No abstract

The CH 2 P N 2 reaction over the ground state potential energy surface has been investigated at the G2M level of theory. This reaction is directly relevant to hydrocarbon combustion chemistry, in particular, to`prompt NO' formation. A detailed mechanism via stepwise and concerted pathways to form HNCN, involving chain and cyclic intermediates, is presented. The proposed mechanism for NO formation is more favorable than the commonly assumed spin-forbidden path producing HCN N 4 S. The theoretically predicted heats of formation for NCN and HNCN are in excellent agreement with the recently reported experimental values. Ó

Articles you may be interested inAccurate combined-hyperbolic-inverse-power-representation of ab initio potential energy surface for the hydroperoxyl radical and dynamics study of O + OH reaction

We have performed kinetic simulations of the behavior of acetylene hydrogenation under ethylene rich conditions at a number of temperatures and feed gas compositions employing Pd and Pd/Ag alloy catalysts. The results of these simulations form a clear and consistent picture as to the origins of selectivity, thermal runaway, oligomer formation, the role of CO as a promoter of selectivity and inhibitor of oligomer formation, and the importance of proton transfer among carbonaceous species. The modeling gives insight into mechanistic details and provides an explanation for the influence of alloying catalyst on these phenomena.

The kinetics and mechanism for the C6H5 + CH2O reaction were investigated by the cavity ringdown spectrometric (CRDS) and pulsed laser photolysis/mass spectrometric (PLP/MS) methods at temperatures between 298 and 1083 K. With the CRDS method, the rate constant was measured by monitoring the decay times of injected probing photons in the absence (t c 0) and presence (t c) of the C6H5 radical. In the PLP/MS experiment at higher temperatures, the rate constant was determined by kinetic modeling of the absolute yields of C6H6. The values of the rate constants obtained by the two different methods agree closely, suggesting that the C6H5 + CH2O → C6H6 + CHO reaction 1 is the dominant channel. A weighted least-squares analysis of the two sets of data gave k 1 = (8.55 ± 0.25) × 104 T 2.19±0.25 exp[−(19 ± 13)/T] cm3 mol-1 s-1 for the temperature range studied. The mechanism for the C6H5 + CH2O reaction was also elucidated with a quantum-chemical calculation employing a hybrid density functional theory (B3LYP) using the aug-cc-PVTZ basis set. The theory predicts the barriers for the abstraction producing C6H6 and the addition giving C6H5CH2O and C6H5OCH2 to be 0.8, 1.4, and 9.1 kcal/mol, respectively. The rate constant calculated for the H-abstraction process using the canonical variational transition-state theory with a 1.1 kcal/mol barrier agrees closely with the experimental result over the entire range of temperatures studied.