Standard enthalpies and heat capacities of solution of 2,4-dimethyl- and 2,4-diethylglycolurils in water at temperatures from (278.15 to 313.15) K

Abstract The molar enthalpies of solution of 2,4-dimethyl- and 2,4-diethylglycolurils (2,4-DMGU and 2,4-DEGU) in water in the temperature range between (278.15 and 313.15) K were measured by microcalorimetry at ambient pressure. Experimental results were used to calculate the standard (at infinite dilution) molar enthalpies of these bicyclic compounds. The changes in molar heat capacities during the dissolution process were derived, too. The enthalpies of solution of both 2,4-DMGU and 2,4-DEGU are positive and increase with temperature. In the case of 2,4-DEGU, the temperature influence on the dissolution enthalpy was found to be more significant. Based on the data on the standard heat capacity of solution, a conclusion was drawn that the hydrophobic hydration of a solute is more pronounced in the aqueous medium containing 2,4-DEGU.