Proton-Catalyzed Decomposition of Multifunctionalized Organic Hydroperoxides Derived from the Reactions of Criegee Intermediates with Ethylene Glycol in Aqueous Organic Media

Abstract

Organic hydroperoxides (ROOHs) are ubiquitous, reactive oxygen species that play central roles in atmospheric, environmental, and biological chemistry. Because atmospheric ROOHs possess not only −OOH but in most cases other functionalities such as −C(═O) and −OH, they are expected to reside in condensed phases such as aerosols, fog and cloud droplets, and wet films of leaves and soils. Here, we report a study of the kinetics of the liquid-phase decomposition of multifunctionalized C12 α-alkoxyalkyl hydroperoxides (α-AHs) that possessed an ether, a carbonyl, a hydroperoxide, and two hydroxy groups. We derived the rate coefficients (k) from single exponential decays of the α-AH signal in water/ethylene glycol solutions acidified by acids found in the atmosphere. Our discovery that the k of the decomposition of the α-AHs increased exponentially from pH 5.1 to 3.9 but independently of the properties of the acid provided firm evidence that the decomposition was catalyzed by H+. The temperature dependence of k and an Arrhenius plot yielded an activation energy (Ea) of 15.0 ± 0.3 kcal mol–1 for the decomposition of C12 α-AHs in solution. The proposed H+-catalyzed decomposition of ROOHs may be a general process that provides H2O2 and multifunctionalized compounds to atmospheric condensed phases that are acidic in nature.