- Study of the hydrolysis of a sulfonylurea herbicide using liquid chromatography with diode array detection and mass spectrometry by three-way multivariate curve resolution - Alternating least squares
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This research is focused on the development of a novel, automated chemometric method for obtaining relevant chemical information from time-course measurements of an evolving chemical system. This paper describes an investigation of the hydrolysis of Ally, which is a sulfonylurea herbicide. The hydrolysis of this compound is observed at different pHs and temperatures by reversed-phase liquid chromatography using a diode array detector. The data are analyzed using a three-way, multivariate curve resolution technique. Of special interest was the application of a closure constraint in the kinetic dimension followed by the determination of the rate constants for each step of the pathway by using a differential equation solver and nonlinear fitting of the data.
- Bezemer,Rutan
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- Abiotic degradation of iodosulfuron-methyl-ester in aqueous solution
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The abiotic degradation of iodosulfuron-methyl-ester was investigated under both alkaline and acidic pH conditions in the dark, and results showed it to be a rather stable molecule in neutral or slightly alkaline environments. Photochemical reactions were studied using a high-pressure mercury arc lamp, and results showed that direct phototransformation is possible under normal environmental conditions (λ > 290 nm). High-performance liquid chromatography (HPLC-UV and HPLC-MS) analyses were used to identify the degradates and to study the kinetics of photodecomposition and hydrolysis. Five main products of iodosulfuron-methyl-ester degradation were tentatively identified, and one of them (4-methoxy-6-methyl-1,3,5-triazin-2-amine) was confirmed using an authentic standard. Among the phototransformation mechanisms, photosubstitution of the iodide atom by a hydroxyl group, photodissociation of the N-S bond, and photoassisted hydrolysis were observed. The quantum efficiencies (multiwavelength quantum yield) of the photodegradation under different conditions were determined, and values of 0.054 ± 0.02 (pH 9.6), 0.08 ± 0.02 (pH 7), and 0.044 ± 0.008 (pH 5.3) were obtained.
- Brigante,Emmelin,Previtera,Baudot,Chovelon
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- Collection of ion-trap mass spectre of sulfonylurea pyrolysis products
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The pyrograms of 14 sulfonylureas, i.e. herbicides characterized by high biological activity and low application dose are discussed and the mass spectra of over 30 relevant pyrolysis products as obtained with a heated filament pyrolyzer interfaced to a capillary gas chromatograph/ion-trap detector mass spectrometer are presented. Such a data compilation is useful for diagnostic purposes for both intact sulfonylureas and their metabolites after degradation in soil, because metabolites and pyrolysis products are often identical and most of their mass spectra are lacking in commercially available mass spectral libraries. The performance of the ion-trap detector based on the quality of the mass spectra is briefly discussed.
- Galletti,Dinelli,Chiavari
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- Application of liquid chromatography/electrospray ionization tandem mass spectrometry for the elucidation of hydroxyl radical oxidation of metsulfuron methyl and related sulfonylurea pesticide products: evidence for the triazine skeleton scission
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Rationale Sulfonylureas are among the most important class of antidiabetic and herbicides. Solar light excitation and Advanced Oxidation Processes may result in the formation of a wide array of products owing to the relative complex structure. These products, that should be identified, may present a more toxic effect than the parent compound. Methods Liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry (LC/ESI-QTOFMS) with accurate mass determination emerges as a valuable technique for the precise elucidation of all possible byproducts. The hydroxyl radical was generated by excitation of the iron(III) aquacomplex [Fe(H2O)OH]2+ and hydrogen peroxide at pH3.5. Three different sulfonylureas were studied: metsulfuron methyl, cinosulfuron and thifensulfuron methyl. Results Several products owing to the reactivity of hydroxyl radicals with sulfonylurea were obtained. They arise from scission of the sulfonylurea bridge, hydroxylation of the aromatic ring, demethylation of the methoxy group and more importantly and unequivocally from the rupture of the triazine skeleton. To reach such scission, a primary demethylation of the methoxy group on the triazine moiety seems to act as a precursor process. Such a process was observed with the three studied sulfonylurea compounds. Conclusions The reported results demonstrated the usefulness of accurate mass measurements undertaken by LC/ESI-QTOFMS for structural elucidation of the unknown byproducts that were generated during hydroxyl radical reactions with some sulfonylureas. It has been possible herein to identify the structures of products arising from the opening of the recalcitrant triazine structure via hydrolysis processes in acidic solutions.
- Chahboune, Rajae,Mountacer, Hafida,Sarakha, Mohamed
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- Rearrangement products in aqueous photolysis of thifensulfuron methyl
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Photo-degradation of [14C]-thifensulfuron methyl has been investigated in aqueous media using a light source which simulates sunlight. Degradation of thifensulfuron methyl proceeds predominantly via sulfonylurea bridge ipso-contraction, and via cleavage of the bridge structure, to yield products in which the thiophene and the triazine rings have disconnected. One significant degradation product, which accounts for nearly 10%, retained both rings with truncated bridge moiety. Surprisingly, this product had thiophene ring substituents rearranged from their original locations. Other laboratories have reported photodegradation of thifensulfuron-methyl, and identified similar degradation products as well. The structure of the rearrangement product has been misidentified in previous reports because the rearrangement of the thiophene ring is not widely recognized. An unambiguous identification of this product and potential rearrangement mechanisms are presented in this report.
- Sharma, Ashok K.,Ryan, David L.,Marr, Nina L.,Wadsley, Michael P.,Cheatham, Steve F.
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p. 401 - 410
(2017/06/29)
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- Photophysical and photochemical studies of thifensulfuron-methyl herbicide in aqueous solution
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The photophysical and photochemical studies of a sulfonylurea herbicide, thifensulfuron-methyl (THM), have been investigated in a buffered aqueous solution. In the first part, the influence of pH on the spectroscopic properties was studied. This allowed the determination of the ground and excited state acidity constants, pKa=4 and 4.4, respectively, thus exhibiting the potential existence of a photoinduced protonation in the singlet state. In the second part, the photolysis kinetics was studied at different pH and varying oxygen concentrations, using an HPK 125W lamp and followed up by the identification of photoproducts formed under continuous photo-irradiation. The kinetics results suggest that the photolysis process is faster in acidic (k=3×10-4s-1) than in basic medium (k=9.8×10-5s-1). The photolysis products were identified by high performance liquid chromatography HPLC-DAD, HPLC-MS and HPLC-MS-MS. In order to obtain a better understanding of the photodegradation mechanism, a laser flash photolysis study was performed. By comparing the quenching rate constant (kq=9.64×108mol-1ls-1) obtained from triplet state quenching by molecular oxygen and from the Stern-Volmer relation (kq=0.41×108mol-1ls-1), the role of the singlet state in the photodegradation process was demonstrated. The photoproducts originating from both singlet and triplet excited states have been identified and hypothetical photodegradation pathways of the thifensulfuron-methyl in aqueous solution are proposed.
- Aziz, Saadia,Dumas, Stéphane,El Azzouzi, Mohammed,Sarakha, Mohamed,Chovelon, Jean-Marc
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scheme or table
p. 210 - 218
(2010/10/01)
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- Simulated sunlight-induced photodegradations of triasulfuron and cinosulfuron in aqueous solutions
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To elucidate the photochemical behavior of two sulfonylureas (cinosulfuron and triasulfuron) for which the chemical formulas are relatively close, their photodegradation was studied in water. All experiments were carried out under laboratory conditions using a xenon arc lamp as the source of radiation to simulate environmental conditions. Polychromatic quantum efficiencies were calculated to determine the photochemical pesticide lifetimes at pH 7, and a comparison with hydrolysis lifetimes has been performed. The results obtained showed clearly that at pH 7, photodegradation becomes a more important pathway than chemical degradation. HPLC-DAD was used to study the kinetics for both sulfonylureas and their photoproducts, whereas HPLC-MS (ESI in positive and negative modes) was used to identify photoproducts. These results suggest that the photodegradation of these two sulfonylureas proceeds via a number of reaction pathways: (1) cleavage of the sulfonylurea bridge; (2) desulfonylation, which can proceed either by a carbon-sulfur cleavage or a nitrogen-sulfur cleavage; (3) O-demethylation of methoxy moieties present on the triazine ring; and (4) O-dealkylation of benzene derivatives. In addition, it was found that the desulfonylation represented the main step and that it was wavelength dependent.
- Vulliet,Emmelin,Grenier-Loustallot,Paisse,Chovelon
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p. 1081 - 1088
(2007/10/03)
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- Kinetics and Hydrolysis Mechanism of Triasulfuron
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The hydrolysis of the sulfonylurea herbicide triasulfuron [(2-(2-chloroethoxy)-N-[[4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl] benzenesulfonamide] was studied in aqueous buffers of pH values 2, 3, 4, 5, 6, 7, and 9. The reaction was of first-order and pH-dependent. Triasulfuron was more persistent in neutral or weakly basic than in acidic solution. Five metabolites have been isolated and identified. At all pH values studied, the primary pathway of degradation was the cleavage of the sulfonylurea bridge. However, minor degradation pathways have also been observed like O-demethylation and opening of the triazine ring. The product distribution was pH-dependent.
- Braschi, Ilaria,Calamai, Luca,Cremonini, Mauro Andrea,Fusi, Paolo,Gessa, Carlo,Pantani, Ottorino,Pusino, Alba
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p. 4495 - 4499
(2007/10/03)
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- Kinetics and Hydrolysis Mechanism of Chlorsulfuron and Metsulfuron-Methyl
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In acidic media, hydrolysis of chlorsulfuron and metsulfuron-methyl occurs via two consecutive reactions which were followed by ultraviolet spectrophotometry. For these two reactions, the pseudo-first-order rate constants increase proportionally to the concentration of hydronium ion in the more acidic media and to the square of this concentration at higher pH values. A kinetic study by HPLC shows that the first reaction leads to the formation of 4-methoxy-6-methyl-1,3,5-triazin-2-amine and (o-chlorophenylsulfonyl) carbamic acid for chlorsulfuron or (o-methoxycarbonylphenylsulfonyl) carbamic acid for metsulfuron-methyl. The second reaction is the conversion of these sulfonylcarbamic acids to sulfonamides and carbon dioxide. The complete lack of saccharin and of o-sulfamoyl benzoic acid proves that the ester function of the methoxycarbonyl group is stable. The lack of general acid-base catalysis and a solvent deuterium isotope effect less than unity are consistent with a rate-determining cleavage of the protonated substrate. In the basic pH range (10-14) a single reaction occurs, the nucleophilic substitution of the methoxy group on the triazine by a hydroxide group.
- Hemmamda, Saadi,Calmon, Michelle,Calmon, Jean P.
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- Process for the preparation of 2-amino-4-methyl-6-methoxy-1,3,5-triazine
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A process for preparing 2-amino-4-methyl-6-methoxy-1,3,5-triazine by reacting dialkyl-N-cyanoimidocarbonate with acetamidine hydrochloride or an O-alkylacetamidate hydrochloride under basic conditions.
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- Preparation of 2-amino-4-alkoxy-s-triazines
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2-Amino-4-alkoxy-s-triazines which are substituted by an alkyl, aryl or aralkyl moiety in the 6-position and which are useful as pharmaceutical agents and as intermediates for herbicides, dyes and optical brighteners are prepared by reacting a dialkyl (N-cyanoimido)carbonate with an amidine salt in the presence of an inert solvent and a base.
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- Process for producing sulfonylureas
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There is described a novel process for producing sulfonylureas of formula I STR1 wherein R1 is hydrogen or alkyl, R2 is STR2 E is =N-- or =CH--, R3 is alkyl, alkoxy or halogen, R4 is alkyl, cycloalkyl, alkoxy, halogen, alkoxy-alkyl, halo-alkyl or halo-alkoxy, R5 is hydrogen or alkyl, T is a substituted phenyl group STR3 Y is hydrogen or halogen, X is hydrogen, halogen, alkyl, halo-alkyl, alkenyl, halo-alkenyl, alkynyl, alkoxy, halo-alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, halo-alkylthio, alkylsulfonyloxy, phenylsulfonyloxy, phenylsulfonyloxy mono- or polysubstituted by alkyl, or is di-alkylsulfamoyl, and A is a bridge member which has 3 or 4 atoms and which contains 1 or 2 hetero atoms, selected from the group consisting of oxygen, sulfur and nitrogen, the said process comprising reacting a silfonamide of the formula II in the presence of a base, with diphenyl carbonate to form a salt of a phenyl carbamate converting this salt into the free phenyl carbamate and reacting this further with an amine. Sulfonylureas are herbicidally effective compounds.
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- Process for the preparation of 2-amino-s-triazines
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The present invention relates to a process for the preparation of 2-amino-s-triazines in three stages. In the first stage nitriles, alcohols and hydrogen chloride are reacted to form the corresponding imido-ester hydrochlorides. In the second stage, the imido-ester hydrochlorides are reacted with cyanamide in the aqueous phase to form the N-cyanimido-esters, which comprises carrying out the first stage in the presence of acetic acid esters and the second stage in an aqueous solution which has been brought to a pH value of 5-8 by addition of bases, and reacting the N-cyanimido-esters with O-alkylisourea, S-alkylisothiourea, guanidine or amidine salts in the presence of a base in the third stage. The 2-amino-s-triazines can be prepared in a high purity and with good yields in this manner.
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- PREPARATION OF SUBSTITUTED 5-PYRIMIDINECARBONITRILES AND 1,3,5-TRIAZINES FROM ALKYL N-CYANOIMIDATES
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Sodium methoxide induced the cyclization of alkyl N-cyanoimidates 1 with propanedinitrile affording the 5-pyrimidinecarbonitriles 2.The reaction of 1 with methyl cyanoaetate led to the methyl 3-propenoates 7 and the 2,4-dioxo-5-pyrimidinecarbonitrile 8.An analogous cyclization of 1 with cyanamide yielded the 1,3,5-triazines 10.
- Perez, Miguel A.,Soto, Jose L
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p. 463 - 468
(2007/10/02)
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