Resumo

YASIN, Shalaby A.. Electrochemical Studies and Thermodynamic Parameters of Citrazinic Acid Azo Dye and its Nitro Derivatives in DMF-Aqueous Solutions . Port. Electrochim. Acta [online]. 2006, vol.24, n.1, pp.23-36. ISSN 0872-1904.

The electrochemical behavior of citrazinic acid azo dye derivatives (I-V) was recorded in aqueous buffer solutions containing 10% (v/v) DMF using DC-polarography and cyclic voltammetry. The DC-polarograms displayed one or two reduction waves depending on the nature of substituent and the pH of the electrolyte solution. The reduction process takes place irreversibly and diffusion controlled at the electrode surface through the uptake of four electron/molecules for compound I and eight electron/molecules for each of compounds II-V. The recorded cyclic voltammograms displayed two irreversible cathodic peaks at different pH values. The kinetic parameters of the electrode process such as, an, heterogeneous rate constant (k_s) and activation energy (ΔG^#) were evaluated and discussed from cyclic voltammetry. Also, the electrode reaction mechanism is proposed and discussed. The effect of introducing substituents on the half-wave potential of the reduction process is illustrated. The different thermodynamic parameters such as activation energy (ΔG^#), enthalpy change (ΔH^#) and entropy change (ΔS^#) revealed the endergonic nature of the electrode reaction.

Palavras-chave : citrazinic azo dyes; polarography; cyclic voltammetry; thermodynamic parameters.

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