Kinetics of hemolytic dehydrogenation by chloranil

1-Phenylsemicarbazide is dehydrogenated to phenylazoformamide by chloranil in dioxane medium. The reaction obeys second order rate laws [first order with respect to each reactant]. Unlike the dehydrogenation in alcohol and alcohol water media, no semiquinone radical anion was observed during the progress of the reaction. Furthermore, the positive entropy of activation [delta S[number sign] = 7.0 + 0.5 J.K[-1]. Mol[-1]] suggests that the dehydrogenation proceeds by a homolytic mechanism in which abstraction of hydrogen atom by chloranil gave tetrachloroquinol radical in a slow step, followed by a fast abstraction of hydrogen atom

Kinetics and mechanism of the oxidation of 1-phenylsemicarbazide by hexacyanoferrate [III] ion in aqueous acid solution

Kinetics of the oxidation of 1-phenylsemicarbazide by hexacyanoferrate [III] ions has been investigated by stopped-flow technique as a function of reactants concentrations, temperature, ionic strength and pH. The redox reaction is first order with respect to hexacyanoferrate [III]. The depence of K[obs] on phenylsemicarbazide concentration [C[PSC]] is given by K[obs]=Y+XC[PSC] where Y is constant and X depends on hydrogen ion concentration. A detailed mechanism was proposed to explain these results. It was concluded that Fe [CN] 3-/6 and HFe [CN] 2-/6 are the reactive oxidizing species

Kinetics and thermodynamic consequences of oxidation of mandelic acid by potassium bromate

The rate of oxidation of mandelic acid by potassium bromate in acetic acid-water medium was followed iodometrically under pseudo first orderconditions. The stoichiometry of the reaction was found to be 1:1; while the dependence of the rate of the reaction on the mandelic acid concentration is not a simple one. The effect of acidity on the rate of oxidation has been investigated in the light of the behaviour of the sulphuric acid in acetic acid-water medium. The effect of temperature on the reaction rate have been studied within the range 318-333 K for different acidities and solvent compositions. The thermodynamic properties of the activated complex, delta G[*], delta H[*] and delta S were computed and an extrathermodynamic analysis of the rate of the reaction was investigated according to the isokinetic relationship. A suitable reaction mechanisim was proposed