INFRARED ABSORPTION OF CH$_{3}$SONO DETECTED WITH TIME-RESOLVED FOURIER-TRANSFORM SPECTROSCOPY
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Date
2011
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Ohio State University
Abstract
A step-scan Fourier-transform spectrometer coupled with a 6.4-m multipass absorption cell was employed to detect time-resolved infrared absorption spectra of reaction intermediates produced upon UV irradiation of a flowing mixture of CH$_{3}$SSCH$_{3}$ and NO$_{2}$ in CO$_{2}$. Irradiation of CH$_{3}$SSCH$_{3}$ at 248 nm produces CH$_{3}$S radicals that subsequently react with NO$_{2}$. Under a total pressure of 100 Torr, we observed bands near 1560 cm$^{-1}$, assignable to mainly the N=O stretching mode of CH$_{3}$SONO, with a small contribution from CH$_{3}$SNO$_{2}$. Calculations with density-functional theory (B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ) predicted the geometry, vibrational wavenumbers, and rotational parameters of CH$_{3}$SONO and CH$_{3}$SNO$_{2}$. Based on these predicted rotational parameters, the simulated absorption band agrees satisfactorily with experimental results. Under a total pressure of 16 Torr, bands near 1560 and 1260 cm$^{-1}$ are assigned to NO$_{2}$ asymmetric and symmetric stretching modes of CH$_{3}$SNO$_{2}$, respectively; the former is overlapped with the N=O stretching mode of CH$_{3}$SONO. An additional band near 1070 cm$^{-1}$ is assigned to the S=O stretching mode of CH$_{3}$SO, reported previously as a secondary product in the reaction of CH$_{3}$S + O$_{2}$. nderline{133}, 184303 (2010).} Reaction of CH$_{3}$S + NO$_{2}$ at high pressure clearly yields CH$_{3}$SONO, rather than CH$_{3}$SNO$_{2}$, as a major product.
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Author Institution: Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan; Department of Applied Chemistry, National Chiao Tung University, Hsinchu 30010, Taiwan