S. Coussan et al., ROTATIONAL-ISOMERISM OF ETHANOL AND MATRIX-ISOLATION INFRARED-SPECTROSCOPY, The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 102(29), 1998, pp. 5789-5793
The vibrational spectrum of ethanol monomer trapped in argon and nitro
gen matrices has been recorded in various conditions of temperature an
d irradiation. The structures and vibrational properties of the anti a
nd gauche conformers have been investigated by ab initio calculations
according to the DFT method. The comparison between observed and calcu
lated frequencies allows an explanation of the matrix data and a propo
sal of a complete assignment for both conformers. The striking spectra
l changes observed in nitrogen matrices upon temperature cycling in th
e range 8-30 K are interpreted in term of anti --> gauche conversion.
In contrast with these observations, the spectrum obtained in an argon
matrix is unsensitive to thermal effects, the anti form being the onl
y one to be stabilized. Monochromatic irradiations in the OH and CO st
retching regions were carried out with the purpose of inducing photoro
tamerization. In all cases only changes of trapping sites were observe
d, despite an interconversion barrier lower than the energy of the abs
orbed photons.