RATE COEFFICIENTS FOR THE REACTIONS OF OH RADICALS WITH METHYLGLYOXAL AND ACETALDEHYDE

Rate coefficients have been measured for the reaction of OH radicals with methylglyoxal from 260 to 333 K using the discharge flow technique and laser-induced fluorescence detection of OH. The rate coefficient was found to be (1.32 +/- 0.30) x 10(-11) cm(3) molecule(-1) s(-1) at room temperature, with a distinct negative temperature dependence (E/R of -830 +/- 300 K). These are the first measurements of the temperature dependence of this reaction. The reaction of OH with acetaldehyde was also investigated, and a rate coefficient of (1.45 +/- 0.25) x 10(-11) cm(3) molecule(-1) s(-1) was found at room temperature, in accord with recent studies. Experiments in which O-2 was added to the flow showed regeneration of OH following the reaction of CH3CO radicals with O-2. However, chamber experiments at atmospheric pressure using FTIR detection showed no evidence for OH production. FTIR experiments have also been used to investigate the chemistry of the CH3COCO radical formed by hydrogen abstraction from methylglyoxal. (C) 1995 John Wiley & Sons, Inc.