Kinetics and mechanism of the oxidation of organic sulphides by 2,2′-bipyridinium chlorochromate

Abstract

The oxidation of 34 organic sulphides by 2,2′-bipyridinium chlorochromate (BPCC) resulted in the formation of the corresponding sulphoxides. The reaction is first order with respect to both BPCC and the sulphide, and is catalysed by hydrogen ions. The hydrogen-ion dependence has the form: k obs = a + b [H + ]. The oxidation was studied in 19 different organic solvents. An analysis of the solvent effect by Swain's equation showed that the both cation-and anion-solvating powers of the solvents play important roles. The rates of oxidation meta-and p-substituted phenyl methyl sulphides were correlated with Charton's LDR equation. The rates of the o-compounds showed excellent correlation with the LDRS equation. Oxidation of the p-compounds is more susceptible to the delocalization effect. Oxidation of the mcompounds exhibited a greater dependence on the field effect. In the oxidation of the o-compounds, the contribution of delocalized effect is slightly more than that of the field effect. The oxidation of alkyl phenyl sulphides is subject to both polar and steric effects of the alkyl groups. Polar reaction constants are negative, indicating an electron-deficient sulphur centre in the rate-determining step. A mechanism involving formation of a sulphurane intermediate in the slow step has been proposed.

Oxidation of some α‐hydroxy acids by tetraethylammonium chlorochromate: A kinetic and mechanistic study

“…There seems to be no report on the oxidation aspects using TEACC. We have been interested in the kinetic and mechanistic aspects of the oxidation by complexed Cr(VI) species, and several studies on halochromates have already been reported [9][10][11][12]. In continuation of our earlier work, we now report the kinetics of oxidation of some hydroxy acids by TEACC in DMSO as solvent.…”

“…The formation of a protonated Cr(VI) species has earlier been postulated in the reactions of structurally similar 2,2-bipyridinium chlorochromate [9] and morpholinium chlorochromate [12].…”

“…The data on the solvent effect were analyzed in terms of Swain and coworkers' equation [19] of cationand anion-solvating concept of the solvents also (9).…”

Kinetics and Mechanism of Oxidation of Aliphatic Secondary Alcohols by Benzimidazolium Fluorochromate in Dimethyl Sulphoxide Solvent

“…Both β and α played relatively minor roles 29 . Solvent effect data were analyzed in relation to Swain's equation 35 (10), which included the cation and anion solvating 36,37 conception of the solvent. log k 2 = aA + bB + cC (10) Where A denotes the anion-solvating power of the solvent and B denotes the cation-solvating power, C denotes the intercept term and (A+B) indicates the polarity of solvent 33 .…”

“…The rate was determined in different solvents in terms of eqn. (10), by using A and B and separately with (A + B) 36,37 . The rate of oxidation of 2-propanol and other secondary alcohols in different solvents 16 showed excellent correlativity in terms of Swain's equation 35 (cf.…”