An ab initio investigation of five conformers of 3-butyn-1-ol and the structure of the most stable species from microwave spectroscopy

The microwave spectrum for the lowest energy conformer of 3-butyn-1-ol has been remeasured and refitted to include quartic distortion constants, leading to a better determination of the rotational constants and a significant improvement in the fit compared to a previous microwave study. In addition, rotational spectra for isotopomers with a single isotopic substitution at each of the carbon atoms, the oxygen atom, and the hydroxyl hydrogen have been measured, and a complete heavy atom structure determined via Kraitchman’s single substitution equations, a least squares inertial fit and ab initio methods. Ab initio calculations at the MP2 level accurately reproduced the difference between the free and H-bonded OH stretching frequency (,50 cm21) and provided relative stabilities for the five conformers. Comparison between experimental and ab initio structural parameters for the lowest energy conformer gives good agreement. Dipole moment values from the ab initio calculations are also found to be in reasonable agreement with the previous microwave study. q 2004 Elsevier B.V. All rights reserved.