Direct Evidence for Base-Mediated Decomposition of Alkyl Hydroperoxides (ROOH) in the Gas Phase

The reaction of F- with CH3OOH has been studied in the gas phase using a tandem flowing afterglow-selected ion flow tube apparatus. The reaction is rapid (k = 1.23 × 10-9 cm3 s-1, 49% efficiency), and formation of HO- + CH2O + HF is the major reaction channel observed (85%). Isotopic labeling, reactions of F- with larger alkyl hydroperoxides, and computational studies demonstrate that the major product ion, HO-, is formed via a concerted elimination mechanism that appears to be general to all alkyl hydroperoxides possessing an α-hydrogen. This mechanism represents a base-mediated decomposition of alkyl hydroperoxides in the gas phase that may have important implications for solution and biochemical reactions. The reverse reaction, CH3OO- + HF is also efficient (k = 2.43 × 10-9 cm3 s-1). The major product ensemble HO- + CH2O + HF (81%) is identical to that of the forward reaction, and represents a novel neutral-catalyzed decomposition of the anion.