M. Wrona, G. Dryhurst
Jan 25, 1990
Citations
2
Influential Citations
47
Citations
Journal
Journal of Electroanalytical Chemistry
Abstract
Abstract The electrochemical oxidation of 5-hydroxytryptamine (5-HT) has been studied at a pyrolytic graphite electrode in aqueous solution at pH 2. The mechanism associated with the first voltammetric oxidation peak I a , of 5-HT has been elucidated based upon electrochemical results and isolation and structural characterization of many products. An initial, reversible one electron abstraction generates a radical cation 5-HT .+ which, in a rate-controlling reaction, generates the neutral radical 5-HT . in which the unpaired electron is located at C(4). This radical is attacked by 5-HT to generate four simple dimers all of which contain at least one 5-HT residue linked at C(4). An unusual C(3)–C(4') linked indolenine-indole dimer can be oxidized further at peak I a , potentials to an indolenine-quinone imine dimer. The latter compound is unstable and decomposes spontaneously to several products, three of which have been structurally characterized including an unusual quinoline-indole dimer. The C(4)-centered indolic radical 5-HT . can be further oxidized to a quinone imine which is rapidly attacked by nucleophiles such as water or Cl − to yield ultimately tryptamine-4,5-dione and 4-chloro-5-hydroxy-tryptamine, respectively.