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

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 [Xee = 44% (at 0.05 mol L−1) to 59% (at 0.40 mol L−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% (ΔGee-aa = 1.72 kJ mol−1) in cyclohexane (C6D12) to 97% (ΔGee-aa = −8.41 kJ mol−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 (ΔGae-ea = 0.84 kJ mol−1), to 49%, in DMSO (ΔGae-ea = 0.13 kJ mol−1). A value of 18.4 kJ mol−1 for the strength of IAHB in cis-3-MCH was obtained, from the theoretical data, through the CBS-4M method.