Electrochemical studies of certain nitro substituted pyrazolin-5-ones

The polarographic behavior of 1-(Toluenyl sulfonyl)-3-amino-4-(2'-nitro aryl hydrazono)-2-pyrazolin-5-one and 1-(Toluenyl sulfonyl)-3-amino-4-(4'-nitro aryl hydrazono)-2-pyrazolin-5-one is investigated in the acidic as well as in basic media. The compounds gave two well defined, diffusion controlled, irreversible waves in Britton-Robinson buffers of pH range 1.0-7.0. In alkaline medium three well defined, diffusion controlled and irreversible waves were obtained. Effect of various solvents, cations and surfactants on the reduction is presented. The effect of substituent and its correlation with the Hammett substituent constant (δ) is detailed. Based on the results, a detailed reduction mechanism in acidic as well as basic media is proposed.

Adsorption Wave of Vanadium Complex with 2,3–Dihydroxybenzaldehyde

The polarographic behavior of the complex formed by V(V) and 2,3–dihydroxybenzaldehyde (2,3–DHBA) in the solution containing acetate buffer (pH 5,2) has been investigated. By means of a.c. polarography, chronovoltammetry and other techniques, it has been shown that the electrode process is complicated by the adsorption of 2,3-DHBA and its vanadium complex. The kinetic and adsorption parameters of the electrode process have been determined: adsorption equilibrium constant B= 1,32⋅105 mol-1⋅dm3, the attraction constant γ = 1,2, the maximum surface concentration Гmax = 9,10⋅10-11 mol⋅ cm-2; the share of the electrode surface occupied by one particle of the adsorbed complex S = 1,81 nm2 and the free adsorption energy ΔG = - 39,1 kJ· mol-1.