Solvation and the state of ammonium bromide and ammonium fluoroborate in the water-hexamethylphosphoramide system

A variable-temperature calorimeter. was used to measure the enthalpies of s olution of ammonium bromide and ammonium fluoroborate in water-hexamethylph osphoramide (HMPA) in the entire range of compositions of the mixed solvent at 25 degreesC. The standard enthalpies of solution and transfer of the sa lts from water into its mixtures with HMPA were calculated. The specific fe atures of the solvation of the Br- and BF4- ions in water and in HMPA were considered. Based on the MacMillan-Meyer formalism, the coefficients of pai r interactions were calculated for the electrolyte-HMPA system in aqueous s olutions. The character of the solvation of the Br- and BF4- anions in bina ry mixtures lean in the organic component. The proposed model predicts that the solvate shells of the solutes are enriched in water.