Ouyang Bin, Howard Brian J
Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
J Phys Chem A. 2008 Sep 11;112(36):8208-14. doi: 10.1021/jp802422b. Epub 2008 Aug 16.
High-resolution microwave spectra of the propanoic acid monomer (PPA) and two of its hydrates, the PPA-(H2O) and the PPA-(H2O)2, were recorded using a pulsed nozzle Fourier transform microwave spectrometer. The rotational and centrifugal distortion constants of these species were determined. Agreements between the experimental and ab initio results of these constants, and of the planar moment of inertia, the dipole moments, and the orientation of the PPA relative to the H2O confirm the geometry of the hydrates, i.e. H2O binds to the carboxylic group of PPA and forms hydrogen-bonded ring complexes. The equilibrium constant and the change of entropy and enthalpy for the formation of PPA-(H2O) were also derived, based on the calculation of partition functions, to evaluate the abundance of this monohydrate in the troposphere.
使用脉冲喷嘴傅里叶变换微波光谱仪记录了丙酸单体（PPA）及其两种水合物PPA-(H₂O)和PPA-(H₂O)₂的高分辨率微波光谱。确定了这些物种的转动常数和离心畸变常数。这些常数以及平面转动惯量、偶极矩和PPA相对于H₂O的取向的实验结果与从头算结果之间的一致性证实了水合物的几何结构，即H₂O与PPA的羧基结合并形成氢键环络合物。基于配分函数的计算，还推导了PPA-(H₂O)形成的平衡常数以及熵和焓的变化，以评估这种一水合物在对流层中的丰度。
