Electrochemical Oxidation of Caffeic and Ferulic Acid Derivatives in Aprotic Medium

Abstract

O comportamento eletroquímico em função da estrutura de uma série de derivados dos ácidos cafeico e ferúlico, assim como de seus precursores catecol e guaiacol, eletroquimicamente ativos, foi avaliado por voltametria cíclica. Os resultados revelaram que as condições experimentais são a chave para as mudanças no mecanismo de oxidação do guaiacol e ácido ferúlico. A oxidação eletroquímica dos derivados amida do ácido ferúlico revelou que o átomo de nitrogênio desempenha um papel importante na derivatização da superfície do eletrodo. Além disso, a atividade sequestradora de radicais dos compostos, avaliada através da porcentagem de inibição do radical 2,2'-difenil-1-picril-hidrazila, mostrou uma boa correlação com os potenciais de oxidação.We studied the electrochemical behaviour as a function of the structure of a series of caffeic and ferulic acids derivatives as well as their corresponding redox moieties catechol and guaiacol by cyclic voltammetry. Results revealed that the medium is key for changes in the oxidation mechanism of guaiacol and ferulic acid. Electrochemical oxidation of the ferulic acid amide derivatives revealed that the nitrogen atom plays an important role in the derivatization of the electrode surface. In addition, radical scavenging activity of the compounds evaluated through the percentage of inhibition of the 2,2'-diphenyl-1-picrylhidrazyl radical showed a good relationship with the oxidation potentials.

Potent 1,2,4‐Triazole‐3‐thione Radical Scavengers Derived from Phenolic Acids: Synthesis, Electrochemistry, and Theoretical Study

“…Here the peaks at +0.83 V and +1.04 V are influenced by a chemical reaction following the process at +0.66 V. Since the peak at +0.83 V prevails at higher scan rates and rapidly diminishes at lower ones, but behavior of the most positive peak is reversed, it can be concluded that the first two peaks are connected by E−E process, while the first and third peak are chemically coupled. This probably means that at +1.04 V oxidizes a deprotonated form of 4 d as reported for similar compounds . Here also DMF could play a stabilizing role as a proton‐accepting solvent, similarly to DMSO as already described …”

“…This probably means that at +1.04 V oxidizes a deprotonated form of 4 d as reported for similar compounds . Here also DMF could play a stabilizing role as a proton‐accepting solvent, similarly to DMSO as already described …”

“…The acids which served as parent compounds for triazole derivatives behave similarly in DMF as already described in other media (DMSO, AN and EtOH‐H 2 O, pH 7). Basically, all four compounds ( 1 a, 1 d, 1 f and 1 h ) release 2 electrons in one complex peak combined of two partially overlapped peaks.…”

Effect of 1‐ethyl‐3‐methylimidazolium acetate on the oxidation of caffeic acid benzyl ester: An electrochemical and theoretical study

“…Similitudes between the voltammogram of CABE and those reported before, for caffeic acid and for some of its ester and amides derivatives in aprotic media, allow us to infer that the oxidation of CABE follows an electrochemical‐chemical‐electrochemical (ECE) mechanism, which involves the loss of an electron from the catechol moiety, followed by a fast deprotonation reaction and the subsequent loss of a second electron.…”

“…In the case of caffeoyl derivatives, a further deprotonation has been proposed from experimental evidence, as the last step; this is shown in Scheme …”