THEORETICAL-STUDY OF THE REACTION CH(X-2-PI)-2-PI) - 3 - DETERMINATION OF THE BRANCHING RATIOS(NO(X)

In this paper, which is the third of a series devoted to the title rea ction, we present theoretical calculations of branching ratios for the product channels involved in the reaction. In the first paper of this series (Marchand, N.; Jimeno, P.; Rayez, J. C.; Liotard, D. J. Phys. Chem. 1997, 1O1, 6077.), we explored the topology of the lowest triple t potential energy surface determined with sophisticated ab initio met hods and proposed several reaction paths connecting the reactants to t he products. We have used these results to determine the branching rat ios using two methods based on multichannel Rice-Ramsperger-Kassel-Mar cus (RRKM) calculations: a mu VTST/RRKM (mu VTST = microcanonical vari ational transition state theory) method developed by one of us and an ACIOSA/RRKM (ACIOSA = adiabatic capture model using the infinite order sudden approximation) method dealing with a capture rate constant cal culation (Marchand, N.; Stoecklin, T.; Rayez, J. C. To be submitted, o f this series). Our present results reveal that, at 300 K, HCN + O is the major product channel involved in the reaction (72.0%), the other branching ratios being 13.9% for NCO + H, 8.2% for CO + NH, 3.3% for C NO + H, and 1.4% for CN + OH. All the others channels contribute for l ess than 1% each. These theoretical results are in agreement with the results of several experimental studies, especially those very recentl y obtained in our laboratory by Bergeat et al. Moreover, we observe no significant temperature dependence of the branching ratios.