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Title: A Gaussian-2 ab initio study of [C2H5S]+ ions: II. Fragmentation pathways of CH3SCH+/2 and CH2CHSH+/2 revisited
Authors: Chiu, S.-W.
Cheung, Y.-S.
Ma, N.L. 
Li, W.-K.
Ng, C.Y.
Keywords: [C2H5S]+ ions
Gaussian-2 theory
Ion- molecule complexes
Ion-radical complexes
Unimolecular dissociations
Issue Date: 9-Aug-1999
Source: Chiu, S.-W.,Cheung, Y.-S.,Ma, N.L.,Li, W.-K.,Ng, C.Y. (1999-08-09). A Gaussian-2 ab initio study of [C2H5S]+ ions: II. Fragmentation pathways of CH3SCH+/2 and CH2CHSH+/2 revisited. Journal of Molecular Structure: THEOCHEM 468 (1-2) : 21-37. ScholarBank@NUS Repository.
Abstract: Gaussian-2 ab initio method was performed to examine the five modes of unimolecular dissociation of CH3SCH+/2 (1+) and CH2CHSH2/+ (5+): 1+ → CH3 + H2CS+ (1); 1+ → CH3/+ + H2CS (2); 1+ → CH4 + HCS+ (3); 5+ → H2S + [C2H3]+(4); and 5+ → H3S+ + C2H2 (5). Both reactions 1 and 2, with endothermicities 359 and 395 kJ mol-1 respectively, proceed without a reverse barrier. Loss of CH4 from 1+ (reaction 3) proceeds via a transition state resembling an ion-radical complex CH3 H2CS+. The elimination reaction has an energy barrier of 332 kJ mol-1 Loss of H2S from 5+ (reaction 4) initially proceeds through either cleavage of the C-S bond or formation of the ion-molecule complex H2S/[C2H3]+ (8+/9+), followed by dissociation of the complex. The endothermicity of reaction 4 is calculated to be 245-261 kJ mol-1. Reaction 5, the lowest energy process among the dissociation pathways studied in this work, proceeds via intermediates 9+ and H3S+/C2H2 (10+). Its rate-determining step 5+ → 9+ has an energy barrier of 220 kJ mol-1.
Source Title: Journal of Molecular Structure: THEOCHEM
ISSN: 01661280
DOI: 10.1016/S0166-1280(98)00494-1
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