Mechanistic Study of Electrochemical Oxidation of 4-Morpholinoaniline in Aqueous Solution: Experimental and Theoretical Studies

Electrochemical oxidation of 4-morpholinoaniline (4-MA) has been studied at various conditions using cyclic voltammetry and controlled potential coulometry. Also theoretical study of the electrochemical oxidation of 4-MA (1) was performed using DFT (B3LYP) level of theory and 6-311+ G(p, d) basis set. The results indicate that the electrochemically generated p-quinonediimine (1ox(+) and 1Hox(2+)) is unstable and participates in different types of reactions. Instability of the produced p-quinonediimine depends on its structure and pH of solution. In strong acidic pHs the produced 1Hox(2+) is hydrolyzed, but in the intermediate pHs the produced 1ox(+) reacts with 4-MA and converts to 4-morpholinoaniline-trimer. Also electrochemical oxidation of 4-MA in the presence of p-toluenesulfinic acid was studied in viewpoint of the thermodynamic. In the current paper thermodynamic investigation and mechanistic study of the electrochemical oxidation of 4-MA at various conditions indicates that the mechanisms proceed in the thermodynamically favored directions. Using Natural Bond Orbital (NBO) analyses the effect of the charge of reaction site (C-1) and N-1=C-1 bond order (Wiberg bond indexes) on the hydrolysis rate were studied. (C) 2016 The Electrochemical Society. All rights reserved.