Department of Chemistry and Biochemistry, University of Regina, Regina, SK S4S 0A2, Canada.
Phys Chem Chem Phys. 2020 Apr 7;22(13):7119-7125. doi: 10.1039/c9cp06589j. Epub 2020 Mar 23.
Liquid ethylenediamine contains both trans and gauche conformers, but there are conflicting claims in the literature that the relative abundance of gauche conformers is either completely quenched (J. Mol. Struct., 1999, 482, 639-646) or enhanced (Phys. Chem. Chem. Phys., 2016, 18, 26192-26198) in 1 M aqueous solutions. Density-functional-theory spectra predictions are employed here to resolve the conflict. In both the 1999 and 2016 reports, the effects seen were misinterpreted, and are instead due to loss of direct amine-amine H-bond interaction upon dilution, which appears to be complete at ∼0.66 mole fraction of water. Both trans and gauche conformers of ethylenediamine are concluded to be present, in both liquid and aqueous phases, with as yet no solid evidence for a shift in conformer ratio.
液态乙二胺中同时存在反式和 gauche 构象，但文献中存在相互矛盾的说法，即 gauche 构象的相对丰度要么完全被猝灭（J. Mol. Struct.，1999，482，639-646），要么增强（Phys. Chem. Chem. Phys.，2016，18，26192-26198）在 1 M 的水溶液中。这里采用密度泛函理论光谱预测来解决冲突。在 1999 年和 2016 年的报告中，观察到的效应被误解了，而这是由于稀释时直接胺-胺 H 键相互作用的丧失，这种相互作用似乎在约 0.66 摩尔分数的水时完全丧失。乙二胺的反式和 gauche 构象都被认为存在于液态和水相，目前还没有固体证据表明构象比例发生了变化。
