK-1mol-1. Extrema found in the variation of the enthalpy and entropy of activation with solvent composition correlated very well with extrema in the variation of the physical properties of mixture which relate to sharp change in the solvent structure. The reaction mechanism was discussed in terms of correlation diagrams involving the exess molar Gibbs function of mixing for the binary mixtures. The behavior of this cobalt(Ⅲ) complex was compared with that of t-butyl chloride. The application of free energy cycle to the process initial state to transition state in water and in the mixture showed that the solvation of transition state had dominant effect on the rates in the mixtures. It was found that SN1 character was increased with increasing the content of co-solvent in the mixture.
Page
309 - 313
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