MICROWAVE ROTATIONAL SPECTRUM AND INTERNAL-ROTATION IN GAUCHE ETHYL-ALCOHOL

The microwave torsional-rotational spectra of several species of gauche ethyl alcohol have been assigned and analyzed. The species studied are CH 3CH2OH, CH3CH2OD, CH 2DCH2OH, and CH2DCH2OD, both methyl symmetric and asymmetric forms of the last two species. Rotational coefficients have been determined for all species. For the normal species, the components of the dipole moment have been determined as |μa|=1.264±0.010 D, |μb|=0.104±0.008 D, and |μc|=1. 101±0.016 D. The tunneling frequency between the two gauche substrates is measured to be Δ=96 739.3 MHz and the gauche-trans energy difference is measured to be 41.2±5.0 cm-1 for the normal species. The first three coefficients in the Fourier expansion of the hydroxyl internal rotation potential energy are determined to be V1=57.0 cm-1, V 2=0.8 cm-1, and V3=395.0 cm-1. The barrier to methyl internal rotation for gauche CH3CH3OH is The barrier to methyl internal rotation for gauche CH3CH 3OH is determined to be V3=1331 cm-1. Analysis of the interaction between methyl and hydroxyl internal rotations for CH 2DCH2OH and CH2DCH2OD determine, for -OH: Vs1s2=8±2 cm-1; and for -OD: V s1s2=4±1 cm-1 for the coefficient of sinα1sinα2 in the effective internal rotation potential energy for these low symmetry species. © 1980 American Institute of Physics.