Rate constant and RRKM product study for the reaction between CH3 and C2H3 at T = 298 K

Abstract

The total rate constant k 1 has been determined at P ϭ 1 Torr nominal pressure (He) and at T ϭ 298 K for the vinyl-methyl cross-radical reaction: (1) CH 3 ϩ C 2 H 3 : Products. The measurements were performed in a discharge flow system coupled with collision-free sampling to a mass spectrometer operated at low electron energies. Vinyl and methyl radicals were generated by the reactions of F with C 2 H 4 and CH 4 , respectively. The kinetic studies were performed by monitoring the decay of C 2 H 3 with methyl in excess, 6 Ͻ [CH 3 ] 0 / [C 2 H 3 ] 0 Ͻ 21. The overall rate coefficient was determined to be k 1 (298 K) ϭ (1.02 Ϯ 0.53) ϫ 10 Ϫ10 cm 3 molecule Ϫ1 s Ϫ1 with the quoted uncertainty representing total errors. Numerical modeling was required to correct for secondary vinyl consumption by reactions such as C 2 H 3 ϩ H and C 2 H 3 ϩ C 2 H 3 . The present result for k 1 at T ϭ 298 K is compared to two previous studies at high pressure (100-300 Torr He) and to a very recent study at low pressure (0.9-3.7 Torr He).Comparison is also made with the rate constant for the similar reaction CH 3 ϩ C 2 H 5 and with a value for k 1 estimated by the geometric mean rule employing values for k(CH 3 ϩ CH 3 ) and k(C 2 H 3 ϩ C 2 H 3 ). Qualitative product studies at T ϭ 298 K and 200 K indicated formation of C 3 H 6 , C 2 H 2 , and C 3 H 5 as products of the combination-stabilization, disproportionation, and combination-decomposition channels, respectively, of the CH 3 ϩ C 2 H 3 reaction. We also observed the secondary C 4 H 8 product of the subsequent reaction of C 3 H 5 with excess CH 3 ; this observation provides convincing evidence for the combination-decomposition channel yielding C 3 H 5 ϩ H. RRKM calculations with helium as the deactivator support the present and very recent experimental observations that allylic C-H bond rupture is an important path in the combination reaction. The pressure and temperature dependencies of the branching fractions are also predicted. . Reaction rate constants and product channel information are required for all such models that attempt to account quantitatively for the observed atmospheric composition and structure. Hydrocarbon photochemistry is initiated by the photodissociation of methane in the upper

Trends in incidence and survival of pediatric and adolescent patients with germ cell tumors in the United States, 1975 to 2006

“…b) The observed line at 392.1 corresponding to the C 3 H 5 species can be populated via reaction (1), followed by The mechanism of radical–radical reaction (5) was studied by quantum chemical methods27 and Thorn et al28 qualitatively observed formation of C 3 H 5 as a primary product of reaction (5) at 133.3 Pa. This reaction plays an important role in the mechanisms of evolution of planetary atmospheres.…”

Methylacetylene (CH3CCH) and propene (C3H6) formation in cold dense clouds: A case of dust grain chemistry

“…CH + C 3 H 4 → H + CH 2 CHC 2 H 4.2e-10 0 0 1.4 14 , Butler et al 1981, Daugey et al 2005, Goulay et al 2009, Loison & Bergeat 2009 12.! At low pressure (Fahr et al 1999, Stoliarov et al 2000, Hébrard et al 2013, Thorn et al 2000 → Rate constant in the 10-50K deduced from (Sabbah et al 2007), branching ratio mainly from (Savee et al 2012) (see also (Knyazev et al 1992, Cavallotti et al 2014, Leonori et al 2015 35.! 86.7 % de C 3 H x (supposed to be C 3 H 4 **) and 13.3% of CH x + C 2 H y (Angelova et al 2004a, Angelova et al 2004b.…”

Laboratory studies of photochemistry and gas phase radical reaction kinetics relevant to planetary atmospheres

“…Many hydrocarbon species, for example CH 3 and C 2 H 3 are be generated by the reaction of F atoms (produced from a micro-wave discharge of F 2 , a clean process) with methane or ethene. 109 However production of highly endothermic species such as CH requires use of metal atom stripping (Na or K) 110,111 and careful control of conditions to ensure clean radical production.…”

“…Stief and co-workers have studied a range of radical-radical reactions including Cl + CH 3 , 129 H + C 2 H 5 , 130 CH 3 + CH 3 , 127,131 CH 3 + C 2 H 3 , 109 C 2 H 3 + C 2 H 3 , 132 H + C 2 H 3 , 133 N + C 2 H 5 , 134 N + C 2 H 3135 and N + CH 3136 using discharge flow techniques coupled with mass spectrometric detection. The reaction of C 2 H 3 with CH 3 illustrates many of the issues 109. …”