Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Bulletin of the Polish Academy of Sciences. Chemistry

Powiadomienia systemowe

Sesja wygasła!

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Pyridinium dichromate oxidation of some primary and secondary alcohols in nonaqueous medium. A kinetic study

Meenakshisundaram S., Amutha M.

Bulletin of the Polish Academy of Sciences. Chemistry

2001

Vol. 49, No. 2

167-174

The kinetics and mechanism of oxidation of some primary and secondary alcohols with pyridinium dichromate (PDC) catalyzed by p-toluenesulphonic acid (TsOH) has been investigated in acetonitrile medium. The reaction exhibits first-order dependence on [PDC]. Michaelis-Menten dependence is observed on [alcohol]. TsOH enhances the rate of the reaction remarkably. Order dependence on [TsOH] is more than a first-order and less than a second-order. Pyridine retards the rate of oxidation significantly indicating the possibility of a parallel competitive reaction with TsOH. Studies indicate the formation of water even under anhydrous conditions. The kinetic results are analyzed in terms of Taft's original constants (a and Es) and the improved constants (cr* and El). Minor importance of steric effects is well justified by the low values of steric reaction constants.

Mechanistic studies on the oxidation of some organic sulphides with quinolinium fluorochromate in nonaqueous medium

Meenakshisundaram S., Sathiyendiran V.

Bulletin of the Polish Academy of Sciences. Chemistry

1999

Vol. 47, No. 2

167-174

The oxidation kinetics of diphenyl, dialkyl and methyl phenyl sulphides has been investigated under pseudo-first-order conditions with quinolinium fluorochromate (QFC), a newly developed Cr(VI) reagent in acetonitrile medium. p- Toluene sulphonic acid (TsOH) is used for catalyzing the reaction. Initial-rate methods are used for determining the orders with respect to reactants in dialkyl sulphides. The oxidation is first-order with respect to [QFC] and second-order dependence is observed on [TsOH]. [Sulphide] has no effect on the reaction rate. Diphenyl sulphide (DPS) oxidation follows the rate law, v = k2Rrl [S][Ox][TsOH]. Acrylonitrile retards the rate of oxidation significantly in diphenyl sulphides indicating the involvement of free radical cation sulphur intermediate in the rate-limiting step. The Michaelis-Menten dependence each on [sulphide] and [TsOH] can be well explained by a two-pathway mechanism in methyl phenyl sulphide oxidation. The derived rate law, v = k1[Ox][TsOH] -+ k3[OX][S] is consistent with experimental observations.