Effect of Temperature on the Process of Hydrophobic Hydration. Part I. Hydrophobic Hydration of 1,4-Dioxane and 12-Crown-4 Ethers

The dissolution enthalpy of 1,4-dioxane and 12-crown-4 ethers in the mixture of water and N,N-dimethylformamide was measured at four temperatures within the range from (293.15 to 308.15) K. The values of partial molar heat capacity (C(p,2)(0)) and hydrophobic hydration effect, Hb(W), were determined. The effect of temperature on the process of hydrophobic hydration of cyclic ethers has been interpreted. An increase in temperature results in the increased values of the standard enthalpies of solution, Delta(sol)H(m)(o) (a lower exothermic effect), while the exothermic enthalpic effect of hydrophobic hydration, Hb(W), decreases with increasing temperature.