Ab Initio/Density Functional Theory and Multichannel RRKM Study for the ClO CH2O Reaction.

The potential energy surface for the CH2O ClO reaction was calculated at the QCISD(T)/6-311G(2d,2p)//B3LYP/6-311G(d,p) level of theory. The rate constants for the lower barrier reaction channels producing HOCl HCO, H atom, OCH2OCl, cis-HC(O)OCl and trans-HC(O)OCl have been calculated by TST and multichannel RRKM theory. Over the temperature range of 200−2000 K, the overall rate constants were k(200−2000K) 1.19 × 10-13T0.79exp(−3000.00/T). At 250 K, the calculated overall rate constant was 5.80 × 10-17cm3molecule-1s-1, which was in good agreement with the experimental upper limit data. The calculated results demonstrated that the formation of HOCl HCO was the dominant reaction channel and was exothermic by 9.7 kcal/mol with a barrier of 5.0 kcal/mol. When it retrograded to the reactants CH2O ClO, an energy barrier of 14.7 kcal/mol is required. Furthermore, when HOCl decomposed into H ClO, the energy required was 93.3 kcal/mol. These results suggest that the decomposition in both the forward and backward directions for HOCl would be difficult in the ground electronic state. [ABSTRACT FROM AUTHOR]