THEORETICAL CHARACTERIZATION OF THE REACTION OF HO2 WITH FORMALDEHYDE

The reaction of HO2+ formaldehyde is characterized at both the semiemp irical and ab initio levels. It is shown that semiempirical methods do not furnish the information necessary to rationalize the kinetics of the formation of OOCH2OH. The mechanism of this reaction is rationaliz ed at both the MP4/6-31G* and BAC MP4/6-31G** levels. The critical tr ansition state for this reaction involves the simultaneous addition of the terminal oxygen atom of HO2 to the carbon of the CO bond and tran sfer of a proton from OOH to the oxygen of this same bond. It is shown that the previously proposed mechanism involving the intermediate for mation of the HOOCH2O radical is incorrect. Kinetic modeling indicates that the critical transition state has an energy close to the incomin g HO2 + CH2O channel and that a large deuterium isotope effect should occur in the reaction of DO2 + CH2O.