与反式-3-甲氧基环己醇和顺式-1,3-二甲氧基环己烷相比，分子内氢键对顺式-3-甲氧基环己醇构象平衡的相关影响。

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.

作者信息

de Oliveira Paulo R, Rittner Roberto

机构信息

Physical Organic Chemistry Laboratory, Instituto de Química, UNICAMP, Caixa Postal 6154, 13084-971 Campinas, SP, Brazil.

出版信息

Spectrochim Acta A Mol Biomol Spectrosc. 2005 Jun;61(8):1737-45. doi: 10.1016/j.saa.2004.07.004.

DOI:10.1016/j.saa.2004.07.004

PMID:15863042

Abstract

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 increases with the solvent polarity, from 33% (DeltaG(ee-aa) = 1.72 kJmol(-1)) in cyclohexane (C6D12) to 97% (DeltaG(ee-aa) = -8.41 kJmol(-1)) in DMSO. For trans-3-methoxycyclohexanol (trans-3-MCH), 1ae and 1ea conformers are almost equally present in the studied solvents, 1ae increasing from 41%, in C6D12 (DeltaG(ae-ea) = 0.84 kJmol(-1)), to 49%, in DMSO (DeltaG(ae-ea) = 0.13 kJmol(-1)). A value of 18.4 kJmol(-1) for the strength of IAHB in cis-3-MCH was obtained, from the theoretical data, through the CBS-4M method.

摘要

1H核磁共振数据表明，顺式-3-甲氧基环己醇（cis-3-MCH）浓度的增加会使构象平衡从由分子内氢键（IAHB）稳定的1aa构象体转变为1ee构象体[在CCl4中，X(ee)从0.05 molL(-1)时的44%增加到0.40 molL(-1)时的59%]，红外数据证实该构象体形成分子间氢键（IEHB）。1ee构象体的百分比随溶剂极性增加，从环己烷（C6D12）中的33%（ΔG(ee-aa) = 1.72 kJmol(-1)）增加到二甲基亚砜（DMSO）中的97%（ΔG(ee-aa) = -8.41 kJmol(-1)）。对于反式-3-甲氧基环己醇（trans-3-MCH），在研究的溶剂中1ae和1ea构象体几乎等量存在，1ae从C6D12中的41%（ΔG(ae-ea) = 0.84 kJmol(-1)）增加到DMSO中的49%（ΔG(ae-ea) = 0.13 kJmol(-1)）。通过CBS-4M方法从理论数据得出顺式-3-MCH中IAHB强度的值为18.4 kJmol(-1)。