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Developments in the mechanism of photodegradation of triazine‐based pesticides
Author(s) -
Canle L. M.,
Fernández M. I.,
Santaballa J. A.
Publication year - 2005
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.874
Subject(s) - chemistry , photodegradation , photochemistry , radiolysis , flash photolysis , adduct , triazine , singlet state , radical , excited state , radical ion , reaction rate constant , solvated electron , reaction mechanism , triplet state , photocatalysis , kinetics , catalysis , ion , organic chemistry , molecule , physics , quantum mechanics , nuclear physics
Developments in the mechanisms of the direct, photosensitized and photocatalyzed photodegradation and of photochemically generated hydroxyl radical‐based degradation of triazine‐based pesticides are reviewed. Recent results are accounted for: steady‐state irradiation photoproducts suggest the participation of both singlet and triplet excited states in the direct photodegradation of triazines, their concurrency being confirmed by luminescence studies. Both low‐lying excited states have been theoretically characterized. Laser flash photolysis and pulse radiolysis studies evidence the participation of short‐lived radical cations and radical anions, in addition to HO . adducts, in the mechanism of photodegradation. E ° values were estimated for both the triazine ( ca. ∼1.1 V vs NHE) and triazinyl radical cation (2.3 ± 0.1 V vs NHE) and also the p K a for the HO . adduct of triazines ( ca. ∼11). Sub‐diffusion control rate constants were measured for the one‐electron oxidation of triazines by SO and (UO 2 2+ )*, one‐electron reduction by e − aqand HO . addition. Copyright © 2004 John Wiley & Sons, Ltd.