Kinetics and mechanism of the NCCO + NO reaction.
The kinetics of the NCCO + NO reaction was studied by diode infrared laser spectroscopy. The results show that the total rate coefficient of the reaction is highly pressure dependent, with k(1) (298 K) = (3.2 +/- 0.5 to 27.1 +/- 2.0) x 10(-13) cm(3) molecule(-1) s(-1) over the total pressure range 3-25 Torr. Only very small yields of CO(2) and CO products were detected, with upper limits on branching ratios estimated at Phi (CO(2) + NCN) < or = 0.01, Phi (2NCO) < or = 0.01, and Phi(CO + NCNO) < or = 0.06. The reaction mechanism was investigated by calculating the potential energy surface (PES) using ab initio methods at the DFT-B3LYP/6-311++G**//CCSD(T)/6-311++G** level. The PES shows that pathways leading to bimolecular/trimolecular product channels involve high barriers. Both experiment and theory therefore indicate that the major pathway is formation and collisional stabilization of an NCC(NO)O adduct.