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

Enthalpies of mixing in water of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyri midone (DMPU) with several alkali-metal halides (LiCl, NaCl, KCI, CsCl, KF, KBr, KI) and tetra-n-alkylammonium bromides, R4NBr (R=Me, Et, Pr, Bu) have been determined by flow microcalorimetry at 298.15 K. The results were use d to calculate enthalpic pair interaction coefficients, h(NE), Of virial ex pansion of excess enthalpy. A decrease of the h(NE) coefficient with anioni c size in the potassium halides series is observed. In the tetra-n-alkylamm onium bromides series, the coefficients are positive and they become more p ositive when the number of carbon atoms in the hydrocarbon chain is increas ed. A comparison to other systems obtained from the literature is reported. (C) 1999 Elsevier Science B.V. All rights reserved.