IRON-MEDIATED HYDROXYLATION OF PHTHALIC HYDRAZIDE

The non-luminescent 2,3-dihydro-1,4-phthalazinedione (phthalic hydrazide) is converted upon hydroxylation of its aromatic ring into a light emitting species.¹ The sequence of reactions leading to the formation of the emitter is rather complex and well studied for 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol), the amino derivative of phthalic hydrazide. It includes the oxidation of the hydrazide moiety to a diazaquinone intermediate, the nucleophilic addition of the anion of hydrogen peroxide to the latter one with the formation of an α-hydroxy-hydroperoxide, its further conversion into an endoperoxide species and finally the repulsion of nitrogen that leads to derivatives of phthalic acid in the excited state.² Previous introduction of electron donating groups into the aromatic ring of non-substituted phthalic hydrazide is necessary to form molecules in the excited state.¹ An additional amino group leads to the well known luminescent derivatives of phthalic hydrazide, luminol and isoluminol. Also a hydroxylation causes luminescent molecules. The hydroxylation of phthalic hydrazide has been used by our group to investigate the hydroxylation of selected carbohydrates by a mixture of ferrous ions and hydrogen peroxide, the Fenton reagent…