Borho Nicole, Xu Yunjie
Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada.
Phys Chem Chem Phys. 2007 Aug 28;9(32):4514-20. doi: 10.1039/b705746f. Epub 2007 Jun 25.
High resolution rotational spectroscopy complemented by ab initio calculations has been used to elucidate the diastereomeric interactions in 1 : 1 complexes of ethanol, a transient chiral alcohol, hydrogen-bonded to oxirane (achiral) or trans-2,3-dimethyloxirane (DMO, 2 stereocenters). Two conformers of oxirane[dot dot dot]ethanol and three conformers of DMO[dot dot dot]ethanol have been identified, and their structures as well as their stability ordering have been determined. This completes, together with previous results on the propylene oxide...ethanol complex (N. Borho and Y. Xu, Angew. Chem., 2007, 119, 2326-2329; Angew. Chem., Int. Ed., 2007, 46, 2276-2279.), the study of a set of model systems with zero, one, and two methyl functional groups at the hydrogen bond acceptor oxirane. The dependence of the observed rotational line intensities on pressure, nozzle temperature, and different carrier gases has been investigated for the case of DMO[dot dot dot]ethanol. This provides insight into the kinetical and thermodynamical influence on the formation of different conformers. Comparison of the subtle energy differences among the complexes and within each set of conformers allows for a detailed analysis of molecular recognition in this benchmark system.
高分辨率转动光谱结合从头算计算已被用于阐明乙醇（一种瞬态手性醇）与环氧乙烷（非手性）或反式-2,3-二甲基环氧乙烷（DMO，有2个立体中心）形成的1:1配合物中的非对映体相互作用。已鉴定出环氧乙烷……乙醇的两种构象异构体和DMO……乙醇的三种构象异构体，并确定了它们的结构及其稳定性顺序。这与先前关于环氧丙烷……乙醇配合物的结果（N. Borho和Y. Xu，《德国应用化学》，2007年，119卷，2326 - 2329页；《德国应用化学》，国际版，2007年，46卷，2276 - 2279页）一起，完成了对一组在氢键受体环氧乙烷上具有零个、一个和两个甲基官能团的模型体系的研究。对于DMO……乙醇的情况，研究了观察到的转动谱线强度对压力、喷嘴温度和不同载气的依赖性。这为不同构象异构体形成过程中的动力学和热力学影响提供了深入了解。配合物之间以及每组构象异构体内部细微能量差异的比较，有助于对这个基准体系中的分子识别进行详细分析。
