The relevant effect of an intramolecular hydrogen bond on the conformational equilibrium of cis-3-methoxycyclohexanol compared to trans-3-methoxycyclohexanol and cis-1,3-dimethoxycyclohexane
作者:Paulo R. de Oliveira、Roberto Rittner
DOI:10.1016/j.saa.2004.07.004
日期:2005.6
1H NMR data show that an increase in the concentration of cis-3-methoxycyclohexanol (cis-3-MCH) shifts the conformational equilibrium from the 1aa conformer, stabilized by an intramolecular hydrogen bond (IAHB), to the 1ee conformer [X(ee) = 44% (at 0.05 molL(-1)) to 59% (at 0.40 molL(-1)), in CCl4], which forms intermolecular hydrogen bonds (IEHB), as confirmed by IR data. The percentage of 1ee conformer
1 H NMR数据表明,顺式-3-甲氧基环己醇(cis-3-MCH)浓度的增加将构象平衡从由分子内氢键(IAHB)稳定的1aa构象异构体转移到1ee构象异构体[X(ee )= 44%(在0.05 molL(-1)时)到59%(在0.40 molL(-1)时,在CCl4中),这形成了分子间氢键(IEHB),由IR数据证实。1ee构象剂的百分比随着溶剂极性的增加而增加,从在环己烷(C6D12)中的33%(DeltaG(ee-aa)= 1.72 kJmol(-1))增加到97%(DeltaG(ee-aa)= -8.41 kJmol(-) 1))。对于反式3-甲氧基环己醇(反式3-MCH),在研究的溶剂中几乎平等地存在1ae和1ea构象异构体,在C6D12中1ae从41%增加(DeltaG(ae-ea)= 0.84 kJmol(-1)) ,至DMSO中的49%(DeltaG(ae-ea)= 0.13