Microwave spectrum and intramolecular hydrogen bonding of 2-propene-1-selenol (H(2)C=CHCH(2)SeH).

The microwave spectrum of 2-propene-1-selenol, H(2)C=CHCH(2)SeH, has been investigated in the 45-80 GHz spectral range at -30 degrees C. The spectra of six isotopologues of one conformer, which has an anticlinal orientation for the C=C-C-Se chain of atoms and a synclinal conformation for the C-C-Se-H link, were assigned. This conformational preference allows for the formation of an intramolecular hydrogen bond between the hydrogen atom of the selenol group and the pi electrons of the double bond. This hydrogen-bonded conformer is at least 3 kJ/mol more stable than any further rotameric form of the molecule. The microwave study has been augmented by quantum chemical calculations at the MP2/6-311++G(3df,3pd) and B3LYP/6-311++G(3df,3pd) levels of theory. These calculations indicate that additional rotamers have higher energies, by approximately 3-12 kJ/mol, than the identified conformer. The conformational properties and internal hydrogen bonding of H(2)C=CHCH(2)SeH is compared with their counterparts of the corresponding alcohol and thiol.