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Auteur Claire Richard |
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Affiner la recherche Interroger des sources externesPhototransformation de l’acide 5-chlorosalicylique en solution aqueuse et sur cuticule foliaire simulee. / Radia Tafer
Titre : Phototransformation de l’acide 5-chlorosalicylique en solution aqueuse et sur cuticule foliaire simulee. Type de document : texte imprimé Auteurs : Radia Tafer, Auteur ; Abdelaziz Boulkamh, Directeur de thèse ; Claire Richard, Directeur de thèse Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2019 Importance : 201 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles
Langues : Français (fre) Catégories : Français - Anglais
ChimieTags : Chimie: chimie analytique, physique et environnement Phototransformation acide 5-chlorosalicylique éliciteur triplet radicaux hydroxyle 5-chlorosalicylic acid elicitor hydroxyl radicals تحول ضوئي حمض -5كلورو ساليسيليك محفز الدفاع الذاتي للنبات الفئة الثلاثية جذور الهيدروكسيل Index. décimale : 540 Chimie et sciences connexes Résumé :
The photochemical reactivity of 5-chlorosalicylic acid (Cl-C6H3-OH,COOH; 5-ClSA), an elicitor of natural plant defense mechanisms, was examined under different experimental conditions. In neutral aqueous solution and under the action of a simulated solar irradiation (suntest), the monoanionic form (5-ClSA‒) is phototransformed relatively quickly, dechlorination being the predominant primary step. This leads mainly to the respective conjugated bases of 2,5- dihydroxybenzoic acid (DHBA, P3), by photohydrolysis, and 2-carboxy-3-hydroxy-1,4- benzoquinone (P1), by photooxidation. A hydroxylation compound of 5-ClSA‒ (5ClSA-OH) and several dimeric compounds are also formed, but in smaller proportions. The phototransformation of DHBA, experimented separately, leads to the formation of dihydroxycyclopentadiene acid, through a very exceptional ring-contraction reaction. By fusion with P1, DHBA generates a polysubstituted biphenyl and by molecular association with the same P1, a quinhydrone-like complex, via an intermolecular charge transfer, a phenomenon that is just as rarely observed as the contraction of the cycle. About 40 photoproducts, comprising from 19 to 01 C atoms (formaldehyde), diversely oxygenated, comprising aromatic, aliphatic, polycyclic, monocyclic or acyclic compounds, in trace or ultra-trace concentrations, have been identified, revealing the nature of the detectable successive photoproducts, up to quasi-mineralization. The latter was confirmed by measuring the residual content of Total Organic Carbon. The production and involvement of hydroxy radicals (OH•), produced by ""light-induced secondary OH precursors "", in the mineralization of 5-ClSA, has been experimentally proven. The mechanism of photolysis of 5-ClSA, established through the identification of its photoproducts, has been refined by the identification of transient species, at the top of which is the triplet of 5-ClSA, a fleeting species holding nevertheless a central role. The solvated electron, the 2-carboxy-4-chlorophenoxyl radical and the carbene ""4-oxocyclohexa-2,5- dienylidene"" complete the picture. Singlet oxygen (1O2), the corollary of the triplet, was evidenced by phosphorescence. On a leaf model, 5-ClSA, without additives, resists to phototransformation. The presence of a surfactant, added in commercial formulations, considerably accelerates the phototransformation, while orienting it towards reduction. Salicylic acid (SA), the only photoproduct that accumulates, is also a mediator in the response of plants to pathogens.Note de contenu :
Annexes.Diplôme : Doctorat en sciences En ligne : ../theses/chimie/TAF7533.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=11372 Phototransformation de l’acide 5-chlorosalicylique en solution aqueuse et sur cuticule foliaire simulee. [texte imprimé] / Radia Tafer, Auteur ; Abdelaziz Boulkamh, Directeur de thèse ; Claire Richard, Directeur de thèse . - جامعة الإخوة منتوري قسنطينة, 2019 . - 201 f. ; 30 cm.
2 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
ChimieTags : Chimie: chimie analytique, physique et environnement Phototransformation acide 5-chlorosalicylique éliciteur triplet radicaux hydroxyle 5-chlorosalicylic acid elicitor hydroxyl radicals تحول ضوئي حمض -5كلورو ساليسيليك محفز الدفاع الذاتي للنبات الفئة الثلاثية جذور الهيدروكسيل Index. décimale : 540 Chimie et sciences connexes Résumé :
The photochemical reactivity of 5-chlorosalicylic acid (Cl-C6H3-OH,COOH; 5-ClSA), an elicitor of natural plant defense mechanisms, was examined under different experimental conditions. In neutral aqueous solution and under the action of a simulated solar irradiation (suntest), the monoanionic form (5-ClSA‒) is phototransformed relatively quickly, dechlorination being the predominant primary step. This leads mainly to the respective conjugated bases of 2,5- dihydroxybenzoic acid (DHBA, P3), by photohydrolysis, and 2-carboxy-3-hydroxy-1,4- benzoquinone (P1), by photooxidation. A hydroxylation compound of 5-ClSA‒ (5ClSA-OH) and several dimeric compounds are also formed, but in smaller proportions. The phototransformation of DHBA, experimented separately, leads to the formation of dihydroxycyclopentadiene acid, through a very exceptional ring-contraction reaction. By fusion with P1, DHBA generates a polysubstituted biphenyl and by molecular association with the same P1, a quinhydrone-like complex, via an intermolecular charge transfer, a phenomenon that is just as rarely observed as the contraction of the cycle. About 40 photoproducts, comprising from 19 to 01 C atoms (formaldehyde), diversely oxygenated, comprising aromatic, aliphatic, polycyclic, monocyclic or acyclic compounds, in trace or ultra-trace concentrations, have been identified, revealing the nature of the detectable successive photoproducts, up to quasi-mineralization. The latter was confirmed by measuring the residual content of Total Organic Carbon. The production and involvement of hydroxy radicals (OH•), produced by ""light-induced secondary OH precursors "", in the mineralization of 5-ClSA, has been experimentally proven. The mechanism of photolysis of 5-ClSA, established through the identification of its photoproducts, has been refined by the identification of transient species, at the top of which is the triplet of 5-ClSA, a fleeting species holding nevertheless a central role. The solvated electron, the 2-carboxy-4-chlorophenoxyl radical and the carbene ""4-oxocyclohexa-2,5- dienylidene"" complete the picture. Singlet oxygen (1O2), the corollary of the triplet, was evidenced by phosphorescence. On a leaf model, 5-ClSA, without additives, resists to phototransformation. The presence of a surfactant, added in commercial formulations, considerably accelerates the phototransformation, while orienting it towards reduction. Salicylic acid (SA), the only photoproduct that accumulates, is also a mediator in the response of plants to pathogens.Note de contenu :
Annexes.Diplôme : Doctorat en sciences En ligne : ../theses/chimie/TAF7533.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=11372 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité TAF/7533 TAF/7533 Thèse Bibliothèque principale Thèses Disponible
Titre : Phototransformation d'un fongicide foliaire, le chlorothalonil, dans un solvant mixte eau/acétonitrile. Type de document : texte imprimé Auteurs : Samira Bouchama, Auteur ; Abdelaziz Boulkamh, Directeur de thèse ; Claire Richard, Directeur de thèse Mention d'édition : 17 Avril 2019 Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2019 Importance : 135 f. Format : 30 cm. Note générale : 1 copies imprimées disponibles
Langues : Français (fre) Catégories : Français - Anglais
ChimieTags : Chimie: Chimie analytique et physique chlorothalonil aqueux photoproduits espèces transitoires oxygène singulet mécanisme réactionnel aqueous photoproducts transient species singlet oxygen reaction mechanism كلوروثالونيل مائي منتجات ضوئية الأنواع العابرة الأوكسجين الأحادي آلية التفاعل Index. décimale : 540 Chimie et sciences connexes Résumé :
Chlorothalonil (CT ; 1,3-dicyano-2,4,5,6-tetrachlorobenzene), a broad-use fungicide, is likely to reach water supplies and contaminate them. Its phototransformation in water, assisted by acetonitrile (ACN) as a co-solvent, was studied under concentration and irradiation conditions close to those prevailing in the environment. It appears that direct photolysis is slow, but accelerated by photoproducts of CT or acetonitrile. The dissolved molecular oxygen acts strongly on the reaction rate, its suppression accelerating the reaction by a factor of 110. Four major photoproducts were identified. Their distribution varies considerably with the concentration of oxygen. In the water-rich medium, the major product is trichloro-1,3- dicyanobenzene (HCT, obtained by substitution of Cl by H). The formation of 4-OHCT (substitution of Cl at position 4 by OH) and CTOOH (removal of Cl, gain of OOH) is substantially favoured by enrichment of the medium with ACN and, in parallel, with O2. Conversely, the deoxygenation of the medium completely cancels the formation of these two products, in favour of CTH and a positional isomer of 4-OHCT, which quantum calculations assign to 2-OHCT. Whatever the conditions prevailing in the reaction medium, dechlorination, with the formation of HCl, is the privileged reaction pathway for degradation of CT and its photoproducts. Transient spectroscopy demonstrated the formation and participation of the triplet excited state of CT (3CT*) and the CTH• radical, derived from the triplet by addition of H, in the CT transformation. The kinetic and spectral characteristics of the triplet were evaluated, as well as the quantum efficiency of the intersystem crossing (ISC). The formation of singlet oxygen (1O2) was established by phosphorescence measurements. The quantum yield of 1O2 production varies from 0.85 (in 100% ACN) to 0.69 (in 30% ACN). In air saturated solutions, the triplet fraction that is trapped by oxygen ranged from 0.88 in pure ACN
to 0.48 in water-acetonitrile (95:5, % v/v). In agreement with the various results, a phototransformation mechanism is proposed. In surface water, one may expect that the disappearance of chlorothalonil will be promoted mainly by the organic compounds that this water contains and that are able of reducing the triplet. Chlorothalonil, in turn, generates high amounts of singlet oxygen, a species that is able of efficiently oxidizing a large number of pollutants in surface water.
Note de contenu :
Annexes.Diplôme : Doctorat en sciences En ligne : ../theses/chimie/BOU7651.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=11485 Phototransformation d'un fongicide foliaire, le chlorothalonil, dans un solvant mixte eau/acétonitrile. [texte imprimé] / Samira Bouchama, Auteur ; Abdelaziz Boulkamh, Directeur de thèse ; Claire Richard, Directeur de thèse . - 17 Avril 2019 . - جامعة الإخوة منتوري قسنطينة, 2019 . - 135 f. ; 30 cm.
1 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
ChimieTags : Chimie: Chimie analytique et physique chlorothalonil aqueux photoproduits espèces transitoires oxygène singulet mécanisme réactionnel aqueous photoproducts transient species singlet oxygen reaction mechanism كلوروثالونيل مائي منتجات ضوئية الأنواع العابرة الأوكسجين الأحادي آلية التفاعل Index. décimale : 540 Chimie et sciences connexes Résumé :
Chlorothalonil (CT ; 1,3-dicyano-2,4,5,6-tetrachlorobenzene), a broad-use fungicide, is likely to reach water supplies and contaminate them. Its phototransformation in water, assisted by acetonitrile (ACN) as a co-solvent, was studied under concentration and irradiation conditions close to those prevailing in the environment. It appears that direct photolysis is slow, but accelerated by photoproducts of CT or acetonitrile. The dissolved molecular oxygen acts strongly on the reaction rate, its suppression accelerating the reaction by a factor of 110. Four major photoproducts were identified. Their distribution varies considerably with the concentration of oxygen. In the water-rich medium, the major product is trichloro-1,3- dicyanobenzene (HCT, obtained by substitution of Cl by H). The formation of 4-OHCT (substitution of Cl at position 4 by OH) and CTOOH (removal of Cl, gain of OOH) is substantially favoured by enrichment of the medium with ACN and, in parallel, with O2. Conversely, the deoxygenation of the medium completely cancels the formation of these two products, in favour of CTH and a positional isomer of 4-OHCT, which quantum calculations assign to 2-OHCT. Whatever the conditions prevailing in the reaction medium, dechlorination, with the formation of HCl, is the privileged reaction pathway for degradation of CT and its photoproducts. Transient spectroscopy demonstrated the formation and participation of the triplet excited state of CT (3CT*) and the CTH• radical, derived from the triplet by addition of H, in the CT transformation. The kinetic and spectral characteristics of the triplet were evaluated, as well as the quantum efficiency of the intersystem crossing (ISC). The formation of singlet oxygen (1O2) was established by phosphorescence measurements. The quantum yield of 1O2 production varies from 0.85 (in 100% ACN) to 0.69 (in 30% ACN). In air saturated solutions, the triplet fraction that is trapped by oxygen ranged from 0.88 in pure ACN
to 0.48 in water-acetonitrile (95:5, % v/v). In agreement with the various results, a phototransformation mechanism is proposed. In surface water, one may expect that the disappearance of chlorothalonil will be promoted mainly by the organic compounds that this water contains and that are able of reducing the triplet. Chlorothalonil, in turn, generates high amounts of singlet oxygen, a species that is able of efficiently oxidizing a large number of pollutants in surface water.
Note de contenu :
Annexes.Diplôme : Doctorat en sciences En ligne : ../theses/chimie/BOU7651.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=11485 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité BOU/7651 BOU/7651 Thèse Bibliothèque principale Thèses Disponible
