A Product Study of the Reaction of HO2 Radicals with Selected Organic Peroxy Radicals

The reaction between HO2 and RO2 radicals represents an important chemical sink for HOx radicals in the troposphere. On the basis of a few studies, several carbonyl-containing organic peroxy radicals may react via three different channels. (R1a-c): RO2 + HO2 → ROOH + O2 (R1a), RO2 + HO2 → ROH + O3 (R1b), RO2 + HO2 → RO + O2 + OH (R1c). The relative yields of these products may play a role in both air quality and climate change. To evaluate whether these reactions are a general feature of carbonyl-containing peroxy radicals, branching ratios for Reaction R1 were measured for four species: butionyl peroxy (CH3(CH2)2C(O)O2), isobutionyl peroxy (CH3C(CH3)HC(O)O2), pentionyl peroxy (CH3(CH2)2C(O)O2), and 2,4-dimethyl-3-pentionyl-2-peroxy (CH3C(CH3)(O2)C(O)C(CH3)HCH3) radicals. Product yields were measured using a combination of Fourier transform infrared spectroscopy, high-performance liquid chromatography with fluorescence detection, gas chromatography with flame-ionized detection, and gas chromatography with mass spectrometry. The atmospheric implications of the results will be discussed.