Evidence for HOOO Radicals in the Formation of Alkyl Hydrotrioxides (ROOOH) and Hydrogen Trioxide (HOOOH) in the Ozonation of C−H Bonds in Hydrocarbons¹

Abstract

Low-temperature ozonation of cumene (1a) in acetone, methyl acetate, and tert-butyl methyl ether at -70 degrees C produced the corresponding hydrotrioxide, C(6)H(5)C(CH(3))(2)OOOH (2a), along with hydrogen trioxide, HOOOH. Ozonation of triphenylmethane (1b), however, produced only triphenylmethyl hydrotrioxide, (C(6)H(5))(3)COOOH (2b). These observations, together with the previously reported experimental evidence, seem to support the "radical" mechanism for the first step of the ozonation of the C-H bonds in hydrocarbons, i.e., the formation of the caged radical pair (R(**)OOOH), which allows both (a) collapse of the radical pair to ROOOH and (b) the abstraction of the hydrogen atom from alkyl radical R(*) by HOOO(*) to form HOOOH. The B3LYP/6-311++G(d,p) (ZPE) calculations revealed that HOOO radicals are considerably stabilized by forming intermolecularly hydrogen-bonded complexes with acetone (BE = 8.55 kcal/mol) and dimethyl ether (7.04 kcal/mol). This type of interaction appears to be crucial for the relatively fast reactions (and the formation of the polyoxides in relatively high yields) in these solvents, as compared to the ozonations run in nonbasic solvents. However, HOOO radicals appear to be not stable enough to abstract hydrogen atoms outside the solvent cage, as indicated by the absence of HOOOH among the products in the ozonolysis of triphenylmethane. The decomposition of alkyl hydrotrioxides 2a and 2b involves a homolytic cleavage of the RO-OOH bond with subsequent "in cage" reactions of the corresponding radicals, while the decomposition of HOOOH is most likely predominantly a "pericyclic" process involving one or more molecules of water acting as a bifunctional catalyst to produce water and singlet oxygen (Delta(1)O(2)).

Existence of a New Reactive Intermediate Oxygen Species in Hypoxanthine and Xanthine Oxidase Reaction

“…12) As a case of biological system, it has been reported that all antibodies are capable of catalyzing the oxidation of water by singlet oxygen ( 1 O 2 ) to generate H 2 O 2 and probably O 3 . The authors postulated that these antibodies carried the reaction through H 2 O 3 (HOOOH) as a key intermediate in the following way.…”

Dispersed-phase Interfaces between Mist Water Particles and Oxygen Plasma Efficiently Produce Singlet Oxygen (¹O₂) and Hydroxyl Radical (•OH)

“…10 The •OH may form a variable intermediate in this complex system; however we suggest that reaction (5) may occur because of efficient ROS production. The hydroxyl radical is probably recycled in these reactions.…”

Theoretical study on the atmospheric transformation mechanism of pirimiphos-methyl initiated by O3

“…Generally, after H abstraction by O 3 , the Å OOOH radical will either recombine with R Å to form ROOOH or decompose into the Å OH radical and singlet oxygen (Timerghazin et al, 1999;Cerkovnik et al, 2002;Tuttle et al, 2004). In this study, addition of an Å OH radical onto the intermediate (IM1) will result in the formation of hydroxylation product P1, an a-amino alcohol.…”

“…Studies have shown that ozonation of the CH bond in saturated hydrocarbons initiates with H abstraction by O 3 , followed by the formation of an R Å Å OOOH radical pair (Cerkovnik et al, 2002;Yang et al, 2008;Voukides et al, 2009). Within the structure of PMM, seven different kinds of hydrogen can be abstracted by O 3 , as shown in Fig.…”