Sulphines. Part III. Kinetics of oxidation of thiobenzophenones with peroxybenzoic acid

Abstract

The oxidation of thiobenzophenones with peroxybenzoic acid is a two-step reaction, leading first to sulphines and then to the corresponding benzophenones. The first stage of the reaction is much faster than the second, so that the latter does not interfere with the kinetics of the former. A kinetic study of the first stage was carried out. The second-order rate constants measured a t 25" in carbon tetrachloride for a series of thiobenzophenones fit the Hammett equation giving p = -0-88. The reaction rates of thiobenzophenone measured in carbon tetrachloride, methylene chloride, 1,4-dioxan, and ethanol correlate with the data reported for the oxidation of a sulphide and an olefin with the same peracid in the same solvent series. The results suggest that the relevant details of the mechanism of the reaction investigated here, are similar to those of the oxidation of sulphides to sulphoxides. Eteroatorni e loro Applicazioni, Ozzano E. ,

Oxidation of thiones to sulphines (thione S-oxides) with N-sulphonyloxaziridines: synthetic and mechanistic aspects

“…Second-order rate constants were o btained by varying the initial concentration of the reactants by a factor of ca. 5. Rate constants appeared to increase with the electron-releasing ability of the thione substituents (Table 1).…”

Kinetics and Mechanism of the Methyltrioxorhenium-Catalyzed Sulfoxidation of Thioketones and Sulfines

“…Identification and Isolation of the Sulfines. The initially formed sulfines were identified by their UV−vis, 1 H NMR, and mass spectra in comparison with those of the known compounds. ,,,,,− These spectra and those of the starting thiones and final product ketones are given in the Supporting Information. The only exceptions to that are two of the sulfines, which have evidently not been previously reported.…”

“…The oxidation of sulfines to ketones may proceed through a sultine or sulfene intermediate, as written in eq 5, or in some other manner. It had been suggested previously, in the oxidation of sulfines with monoperphthalic acid 8 and perbenzoic acid, that the second oxygen was added to the CS double bond. Theoretical calculations showed that the sultine intermediate so obtained was more stable than its isomer, the sulfene.…”

“…Theoretical calculations showed that the sultine intermediate so obtained was more stable than its isomer, the sulfene. It was further suggested that the sultine would rapidly eliminate the ketone, forming sulfur monoxide. ,,, That sulfur monoxide could disproportionate, and it was the previous basis for suggesting the sultine. The oxidation of SO by peroxorhenium complexes seems more probable in this medium; no elemental sulfur was found in our experiments.…”

“…Sulfines (thioketone S-oxides) are attractive heterocumulenes that participate in the thioepoxidation of alkenes, nucleophilic addition, and cycloaddition reactions. − They are usually prepared by oxidizing the thioketones with peracids, − ozone, , or singlet oxygen . The sulfines can be further oxidized, leading ultimately to the ketone.…”