Ionic solvation in protic and aprotic solvents



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Enthalpies of solution ([delta]H[lowered s]) of sixteen organic and inorganic salts have been measured in methanol, di methyl sulfoxi de, N,N-dimethylformamide, N-methylpyrrolidi none, N-ethylacetamide, and water, and of the lithium halides in hexamethyl phosphoric triamide. Solvation enthalpies of the alkali halide salts in the above solvents have been determined. Single ion enthalpies of transfer ([delta][delta]H[lowered s]) from methanol to the other solvents have been calculated on the basis of three different extrathermodynamic assumptions: [delta][delta]H[lowered s] (C[lowered 4]H[lowered 9])[lowered 4]N[raised +] = [delta][delta]H[lowered s] [raised -]B(C[lowered 4]H[lowered 9])[lowered 4], [delta][delta]H[lowered s] (C[lowered 5]H[lowered 11])[lowered 4]N[raised +] = [delta][delta]H[lowered s] [raised -]B(C5Hn)4, and [delta][delta]H[lowered s] (C[lowered 6]H[lowered 5])[lowered 4]As[raised +] = [delta][delta]H[lowered s] [raised -]B(C[lowered 6]H[lowered 5])[lowered 4]. There is good agreement in all cases between single ion enthalpies of transfer calculated from the first two assumptions, but values based on the tetraphenyl arsonium tetraphenyl borate assumption show deviations. The solvation enthalpies of the alkali halides show that the order of solvation of the halide ions in all of the solvents is: Cl[raised -]>Br[raised -]>I[raised -].