Abstract
Isoprene, C5H8, inserts about half of the non-methane carbon flux of biogenic origin into the atmosphere. Its degradation is primarily initiated by the reaction with hydroxyl radicals. Here we show experimentally the formation of reactive intermediates and corresponding closed-shell products from the reaction of hydroxyl radicals with isoprene for low nitric oxide and low hydroperoxy radical conditions. Detailed product analysis is achieved by mass spectrometric techniques. Quantum chemical calculations support the usefulness of applied ionization schemes. Observed peroxy radicals are the isomeric HO-C5H8O2 radicals and their isomerization products HO-C5H8(O2)O2, bearing most likely an additional hydroperoxy group, and in traces HO-C5H8(O2)2O2 with two hydroperoxy groups. Main closed-shell products from unimolecular peroxy radical reactions are hydroperoxy aldehydes, C5H8O3, and smaller yield products with the composition C5H8O4 and C4H8O5. Detected signals of C10H18O4, C10H18O6, and C5H10O2 stand for products arising from peroxy radical self- and cross-reactions.
Highlights
Isoprene, C5H8, inserts about half of the non-methane carbon flux of biogenic origin into the atmosphere
Efficient mass spectrometric detection of RO2 radicals and closed-shell products is achieved by atmospheric pressure ionization using aminium, i.e., protonated n-propyl, ethyl- or methylamine, or hydrazinium, i.e., protonated hydrazine, as the reagent ions. n-Propyl-aminium was already applied in a former study for the detection of RO2 radicals and other oxidized products[23]; the others are used here for the first time
It should be noted that OH radical formation via O3 + TME is directly associated with the formation of acetonyl peroxy radicals, CH3C(O)CH2O2, representing additional RO2 radicals in the reaction system[23,29]
Summary
C5H8, inserts about half of the non-methane carbon flux of biogenic origin into the atmosphere. We show experimentally the formation of reactive intermediates and corresponding closedshell products from the reaction of hydroxyl radicals with isoprene for low nitric oxide and low hydroperoxy radical conditions. Isoprene’s degradation process is initiated by the reaction with atmospheric oxidants where the reaction with OH radicals is distinctly dominant[4]. The products from this reaction are marked with “I”. The formation of the analogous products starting from OH attack at the 4-position, marked with “II”, is depicted in
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
