Electrochemical Oxidation of Aliphatic Amines and Their Attachment to Carbon and Metal Surfaces

Abstract

The electrochemical oxidation of aliphatic amines (primary, secondary, and tertiary) has been investigated by cyclic voltammetry and preparative electrolysis. The oxidation mechanisms have been established, and the lifetimes of the radical cations have been measured for secondary and tertiary amines. These results have been put in parallel with the attachment of amines to glassy carbon, Au, and Pt electrodes by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and infrared reflection-absorption spectroscopy (IRRAS). It is then possible to show that it is not the radical cation but the radical obtained after the deprotonation which reacts with the electrode surface. XPS results also point to the existence of a covalent bond between Au or Pt and the organic moiety.

Rapid Screening Method for New Psychoactive Substances of Forensic Interest: Electrochemistry and Analytical Determination of Phenethylamines Derivatives (NBOMe) via Cyclic and Differential Pulse Voltammetry

“…In this case it is likely that peak I is a result of the electrochemical oxidation of the secondary amine present in the NBOMe molecule. Moreover the oxidation potentials observed are similar to those previously described in the literature for other similar compounds containing secondary amines [25][26][27] . The oxidation of the secondary amine (peak I) involves a removal of an electron of the amino-nitrogen atom, leading to the formation of a primary amine which will be attached to the electrode and an aldehyde and likely free primary amine once the latter reached saturation on the SPCE surface ( Figure 1).…”

“…If further scans are performed in the voltammetric analysis a decrease in the amine oxidation peak (I) and a progressive increase in the current corresponding to redox couple (III/IV) can be noticed. This feature has been previously described during electrochemical grafting experiments and constitutes a clear indication of such a reaction 26 . Also, the apparition of a redox couples by interaction of electroactives compounds at high potentials are typical in carbon electrodes 29 .…”

Electrochemical and spectroscopic characterisation of amphetamine-like drugs: Application to the screening of 3,4-methylenedioxymethamphetamine (MDMA) and its synthetic precursors

“…The appearance of a peak at this E p value resulting from the oxidation of aliphatic secondary amines has also been described in the literature for other aliphatic amines [36,37]. Previous published works using compounds structurally related with MDMA also showed the occurrence of an anodic wave that has been undoubtedly attributed to the oxidation of the secondary amine [37][38][39].…”

Covalent modification of graphitic carbon substrates by non-electrochemical methods

“…1.49 to 1.54 V vs SCE [56] and hence electrografting is not posssible at easily oxidised metals. It has been demonstrated [17,23] that the electrooxidation of primary amines yields the radical cation that quickly deprotonates giving a radical with tautomeric forms. XPS spectra of modified metallic electrodes show peaks which can be assigned to metal-nitrogen bonding indicating that covalent attachment occurs through the amine nitrogen atom (Fig.…”

“…The modification of carbon surfaces by this route is a very active field of research and has been reviewed recently [18,19]; aspects pertinent to this review are discussed briefly below. Reduction of iodonium salts leading to grafting of phenyl and alkynyl groups [11,20], and oxidation of primary amines [17,21,22,23,24] and arylacetates [15,25] giving amine and methylene-based radicals respectively, are other approaches to electrografting.…”