Prediction of absolute rate coefficients and product branching ratios for the C(3P)+allene reaction system

Abstract

An ab initio/Rice-Ramsperger-Kassel-Marcus prediction of rate constant and product branching ratios for unimolecular decomposition of propen-2-ol and related H + CH 2 COHCH 2 reaction J. Chem. Phys. 129, 234301 (2008) Complex chemical reactions in the gas phase can be decomposed into a network of elementary ͑e.g., unimolecular and bimolecular͒ steps which may involve multiple reactant channels, multiple intermediates, and multiple products. The modeling of such reactions involves describing the molecular species and their transformation by reaction at a detailed level. Here we focus on a detailed modeling of the C( 3 P)ϩallene (C 3 H 4 ) reaction, for which molecular beam experiments and theoretical calculations have previously been performed. In our previous calculations, product branching ratios for a nonrotating isomerizing unimolecular system were predicted. We extend the previous calculations to predict absolute unimolecular rate coefficients and branching ratios using microcanonical variational transition state theory ͑-VTST͒ with full energy and angular momentum resolution. Our calculation of the initial capture rate is facilitated by systematic ab initio potential energy surface calculations that describe the interaction potential between carbon and allene as a function of the angle of attack. Furthermore, the chemical kinetic scheme is enhanced to explicitly treat the entrance channels in terms of a predicted overall input flux and also to allow for the possibility of redissociation via the entrance channels. Thus, the computation of total bimolecular reaction rates and partial capture rates is now possible.

C3H4: Density functional study of interconversion of isomers

“…Details of the calculations are described elsewhere 38. Although a recent study 39 suggested that the neglect of angular momentum conservation may be justified in some cases, it needs to be tested for specific cases. Accordingly, angular momentum conservation was incorporated in the calculations, as some of the reactions involve the movement of the relatively heavy carbon atoms.…”

Quantum Chemical Evaluation of the Astrochemical Significance of Reactions between S Atom and Acetylene or Ethylene

“…In addition to possessing little or no impeding barriers anywhere along the pathway, reactions must also be at least minimally exothermic to be relevant to gas-phase chemistry in the interstellar medium. A number of addition reactions involving radicals such as C 2 H, CN, and C and various hydrocarbons possessing double or triple bonds have been shown both experimentally and theoretically to meet these criteria. − Examples of both cyclic and noncyclic hydrocarbon reactants are known.…”

Reaction of carbon atoms, C (2p2, 3P) with C3H4(allene and methylacetylene), C3H6(propylene) and C4H8(trans-butene): Overall rate constants and atomic hydrogen branching ratios.

“…Insertion-elimination reactions of the type C þ C n H m -C n11 H mÀ1 þ H have been invoked in the synthesis of large carbon-bearing species in ISCs. 1 Ab initio calculations have been performed on the C þ allene, 8,9 C þ propyne 8,10 and C þ propylene 11 systems, indicating that hydrogen atom production is one of the major exit channels. Additional theoretical predictions of product branching ratio have been performed on C þ allene reaction 9 using microcanonical variational transition state theory.…”

“…1 Ab initio calculations have been performed on the C þ allene, 8,9 C þ propyne 8,10 and C þ propylene 11 systems, indicating that hydrogen atom production is one of the major exit channels. Additional theoretical predictions of product branching ratio have been performed on C þ allene reaction 9 using microcanonical variational transition state theory. There are only two experimental studies on products.…”