On the use of CO as scavenger for OH radicals in the ozonolysis of simple alkenes and isoprene

Abstract

The OH radical yields generated in the ozonolysis of ethene (ET), propene (PR), cis-2-butene (CB), trans-2-butene (TB), 2,3-dimethyl-2-butene (TME), and isoprene (ISP) in the presence of 20 Vol.% O 2 have been determined in a darkened glass reactor at 1 bar total pressure. The hydroxyl radicals formed were scavenged by an excess of CO added to the systems. The O 2 present converted H atoms formed in this reaction into HO 2 . From measurements of the increase in CO 2 generation by FTIR the OH formation yields were determined to be 0.08 (ET), 0.18 (PR), 0.17 (CB), 0.24 (TB), 0.36 (TME), and 0.19 (ISP), respectively, per molecule of reacted ozone. The combined error in the OH determinations is estimated to be Ͻ10%.

The stable-carbon kinetic isotope effects of the reactions of isoprene, methacrolein, and methyl vinyl ketone with ozone in the gas phase

“…derived from the inverse carbon number dependence by Iannone et al (2003) by using MM = 14· N C . Table 1 Comparison between mean ozone-alkene relative rate constants from the GC-FID and GCC-IRMS studies of this investigation and literature rate constants (298 K) Studied Alkene Gutbrod et al, 1997;Lewin et al, 2001;Rickard et al, 1999;Marston et al, 1998;Paulson et al, 1998;Neeb and Moortgat, 1999;and Zhang et al, 2002. c Value taken from the Master Chemical Mechanism (MCMv3) (Jenkin et al, 2003).…”

“…Although the addition of 1 × 10 4 ppmV CO to the chamber reduces the steady state OH radical concentration (Gutbrod et al, 1997), there still will be competitions between VOCs and CO for reaction with OH radicals since for practical reasons we limited the concentration of CO. A comparison of rate constant ratios O3 k/ OH k for the studied VOCs (Table 2) reveals that MACR has the lowest ratio, and thus experiences the highest relative contribution to VOC loss due to OH radicals.…”

Kinetic Study of the OH‐isoprene and O3‐isoprene reaction in the atmosphere simulation chamber, SAPHIR

“…The presence of OH radicals in an ozonolysis experiment would lead to the fast reaction of OH with isoprene and thus would interfere with the determination of the rate coefficient of O 3 with isoprene. For this reason, an excess concentration of CO [Gutbrod et al, 1997] is used in most kinetic studies to scavenge OH.…”

Mainz Isoprene Mechanism 2 (MIM2): an isoprene oxidation mechanism for regional and global atmospheric modelling

“…For instance, the OH-pathway has been investigated extensively in a number of studies (Tuazon and Atkinson, 1990;Paulson et al, 1992a;Miyoshi et al, 1994;Kwok et al, 1995;Benkelberg et al, 2000;Ruppert and Becker, 2000;Sprengnether et al, 2002;Lee et al, 2005;Paulot et al, 2009). Fewer studies on the stable products from the O 3 -pathway have been performed (Paulson et al, 1992b;Grosjean et al, 1993;Aschmann and Atkinson, 1994;Atkinson et al, 1994;Sauer et al, 1999), while a number of studies focused specifically on the OH-yields (Atkinson et al, 1992;Gutbrod et al, 1997;Paulson et al, 1998;Neeb and Moortgat, 1999;Rickard et al, 1999;Lewin et al, D. Taraborrelli et al: An isoprene oxidation mechanism for atmospheric modelling 2001). On the other hand, chemical properties have been determined for a few oxidation products (Atkinson et al, 2006).…”