Hyperconjugation and the Increasing Bulk of OCOCX<sub>3</sub> Substituents in Trans-1,4-Disubstituted Cyclohexanes Destabilize the Diequatorial Conformer
作者:Erich Kleinpeter、Nadja Rolla、Andreas Koch、Ferdinando Taddei
DOI:10.1021/jo0600858
日期:2006.6.1
respect to the established models of conformational analysis, viz., steric 1,3-diaxial and hyperconjugative interactions. Interestingly, the hyperconjugative interactions σC-C/σC-H→σ*C-O, together with a steric effect which also destabilizes the equatorial,equatorial conformers on increasing bulk of the substituents, proved to dominate the position of the conformational equilibria. In addition, the preference
1,4-环己二醇与多种乙酸类似物CX 3 COOH的反式二酯,这些乙酸类似物具有不同的位阻和极性(CX 3 = Me,Et,iso -Pr,叔-Bu,CF 3,CH 2 Cl,合成了CHCl 2,CCl 3,CH 2 Br,CHBr 2,CBr 3),并通过低温1 H NMR光谱研究了CD 2 Cl 2中的轴向,轴向/赤道,赤道构象平衡。在理论上的MP2 / 6-311G *和MP2 / 6-311 + G *的水平上计算了轴向,轴向和赤道,赤道构象异构体的结构和相对能,仅通过包括扩散函数,可以计算出ΔG °与ΔG ° exptl的良好相关性。相对于已建立的构象分析模型,即空间1,3-双轴和超共轭相互作用,讨论了轴向,轴向和赤道,赤道构象异构体的结构和能量差。有趣的是,hyperconjugative相互作用σ Ç - C / σ Ç - ħ →σ* C ^ - Ò连同立体效应,该立体效应