Implications of intramolecular OH•••Se hydrogen bonding and CH•••O interaction in the conformational stabilization of 2-(methylseleno)ethanol studied by vibrational spectroscopy and density functional theory

The conformational stability of 2-(methylseleno)ethanol has been studied by vibrational spectroscopy and density functional theory. In an argon matrix, the molecules assume primarily the gauche(+/-)-gauche(+/-)-gauche(-/+) (GGg') and gauche(-/+)-gauche(+/-)-gauche(-/+) (G'Gg') conformations around the CH3Se-CH2-CH2-OH bonds, being consistent with the theoretical energies of the conformers. The GGg' and G'Gg' conformers are stabilized by intramolecular OH Se hydrogen bonding. The conformational stabilization energy by this hydrogen bonding was estimated by density functional calculations as 14.5 kJ mol(-1), which is substantially the same as the corresponding energies for OH . . .O and OH . . .S hydrogen bonding. These experimental and theoretical results show that intramolecular OH . . . Se hydrogen bonding is as strong as OH . . .O and OH . . .S hydrogen bonding. An additional intramolecular CH . . .O interaction with its stabilization energy 5.6 kJ mol(-1) stabilizes the G'G conformation around the CH3Se-CH2-CH2OH bonds. The spectral observation that the wavenumbers of the hydrogen-bonded O-H stretching mode for 2-(methylseleno)ethanol and the thio-analogue are significantly lower than the wavenumber for the oxy-analogue was also discussed.