MICROWAVE IDENTIFICATION OF A SECOND GEOMETRICAL ISOMER OF THE ONION LACHRYMATOR, (E) - PROPANETHIAL S-OXIDE
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Date
1995
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
Pulsed beam Fourier transform microwave spectroscopy has been used to characterize the Z form of ethyl sulfine, $CH_{3}CH_{2}CH=SO,$ the compound from cut onions which causes the formation of $tears.^{1}$ This unstable species was produced and its microwave spectrum investigated by carrying the precursor, 2-methyl-2-propyl vinyl sulfoxide, in an argon flow through a furnace coupled to a pulsed nozzle. Using the same flow conditions, a previously unknown microwave spectrum was observed and found to arise from a second geometrical isomer of ethyl sulfine, (E)-propanethial S-oxide. A fit of the measured a-type rotational transitions to a Watson Hamiltonian gives the rotational constants A = 16133(76) MHz, B = 1823.6187(7) MHz and C = 1785.7218(7) MHz. The microwave spectrum of the E-isomer is approximately a factor of two more intense than the $^{13}C$ isotopomers of Z ethyl sulfine which means the pyrolysis produces the E-and Z-isomers of ethyl sulfine in a ratio of 2/98. Internal rotation of the ethyl group about the C-C bond in both geometrical isomers permits rotational isomerism. The E-isomer, like the Z-isomer reported $previously,^{1}$ has a skew conformation.
Description
1. J. Z. Gillies, C. W. Gillies, H. E. Warner and R. Malloy, 49th Int. Sym. Mol. Spectros., RF3, 1994, Columbus, Ohio.
Author Institution: Rensselaer Polytechnic Institute, Troy, NY 12180.; Siena College, Loudonville, NY 12211.
Author Institution: Rensselaer Polytechnic Institute, Troy, NY 12180.; Siena College, Loudonville, NY 12211.