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Title:VERY DIFFERENT CH3 INTERNAL ROTATION BARRIERS IN THE SYN- AND ANTI- FORMS OF THIOACETIC ACID: MICROWAVE MEASUREMENTS AND ENERGY DECOMPOSITION ANALYSIS
Author(s):Smith, CJ
Contributor(s):Mo, Yirong; Zhang, Huaiyu; Leopold, Ken; Huff, Anna
Subject(s):Small molecules
Abstract:Rotational spectra of two conformers 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- forms of the parent species, as well as for five isotopologues which include $^{34}$S and $^{13}$C substitution on the methyl and carboxyl atoms. Spectra were fit using two different internal rotation fitting programs, XIAM and BELGI-Cs, and comparisons between their performances will be discussed. The experimental internal rotation barriers for the parent syn- and anti-thioacetic acid obtained from BELGI-Cs are 69.3(10) and 435.2(22) \wn, respectively, and compare favorably with the computed values of 83 and 344 \wn at the M06-2X/6-311+G(d,p) level of theory. An energy decomposition analysis using the block localized wavefunction method indicates that the steric (including both Pauli and electrostatic) repulsion between the -SH and CH$_{3}$ groups, which is further enhanced by the pi-conjugation from the -SH to the carbonyl group, is largely responsible for the large difference in the internal rotation barrier between the syn- and anti- forms.
Issue Date:06/20/18
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Genre:Conference Paper / Presentation
Type:Text
Language:English
URI:http://hdl.handle.net/2142/100577
DOI:10.15278/isms.2018.WH07
Other Identifier(s):WH07
Date Available in IDEALS:2018-08-17
2018-12-12


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