Multigenerational Theoretical Study of Isoprene Peroxy Radical 1–5-Hydrogen Shift Reactions that Regenerate HOx Radicals and Produce Highly Oxidized Molecules

Isoprene Peroxy Radical Dynamics.

Approximately 500 Tg of 2-methyl-1,3-butadiene (isoprene) is emitted by deciduous trees each year. Isoprene oxidation in the atmosphere is initiated primarily by addition of hydroxyl radicals (OH) to C4 or C1 in a ratio 0.57 ± 0.03 (1σ) to produce two sets of distinct allylic radicals. Oxygen (O2) adds to these allylic radicals either δ (Z or E depending on whether the allylic radical is cis or...

Rapid Hydrogen Shift Scrambling in Hydroperoxy-Substituted Organic Peroxy Radicals.

Using quantum mechanical calculations, we have investigated hydrogen shift (H-shift) reactions in peroxy radicals derived from the atmospheric oxidation of 1-pentene (CH2═CHCH2CH2CH3) and its monosubstituted derivatives. We investigate the peroxy radicals, HOCH2CH(OO)CR1HCH2CH3, HOCH2CH(OO)CH2CR1HCH3, and HOCH2CH(OO)CH2CH2CR1H2, where the substituent R1 is an alcoholic (OH), a hydroperoxy (OOH)...

HOx Radical Regeneration in Isoprene Oxidation via Peroxy Radical Isomerisation. II: Experimental Evidence and Global Impact - Electronic Supporting Information (ESI) -

p. 2: Revised isoprene oxidation mechanism for low to moderate NOx conditions as proposed earlier (Peeters et al., PCCP, 2009), with 303 K rate coefficients from first principles; Figs. S1 and S2 p. 3: Temperature-dependent rate coefficient expressions for the unimolecular reactions of isoprene hydroxyperoxy radicals, T = 280 to 320 K, as used in this work; Table S1 p. 4: Effects of allyl-stabi...

Peroxy radical isomerization in the oxidation of isoprene.

We report experimental evidence for the formation of C(5)-hydroperoxyaldehydes (HPALDs) from 1,6-H-shift isomerizations in peroxy radicals formed from the hydroxyl radical (OH) oxidation of 2-methyl-1,3-butadiene (isoprene). At 295 K, the isomerization rate of isoprene peroxy radicals (ISO2•) relative to the rate of reaction of ISO2• + HO2 is k(isom)(295)/(k(ISO2•+HO2)(295)) = (1.2 ± 0.6) x 10(...

Theoretical study of reaction of trifluoromethyl radical with hydroxyl and hydrogen radicals