Classical Dynamics Study of the Unimolecular Decomposition of CH3SH+

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• 作者：Emilio Martí ; nez-Nú ; &ntilde ; ez and Saulo A. Vá ; zquez
• 刊名：Journal of Physical Chemistry A
• 出版年：1999
• 出版时间：December 2, 1999
• 年：1999
• 卷：103
• 期：48
• 页码：9783 - 9793
• 全文大小：107K
• 年卷期：v.103,no.48(December 2, 1999)
• ISSN：1520-5215

文摘

The dynamics of three decomposition channels of the mercapto cation (CH<SUB>3SH⁺) were investigated by classicaltrajectories and RRKM formalisms. The three channels are (I) CH bond dissociation through a "tight" transitionstate, (II) CS bond cleavage, and (III) SH bond scission. These calculations were performed with an analyticalpotential energy surface constructed from theoretical and experimental data available in the literature. Therelative yields of CH₃⁺ and CH₂SH⁺ products are in qualitative agreement with charge-exchange experiments.The dynamical calculations revealed that the system is intrinsically non-Rice-Ramsperger-Kassel-Marcus(RRKM) at the energies selected in this study. Under nonrandom initial conditions, the system showed strongmode specificity, which may be rationalized by weak couplings between the low- and high-frequency modes,particularly the CH₃ stretching normal modes, which is consistent with collisional activation studies. Theclassical trajectory calculations revealed an inverse isotope effect for both the CS and SH scission channelsand a normal isotope effect for the CH bond dissociation process. Finally, we have found that molecularrotation decreases the mercapto cation decomposition rate and that orbital angular momentum dramaticallymodifies the relative yields of CH₃⁺ and CH₂SH⁺ products.