Electrochemical thermospray mass spectrometry - anodic oxidation of N,N-dialkylanilines

The coupling of an electrochemical cell on-line with a thermospray mass spectrometer can be used for the identification of reaction products. The objective of this study was to demonstrate the performance of electrochemical thermospray mass spectrometry (ETMS). The anodic oxidation of N,N-dialkylanilines in 0.1 M NH4OAc was studied. Structural information on the products were obtained by measurements in D2O-based electrolyte solution. The first step was the oxidation of dialkylaniline to radical cations. Recombination of the radical cations formed benzidine as the chief product. In the main side reaction the radical cations were deprotonated at the C-H acid cc-carbon atom to radicals. A part of these radicals was oxidised at the electrode to immonium ions. By follow up reactions, such as hydrolysis, dealkylation, oxidation and recombination with monomeric radical cations, dimers were formed. Repeating the side reaction, these dimers reacted to give trimers and higher oligomers. A scheme of the different reaction pathways is presented. (C) 1998 Elsevier Science S.A. All rights reserved.