Theoretical Study on the Water-Assisted Reaction ofNCO with HCHO.

In this study, the reaction mechanismand kinetics of the hydrogenabstraction and addition reactions of NCO with HCHO in the absenceand presence of water have been investigated theoretically for thefirst time. Our theoretical results indicate that direct hydrogenabstraction is favored in the formation of HNCO instead of HOCN andthe addition pathways are negligible with and without water. The rateconstants calculated at the CCSD(T)/aug-cc-pVTZ//BH&HLYP/6-311(3df,3pd)level with zero-point energy correction range from 1.60 × 10–12to 4.99 × 10–12cm3molecule–1s–1between 220 and769 K without water and are in good agreement with the available experimentalvalues. However, with the inclusion of water, the rate constants areslower by 2–8 orders of magnitude than those of the reactionwithout water. Accordingly, the effect of water on the reaction ofNCO with HCHO is negligible in the atmosphere. [ABSTRACT FROM AUTHOR]