The oxidation to the corresponding sulphoxides of two dialkyl sulphides, Bun-S-Bun and Bun-S-But, and three aryl alkyl sulphides, p-methyl-phenyl sulphide, p-chlorophenyl methyl sulphide and phenyl t-butyl sulphide, with hydrogen peroxide in the presence of catalytic amounts of TiO-(acac)2 has been studied in aqueous ethanol, at 25 °C. Kinetic experiments show that the oxidation rate is first-order in the catalyst and almost zero-order in hydrogen peroxide. This latter feature is interpreted as arising from a large value of the association constant H2O2-Ti(IV) to form a side-bonded peroxotitanium(IV) species. A non-linear dependence of rates on substrate concentration is observed for sulphides which are not sterically hindered, whereas for the two t-butyl derivatives, a kinetic first order is found. This behaviour suggests that non-bulky sulphides coordinate to Ti(IV) in solution. The consenquences of such a process on the efficiency of the oxidizing system are discussed and, in partic...
Metal Catalysis in Oxidation by Peroxides. Part 16. Kinetics and Mechanism of Titanium-Catalyzed Oxidation of Sulphides with Hydrogen Peroxide
BORTOLINI, Olga;
1982
Abstract
The oxidation to the corresponding sulphoxides of two dialkyl sulphides, Bun-S-Bun and Bun-S-But, and three aryl alkyl sulphides, p-methyl-phenyl sulphide, p-chlorophenyl methyl sulphide and phenyl t-butyl sulphide, with hydrogen peroxide in the presence of catalytic amounts of TiO-(acac)2 has been studied in aqueous ethanol, at 25 °C. Kinetic experiments show that the oxidation rate is first-order in the catalyst and almost zero-order in hydrogen peroxide. This latter feature is interpreted as arising from a large value of the association constant H2O2-Ti(IV) to form a side-bonded peroxotitanium(IV) species. A non-linear dependence of rates on substrate concentration is observed for sulphides which are not sterically hindered, whereas for the two t-butyl derivatives, a kinetic first order is found. This behaviour suggests that non-bulky sulphides coordinate to Ti(IV) in solution. The consenquences of such a process on the efficiency of the oxidizing system are discussed and, in partic...I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
