Bicyclic Peroxy Radicals in the Oxidation of Toluene
J. Phys. Chem. A, Vol. 114, No. 39, 2010 10663
Seinfeld, J. H., Wallington, T. J., Yarwood, G., Eds.; Oxford University
Press: Oxford, U.K., 2002.
reaction 11. However, since the scavenger was added after the
toluene oxidation system had 50 ms to react, it is even more
difficult to estimate the relevant RO2 and HO2 concentrations
than it is for the early stages of the toluene oxidation process.
However, if a value for both species of 1 × 1011 molecules
cm-3 is assumed, the inferred rate constant for reaction 11 is
about 1 × 10-11 cm3 molecule-1 s-1, which is a significant
fraction of the generic RO2 + HO2 rate constant used in the
MCM. While the calculations are somewhat speculative, they
do provide quantitative support for the supposition that reaction
11 is potentially a major reaction pathway for bicyclic peroxy
radicals under our experimental conditions. Further, since
reaction 11 is also one of the proposed routes by which
methylbutenedial forms under NOx-free conditions, the large
product yield of this species also provides support for the
hypothesis that reaction 11 is a major reaction pathway for the
bicyclic peroxy radical.
As discussed in the Introduction, when tested against the
results of environmental chamber experiments for the photo-
oxidation of toluene, the MCM seems to be missing processes
that regenerate OH with little NO to NO2 conversion.4,5 Our
results suggest that, at least at high HO2 and/or low NO
concentrations, RO2 + HO2 reactions involving the bicyclic
peroxy radical can be competitive with the RO2 + NO reactions
that facilitate NO to NO2 conversion. Therefore, it seems
possible, particularly for experimental conditions of high HO2
and/or low NO, that the environmental chamber results may
have been affected by RO2 + HO2 reactions. Further, since
reaction 11 also produces OH, it can also explain the environ-
mental chamber observation of significant OH regeneration.
(2) Offenberg, J. H.; Lewis, C. W.; Lewandowski, M.; Jaoui, M.;
Kleindienst, T. E.; Edney, E. O. EnViron. Sci. Technol. 2007, 41, 3972.
(3) Velasco, E.; Lamb, B.; Westberg, H.; Allwine, E.; Sosa, G.; Arriaga-
Colina, J. L.; Jobson, B. T.; Alexander, M. L.; Prazeller, P.; Knighton, W. B.;
Rogers, T. M.; Grutter, M.; Herndon, S. C.; Kolb, C. E.; Zavala, M.; de
Foy, B.; Volkamer, R.; Molina, L. T.; Molina, M. J. J. Atmos. Chem. Phys.
2007, 7, 329.
(4) Bloss, C.; Wagner, V.; Jenkin, M. E.; Volkamer, R.; Bloss, W. J.;
Lee, J. D.; Heard, D. E.; Wirtz, K.; Martin-Reviejo, M.; Rea, G.; Wenger,
J. C.; Pilling, M. J. Atmos. Chem. Phys. 2005, 5, 641.
(5) Wagner, V.; Jenkin, M. E.; Saunders, S. M.; Stanton, J.; Wirtz,
K.; Pilling, M. J. Atmos. Chem. Phys. 2003, 3, 89.
(6) Arey, J.; Obermeyer, G.; Aschmann, S. M.; Chattopadhyay, S.;
Cusick, R. D.; Atkinson, R. EnViron. Sci. Technol. 2009, 43, 683.
(7) Noda, J.; Volkamer, R.; Molina, M. J. J. Phys. Chem. A 2009, 113,
9658.
(8) Baltaretu, C. O.; Lichtman, E. I.; Hadler, A. B.; Elrod, M. J. J.
Phys. Chem. A 2009, 113, 221.
(9) Volkamer, R.; Platt, U.; Wirtz, K. J. Phys. Chem. A 2001, 105,
7865.
(10) Moschonas, N.; Danalatos, D.; Glavas, S. Atmos. EnViron. 1999,
33, 111.
(11) Klotz, B.; Sorensen, S.; Barnes, I.; Becker, K. H. J. Phys. Chem.
A 1998, 102, 10289.
(12) Smith, D. F.; McIver, C. D.; Kleindienst, T. E. J. Atmos. Chem.
1998, 30, 209.
(13) Becker, K. H.; Barnes, I.; Bierbach, A.; Brockmann, K. J.; Kirchner,
F. Chemical processes in atmospheric oxidation; Springer-Verlag: Berlin,
Germany, 1997; pp 79-90.
(14) Seuwen, R.; Warneck, P. Int. J. Chem. Kinet. 1996, 28, 315.
(15) Atkinson, R.; Arey, J.; Tuazon, E. C.; Aschmann, S. M.; Bridier,
I. Experimental InVestigation of the Atmospheric Chemistry of Aromatic
Hydrocarbons and Long-Chain Alkanes, (ARB-R-94/550; Order No. PB95
109591); Statewide Air Pollution Res. Cent., California University:
Riverside, CA, 1994.
(16) Atkinson, R.; Aschmann, S. M.; Arey, J.; Carter, W. P. L. Int.
J. Chem. Kinet. 1989, 21, 801.
(17) Dumdei, B. E.; Kenny, D. V.; Shepson, P. B.; Kleindienst, T. E.
EnViron. Sci. Technol. 1988, 22, 383.
The proposed RO2 + HO2 reaction pathway might also be
important in the oxidation of toluene in the atmosphere. For
example, it is well-known that isoprene oxidation chemistry in
the atmosphere is dominated by RO2 + HO2 chemistry under
low NOx conditions, while RO2 + NO chemistry dominates at
high NOx conditions.35 However, since aromatic compounds are
largely anthropogenic in origin, while isoprene is almost
exclusively biogenic in origin, high aromatic concentrations will
be more often accompanied by high NO concentrations, whereas
high isoprene concentrations are often accompanied by low NO
concentrations. Nonetheless, if high enough HO2/NO ratios exist
for certain atmospheric aromatic oxidation conditions, it is
possible that RO2 + HO2 reactions could be important. In order
to determine what HO2/NO ratios are necessary for these
reactions to be important in the atmosphere, it will likely be
necessary to experimentally determine the specific rate constants
for the RO2 + HO2 and RO2 + NO reactions for toluene-derived
bicyclic peroxy radicals.
(18) Tuazon, E. C.; MacLeod, H.; Atkinson, R.; Carter, W. P. L. EnViron.
Sci. Technol. 1986, 20, 383.
(19) Gery, M. W.; Fox, D. L.; Jeffries, H. E.; Stockburger, L.; Weathers,
W. S. Int. J. Chem. Kinet. 1985, 17, 931.
(20) Bandow, H.; Washida, N.; Akimoto, H. Bull. Chem. Soc. Jpn. 1985,
58, 2531.
(21) Shepson, P. B.; Edney, E. O.; Corse, E. W. J. Phys. Chem. 1984,
88, 4122.
(22) Glowacki, D. R.; Wang, L.; Pilling, M. J. J. Phys. Chem. A 2009,
113, 5385.
(23) Bohn, B. J. Phys. Chem. A 2001, 105, 6092.
(24) Jenkin, M. E.; Glowacki, D. R.; Rickard, A. R.; Pilling, M. J. J.
Phys. Chem. A 2009, 113, 8136.
index.jsp (accessed June 2010).
(26) Miller, A. M.; Yeung, L. Y.; Kiep, A. C.; Elrod, M. J. Phys. Chem.
Chem. Phys. 2004, 6, 3402.
(27) Seeley, J. V.; Meads, R. F.; Elrod, M. J.; Molina, M. J. J. Phys.
Chem. 1996, 100, 4026.
(28) Frankcombe, T. J. J. Phys. Chem. A 2008, 112, 1572.
(29) Zhao, J.; Zhang, R.; Misawa, K.; Shibuya, K. J. Photochem.
Photobiol., B 2005, 176, 199.
(30) Berndt, T.; Bo¨ge, O. Phys. Chem. Chem. Phys. 2001, 3, 4946.
(31) Yu, J.; Jeffries, H. E. Atmos. EnViron. 1997, 31, 2281.
(32) Jenkin, M. E.; Hayman, G. D. J. Chem. Soc. Faraday Trans. 1995,
91, 1911.
(33) Hasson, A. S.; Tyndall, G. S.; Orlando, J. J. J. Phys. Chem. A 2004,
108, 5979.
Acknowledgment. This material is based upon work sup-
ported by the National Science Foundation under Grant No.
0753103.
(34) Dillon, T. J.; Crowley, J. N. Atmos. Chem. Phys. 2008, 8, 4877.
(35) Paulot, F.; Crounse, J. D.; Kjaergaard, H. G.; Ku¨rten, A.; St. Clair,
J. M.; Seinfeld, J. H.; Wennberg, P. O. Science 2009, 325, 730.
References and Notes
(1) In The mechanisms of atmospheric oxidation of aromatic hydro-
carbons; Calvert, J. G., Atkinson, R., Becker, K. H., Kamens, R. M.,
JP105467E