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Peroxy radical isomerization in the oxidation of isoprene

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 (30). pp. 13607-13613. ISSN 1463-9076.

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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.

Item Type:Article
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URLURL TypeDescription
Crounse, John D.0000-0001-5443-729X
Paulot, Fabien0000-0001-7534-4922
Kjaergaard, Henrik G.0000-0002-7275-8297
Wennberg, Paul O.0000-0002-6126-3854
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.
Funding AgencyGrant Number
Danish Council for Independent Research-Natural SciencesUNSPECIFIED
Danish Center for Scientific Computing (DCSC)UNSPECIFIED
NASA Earth and Space Science FellowshipUNSPECIFIED
Issue or Number:30
Record Number:CaltechAUTHORS:20110707-082741650
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:24329
Deposited By: Jason Perez
Deposited On:11 Jul 2011 17:39
Last Modified:09 Mar 2020 13:19

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