G. Kokkinidis et al., OXIDATION PATHWAYS OF HYDROXYDOPAMINES AND THEIR CHLORIDE AND BROMIDESALTS - AN ELECTROCHEMICAL STUDY IN ACIDIC SOLUTIONS, Canadian journal of chemistry, 74(9), 1996, pp. 1709-1717
The anodic oxidation of 6-hydroxydopamine and 5-hydroxydopamine and th
eir chloride and bromide salts was studied in aqueous acidic solutions
. The electrodes used were Pt and Pt/M (UPD) (M = Bi, Tl, Pb) modified
surfaces. The electrochemical studies revealed that the first two-ele
ctron oxidation leads to formation of reactive quinoid intermediates.
Reactions of these quinoid intermediates with nucleophiles yield subst
ituted quinones that are not stable in solution. The reactions are ini
tiated by the oxidation of the third hydroxyl group at more positive p
otentials. Cyclic voltammetry and rotating ring-disc electrode voltamm
etry were used to elucidate the reaction mechanisms. These techniques
provide powerful tools to generate and detect transient intermediates
and products and give valuable information regarding the pathways and
mechanisms of the redox reactions.