Mechanism of the decomposition of CH3SCN, CH3NCS and CH3CN in a radio-frequency pulse discharge

Abstract

The decomposition of CH₃SCN by a short-lived radio-frequency pulse has been investigated. The main primary dissociation steps are: CH₃SCN → CH₃+ S + CN (1), CH₃SCN → CH₂+ H + SCN (3), CH₃SCN → CH + H₂+ SCN. (4) Subsequent reactions of the hydrocarbon fragments yield methane, ethane, ethene and ethyne as major products. SCN is removed in the reaction 2SCN → N₂+ 3CS (5) for which k₅= 8 ± 4 × 10¹⁰ mol^–1 dm³ s^–1. The absorption coefficient for SCN, ε(382 nm)= 1.5 ± 0.7 × 10⁴ mol^–1 dm³ cm^–1, and that for CS, ε(257 nm)= 2.2 ± 1.0 × 10⁴ mol^–1 dm³ cm^–1. In the decomposition of CH₃NCS the primary processes are analogous to reactions (1), (3) and (4). For CH₃CN, the most probable primary reactions are: CH₃CN → CH + H₂+ CN, CH₃CN → CH₂+ H + CN, CH₃CN → CH₃+ CN(B²∑).