The study of the vapor pressure and the enthalpy of vaporization of ionic liquids

由于许多原因，对RTILs蒸汽压的可靠了解具有相当大的意义。这些数据对于测试基于MD技术或其他技术的蒸汽压力和汽化热的理论计算是重要的。文献中已经进行了几次尝试，以或多或少半经验的方式估计RTILs的蒸汽压。我们已经开发了一种概念，它提供了一种直接的方法来测量RTILs的蒸汽压，使用扩展版的“蒸腾技术”，该技术已成功地应用于确定我们实验室中非常低挥发性物质的蒸汽压。此外，将使用我们集团提供的“旋转炸弹”量热计对不同RTILs的燃烧热进行高精度测量。这直接导致了液态RTILs的生成热。气态的生成热将通过高水平的量子力学计算得到，这种计算今天已经达到了一定的质量，可以保证气态的生成热的精度达到百分之几。气态和液态的生成热之差就是汽化热。用这种方法得到的值将与由测量的蒸汽压的温度依赖关系得到的实验值进行比较，为两种方法获得汽化热提供了一种灵敏但不可或缺的一致性测试。所描述的理论计算将与罗斯托克理论化学小组（Ludwig教授）合作进行，那里的计算机容量尽可能高，可以可靠地保证所需的计算。

A reliable knowledge of the vapor pressure of RTILs is of considerable interest for many reasons. Such data would be import for testing theoretical calculations of vapor pressures and heats of vaporization based on MD technique or other techniques. Several attempts have been made in the literature to estimate vapor pressures of RTILs in a more or less semiempirical way. We have developed a concept, which offers a direct way to measure the vapor pressure of RTILs using an extended version of the ¿transpiration technique¿, which has successfully been applied for determining vapor pressures of substances of very low valatility in our laboratory. In addition high precision measurements of the heats of combustion of different RTILs will be carried out using a ¿rotating bomb¿ calorimeter available in our group. This leads immediately to the heats of formation of RTILs in the liquid state. Heats of formation in the gaseous state will be obtained by high level quantum mechanical calculations, which have reached today a quality ensuring the required accuracy of a few percent for heats of formation in the gaseous state. The difference of the heats of formation in the gaseous and the liquid state is the heat of vaporization. Values obtained by this method will be compared with experimental values derived from the temperature dependence of the measured vapor pressure providing a sensitive but indispensable consistency test of both ways to obtain heats of vaporization. Theoretical calculations described will be performed in cooperation with the group of Theoretical Chemistry in Rostock (Prof. Ludwig) where the highest possible computer capacities guarantee the required reliably.