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991.
Organophosphorus pesticides parathion, chlorpyrifos, and malathion inhibit the enzyme acetylcholinesterase (AChE; EC 3.1.1.7)
via phosphorylation of its active site. AChE reactivators and anticholinergics are compounds used as antidotes in the case of
intoxication by these AChE inhibitors. In this work, chlorpyrifos, a representative member of this pesticide family, was used
to inhibit the AChE activity of rat brain. The effect of twenty-one structurally different AChE reactivators was tested in vitro and subsequently, the relationship between their chemical structure and biological activity was outlined. 相似文献
992.
The oxygenation of the potassium salt of flavonol (flaH) in absolute DMF leads to potassium O-benzoylsalicylate and carbon monoxide in 95% yield at 40 degrees C. Kinetic measurements resulted in the rate law -d[flaK]/dt = k(2)[flaK][O(2)]. The rate constant, activation enthalpy, and entropy at 313.16 K are as follows: k(2)/M(-)(1) s(-1) = (3.28 +/- 0.10) x 10(-1), DeltaH()/kJ mol(-1) = 29 +/- 2, DeltaS/J mol(-1) K(-1) = -161 +/- 6. The reaction fits a Hammett linear free energy relationship for 4'-substituted flavonols, and electron-releasing groups make the oxygenation reaction faster. The anodic oxidation wave potentials E(a) of the 4'-substituted flavonolates correlate well with reaction rates. At more negative E(a) values faster reaction rates were observed. EPR spectrum of the reaction mixture (g = 2.0038, dH = 1.8 G, a(H) = 0.9 G) showed the presence of flavonoxyl radical as a result of a SET from the flavonolate to dioxygen. 相似文献
993.
C. Acero J. M. Ribó R. Solé F. R. Trull 《Monatshefte für Chemie / Chemical Monthly》1993,124(4):401-417
Summary Characteristic oxidation reactions of bilin-1,19-diones (biliverdins) and biladien-ac-1,19-diones (bilirubins) were reinvestigated. These include bromine and iodine oxidation of biliverdin IX, bilirubin IX and their Zn(II) complexes, the reaction described by Siedel (1941) of mesobilirubin XIII dimethyl ester with nitric acid (Gmelin reaction) and Smith's oxidation (1977) of etiobiliverdin IV using Tl triacetate and Pb tetra-acetate. For some of these reaction products new structures were assigned on the basis of their spectrometric data. These structures agreed with the expected reactivity pattern of biliverdins and bilirubins.
Reaktivität von Pyrrolpigmenten, 15 Mitt.: Über die Oxidation von Bilirubinen und Biliverdinen
Zusammenfassung Einige bekannte Oxydationen von Bilin-1,19-dionen (Biliverdinen) und Biladien-ac-dionen (Bilirubinen) wurden neuerlich untersucht, und zwar die Brom- und Jodoxydation von Biliverdin IX und Bilirubin IX sowie der entsprechenden Zn(II)-Komplexe, die Reaktion des Dimethylesters von Mesobilirubin XIII mit HNO3 (Gmelinreaktion; Siedel 1941) und Smith's Oxydation von Etiobiliverdin IV mit Thaliumtriacetat und Bleitetraacetat. Für einige Reaktionsprodukte wurden aufgrund spektroskopischer Daten neue Strukturen-konsistent mit dem bekannten Reaktionsverhalten von Biliverdinen und Bilirubinen-formuliert.相似文献
994.
The excess volumes of mixing for methanol and ethanol with secondary amines (diethylamine, di-n-propylamine and di-n-butylamine) have been measured over the whole composition range at 293.15 and 323.15 K. The excess volumes have been fitted to an equation of the type $$V^E /cm^3 mol^{--1} = x \left( {1 - x} \right) \sum\limits_{n = 0}^3 { A_n \left( {1 - 2x} \right)^n } $$ The different temperature dependences of the mixtures were explained by means of the association theory. 相似文献
995.
Oxidative cyclization of 2-pyrrolidinyl-acetamide and 2-pyrrolidinyl-propionamide local anaesthetics
2 - Pyrrolidinyl - acetamide and -propionamide local anaesthetics (1a–d) on oxidation with mercuric acetate, potassium hexacyanoferrate(III) and potassium permanganate underwent oxidative cyclization to give new bicyclic compounds, hexahydro - 1H - pyrrolo[1,2 - a]imidazolin - 2 - ones (2a–d). The propionamides (1c–d) yielded mixtures of the two possible diastereoisomers of 2c and 2d. These were separated; in solution and above their melting points they epimerized via ring opening and reclosure between the 7a-carbon and 1-nitrogen atoms. 相似文献
996.
The obtention of (tetradecachloro-4-oxidotriphenylmethyl)–. M+ (M=Li, Na, K, n-Bu4N) salts in ethereal solution and the isolation of some alkaline complexed salts (M=Li-12C4, Na-18C6, K-18C6, K(THF)1–(H2O)3–4, n-Bu4N) are described and discussed. The association phenomena of these salts has been studied by electronic spectroscopy, osmometry and electron spin resonance. Linear correlations between radii counterions and the position maxima of the electronic spectra bands permit the study of the species present in solution (free ions, ion pairs and quadrupolar aggregates). 相似文献
997.
Zusammenfassung Die Oxydation von Tiron durch H2O2 in basischem Milieu wird durch Kobalt stark katalysiert. Die katalysierten Vorgänge sind pH-abhängig. Im pH-Bereich 9 bis 11 entsteht ein rotes Oxydationsprodukt unbekannter Struktur; wahrscheinlich handelt es sich um ein o-Chinonderivat. Mit Hilfe der katalytischen Reaktion können 10–4
g Kobalt/5 ml nachgewiesen werden. In diesem pH-Bereiche stabilisiert Tiron H2O2 bei 100° C, bei 40° C jedoch katalysiert es — in Abhängigkeit von der Konzentration des Tirons — den Zerfall des H2O2. Der Effekt spielt im Mechanismus der katalysierten Reaktion wahrscheinlich eine Rolle, doch können die Zusammenhänge an Hand der bisher veröffentlichten Angaben nicht klar gedeutet werden. Der die Reaktion begleitende bzw. ihr folgende Nebenvorgang kann auf den katalytischen Zerfall des H2O2 · OOH-Komplexes zurückgeführt werden. Zwischen pH 7 und 9 entsteht bei der katalysierten Reaktion Semichinon, über pH 11 oxydiert Tiron das Semichinon unter Ringspaltung und Abspaltung von 1 Mol Sulfat zu Verbindungen, die Säurecharakter tragen.
Summary The oxidation of Tiron by H2O2 in basic milieu is strongly catalyzed by cobalt. The catalyzed reactions are pH-dependent. A red oxidation product of unknown structure results in the pH range 9 to 11; probably it is ano-quinone product. As little as 10–4 g cobalt/5ml can be detected by this catalytic action. In this pH region, Tiron stabilizes H2O2 at 100° C, but at 45° C it catalyzes the decomposition of H2O2, in relation to the concentration of the Tiron. The effect probably plays a rôle in the mechanism of the catalyzed reaction, but the up to now published informations are not sufficient to clarify the relationships. The auxiliary process, accompanying or following the reaction, can be attributed to the catalytic decomposition of the H2O2-OOH– complex. Semiquinone is produced by the catalytic reaction between pH 7 and 9, above pH 11, the Tiron oxidizes the semiquinone with opening of the ring and splitting off of 1 mol of sulfate yielding compounds which have an acidic character.
Résumé L'oxydation du Tiron par H2O2 en milieu basique est fortement catalysée par le cobalt. Les processus de catalyse dépendent du pH. Dans le domaine de pH de 9 à 11, il apparaît un produit d'oxydation rouge, de structure inconnue; il s'agit probablement d'un dérivé de l'o-quinone. La réaction catalytique permet de déceler 10–4 g cobalt/5 ml. Dans ce domaine de pH, à 100° C le Tiron stabilise l'eau oxygénée et à 45° C, suivant sa concentration, il catalyse la décomposition de l'eau oxygénée. L'effet joue probablement un rôle sur le mécanisme de la réaction catalysée; on ne peut pourtant pas interpréter clairement ces relations au moyen des indications publiées jusqu'ici. Le processus secondaire qui accompagne la réaction ou qui la suit, peut être ramené à la décomposition catalytique du complexe H2O2-OOH–. Entre pH 7 et 9, la réaction catalysée donne naissance à une semiquinone; au-dessus de pH 11, le Tiron oxyde la semi-quinone avec ouverture du cycle et élimination d'une mole de sulfate ce qui donne ensuite des composés qui portent le caractère acide.相似文献
998.
The feasibility of potabilization of sulfurous water was investigated by photochemical oxidation processes using a batch photoreactor and a continuous-flow photoreactor, equipped with UV lamps of 1000 W and 1500 W, respectively. Additionally, two advanced processes of oxidation were applied i.e. with a use of a UV light/H2O2/air and UV light/H2O2/O3/air. These two processes were compared for their efficiency to the direct oxidation process where ozone is used in the absence of UV light. Results obtained for both advanced processes showed better oxidation than takes place by ozone in the absence of UV light. After the photooxidation processes, different processes for the absorption or precipitation of sulfates were investigated to comply with the World Health Organization (WHO) norm that demands a limit of < or =250 mg L(-1) of SO4(2-) in drinking water. Additionally, reverse osmosis was simulated using Osmonics Inc. software to predict the feasibility of lowering the salt concentration below WHO limits. 相似文献
999.
Utko J Przybylak S Jerzykiewicz LB Mierzwicki K Latajka Z Sobota P 《Inorganic chemistry》2003,42(2):267-269
The reaction of [Ti4(OMe)14Cl2] (1) with an excess of AlMe3 gave the cocrystallite [Ti2(mu-OMe)2(mu-Cl)Cl3(thf)3].[Ti2(mu-OMe)3Cl3(thf)3] (2.3) species in a 1:1 ratio. Similar to 2, [Ti2(mu-OEt)2(mu-Cl)Cl3-(thf)3] (4) was obtained in the reaction of an equimolar mixture of TiCl4 and Ti(OEt)4 with Al/AlMe3. The short distance [2.543(1)av A in 2.3 and 2.599(1) A in 4] between "Ti(+3)" atoms, their diamagnetism, and ELF analysis indicate the presence of a Ti-Ti bond. 相似文献
1000.
Mechanisms explaining the formation of pyrroles obtained by UV irradiation of thiophen, the two methylthiophens, the four dimethylthiophens, 2-phenylthiophen, furan, the two methylfurans, and 2,4- and 2,5-dimethylfuran in the presence of n-propylamine are discussed. A comparison of the structure of thiocarbonyl and carbonyl intermediates most likely to be formed by UV irradiation of the substrates with the structure of the experimentally obtained pyrroles indicates that the formation of pyrroles from thiophenes and furans seems to follow mechanisms described in Schemes 1 and 4. 相似文献