Concentration and solvent effects on the conformational equilibrium of cis-3-ethoxycyclohexanol by 1H NMR and IR spectroscopy
作者:Paulo R. de Oliveira、Danilo S. Ortiz、Roberto Rittner
DOI:10.1016/j.molstruc.2005.11.009
日期:2006.5
Abstract NMR data, in CCl 4 , show that an increase in the concentration of cis -3-ethoxycyclohexanol ( cis -3-ECH) shifts the conformational equilibrium from the ax–ax conformer (X ax–ax =51% at 0.01 mol L −1 ), stabilized by an intramolecular hydrogen bond (IAHB), to the eq–eq conformer (X eq–eq =67% at 0.40 mol L −1 ), which forms intermolecular hydrogen bonds (IEHB), as confirmed by IR data. The
摘要 NMR 数据,在 CCl 4 中,表明顺式 -3-乙氧基环己醇 (cis -3-ECH) 浓度的增加使构象平衡从 ax-ax 构象异构体(X ax-ax = 51% at 0.01 mol L -1 ),通过分子内氢键 (IAHB) 稳定到 eq-eq 构象异构体 (X eq-eq =67% at 0.40 mol L -1 ),形成分子间氢键 (IEHB),如红外数据所证实. 通过红外光谱获得的 Δν 值表明,由于取代基空间和基团电负性效应的增加,顺式 -3-ECH 呈现出比顺式 -3-甲氧基环己醇更强的 IAHB。eq-eq 构象异构体的百分比也随着溶剂碱度的增加而增加,从 51%(ΔG eqeq – axax =-0.03 kcal mol -1 在 CCl 4 中到 97%(ΔG eqeq – axax = -2.05 kcal mol -1)在 DMSO 中) . 4.58