Search results for "Ether"
showing 10 items of 986 documents
Die Synthese reiner Oligo[hydroxy-5-nitro1,3-phenylen)-methylen]e, Verbindungen mit mehreren ortho- bzw. para-Nitrophenolbausteinen im Molekül
1976
Zur Synthese der Oligo[(hydroxy-5-nitro-1,3-phenylen)methylen]e dienten chlormethylierte Nitrophenole sowie mono- und bischlormethylierte Bis- und Tris[(hydroxy-5-nitro-1,3-phenylen)methylen]e. Die Chlormethylierung erfolgte durch Umsetzung mit Chlormethylmethylather in Gegenwart von Zinkchlorid. Die Synthese der Oligomeren gelang mit guten Ausbeuten, wenn die chlormethylierten Verbindungen mit stark uberschussigem Nitrophenol und Zinkchlorid als Katalysator kondensiert wurden. Reaktionsbedingungen und unterschiedliche Reaktionsfahigkeiten werden mitgeteilt. Einige Verbindungen wurden in ihrer Struktur bestatigt, indem sie auf zwei voneinander unabhangigen Wegen dargestellt wurden. Damit wa…
Kinetische Untersuchungen über die kationische Polymerisation von wasserfreiem Formaldehyd. 40. Mitt. Über polyoxymethylene
1971
Die Polymerisation von Formaldehyd in atherischer Losung bei −78°C mit SnCl4 und HClO4 als Initiatoren wurde untersucht. Die Konzentration der aktiven Zentren (Polyoxymethylen-Kationen) wurde bestimmt, indem die Polymerisationen durch Zugabe eines grosen Uberschusses an n-Amylalkohol abgebrochen und die entstandenen Pentoxylendgruppen nach Reinigung und Hydrolyse der Polymeren gaschromatographisch bestimmt wurden. Die Initiierung der Polymerisationerfolgt rasch und fuhrt zu vollstandigem Umsatz des Initiators wahrend der ersten Minuten. Unter gunstigen Reaktionsbedingungen ergibt jedes eingesetzte Initiatormolekul ein Polyoxymethylene-Kation. Ein kinetischer Abbruch wurde nicht festgestellt…
Unveiling the reaction mechanism of novel copper N-alkylated tetra-azacyclophanes with outstanding superoxide dismutase activity.
2020
Quantum chemical and multiscale calculations reveal the mechanistic pathway of two superoxide dismutase mimetic N-alkylated tetra-azacyclophane copper complexes with remarkable activity. The arrangement of the binding site afforded by the bulky alkyl substituents and the coordinated water molecule as a proton source play key roles in the reaction mechanism.
Theoretical Elucidation of β-O-4 Bond Cleavage of Lignin Model Compound Promoted by Sulfonic Acid-Functionalized Ionic Liquid
2019
While the depolymerization of lignin to chemicals catalyzed by ionic liquids has attracted significant attention, the relevant molecular mechanism, especially the cleavage of specific bonds related to efficient depolymerization, still needs to be deeply understood for the complexity of this natural aromatic polymer. This work presents a detailed understanding of the cleavage of the most abundant β-O-4 bond in the model system, guaiacylglycerol β-guaiacyl ether, by a Brønsted acidic IL (1-methyl-3-(propyl-3-sulfonate) imidazolium bisulfate ([C3SO3Hmim][HSO4]) using density functional theory calculation and molecular dynamics simulation. It has been found that [C3SO3Hmim][HSO4] generates zwit…
Rates of Reactions
1986
Inspite of the fact that many organotitanium compounds are well characterized, the number of kinetic studies is limited. This chapter deals primarily with such efforts directed toward elucidating the intricacies of carbonyl addition of CH3Ti(OCHMe2)3. Various other kinetic processes are also briefly discussed (Section 4.2).
Determination of liposoluble vitamins in cooked meals, milk and milk products by liquid chromatography
2002
A method for the simultaneous determination of liposoluble vitamins in cooked meals was established. Saponification was performed with 50% (w/v) KOH at 80 degrees C, and ascorbic acid was added as antioxidant. The subsequent extraction was carried out with diethyl ether. This was followed by a liquid chromatographic separation on a reversed-phase C18 column with methanol-water (94:6, v/v as the mobile phase. Retinyl acetate was used as the internal standard. The analytical parameters linearity, detection limit (0.19 and 8.33 microg/100 g for retinol and alpha-tocopherol, respectively), precision of the method (RSD=5.24 and 6.99% for retinol and alpha-tocopherol, respectively) and recovery a…
The Stroke Riskometer (TM) App: Validation of a data collection tool and stroke risk predictor
2014
Background The greatest potential to reduce the burden of stroke is by primary prevention of first-ever stroke, which constitutes three quarters of all stroke. In addition to population-wide prevention strategies (the ‘mass’ approach), the ‘high risk’ approach aims to identify individuals at risk of stroke and to modify their risk factors, and risk, accordingly. Current methods of assessing and modifying stroke risk are difficult to access and implement by the general population, amongst whom most future strokes will arise. To help reduce the burden of stroke on individuals and the population a new app, the Stroke Riskometer™, has been developed. We aim to explore the validity of the app fo…
Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes
2020
Crown ethers are common building blocks in supramolecular chemistry and are frequently applied as cation sensors or as subunits in synthetic molecular machines. Developing switchable and specifically designed crown ethers enables the implementation of function into molecular assemblies. Seven tailor-made redox-active crown ethers incorporating tetrathiafulvalene (TTF) or naphthalene diimide (NDI) as redox-switchable building blocks are described with regard to their potential to form redox-switchable rotaxanes. A combination of isothermal titration calorimetry and voltammetric techniques reveals correlations between the binding energies and redox-switching properties of the corresponding ps…
Phylogeny and Mycotoxin Characterization of Alternaria Species Isolated from Wheat Grown in Tuscany, Italy
2018
Wheat, the main source of carbohydrates worldwide, can be attacked by a wide number of phytopathogenic fungi, included Alternaria species. Alternaria species commonly occur on wheat worldwide and produce several mycotoxins such as tenuazonic acid (TA), alternariol (AOH), alternariol-monomethyl ether (AME), and altenuene (ALT), provided of haemato-toxic, genotoxic, and mutagenic activities. The contamination by Alternaria species of wheat kernels, collected in Tuscany, Italy, from 2013 to 2016, was evaluated. Alternaria contamination was detected in 93 out of 100 field samples, with values ranging between 1 and 73% (mean of 18%). Selected strains were genetically characterized by multi-locus…
Heterogeneity at the Glass Transition: Translational and Rotational Self-Diffusion
1997
Self-diffusion coefficients, D, have been measured in the glass forming liquids salol, glycerol, phenolphthaleine dimethyl ether (PDE), cresolphthaleine dimethyl ether (CDE), and ααβ-trinaphthylbenzene (TNB) in the supercooled regime. The NMR static magnetic field gradient technique was applied where D >10-14 m2 s-1 can be attained. The results are similar to previous diffusion experiments where an enhancement of translational diffusion was found in comparison with rotational diffusion and shear viscosity. Various models of spatial heterogeneity are related to a phenomenological environmental fluctuation model in view of recent diffusion and relaxation data close to the glass transition.