Water as a solute in aprotic dipolar solvents. 2. D 2O–H 2O solute isotope effects on the enthalpy of water dissolution in nitromethane, acetonitrile and propylene carbonate at 298.15 K

Abstract

The enthalpies of solution of ordinary (H 2O) and heavy (D 2O) water in nitromethane (NM), acetonitrile (ACN) and propylene carbonate (PC) were measured calorimetrically at 298.15 K. Standard (at the infinite dilution) enthalpies of solution and solvation, along with D 2O–H 2O solute isotope effects on the quantities in question, were calculated. The enthalpies of solution of water H/D isotopologues were found to be positive by sign and substantially increasing in magnitude on going from ACN and PC to NM, whereas the corresponding positive solute H/D isotope effect changes in a consequence: NM > ACN > PC. The qualitative interrelations between the enthalpy–isotopic effect of dissolution (solvation) of water and the electron-accepting/donating ability of aprotic dipolar solvent (within a series considered) were found.