Theoretical study of the reaction of CH3 with HOCO radicals.

The reaction of HOCO radicals with CH3 radicals is examined using the coupled cluster method to locate and optimize the critical points on the ground-state potential energy surface. The results show that the CH3 + HOCO reaction can produce both the H2O + CH2CO and the CH4 + CO2 products through acetic acid and enediol intermediates. Direct ab initio dynamics calculations determine the thermal rate coefficients to be k(T/K) = 3.24 x 10(-11)T0.1024 in cm3 x molec(-1) x s(-1) at T </= 1000 K for the overall reaction. In addition, the product branching ratio of (H2O + CH2CO) to (CH4 + CO2) is predicted to be RH2O/CH4(T/K) = 1.52 + (1.95 x 10(-4))T using RRKM theory. Both the thermal rate coefficients and the product branching ratios are weakly temperature dependent.