The oxidation mechanism of tetrabutylammonium carboxylates RCOO^- involves the formation of radicals R^• and carbocations R⁺, whose reactivity towards carbon surfaces allow the covalent grafting of the surface [1]. Experimental results have shown that the presence of the unsaturated terminal groups in the carboxylate structure are a determining factor for the covalent modification [2]. However, the role of these unsaturated groups in the mechanism is unknown. Therefore, in this work the study the oxidation of some carboxylates in presence of molecules with unsaturated groups (naphthalene and hexyne) was done. The results showed the intervention of a redox reaction between the carbocations R⁺ got from the carboxylate oxidation and the unsaturated molecule. This reaction regenerates the radical R^• and allows the covalent modification. When naphthalene was used as additive, this molecule was also attached to the carbon surface. This observation arises from the fact that the oxidation response for the naphthalene groups attached to the surface was observed, confirming the electron transfer between the unsaturated group and the carbocatión R⁺. On the other hand, in the case of the hexyne, the solvent effect in the mechanism was studied, showing an association product between acetonitrile and hexyne. This fact helps to understand the specie that interacts with the carbocation in the redox reaction. These results give new insights about the covalent modification by carboxylate oxidation.

[1] C.P. Andrieux, F. Gonzalez, J.M. Savéant., J. Am. Chem. Soc., 119, 1997, 4292.

[2] D. M. Hernández-Morales, F. J. González., Electrochem. Comm., 46, 2014, 48.