Experimental and ab initio investigation of the O–H overtone vibration in ethanol

Abstract

The effect of weak interactions on the ring puckering potential in the coumaran-argon van der Waals complex: Experimental and ab initio analysis of the intermolecular and low-frequency intramolecular vibrations Ab initio determination of the far infrared spectra of some isotopic varieties of ethanolThe intracavity dye laser photoacoustic absorption spectra of ethanol, ethanol (1,1-d 2 ), and ethanol (2,2,2-d 3 ) are reported for the region 16 550-16 700 cm Ϫ1 , which contains the O-H fourth overtone (⌬ OH ϭ5) vibration. The distinct absorption bands have been assigned to the trans and gauche conformational isomers. Comparison of the spectra reveals a coupling between the OH and methylene CH vibrations in only the gauche conformer of ethanol, an effect that had not been observed in the fundamental spectrum. Ab initio electronic structure and vibrational frequency calculations are used to clarify and support the analysis of the ethanol OH vibrational spectrum and to evaluate the relative energies of the conformers.

Hydrogen bonding in liquid and supercritical 1-octanol and 2-octanol assessed by near and midinfrared spectroscopy

“…At higher temperature, the thermal agitation energy kT has a value of about 1.3 kcal/ mol comparable to the energy of the torsional barrier estimated for analogous simpler alcohols in gaseous phase. 27 As a consequence, the rotation around the C-O axis can be considered as free and different conformers cannot be recognized. The band shape is governed this time by the ␤-␣ equilibrium, for which the population of ␣ groups is no more negligible.…”

The equilibrium OH bond length

“…The empirical substitution (r s ) structure has been determined by microwave spectroscopy [138,139]. The overtone spectrum was measured by Fang et al [140], Lange et al [141], Weibel et al [142], and Hu et al [143] up to v OH ¼ 6. From their work, it is possible to derivẽ !…”

Quantum chemical analysis of the energetics of the anti and gauche conformers of ethanol

“…Senent et al [15] used Dunning's correlation consistent triple zeta basis set with Møller-Plesset perturbation theory up to MP4 and obtained the anti form falling 19 cm -1 below the gauche form. Weibel et al [16] have carried out a number of higher-level ab initio calculations including coupled cluster calculations, and found that both MP4 and CCSD(T) single-point calculations place the gauche form about 0.13 kcal/mol below the anti form. These workers also noted that the narrower potential well for the gauche torsion results in a zero-point energy larger by about 113-125 cm -1 for this form, which can reverse the order.…”