Kinetic and mechanistic studies of reactive intermediates in photochemical and transition metal-assisted oxidation, decarboxylation and alkyl transfer reactions

Reactive species like high-valent metal-oxo complexes and carbon and oxygen centered radicals are important intermediates in enzymatic systems, atmospheric chemistry, and industrial processes. Understanding the pathways by which these intermediates form, their relative reactivity, and their fate after reactions is of the utmost importance. Herein are described the mechanistic detail for the generation of several reactive intermediates, synthesis of precursors, characterization of precursors, and methods to direct the chemistry to more desirable outcomes yielding ‘greener’ sources of commodity chemicals and fuels. High-valent Chromium from Hydroperoxido-Chromium(III) The decomposition of pentaaquahydroperoxido chromium(III) ion (hereafter CraqOOH ) in acidic aqueous solutions is kinetically complex and generates mixtures of products (Craq , HCrO4 , H2O2, and O2). The yield of high-valent chromium products (known carcinogens) increased from a few percent at pH 1 to 70 % at pH 5.5 (near biological pH). Yields of H2O2 increased with acid concentration. The reproducibility of the kinetic data was poor, but became simplified in the presence of H2O2 or 2,2′azinobis(3-ethylbenzothiazoline-6-sulfonate) dianion (ABTS). Both are capable of scavenging strongly oxidizing intermediates). The observed rate constants (pH 1, [O2] ≤ 0.03 mM) in the presence of these scavengers are independent of [scavenger] and within the error are the same (kABTS2= (4.9 0.2) × 10 -4 s and kH2O2 = (5.3 0.7) × 10 -4 s); indicating involvement of the scavengers in post-rate determining steps. In the presence