KINETICS OF THE REACTION BETWEEN HYDROXYMETHYL RADICALS AND HYDROGEN-ATOMS

Kinetics of the reactions H (D) + CH2OH (CD2OD) were studied at room temperature using the fast flow technique coupled with laser magnetic resonance and electron paramagnetic resonance detections. Rate coefficients of 4.1 +/- 0.8, 8.1 +/- 1.1, and 4.8 +/- 1.6 (in 10(13) cm(3) mol(-1) s(-1) units) were determined for the overall reactions H + CH2OH --> products (1), D + CH2OH --> products (2), and D + CD2OD --> products (3), respectively. Branching ratios for OH formation were found to be 25 +/- 5% in reaction 1 and 23 +/- 10% in reaction 2. Formation of H atoms by H/D isotope exchange was found to account for approximate to 12% of reaction 2. On the basis of the kinetic results and simple theoretical considerations, the reaction between H atoms and hydroxymethyl radicals was suggested to occur to about 70% via direct disproportionation leading to formaldehyde formation and to about 30% via indirect mechanism through complex (CH3OH)*. Under the conditions used, CH3 and OH were shown to be the products of the major channel of the complex-forming reaction path. Results determined for reaction H + CH2OH are compared with those obtained previously for H + CH3O. Implications for combustion systems are discussed briefly.