Chemistry of hydrotrioxides. Preparation, characterization, and reactivity of dimethylphenylsilyl hydrotrioxides. hydrogen trioxide (HOOOH), a reactive intermediate in their thermal decomposition?

Article abstract of DOI:10.1021/ja00013a034

The preparation and ¹H, ¹³C, and ²⁹Si NMR spectroscopic characterization of dimethylphenylsilyl hydrotrioxides (2), produced by the low temperature (-78 °C) ozonation of dimethylphenylsilanes (1) in acetone-d₆, methyl acetate, and dimethyl ether is reported. ¹H NMR spectroscopic evidence for the involvement of a transient polyoxide, tentatively assigned to hydrogen trioxide (HOOOH), in the decomposition of 2 is given. All attempts to characterize both types of hydrotrioxides by ¹⁷O NMR spectroscopy failed. The calculated relatively strong binding energy for the intermolecularly hydrogen-bonded cyclic dimer of HOOOH (BE = 7.7 kcal/mol, 6-31G**//6-31G) support the belief that self-association is, similarly to previously studied hydrotrioxides, H₃SiOOOH and CH₃OOOH, the characteristic structural feature of this species. Kinetic and activation parameters for the decomposition of 2, i.e., large negative activation entropies, a rather significant substituent effect on the decomposition of 2a in methyl acetate (Hammett ρ value 1.2 ± 0.1) as well as the observed dependence of the rate of the decomposition of 2a on solvent polarity, indicate the importance of polar decomposition pathways. The results of ESR spin trapping experiments are, together with product studies, discussed in terms of possible contributions of homolytic processes to the overall mechanism of the decomposition of 2. The negative Hammett ρ values for the oxidation of phenyl methyl sulfides to sulfoxides and the latter to the corresponding sulfones with 2 as well as the reactivity order 4-XPhSMe ? 4-XPhSOMe indicate an electrophilic nature of the oxidant.