Product yield study of the reactions of peroxy radicals in the troposphere /by Samuel Hernandez.

The reaction between HO2 and organic peroxy radicals (RO2) radicals represents an important chemical sink for HOx radicals in the troposphere. On the basis of a few studies of carbonyl-containing organic peroxy radicals, they may react via four different product channels RO2 + HO2 ??? ROOH + O2 (R17a), RO2 +HO2 ???ROH+O3 (R17b),RO2 +HO2 ???RO+O2 +OH(R17c),RO2 +HO2 ??? R???C(O)H + H2O +O2. To evaluate whether such reactions are a general feature of carbonyl-containing peroxy radicals, branching ratios for Reaction R17 were measured in this work for n-pentionyl peroxy (CH3(CH2)2C(O)O2); n-butionyl peroxy (CH3(CH2)2C(O)O2), isobutionyl peroxy (CH3C(CH3)HC(O)O2), 2,4- dimethyl-3-pentionyl-2-peroxy (CH3C(CH3)(O2)C(O)C(CH3)HCH3), and 2,4- dimethyl-3-pentionyl-1-peroxy ((CH2O2)C(CH3)HC(O)C(CH3)HCH3) radicals. Branching ratios were measured using a combination of Fourier transform infrared spectroscopy, high-performance liquid chromatography with fluorescence detection, gas chromatography with flame-ionization detection, and gas chromatography with mass spectrometry detection methods. The branching ratios of reaction R17 were measured to be 0.40:0.35:0.25:0.00 for n-butionyl peroxy radical, 0.30:0.60:0.10:0.00 for n-pentionyl peroxy radical, and 0.20:0.50:0.30:0.00 for isobutionyl peroxy radicals for YR17a, YR17b, YR17c, and YR17d respectively. The atmospheric implications of these results will be discussed