es403340g_si_001.pdf (332.82 kB)
Rate Constants and Products of the OH Reaction with Isoprene-Derived Epoxides
journal contribution
posted on 2013-11-19, 00:00 authored by Michael
I. Jacobs, Adam I. Darer, Matthew J. ElrodRecent laboratory
and field work has shown that isoprene-derived
epoxides (IEPOX) are crucial intermediates that can explain the existence
of a variety of compounds found in ambient secondary organic aerosol
(SOA). However, IEPOX species are also able to undergo gas phase oxidation,
which competes with the aerosol phase processing of IEPOX. In order
to better quantify the atmospheric fate of IEPOX, the gas phase OH
reaction rate constants and product formation mechanisms have been
determined using a flow tube chemical ionization mass spectrometry
technique. The new OH rate constants are generally larger than previous
estimations and some features of the product mechanism are well predicted
by the Master Chemical Mechanism Version 3.2 (MCM v3.2), while other
features are at odds with MCM v3.2. Using a previously proposed kinetic
model for the quantitative prediction of the atmospheric fate of IEPOX,
it is found that gas phase OH reaction is an even more dominant fate
for chemical processing of IEPOX than previously suggested. The present
results suggest that aerosol phase processing of IEPOX will be competitive
with gas phase OH oxidation only under SOA conditions of high liquid
water content and low pH.
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Master Chemical Mechanism Version 3.2water contentgas phase OH oxidationgas phase OH reactionfield workproduct formation mechanismsgas phase OH reaction rate constantschemical processingaerosol phase processingflow tube chemical ionization mass spectrometry techniquefateOH ReactionOH rate constantsMCM v 3.2.rate Constantsproduct mechanismgas phase oxidationSOA conditionsIEPOX species
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