Theoretical studies of reaction mechanisms for potential reactions of HNCO with HO2 radicals

Abstract

The reaction mechanism of HNCO with HO2 radicals is investigated by means of the B3PW91/6-311+G(d,p) method to determine a more reasonable pathway. Four possible entrance patterns are designed; however, only three situations are finally confirmed. When HNCO and HO2 are close to each other, they first form an intermediate a2. Then, the terminal O atom in HO2 connects with the C atom of HNCO along with the H atom transferring from HO2 to the O atom of HNCO. After that the C–O bond ruptures again to form i. Finally, product P6(NCO + HOOH) is generated from i via H atom transfer. P6 is the most accessible product with the simplest steps and lowest barrier height. In addition, the energy of several of the routes is refined at the CCSD(T)/6-311+G(d,p) level based on the optimized geometries. Although there are some differences, the most favorable product is still P6. It is expected that this study would be helpful in further studies on HNCO and in understanding its reactions.