Crounse, John D. and Paulot, Fabien and Kjaergaard, Henrik G. and Wennberg, Paul O. (2011) Peroxy radical isomerization in the oxidation of isoprene. Physical Chemistry Chemical Physics, 13 (28). ISSN 1463-9076 http://resolver.caltech.edu/CaltechAUTHORS:20110707-082741650
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We report experimental evidence for the formation of C5-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 (ISO∙_2) relative to the rate of reaction of (ISO∙_2) + HO_2 is (k^(295)_(isom))/(k^(295)_((ISO∙_2) + HO_2) = (1.2±0.6) × 10^8 mol cm^(-2), or k^(295)_(isom)≃0.002 s^(-1). The temperature dependence of this rate was determined through experiments conducted at 295, 310 and 318 K and is well described by (k_(isom))T))/(k_((ISO∙_2)+HO_2) (T) = 2.0 × 10^(21) exp(-9000/T)mol cm^(-3). The overall uncertainty in the isomerization rate (relative to k_((ISO∙_2)+HO_2) is estimated to be 50%. Peroxy radicals from the oxidation of the fully deuterated isoprene analog isomerize at a rate of ~15 times slower than non-deuterated isoprene. The fraction of isoprene peroxy radicals reacting by 1,6-H-shift isomerization is estimated to be 8–11% globally, with values up to 20% in tropical regions.
|Additional Information:||© 2011 the Owner Societies. Received 26 Apr 2011, Accepted 08 Jun 2011; First published on the web 24 Jun 2011. We thank N. C. Eddingsaas for the design and construction of the mini-chamber used in this work, M. R. Beaver for assistance with experiments, J. M. St. Clair for instrumental assistance, K. M. Spencer for providing CIMS calibrations of glycolaldehyde and hydroxyacetone, and D. L. Thomsen and H. C. Knap for assistance with theoretical calulations. We thank NASA (NNX08AD29G) and NSF (ATM-0934408) for funding in support of this work. We thank the Danish Council for Independent Research-Natural Sciences and the Danish Center for Scientific Computing (DCSC) for funding. FP acknowledges support from NASA earth and space science fellowship.|
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|Deposited By:||Jason Perez|
|Deposited On:||11 Jul 2011 17:39|
|Last Modified:||26 Dec 2012 13:22|
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