10.1021/es403340g.s001 Michael I. Jacobs Michael I. Jacobs Adam I. Darer Adam I. Darer Matthew J. Elrod Matthew J. Elrod Rate Constants and Products of the OH Reaction with Isoprene-Derived Epoxides American Chemical Society 2013 Master Chemical Mechanism Version 3.2 water content gas phase OH oxidation gas phase OH reaction field work product formation mechanisms gas phase OH reaction rate constants chemical processing aerosol phase processing flow tube chemical ionization mass spectrometry technique fate OH Reaction OH rate constants MCM v 3.2. rate Constants product mechanism gas phase oxidation SOA conditions IEPOX species 2013-11-19 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Rate_Constants_and_Products_of_the_OH_Reaction_with_Isoprene_Derived_Epoxides/2351941 Recent 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.