Electrochemical behaviour of some industrially important azonaphthol derivatives at glassy carbon electrode

Abstract

Electroreduction of – N = N – and – NO₂ groups of azodyes, 1-(4-nitro phenyl) -azo-2-naphthol (A), 1-(3-nitrophenyl)-azo-2-naphthol (B), 1-(2-nitrophenyl)-azo 2-naphthol (C) has been studied. The azo compound not containing - NO₂ group taken for the study was 1-(2-hydroxyphenyl)-azo-2-naphthol (D). The studies were carried out in partial aqueous media containing organic co-solvents such as acetonitrile, DMF and methanol. The substituent effect on cathodic reduction potentials <i style="">E</i>_pcin case of dyes A, B, C were studied and it was found to be in increasing order i.e. <i style="">E</i>_pc(A) < <i style="">E</i>_pc(B) < <i style="">E</i>_pc(C). During electroreduction of dyes A, B, and C, two separate quasireversible peaks, one for reductive cleavage of – N = N – groups, the other one due to reduction of – NO₂ group into – NH₂ groups were observed. The redox process has been compared with the cyclic voltammetry of the trial compounds, 2-nitroaniline and 4-amino-3-hydroxy naphthalene-1-sulphonic acid. The other data such as effect of <i style="">p</i>H, concentration of active species, supporting electrolyte, scan rate on cathodic reduction peak potential and cathodic peak current has been determined. The process is found to be diffusion controlled.