乙二胺盐酸盐的低温热容和热化学性质

Low-temperature Heat Capacities and Thermochemistry Properties of Ethylene Diamine Dihydrochloride

合成了乙二胺盐酸盐,并表征了其晶体结构.测定了其在78～370 K温度区间的低温热容,通过最小二乘法拟合得到热容对温度的多项式方程.设计了合理的热化学循环,测定了所设计反应的反应物和产物的溶解焓,得到反应焓.利用Hess定律计算出乙二胺盐酸盐的标准摩尔生成焓为-(540.74±1.33)kJ/mol.利用紫外-可见光谱和折光指数的结果检验了所设计热化学循环的可靠性.

Ethylene diamine dihydrochloride was synthesized by solvothermal synthesis.X-ray crystallography was applied to characterize its structure.Low-temperature heat capacities of the title compound were measured by a precision automated adiabatic calorimeter over the temperature range from 78 K to 370 K.A polynomial equation of heat capacities as a function of the temperature was fitted by least square method.A reasonable thermochemical cycle was designed on the basis of a designed thermochemical reaction（1.0 mol/L NaOH solution was chosen as the calorimetric solvent）,and standard molar enthalpies of dissolution for the reactants and products of the reaction in the selected solvent were measured by an isoperibol solution-reaction calorimeter,respectively.Eventually,the standard molar enthalpy of formation of the title compound was derived to be-（540.74±1.33） kJ/mol by the Hess thermochemical cycle.The reliability of the designed thermochemical cycle was verified by UV-Vis spectroscopy and the data of the refractive indices.The standard molar enthalpy of formation of the title compound is negative with a larger absolute value.The results show that the title compound has lower energy and more stable structure in comparison with the stabile elementary substance.