Implications of intramolecular OH center dot center dot center dot Se hydrogen bonding and CH center dot center dot center dot 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(-/+) (G Gg') and gauche(-/+)-gauche(+/-)-gauche(-/+) (G'Gg') conformations around t he CH3Se-CH2-CH2-OH bonds, being consistent with the theoretical energies o f the conformers. The GGg' and G'Gg' conformers are stabilized by intramole cular OH Se hydrogen bonding. The conformational stabilization energy by th is 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 theor etical results show that intramolecular OH . . . Se hydrogen bonding is as strong as OH . . .O and OH . . .S hydrogen bonding. An additional intramole cular CH . . .O interaction with its stabilization energy 5.6 kJ mol(-1) st abilizes the G'G conformation around the CH3Se-CH2-CH2OH bonds. The spectra l observation that the wavenumbers of the hydrogen-bonded O-H stretching mo de for 2-(methylseleno)ethanol and the thio-analogue are significantly lowe r than the wavenumber for the oxy-analogue was also discussed.