Enthalpy of interaction of several electrolytes with 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidone in water at 298.15 K

Abstract

Enthalpies of mixing in water of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidone (DMPU) with several alkali-metal halides (LiCl, NaCl, KCl, CsCl, KF, KBr, KI) and tetra- n-alkylammonium bromides, R 4NBr (R=Me, Et, Pr, Bu) have been determined by flow microcalorimetry at 298.15 K. The results were used to calculate enthalpic pair interaction coefficients, h NE, of virial expansion of excess enthalpy. A decrease of the h NE coefficient with anionic size in the potassium halides series is observed. In the tetra- n-alkylammonium bromides series, the coefficients are positive and they become more positive when the number of carbon atoms in the hydrocarbon chain is increased. A comparison to other systems obtained from the literature is reported.