Role of water in the formation of sulfoxide and sulfone derivatives during the electrochemical oxidation of dibenzothiophene in acetonitrile

Electrochemical oxidation of dibenzothiophene compounds on BDD electrode in acetonitrile–water medium

“…These peaks can be attributed to the formation of sulfone groups (DBTO 2) via oxidation of the corresponding dibenzothiophene sulfoxide (DBTO), as demonstrated below. Note that the formation of DBTO2 around 2.00 V on a glassy carbon electrode in acetonitrile medium and in the presence of water has been previously reported [33].…”

“…The anodic peak that appeared at 1.038-1.150 V within the low potential region, as well as the low maximum anodic current observed in Fig. 3b, curve (c'), suggests the electrochemical oxidation of 4,6-DMDBT by an electrochemicalchemical oxidation mechanism similar those proposed for DBT [33,34], diaryl sulfides [35] and aliphatic sulfides [36]. It means that the direct electrochemical oxidation of 4,6-DMDBT occurred in the potential region corresponding to water stability.…”

“…The high values of the Tafel slopes and the low reaction order possibly arose either from the BDD film deposit onto the porous Nb substrate [38,39] or from a first slow charge transfer step. These values also indicate that the oxidation of these compounds occurred through a multi-stage mechanism, as described previously [33][34][35][36]. The feasible mechanism (direct or indirect oxidation) operating at Ean ˂ 1.50 V or 1.70 ≤ Ean ≤ 2.00 V was explored using chronoamperometric measurements.…”

“…4 start at -0.50 V to better observe the anodic oxidation. No reduction peaks were found during the cathodic scans down to -2.00 V, meaning that the oxidation process was irreversible, probably due to the fast reactions of cation radicals (after abstracting one electron from sulfur) with water molecules present in the reaction medium [33][34][35][36].…”

“…Electrolysis at 2.00 V caused direct electro-oxidation and, in parallel, indirect reaction. A potential of Ean < 1.75 V induced sulfur compound oxidation, as described above, through direct multi-stage electron transfer [33][34][35][36]. To better understand these points, analysis of the extracted products after bulk electrolysis was carried out by FTIR, GC-MS and UPLC-MS.…”