Solvent effects on the thermodynamics of aquocobalamin chloride and model compounds in dioxane–water mixtures

The solubilities of aquocobalamin chloride and eight other cobalt(III) complexes have been measured in dioxane–water mixtures. For aquocobalamin chloride, aquanitrocobaloxime and aquamethylcobaloxime solubilities have also been measured as a function of temperature. The transfer thermodynamic functions ∂mG°, ∂mH° and ∂mS° have been calculated. The results may be accounted for in terms of the cavity energy and specific interactions. A difference has been found between the transfer functions of the aquocobalamin cation in dioxane–water mixtures and those in acetonitrile–water mixtures.