The kinetics of pyrolysis of furan have been investigated theoretically by ab initio quantum chemical techniques and by detailed chemical kinetic modeling of previously reported experimental results. [

No abstract

New rotational line strengths for the C 2 Swan system (d 3 Π g -a 3 Π u ) have been calculated for vibrational bands with v ′ =0-10 and v ′′ =0-9, and J values up to J =34-96, based on previous observations in 30 vibrational bands. Line positions from several sources were combined with the results from recent deperturbation studies of the v ′ =4 and v ′ =6 states, and a weighted global least squares fit was performed. We report the updated molecular constants. The line strengths are based on a recent ab initio calculation of the transition dipole moment function. A line list has been made available, including observed and calculated line positions, Einstein A coefficients and oscillator strengths (f -values). The line list will be useful for astronomers and combustion scientists who utilize C 2 Swan spectra. Einstein A coefficients and f -values were also calculated for the vibrational bands of the Swan system.

Decomposition of the benzyl radical at a range of temperatures, ∼1450−1650 K, has been investigated using ab initio quantum chemical and experimental (shock tube) techniques. Four possible decomposition mechanisms are considered:  (a) via a norbornadienyl intermediate, (b) via a cycloheptatrienyl intermediate, (c) via direct ring opening, and (d) via a 6-methylenebicyclo[3.1.0]hex-3-en-2-yl (MBH) intermediate. On the basis of the quantum chemical calculations, mechanisms c and d are found to be the dominant reaction channels. A theoretically derived rate constant for the overall disappearance of benzyl is k = 1016.6±0.3 exp(−97 ± 3 kcal mol-1/RT) s-1, in reasonable agreement with that obtained in previous studies. The experiments were carried out by shock heating benzyl bromide to temperatures between 1050 and 1650 K, followed by analysis of the spectral components of benzyl bromide, benzyl, and benzyl “fragments”. The rate constants derived from these experiments by using a simple two-step kinetic model are in good agreement with the theoretical values.

The kinetics of pyrolysis of pyrrole have been investigated theoretically by ab initio quantum chemical techniques and by detailed chemical kinetic modeling of previously reported experimental results. [Mackie, J. C.; Colket, M. B.; Nelson, P. F.; Esler, M. Int. J. Chem. Kinet. 1991, 23, 733.] The overall kinetics can be successfully modeled by a 117 step kinetic model that gives good agreement with temperature profiles of major products and also provides an acceptable fit for minor products. The thermochemistry and rate parameters of a number of key reactions have been obtained by ab initio calculations carried out at CASSCF, CASPT2, and G2(MP2) levels of theory. Several reaction pathways were investigated. The major product, HCN, arises principally from a hydrogen migration in pyrrole to form a cyclic carbene with the NH bond intact. Ring scission of this carbene leads to an allenic imine precursor of HCN and propyne. This is the decomposition pathway of lowest energy. Pyrolysis is preceded by the facile tautomerization of pyrrole to 2H-pyrrolenine. The latter can undergo CN fission to form an open chain biradical species, which is the precursor of the butenenitrile isomeric products, cis- and trans-crotononitrile and allyl cyanide. The biradical can also undergo facile H-fission to form cyanoallyl radical, which is an important precursor of acetylene, acetonitrile, and acrylonitrile. H2 also arises principally from H-fission of the biradical.