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[摘要]：At concentrations higher than 2.10(4) M, and below pH 3, the cyclic voltammograms of picloram (=4-amino-3,5,6-tricholoropyridine-2-carboxylic acid) on Hg electrodes show two prepeak systems (named I and Ii attneding to the proximity to the main reductions peak), which can be attributed to the weak adsorption of reactant and the strong adsorption of the product at the electrode surface. The system Ii is due to the uncharged form of picloram, and system 1 to the picloram protonated at thepyridine N-atom. Small amounts of the surfactant Triton X-100 (=alpha-[4-(1,1,3,3,-tetramethylbutyl)phenyl]-omega-hydroxypoly(pxyethane-1,2-diyl)) cause the disappearacne of system I, the shift of system II, and also affect the intensities and widths od anodic and cathodic peaks but not he charge passed in each perak, Thus, the adsorption process responsible for the appearance of system II os pnly modified but he surfactant, becoming an electrochemical process occurring at the potentials corresponding to system !1, which is nore reversible than the observed in the absence of Triton, The addition of Trition permitted the analysis of the main reduction process, Convolution voltammetry of the main redcution peak is consistent with the loss of a Cl-atom in equilibrium which occurs after a reversible electron transfer and is followes byt he reducitons of both species present in the equilibrium (Scheme 2), This is also the reduction mechanism on a glassy carbon electrode but he electron transfer on the carbon electrode increases with respect to the mercury electrodes; in sddition, the loss of the Cl atom doesnot take place on the electrode surface, From the recording of differential capacity-potential curves, it was concluded that picloram is adsorbed on the carbon electrode; but this adsorption is too weak to induce the appearance of prereak systems. |
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