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

✍ Scribed by Kamal H. Halawani; Cecil F. Wells

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 545 KB
• Volume: 27
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550270104

✦ Synopsis

The kinetics of the solvolysis of the hydrophobic ion, Co(4-t-Bupy)dCl:, have been followed in mixtures of water with co-solvents having a hydrophilic tendency, ethane-1,2-diol and 2-methoxyethanol. The variation of ln(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"' ion in the transition state relative to the increase in the stability of Co(4-t-Bupy)4Clzf in the initial state as the co-solvent content rises is greater for 2-methoxyethanol than for ethane-l,a-diol.