Microwave spectrum,conformational preference,intramolecular hydrogen bond,barrier to internal rotation,dipole moment,and centrifugal distortion of 1-fluoro-2-propanol

The microwave spectra of 1-fluoro-2-propanol, CH ₃CH(OH)CH ₂F, and one deuterated species, CH₃,CH(OD)CH₂F, have been investigated in the 18–30 GHz spectral region. Only one rotamer with an intramolecular hydrogen bond formed between the fluorine atom and the hydroxyl group was assigned. This conformation is also characterized by having the C-F bond approximately anti to the methyl group. The FCCO dihedral angle is 59 ± 2° and the HOCC dihedral angle is 58 ± 3°. Further conformations, if they exist, are at least 0.75 kcal mol^?1 less stable. Five vibrationally excited states belonging to four different normal modes were assigned and their fundamental frequencies determined. The barrier to internal rotation of the methyl group was found to be 2796 ± 50 cal mol^?1. The dipole moment is μ_a = 0.510 ± 0.009 D, μ_b = 1.496 t 0.026 D, μ_c = 0.298 ± 0.014 D, and μ_tot = 1.608 ± 0.030 D. Extensive centrifugal distortion analyses were carried out for the ground and the first excited state of the heavy-atom torsional mode and accurate values were determined for all quartic and two sextic coefficients.