Endothermicity Or Exothermicity of Water-alcohol Mixtures

摘要: Excess enthalpies of mixtures water with methanol, ethanol, 1- and 2-propanol, 1-, 2- tert-butanol were determined by dilution calorimetry in the accessible range mole fractions at 25-degrees-C. Ab initio RHF calculations performed on alcohols, their dimers complexes water. A full optimisation 6-31G level was used to obtain properties interest these systems. The calculated H-bond energies are similar for all studied alcohols. Nevertheless, a systematic stabilisation mixed is found, especially secondary tertiary formation chains exothermic does not follow rules geometric mean. To first approximation, experimental excess DELTAH(e) systems equation = C6/1X(W)6X(A) + C1/1X(W)X(A) C1/2X(W)X(A)2 calorimetric results may be explained presence two kinds H-bonds differing about 8.3 kJ mol-1 energy. Upon water, alcohol inserted weak chain renders adjacent water-bond strong. As consequence, an always exothermic. causes but has negative effect non-specific cohesion. forces increases homologous series, making dissolution alcohols endothermic starting from propanol. formed high according sequence: primary < tertiary.