Rotational spectra of thioacetic acid (CH 3 COSH) have been observed by pulsed-nozzle Fourier transform microwave spectroscopy. Spectroscopic constants are reported for both the syn and anti conformers of the parent species, as well as the 34 S and 13 C carbonyl isotopologues. Transitions arising from the lowest A and E internal rotor states of the methyl group have been observed and analyzed. Experimental values of the three-fold internal rotation barrier, V 3 , for the syn and anti conformers of the parent isotopologue are 76.300(12) and 358.056(51) cm −1 , respectively, indicating a large effect of the S−H orientation on the CH 3 internal rotation potential. M06-2X/6-311+G(d,p) calculations are in good agreement with these results. The block localized energy decomposition method has been applied to understand the origins of this strong dependence of V 3 on conformation. The results indicate that π conjugation from the SH to the carbonyl group and steric repulsion between the SH and the methyl group in the anti form are main contributors to the difference.
|Original language||English (US)|
|Journal||Journal of Chemical Physics|
|State||Published - Apr 7 2019|
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation (Grant No. CHE 1563324) and the Minnesota Supercomputing Institute. Anna Huff was supported by a Lester C. and Joan M. Krogh Fellowship, administered through the University of Minnesota.
This work was supported by the National Natural Science Foundation of China (Grant Nos. 11374066 and 11374068).
© 2019 Author(s).