CHIRALITY OF AND GEAR MOTION IN ISOPROPYL METHYL SULFILE: A FOURIER TRANSFORM MICROWAVE STUDY
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Date
2010
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Publisher
Ohio State University
Abstract
Isopropyl methyl sulfide (CH${_3}$)${_2}$CHSCH${_3}$ was investigated by Fourier transform microwave spectroscopy. Two rotational isomers $gauche$ and $trans$ were detected. The rotational spectra of $gauche$ were found fit to an asymmetric rotor pattern, except for being split by the internal rotation of CH${_3}$ attached to S with the potential barrier $V{_3}$ of 601.642 (65) cm$^{-1}$ and for exhibiting the effect of tunneling between the two equivalent $gauche$ forms in a few high-$K$ transitions. The tunneling was discussed from a viewpoint of chirality. The $trans$ spectra appeared generally similar to those of $gauche$, with $V{_3}$ to the S-CH${_3}$ internal rotation of 559.00 (11) cm$^{-1}$, but satellite lines accompanied the ground torsional state lines in some high-$K$ transitions. These satellites were ascribed to the excited state of the C(isop)-S torsion. In fact, the potential function for this torsion was shown by an $ab\:initio$ calculation to be flat or even of double minima around the $trans$ position, which was presumably caused by a gear coupling between the two methyl groups of the isopropyl group and the one in the S-CH${_3}$.
Description
Author Institution: Department of Applied Chemistry, Faculty of Engineering, Kanagawa; Institute of Technology, Atsugi, Kanagawa 243-0292, JAPAN; The Graduate University for Advanced Studies, Hayama, Kanagawa; 240-0193, Japan