Recurring chains following addition of atomic hydrogen to acetylene

Recent Rate Constant and Product Measurements of the Reactions C2H3+ H2and C2H3+ H—Importance for Photochemical Modeling of Hydrocarbons on Jupiter

“…INTRODUCTION to ethylene (C 2 H 4 ), of 2.6 ϫ 10 Ϫ13 ϫ e (Ϫ2646/T) cm 3 sec Ϫ1 , suggested by Callear and Smith (1986). This new value Methane (CH 4 ) is a ubiquitous trace species in the strato-was much higher than that used previously (Yung and spheres of the outer planets (see .…”

The neutral photochemistry of nitriles, amines and imines in the atmosphere of Titan

“…C 2 H 3 CN + H reaction is generally taken from Monks et al (1993). However the data of Monks et al (1993), at room temperature only, are very imprecise and their rate constant for the C 2 H 3 + HCN reaction is notably higher than the rate constant of reactions of C 2 H 3 with unsaturated hydrocarbons (Wang and Frenklach, 1994;Knyazev et al, 1996;Callear and Smith, 1986;Ismail et al, 2007) which is a surprising result as several other atoms and radicals (C 2 , C 2 H, CN, OH, F, Cl) are significantly less reactive with HCN (Frost et al, 1986;Hoobler and Leone, 1997;Fukuzawa and Osamura, 1997;Sander et al, 2011) than with unsaturated hydrocarbons (Nesbitt et al, 1994;Li et al, 2006a,b;Paramo et al, 2008;Daugey et al, 2008;Canosa et al, 2007;Lee et al, 2000;Vakhtin et al, 2001;Sims et al, 1993;Gannon et al, 2007;Atkinson et al, 2004;McKee et al, 2007;Nesbitt et al, 1999;Gu et al, 2006;Mebel et al, 2006;Bouwman et al, 2012;Golden, 2012). We performed theoretical calculations for this reaction finding a barrier in the entrance valley equal to 18.0 kJ/mol at the DFT level (M06-2X/cc-pVTZ), in good agreement with Petrie (2002), and classical transition state theory leads to a rate constant equal to k(C 2 H 3 +HCN) = 1.0 Â 10 À12 exp (À2300/T) cm 3 molecule À1 s À1 , a much lower value than Monks et al (1993).…”

Mechanisms for the formation of benzene in the atmosphere of Titan

“…Notwithstanding these combustion analyses conducted at temperatures of 1000 K and higher, the mechanisms which control aromatic chemistry at temperatures applicable to planetary atmospheres are still unclear. Callear and Smith [1986] provided the first analysis of many of the hydrogen and acetylene addition reactions at lower temperatures (T ≤ 400 K). Analysis of products ratios and modeling led to a determination of the hydrogenating reaction C 2 H 3 + H 2 → C 2 H 4 and rate coefficients for other chain‐propagating reactions relative to k(C 2 H 3 + H 2 ).…”