Search results for "HYDROLYSIS"
showing 10 items of 632 documents
Monomeric vs. polymeric bonded iminodiacetate silica supports in high-performance ligand-exchange chromatography
1983
The synthesis of monomeric and polymeric bonded iminodiacetate-groups on silica supports is described. The polymeric support offers advantages over the monomeric, such as (i) preparation is much simpler, (ii) higher surface concentration of functional groups can be achieved without loss of efficiency and (iii) hydrolytic stability. Cu2+ loaded supports were examined for their kinetic performance, in particular for the C-parameter of the Knox equation, and for their hydrolytic stability. Calculation of the surface coverage shows that only a rather thin polymeric layer is formed; this is in agreement with the results of the kinetic performance. The retention of α-amino acids on the Cu2+ loade…
ChemInform Abstract: Synthesis of Trifluoromethylated 2-Benzoyl- and 2-Aminoimidazoles from Ring Rearrangement of 1,2,4-Oxadiazole Derivatives.
2008
Abstract Fluoroalkylated 2-ylamino-imidazoles have been synthesized by reaction of 3-amino-5-phenyl-1,2,4-oxadiazole with fluorinated β-dicarbonyl compounds and subsequent base-induced Boulton–Katritzky Rearrangement (BKR) of the isolated β-enaminocarbonyl intermediate. Alternatively, one-pot reactions performed in the presence of Montmorillonite K10 favoured the condensation at the 3-amino moiety of the oxadiazole and, in some cases, allowed the direct synthesis of 2-benzoylamino-imidazoles. Hydrolysis of 2-benzoylamino-imidazoles easily yielded fluorinated 2-amino-imidazoles targets.
Synthesis of trifluoromethylated 2-benzoyl- and 2-aminoimidazoles from ring rearrangement of 1,2,4-oxadiazole derivatives
2008
Abstract Fluoroalkylated 2-ylamino-imidazoles have been synthesized by reaction of 3-amino-5-phenyl-1,2,4-oxadiazole with fluorinated β-dicarbonyl compounds and subsequent base-induced Boulton–Katritzky Rearrangement (BKR) of the isolated β-enaminocarbonyl intermediate. Alternatively, one-pot reactions performed in the presence of Montmorillonite K10 favoured the condensation at the 3-amino moiety of the oxadiazole and, in some cases, allowed the direct synthesis of 2-benzoylamino-imidazoles. Hydrolysis of 2-benzoylamino-imidazoles easily yielded fluorinated 2-amino-imidazoles targets.
Identification of drying oils used in pictorial works of art by liquid chromatography of the 2-nitrophenylhydrazides derivatives of fatty acids.
2004
A new HPLC-UV-Vis method for identification of drying oils from binding media or protective film used in pictorial works of art prior to conservation or restoration is proposed. Chromophore derivatization of fatty acids released by hydrolysis of structural drying oils is studied. The derivatization reagent selected was 2-nitrophenylhydrazine with 1-ethyl-3-(3-dimethyl animopropyl)carbodiimide hydrochloride/pyridine as catalyst. This reaction was carried out using microwave heating. Mobile phase was methanol/water/n-propanol/acetic acid (80:14:5:1) running in isocratic mode. Absorbance was measured at 400nm. In these conditions, hydrazides of myristic, palmitic, oleic, and stearic acids were…
Synthese von 2-alkoxysubstituierten Oligo- und Poly(1,4-phenylenethenylen)en und 2-Arylbenzo[b]furanen mit Hilfe der Siegrist-Reaktion
1994
Synthesis of 2-Alkoxy Substituted Oligo- and Poly(1,4-phenyleneethylene)s and 2-Arylbenzo[b]furanes by Applying the Siegrist Reaction Alkylation of 2-hydroxy-4-methylbenzaldehyde (1) yields the 2-alkoxy-4-methylbenzaldehydes (2a-l) which can be easily transformed to the Schiff bases 3a-l. The intermolecular self-condensation in a strongly alkaline medium leads to the oligo- and poly(1,4-phenyleneethenylene)s (4a-i) with an outstanding regular constitution and overall (E)-configuration. The terminal N-arylamino group can be cleaved by hydrolysis generating the compounds 5a-i. An intramolecular condensation forming the benzo[b]furanes 6j,k is observed for 3j,k – due to the activated OCH2 grou…
Micellar fluorescence enhancement of carbamate pesticides
1990
Abstract Different studies have been carried out on the interaction of carbamate pesticides, such as carbofuran and carbaryl, with nonionic and anionic surfactants. Micellar fluorescence enhancements (MEF) of 15–20 for carbofuran in the presence of fatty alcohol ethylene oxide condensates, and of 3.7–8.6 in the presence of anionic surfactants at neutral pH have been obtained. Carbaryl does not interact with surfactants, but when it is hydrolysed to 1-naphthol, MEF values of the order of 2 are obtained in the presence of nonylphenol ethylene oxide condensates. The experimental parameters have been optimized in order to obtain maximum fluorescence. The mechanisms involved in the fluorescence …
Bestimmung des vernetzungsgrades schwach vernetzter, noch löslicher copolymerer aus styrol und bisacrylsäurephenylestern durch hydrolytischen abbau
1970
Aus Styrol und Bisacrylsaurephenylester durch radikalische, vernetzende Polymerisation erhaltene und in Toluol sowie Dioxan noch losliche Copolymere wurden durch alkalische Hydrolyse gezielt in die linear strukturierten Bestandteile zerlegt. Diese enthielten neben sehr vielen Styrolbausteinen wenige aus dem Vernetzer stammende Acrylsaurebausteine. UV-Spektren zeigten, das die Vernetzerreste durch den hydrolytischen Abbau vollstandig abgespalten waren. Von den linearen Baustucken wurden viskosimetrisch, osmometrisch und z. T. colorimetrisch die Molekulargewichte bestimmt. Die Hydrolyseprodukte zeigten eine unerwartet bei 320 mμ auftretende Extinktion, deren Ursache nicht restlos aufgeklart w…
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.
On the Occurrence of Flavonoids in the acrocarpous Mosses
1978
Summary By means of paper chromatography two flavonoids were isolated from the methanolic extract of the moss Mnium undulatum. One substance was identified by chromatographic data, absorption spectra and acid hydrolysis as isovitexin-7-0-glucoside (saponarin). The second substance resists acid hydrolysis and is by chromatography and absorption spectrum identical with apigenin-6,8-di-C-glycoside (viccnin).
HPLC Method for Cyst(e)ine and Methionine in Infant Formulas
1996
Cyst(e)ine and methionine were converted into cysteic acid and methionine sulfone by oxidizing with performic acid. The oxidized samples were then subjected to acid hydrolysis (6N HCl, 105-110°C/24 hr). After derivatization with phenylisothiocyanate, reverse phase HPLC separation was carried out at 48°C and with UV detection. Different gradients and pH values in the eluent were assayed to determine the best resolution. Analytical parameters, detection and quantification limits, linearity, precision and accuracy, were determined. The method was reliable and accurate for measuring cyst(e)ine and methionine in infant formulae.