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Kinetics of solvolysis of trans ‐dichlorotetra ( t ‐butylpyridine)‐cobalt(III) ions in mixtures of water with ethane‐1,2‐diol and with 2‐methoxyethanol. A contrast with the effect of hydrophobic co‐solvents
Author(s) -
Halawani Kamal H.,
Wells Cecil F.
Publication year - 1995
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550270104
Subject(s) - chemistry , solvolysis , enthalpy , solvent , gibbs free energy , reaction rate constant , solvation , kinetics , inorganic chemistry , thermodynamics , organic chemistry , hydrolysis , physics , quantum mechanics
The kinetics of the solvolysis of the hydrophobic ion, Co(4‐ t ‐Bupy) 4 Cl 2 + , have been followed in mixtures of water with co‐solvents having a hydrophilic tendency, ethane‐1,2‐diol and 2‐methoxyethanol. The variation of In(rate constant) with the reciprocal of the dielectric constant is nonlinear for both co‐solvents. The enthalpy and the entropy of activation are rather insensitive to changes in the solvent composition in both mixtures, but low maxima may exist at mol fractions of co‐solvent Ca. 0.10–0.20. The application of a Gibbs energy cycle to the process of the initial state going to the transition state suggest that, in water‐rich conditions, the increase in the stability of the emergent solvated Co III ion in the transition state relative to the increase in the stability of Co(4‐ t ‐Bupy) 4 Cl 2 + in the initial state as the co‐solvent content rises is greater for 2‐methoxyethanol than for ethane‐1,2‐diol. © 1995 John Wiley & Sons, Inc.