Effect of Hydrogen Bonding on the Deformation Frequencies of the Hydroxyl Group in Alcohols

Abstract

The effects of hydrogen bonding on the infrared spectra of aliphatic alcohols have been studied in the range 4000 to 350 cm-I. Twenty-six alcohols were investigated of which 10 were primary, 7 were branched primary, 6 were secondary, and 3 were tertiary. Attention was concentrated on the region of the spectrum between 1500 cm-I and 350 em-I where the deformation vibrations of the OR group occur. Spectra were obtained of the alcohols (a) in dilute solution in nonpolar solvents, (b) in the liquid state, and (c) in the vapor state, the degree of association being followed by observation of the well-known effect of hydrogen bonding in the OR stretching vibration near 3.01", Methanol, ethanol, and hexanol-1 were also investigated after deuteration of the OR group. All the alcohols exhibited a broad diffuse association band with a maximum near 650 em-I. This has been assigned to the out-of-plane deformation vibration of the R atom in the COR group. All the alcohols also exhibited a broad association band which usually had 2 maxima near 1410 cm-I and 1330 em-I. This band (which appears to have been missed by previous workers) is assigned to the in-plane deformation vibration of the R atom in the COR group. The corresponding monomeric band varies between 1200 cm-I and 1330 cm-I in undeuterated alcohols and between 870 cm-I and 930 cm-I in deuterated alcohols. There is in addition a very narrow association band which lies near 1100 cm-I in primary and secondary alcohols and near 1165 cm-I in tertiary alcohols. This is assigned to the effect of hydrogen bonding on the skeletal vibrations, which involve stretching of the CO bond. It appears that the effects of hydrogen bonding on the deformation motions of the OR group are quite complex and that steric effects, rotational isomerism, and interaction with C-R deformation frequencies may all be involved to some extent.

Fundamental and overtone vibrational spectroscopy, enthalpy of hydrogen bond formation and equilibrium constant determination of the methanol–dimethylamine complex

“…The blueshift for the in-plane COH-bending mode is a typical feature of forming a hydrogen bond, and a larger blue shift is expected for stronger hydrogen bonds. 74,75 The MeOH-DMA spectrum in the first OH-stretching overtone (2ñ OH ) region was also measured (Fig. 2).…”

Cryogenic Raman spectroscopy of glycerol

“…This may allow us to assign the 852 and 819 cm 1 vibrations in glycerol to C-C symmetric stretches, arising from C-1 and C-2, respectively. 13 Elsewhere, this band has been attributed rather to an OH in-plane bending in the Raman spectrum of 1-propanol. Figure 2 and Table 3 show a Raman line at 673 cm 1 which is only slightly polarized and undergoes a Raman shift to 678 cm 1 on cooling glycerol to 223 K ( Table 3).…”

Investigation of the Hydrogen Bonding Properties of a Series of Monosaccharides in Aqueous Media by 1H NMR and IR Spectroscopy

“…This is supported by the fact that in alcohols in the vapour state, in which hydrogen-bonded interactions are absent, no upshift of the ν(CϪO) bands is observed upon Odeuteration of these hydroxy compounds. [29] In contrast, hydrogen-bonded alcohols, either in the liquid state or dissolved in nonpolar solvents, show ν(CϪO) upshifts upon deuteration [30] as a result of Fermi resonance involving ν(CϪO) and δ(OϪD) vibrations. Consequently, this ν(CϪO) shifting can be expected whenever OϪH···O hydrogen bonds are present, even in aqueous medium.…”