Thermochemical Examination of NaI, NaBPh4, and Ph4PI in the Mixtures of Acetonitrile with N,N-Dimethylformamide and Dimethylsulfoxide at 298.15 K: Properties of Acetonitrile-Containing Mixtures as Solvents for Electrolytes

Dissolution enthalpies of NaI, NaBPh4, and Ph4PI in the mixtures of N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO) with acetonitrile (AN) over the whole composition range were measured at 298.15 K. From these data the single ion (Na+, I−, BPh4 −, Ph4P+) enthalpies of transfer from AN to AN + cosolvent mixtures and the enthalpic pair interaction coefficients, h xy (NaI−nonelectrolyte), in AN were determined and analyzed together with our earlier data concerning the mixtures of AN with methanol (MeOH), N, N-dimethylacetamide (DMA), propylene carbonate (PC), and 2-methoxyethanol (2-ME). The changes in electrolyte solvation were described with the use of Covington’s preferential solvation (PS) model. The linear relationship between interaction coefficients, h xy , of NaI−nonelectrolyte in AN and ln K 1/n values from PS model for NaI molecule in the mixture of AN and DMA, 2-ME, DMF, and DMSO as well as for Na+ ion in the mixture containing DMA, DMF, 2-ME, and MeOH was demonstrated. The behavior of the mixtures of water, MeOH, DMF, and AN with organic cosolvents when used as solvents for electrolytes was compared.