The electrochemical reduction of substituted aryldiazonium tetrafluoroborate salts has been studied in acetonitrile and aqueous acetonitrile phosphate buffer (pH 7-7.4) by cyclic voltammetry (platinum, glassy carbon and PGE working electrodes).  Substituent effects have been analyzed using Hammett substituent constants (s and s+).    Consistent with our earlier reported work in aqueous acetonitrile, for aryldiazonium salts with electron withdrawing substituents (nitro and cyano), one-electron quasi reversible waves were observed.  As reported in earlier electrochemical literature, the reproducibility of peak potentials in repetitive scans was influenced by electrode fouling and history of the working electrodes with regard to mechanical abrasion. The pH dependence of the quasi reversible waves implicated the anti-diazotate derived from the diazonium ions in aqueous acetonitrile phosphate buffer.  Spectrophotometric titrations confirmed the rapid formation of the anti-diazotates of the aryldiazonium ions with electron withdrawing substituents.  The role of anion desolvation in dipolar aprotic solvents (acetonitrile and dimethyl sulfoxide) in diazohydroxide/diazotate formation will be discussed.

Substituent effect and the role of diazohydroxide/<i>anti-</i>diazotate in electrochemical reduction of aryldiazonium ions

241st National Meeting (2011)

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Substituent effect and the role of diazohydroxide/anti-diazotate in electrochemical reduction of aryldiazonium ions