Naslov
Reduction-mechanism of 3-hydroxy-4- hydroxyiminomethyl-5-hydroxymethyl-1, 2- dimethylpyridinium iodide in an acidic medium

Autori
Raspor, Biserka ; Vorkapić-Furač, Jasna ; Berković, Katarina

Izvornik
Journal of electroanalytical chemistry (1992) (1572-6657) 367 (1994), 1/2; 149-155

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
reactant adsorption ; pulse polarography

Sažetak
The reduction mechanism of the selected oxime, 3- hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-1, 2- dimethylpyridinium iodide (HS10), has been studied by normal pulse polarography (NPP) from a Britton- Robinson buffer of pH 2.6, predominantly on a static mercury drop electrode (SMDE). At pH 2.6, 99% of HS10 is present in the undissociated hydrophobic form. The limiting reduction current is diffusion controlled (diffusion coefficient D = 1.5 x 10(-6) cm2/s ; half-wave potential E1/2 = -0.355 V vs. Ag/AgCl/KCl(sat) reference electrode). The NPP wave of HS10 at pH 2.6 has the characteristic features of a reduction complicated by reactant adsorption. The reduction process is totally irreversible ; the average an = 0.975. Considering the uptake of 4e- during the reductive cleavage of the azomethine group (-C=N-) the estimated cathodic transfer coefficient a = 0.234. During the prepulse period t0 the reactant adsorbs at the mercury electrode, following the linear Henry type of isotherm. For 1.01, 4.05 and 8.10 x 10(-5) mol l-1 bulk concentrations of HS10, the surface excesses. GAMMA0 on SMDE at t = t0 are 0.5, 2.1 and 5.8 x 10(-11) mol cm-2 respectively. For the same concentrations of HS10, according to the Henry isotherm the adsorption constant K has been calculated as 4.9, 5.2 and 7.2 x 10(-4) cm, which indicates weak reactant adsorption during the pre-pulse period t0.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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