DETERMINATION OF THE RATE-CONSTANT RATIO FOR THE REACTIONS OF THE ACETYLPEROXY RADICAL WITH NO AND NO2

The thermal decomposition of acetyl peroxynitrate was studied in a 420 l DURAN glass reaction chamber in the presence of different initial [NO2]/[NO] ratios. From an analysis of the rate data, the following rate constant ratios k2/k1 for the reactions of CH3C(O)O2 radicals with NO(k1) and NO2(k2) were derived at different temperatures and total pressures: 0.45 +/- 0.05 (304 K, 1000 mbar), 0.41 +/- 0.05 (321 K, 1000 mbar), 0.42 +/- 0.02 (313 K, 1000 mbar) 0.39 +/- 0.02 (313 K, 300 mbar), 0.28 +/- 0.04 (313 K, 100 mbar), 0.25 +/- 0.04 (313 K, 30 mbar). Using recent data on k2, a pressure independent rate constant k1 = (2.1 +/- 0.5) . 10(-11) cm3 molecule-1 s-1 was deduced from these ratios at 313 K.