Spectroscopy and kinetics of the peroxy radicals formed by chlorine-initiated oxidation of isoprene

Abstract

Peroxy radicals dominate atm. chem. as important reaction intermediates in the oxidn. of volatile org. compds. (VOCs). Biogenic alkene emissions such as isoprene and 2-methyl-3-buten-2-ol (MBO-232) react rapidly with free radicals to form β-substituted alkylperoxy radicals. Chlorine-initiated oxidn. of VOCs has recently become of interest as more in-land sources of chlorine atoms are discovered. We have directly detected the A-X electronic transition spectrum of chlorine-substituted atmospherically-relevant alkyl peroxy radicals from 7000-9000 cm⁻¹ using cavity ringdown spectroscopy. Spectra of peroxy radicals formed by chlorine-initiated oxidn. of isoprene, 2-butene, 3-methyl-1-butene, and MBO-232 are presented here. Kinetic rate consts. of peroxy radical self-reactions and peroxy radical reactions with HO₂ and NO were obtained by directly observing the near-IR absorption spectrum of the peroxy radical intermediate. These rate consts. will be reported here.