Search results for "composition"
showing 10 items of 2675 documents
ChemInform Abstract: Polycondensed Nitrogen Heterocycles. Part 25. Aminopyrrolo(1,2-f) phenanthridines by Decomposition of 2-(3-Azidophenyl)-1-arylpy…
2010
Acid catalyzed decomposition of the azido derivatives 4a-c gave rise to amino-hydroxy-phenylpyrroles of type 7 and 8 upon hydrolysis of the intermediate aryl nitrenium ions, together with the hydrogen abstraction compounds of type 3. The aminopyrrolo[1,2-f]phenanthridines 10, 11, and 12 were obtained by treatment with TFMSA of the azide 4d in which the ring being attacked was made more nucleophilic by the introduction of the methoxy group.
Compositional analysis of styrene and maleic anhydride copolymerization: Complex model and penultimate model
1985
Potential energy surface for the decomposition of mandelic acid
1997
Abstract The decomposition of mandelic acid has been studied by ab initio calculations at the MP2/6-31G ∗∗ level. Three competitive reaction pathways have been characterized, two are stepwise processes with the formation of an α-lactone intermediate, achieved by the nucleophilic attack of either the carbonylic oxygen atom (mechanism A) or the hydroxylic oxygen atom (mechanism B) of the carboxyl group, followed by a ring opening; the third pathway (mechanism C) is a one-step process. The calculated rate coefficient agrees with experimental data. The decomposition is energetically favourable along mechanism A.
Effect of proteins, phytates, ascorbic acid and citric acid on dialysability of calcium, iron, zinc and copper in soy-based infant formulas.
2000
The possible effect of ascorbic acid, citric acid, proteins and phytate on dialysability of Ca, Fe, Zn and Cu in soy-based infant formulas is studied, taking dialysability as a measure of the amount of element available for absorption. Different dialysis percentages for similar element contents in different formulas are found. A regression analysis was applied between Ca, Zn, Cu and Fe dialysis percentages and soy-based formula components to estimate the possible influence of the latter on the dialysability of the elements. Significant correlations were found between citric acid contents and dialysability of Zn and Fe. No correlations were found between protein, ascorbic acid and phytic aci…
Studies on the UV-photolytic decomposition of some tensides and complexones inhibiting the inverse-voltammetric determination of metal ions
1993
The UV-photolytic decomposition of some tensides and complexones has been investigated using the DPASV peak of indium as an indicator. The results show that UV-irradiation alone can completely decompose these compounds at lower concentrations within a short time. Higher concentrations need an additional oxidising agent.
Steam-activated FeMFI zeolites. Evolution of iron species and activity in direct N2O decomposition
2003
Abstract In this paper the effect of the composition and steaming conditions of FeMFI catalysts on activity in direct N2O decomposition is investigated. MFI zeolites with different framework compositions (FeAlSi, FeGaSi, and FeSi) and without iron ( 100 mbar H2O in N2) favor the extraction of framework iron, enabling the application of lower activation temperatures. The optimum temperature during steam activation is that at which extraction of framework iron is complete without extensive clustering of extra-framework iron species into oxide particles, as was demonstrated by transmission electron microscopy and electrochemical characterization of the samples. Additional experiments show…
Chemical Composition of the Essential Oils ofPistacia atlanticaDesf.
2005
The chemical composition of the three essential oils obtained by hydrodistillation of the resin, leaves and fruits of Pistacia atlantica Desf. (Anacardiaceae) was studied by GC and GC/MS. Monoterpene hydrocarbons constituted the main chemical group in the resin oil, with α-pinene (42.9%) and β-pinene (13.2%) as the major components. Oil of the fruits contained high amounts of oxygenated monoterpenes, with bornyl acetate (21.5%) as the major component, while oxygenated monoterpenes and sesquiterpenes were found to predominate in the oil of leaves among which terpinen-4-ol (21.7%) and elemol (20.0%) were the most abundant components.
Volatiles ofSideritis mugronensisFlower and Leaf
1991
ABSTRACT The composition of the essential oil obtained from the flowers and the leaves of Sideritis mugronensis in two different stages of their reproductive development is described. The major components of the leaf and flower oils were sabinene: 1.30–10.59% and 2.70–15.21%; 1,8-cineole: 11.60–17.19% and 11.06–28.65%; and α-bisabolol: 5.57–25.49% and 3.40–16.12% respectively.
Thermolysis of 3-(carbazol-3-yl)-2-azidopropenoates
2000
Abstract Thermal cyclisation of 2-azido-3-(carbazol-3-yl)propenoic esters produces the 1,6-dihydropyrrolo[3,2- c ]carbazole and not the 1,9-dihydropyrrolo[2,3- b ]carbazole whereas, in the case of the 4-methylcarbazolyl derivative, the 1,9-dihydropyrrolo[2,3- b ]-carbazole is formed in preference to the alternative pyrido[4,3- c ]carbazole.
Synthetic Application of Homogeneous Charge Transfer Catalysis in the Electrocarboxylation of Benzyl Halides
1998
The results of an investigation on the performances of some outer sphere electron transfer homogeneous catalysts in the electrocarboxylation of 1-(p-isobutyl-phenyl)-1-chloroethane to 2-(p-isobutyl-phenyl)-propionic acid (Ibuprofen), using as catalysts the esters of benzoic and o-, m-, and p-phtalic acids, are reported. The performances of the catalysts are evaluated on the basis of the following parameters: faradic yields of the carboxylation and decomposition of the catalyst. The performances of dimethylisophtalate have been examined in greater detail. The rate of decomposition of the catalyst is related to the molar ratio [halide]/[catalyst].