title: Radiolytic degradation of gallic acid and its derivatives in aqueous solution.
abstract: Polyphenols, like gallic acid (GA) released in the environment in larger amount, by inducing some unwanted oxidations, may constitute environmental hazard: their concentration in wastewater should be controlled. Radiolytic degradation of GA was investigated by pulse radiolysis and final product techniques in dilute aqueous solution. Subsidiary measurements were made with 3,4,5-trimethoxybenzoic acid (TMBA) and 3,4,5-trihydroxy methylbenzoate (MGA). The hydroxyl radical and hydrogen atom intermediates of water radiolysis react with the solute molecules yielding cyclohexadienyl radicals. The radicals formed in GA and MGA solutions in acid/base catalyzed water elimination decay to phenoxyl radicals. This reaction is not observed in TMBA solution. The hydrated electron intermediate of water decomposition adds to the carbonyl oxygen, the anion thus formed protonates on the ring forming cyclohexadienyl radical or on the carbonyl group forming carbonyl centred radical. The GA intermediates formed during reaction with primary water radicals in presence of oxygen transform to non-aromatic molecules, e.g., to aliphatic carboxylic acids.
authors.affiliation: Instituto Tecnologico e Nuclear, UCQR, Estrada Nacional No 10, Apartado 21, 2686-953 Sacavém, Portugal.
authors.forename: R
authors.initials: R
authors.lastname: Melo
authors.forename: J P
authors.initials: JP
authors.lastname: Leal
authors.forename: E
authors.initials: E
authors.lastname: Takács
authors.forename: L
authors.initials: L
authors.lastname: Wojnárovits
mesh_terms: D005419:Flavonoids; D005609:Free Radicals / Q000737:chemistry; D005707:Gallic Acid / Q000737:chemistry / Q000528:radiation effects*; D015386:Hazardous Substances; D007220:Industrial Waste / Q000517:prevention & control; D010636:Phenols; D059808:Polyphenols; D011675:Pulse Radiolysis / Q000379:methods*; D012996:Solutions; D014867:Water; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000528:radiation effects
chemical_list: D005419:Flavonoids; D005609:Free Radicals; D015386:Hazardous Substances; D007220:Industrial Waste; D010636:Phenols; D059808:Polyphenols; D012996:Solutions; D014874:Water Pollutants, Chemical; D014867:Water; D005707:Gallic Acid