Singh Ajeet, Ganguly Bishwajit
Central Salt Marine & Chemicals Research Institute, (CSIR) Bhavnagar 364002, Gujarat, India.
J Phys Chem A. 2007 Oct 4;111(39):9884-9. doi: 10.1021/jp074146x. Epub 2007 Sep 12.
The conformational behavior of a 1,3-diazacyclohexane system has been investigated using the DFT B3LYP/6-311+G** level of theory. The structural parameters and relative energies predicted that anomeric effects are operative in the conformations of 1,3-diazacyclohexane. The stability of conformers predicted in the solvent continuum model (water and acetonitrile) is similar to the gas-phase results. The explicit water molecules stabilized the least-stable conformer, and the predictive trend is opposite to that of the gas-phase results. The stability of the conformers in the gas phase is a compromise between avoiding repulsions and maximizing hyperconjugative stabilization. The NBO analysis suggests that the interactions of explicit solvent molecules with 1,3-diazacyclohexane conformers attenuate the anomeric stabilization. The hydrogen-bonding interactions of explicit solvent molecules with 1,3-diazacyclohexane swamped the anomeric effects to alter the conformational stability compared to the gas-phase and solvent continuum model studies.
已使用密度泛函理论（DFT）的B3LYP/6 - 311 + G**水平研究了1,3 - 二氮杂环己烷体系的构象行为。结构参数和相对能量表明，端基异构效应在1,3 - 二氮杂环己烷的构象中起作用。在溶剂连续介质模型（水和乙腈）中预测的构象异构体稳定性与气相结果相似。明确的水分子使最不稳定的构象异构体稳定，且预测趋势与气相结果相反。气相中构象异构体的稳定性是避免排斥和最大化超共轭稳定作用之间的一种平衡。自然键轨道（NBO）分析表明，明确的溶剂分子与1,3 - 二氮杂环己烷构象异构体之间的相互作用减弱了端基异构稳定作用。与气相和溶剂连续介质模型研究相比，明确的溶剂分子与1,3 - 二氮杂环己烷之间的氢键相互作用淹没了端基异构效应，从而改变了构象稳定性。
