FLASH-PHOTOLYSIS STUDY OF THE UV SPECTRUM AND KINETICS OF REACTIONS OF THE ACETONYLPEROXY RADICAL

The flash-photolysis-UV-absorption method was used to study the UV spectrum and the kinetics of the CH3C(O)CH2O2 radical formed in the presence of oxygen via the reaction between Cl atoms and acetone. Results were analysed in the light of the results of the preceding article describing work using end-product analysis. The peroxy radical CH3C(O)CH2O2 absorbs in the UV with two maxima at around 230 and 290 nm. This peroxy radical reacts according to: 2CH3C(O)CH2O2 --> 2CH3C(O)CH2O + O2 (7a) and --> CH3C(O)CH2OH + CH3C(O)CHO + O2 (7b) with k7 = (8.0 +/- 2.0) x 10(-12) CM3 molecule-1 s-1 and k7a/k7 = (0.75 +/- 0.1). The kinetics of the reactions between CH3C(O)CH2O2 and the CH3C(O)O2, CH3O2 and HO2 radicals were determined by adding acetaldehyde, methane or methanol to the photolysis mixtures: CH3C(O)CH2O2 + CH3C(O)O2 --> O2 + CH3C(O)CH2O + CH3 + CO2 (11a); --> O2 + CH3C(O)OH + CH3C(O)CHO (11b); k11 = (5.0 +/- 2.0) x 10(-12) CM3 Molecule-1 s-1; CH3C(O)CH2O2 + CH3O2 --> O2 + CH3C(O)CH2O + CH3O (14a); --> O2 + CH3C(O)CHO + CH3OH (14b); --> O2 + CH3C(O)CH2OH + HCHO (14c); k14 = (3.8 +/- 0.4) x 10(-12) CM3 molecule-1 s-1 and k14a/k14 = 0.3 +/- 0.1 while k14b and k14c could not be distinguished; CH3C(O)CH2O2 + HO2 --> CH3C(O)CH2O2H + O2 (16), k16 = (9.0 +/- 1.0) x 10(-12) Cm3 molecule-1 s-1. All experiments were performed at 298 K and 760 Torr.