Résumé
Oxidation of caffeic acid (3,4-dihydroxycinnamic acid)
1H
3
has been studied by electrochemical methods and by pulse radiolysis in aqueous and organic solvents. The results have been compared with the behaviour of 4-coumaric acid
2H
2
and ferulic acid
3H
2
. The first oxidative intermediates have been characterised by their UV spectra and oxidation potentials. In the case of
2H
2
and
3H
2
, the initial radicals decay by a second order process indicating a radical-radical coupling mechanism. On the contrary, for caffeic acid the oxidation leads to the formation of the corresponding
o-quinone through disproportionation of the initial semiquinone radical.