Kinetics and Thermodynamics of Atmospherically Relevant Aqueous Phase Reactions of α-Pinene Oxide
Recent work has demonstrated that isoprene-derived epoxide intermediates are responsible for a wide variety of chemical species found in ambient secondary organic aerosol (SOA). Since the second most abundant biogenic hydrocarbon, α-pinene, is also known to form an epoxide intermediate, nuclear magnetic resonance techniques were used to study products, kinetics, and equilibria of the aqueous phase reactions of that epoxide, α-pinene oxide. The present results indicate that α-pinene oxide will react very quickly with aqueous atmospheric particles, even under low acidity conditions. Depending on the acid concentration of the aqueous solutions, a number of new products are observed from the reaction of α-pinene oxide, some of which are expected to partition back to the gas phase. In contrast to some previous results, no long-lived organosulfate or organonitrate species are observed, and no species which retain the α-pinene bicyclic carbon backbone are observed. Rather, the overall product distribution can be explained by various rearrangements of the initial carbocation intermediate formed in the ring opening of α-pinene oxide, all of which can be rationalized by the thermodynamically driven relief of the bicyclic ring strain in the α-pinene carbon backbone.
Bleier, D.B. and M.J. Elrod. 2013. “Kinetics and Thermodynamics of Atmospherically Relevant Aqueous Phase Reactions of α-Pinene Oxide.” Journal of Physical Chemistry 117(20): 4223-4232.
American Chemical Society
Journal of Physical Chemistry
Chemistry and Biochemistry
Secondary organic aerosol, Isoprene, Epoxides, Photooxidation, Hydrolysis, Organosulfates, Isomerization