Abstract View
Reaction Products and Pathways of Alkoxy Radicals in the Condensed Phase
VICTORIA BARBER, Yaowei Li, Alexander Zaytsev, Francesca Majluf, Jordan Krechmer, Frank Keutsch, Jesse Kroll, MIT
Abstract Number: 366
Working Group: Aerosol Chemistry
Abstract
Condensed phase processes, such as aerosol oxidation aging and aqueous-phase oxidation, are critical in understanding the composition and properties of atmospheric aerosol. Organic radicals including alkoxy (RO) and peroxy (RO2) radicals are key intermediates in these processes. Because most mechanistic studies of organic radical reactions take place in the gas phase, the underlying radical chemistry that governs these condensed phase processes is comparatively poorly understood. The condensed phase represents a much more complex environment, because locally high concentrations may facilitate additional reactions between organic species, and solvent effects may alter relevant potential energy surfaces. Here, we investigate the condensed-phase chemistry of a photolytically-generated RO radical, which allows for the selection of a specific RO radical isomer, greatly simplifying the subsequent chemistry as compared to oxidation via traditional routes. We generate the 1-pentanoxy radical via photolysis of a 1-pentyl nitrite precursor in hexafluorobenzene. The photolyzed reaction mixture is fed at a constant, low flow rate into an atomizer and nebulized directly into a suite of mass spectrometric instruments, providing real-time chemical kinetics information as well as molecular-formula level identification of the reaction products. Consistent with previous work, the results suggest that the nascent RO radical undergoes only unimolecular reaction, independent of the concentration of the RO radical precursor, and even in the presence of a high concentration of a reaction partner with abstractable H-atoms. This unimolecular reaction produces an alcohol-substituted peroxy radical, with a variety of available product channels, including one that involves successive intramolecular H-atom transfer of RO2 radicals, leading to highly oxidized products. The kinetics and branching ratios associated with these product channels are investigated, and compared to recent gas-phase results for similar systems, providing insight into the effects of the solution-phase environment on organic radical chemistry.