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Zinc(II)-chloride complexes in acetonitrile-water mixtures

Clare, B.W., Hefter, G. and Singh, P. (1990) Zinc(II)-chloride complexes in acetonitrile-water mixtures. Australian Journal of Chemistry, 43 (2). pp. 257-261.

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Equilibrium constants for the formation of ZnCln2-n complexes have been measured in some acetonitrile ( MeCN )-water mixtures ranging from 0 to 100% MeCN at 25°C and I = 0.1 M (Et4NClO4), by potentiometric titration. The equilibria shift strongly in favour of the formation of the higher-order complexes (n = 3, 4) at high MeCN concentrations. This is shown to be due to differences in the magnitude of unfavourable solvation of the Zn2+, Cl - and ZnCln2-n ions in MeCN-H2O solutions. The Gibbs free energies of transfer of all of these ions from water to MeCN-H2O mixtures are strongly positive, but the net change in the transfer function for the formation of the higher-order complexes is favourable. Thus the formation of these complexes is predominant in MeCN -rich aqueous solutions. Approximate measurements in propiononitrile indicate that the ZnCln2-n complexes are even stronger than in acetonitrile.

Item Type: Journal Article
Murdoch Affiliation: School of Mathematical and Physical Sciences
Publisher: Commonwealth Scientific and Industrial Research Organization Publishing
Copyright: © CSIRO 1990
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