Thermodynamic study of deuterium exchange in water + methanol systems

Molar excess enthalpies are reported for the systems H2O + CH3OH, H2O +CH3OD, H2O + CD3OD, D2O + CH3OH, D2O + CH3OD and D2O + CD3OD at 298.15 K. The results are analysed to give the enthalpies of the deuterium exchange reactions CH3OH(1) + HDO(1) = CH3OD(1) + H2O(1) and CH3OH(1) + D2O(1) =CH3OD(1) + HDO(1). A new analysis of previously published partial molar enthalpies of solution gives enthalpies of reaction in good agreement with those obtained from our excess enthalpy results. These calorimetric values are in striking disagreement with statistical mechanical enthalpies of reaction. (author)