Search results for "Anhydride"
showing 10 items of 120 documents
Determination of alcohols in essential oils by liquid chromatography with ultraviolet detection after chromogenic derivatization
2013
Abstract An HPLC-UV method to determine compounds having a hydroxyl functional group in plant essential oils is developed. The sample is diluted with 1,4-dioxane and the analytes are derivatized with phthalic anhydride. The derivatives (phthalates hemiesters) are separated on a C8 column using an acetonitrile (ACN)/water gradient. Separation conditions were optimized using the DryLab® method development software. For the alcohols and phenols present in mint and rose essential oils, optimization led to a ca. 40 min gradient time and a column temperature of 8 °C. The alcohol and its derivatives were identified using HPLC with mass spectrometry (MS) detection. A large sensitivity enhancement w…
Reaction products and pathways in the selective oxidation of C-2-C-4 alkanes on MoVTeNb mixed oxide catalysts
2010
[EN] The catalytic properties of MoVTeNbO catalysts during the selective oxidation of short chain alkanes and olefins (C-2-C-4) have been comparatively studied The main reaction products have been ethylene from ethane acrylic acid from propane maim anhydride from n-butane and methacrolein from isobutane FTIR studies of the adsorption of the main reaction products i e olefins and aldehydes over MoVTeNbO catalyst has been carried out Accordingly the reaction pathway is explained on the basis of the characteristics of the alkane fed the stability and reactivity of both the intermediates and the reaction products and the nature of the catalytic sites involved in each reaction (C) 2010 Elsevier …
Determination of fatty alcohol ethoxylates and alkylether sulfates by anionic exchange separation, derivatization with a cyclic anhydride and liquid …
2011
A method for the separation, characterization and determination of fatty alcohol ethoxylates (FAE) and alkylether sulfates (AES) in industrial and environmental samples is described. Separation of the two surfactant classes was achieved in a 50:50 methanol-water medium by retaining AES on a strong anionic exchanger (SAX) whereas most FAE were eluted. After washing the SAX cartridges to remove cations, the residual hydrophobic FAE were eluted by increasing methanol to 80%. Finally, AES were eluted using 80:20 and 95:5 methanol-concentrated aqueous HCl mixtures. Methanol and water were removed from the FAE and AES fractions, and the residues were dissolved in 1,4-dioxane. In this medium, este…
Determination of non-ionic and anionic surfactants in industrial products by separation on a weak ion-exchanger, derivatization and liquid chromatogr…
2013
Abstract A method for the determination of priority surfactants, including fatty alcohol ethoxylates (FAE), alkylether sulfates (AES) and linear alkylbenzene sulfonates (LAS) is described. The samples were diluted with 50% methanol at pH 4 prior to solid-phase extraction on a weak anionic exchanger (WAX). The AES and LAS surfactant classes were retained, whereas the non-ionic components, including most FAE oligomers were eluted. After washing the WAX cartridge to remove cations, the remaining hydrophobic FAE oligomers were eluted using hot 80% methanol at pH 4 (at ca. 50 °C). These two eluates were combined to constitute the non-ionic fraction. Then, AES and LAS were eluted using 80% MeOH w…
Cycloaddition reactions of 3-vinylthiophen
1987
Abstract Cycloaddition reactions between 3-vinylthiophen and the dienophiles maleic anhydride, methyl acrylate, dimethyl acetylene - dicarboxylate, and methyl propiolate give products including methyl benzo[b]thiophen-7-carboxylate (11) and its dihydroderivative (10), the 6,7-dicarboxylic acid (3), its dimethyl ester (7) and dihydroester (6); the naphtho[a,b]dithiophen (14), and the novel ethano bridged benzo[b]thiophen (15).
Hemoglobin loaded polymeric nanoparticles: preparation and characterizations.
2011
In the present work polymeric nanoparticles based on Poly (maleic anhydride-alt-butyl vinyl ether) 5% grafted with m-PEG (2000) and 95% grafted with 2-methoxyethanol (VAM41-PEG) were loaded with human hemoglobin (Hb) and characterized from a physicochemical point of view. The assessment of structural and functional features of the loaded Hb was performed and the effect of the introduction of different reducing agents as aimed at minimizing Hb oxidation during the nanoparticles formulation process, was also investigated. Nanoparticles possessing an average diameter of 138 ± 10 nm and physicochemical features suitable for this kind of application were successfully obtained. Although the oxida…
Anthraquinones formation on zeolites with BEA structure
1994
Publisher Summary Zeolites with BEA structure are in focus mainly in the field of conversion of hydrocarbons. However, their unique physico-chemical properties let to suppose that these systems can be successfully used in reactions of organic synthesis. Such zeolites can be used as catalysts for the synthesis of large organic molecules. The interaction of phthalic anhydride with aromatic hydrocarbons is a subject for investigation, both for science purposes and for industrial applications. The use of zeolites in this reaction is an example of the acylation of aromatics on solid-acid catalysts; on the other hand, such a study creates the possibilities of developing more appropriate technolog…
Design and synthesis of biobased epoxy thermosets from biorenewable resources
2017
International audience; Biobased diepoxy synthons derived from isoeugenol, eugenol or resorcinol (DGE-isoEu, DGE-Eu and DGER, respectively) have been used as epoxy monomers in replacement of the diglycidyl ether of bisphenol A (DGEBA). Their curing with six different biobased anhydride hardeners leads to fully biobased epoxy thermosets. These materials exhibit interesting thermal and mechanical properties comparable to those obtained with conventional petrosourced DGEBA-based epoxy resins cured in similar conditions. In particular, a high Tg in the range of 90–130 °C and instantaneous moduli higher than 4.3 GPa have been recorded. These good performances are very encouraging, making these n…
Effects of the dual sodium-glucose linked transporter inhibitor, licogliflozinvsplacebo or empagliflozin in patients with type 2 diabetes and heart f…
2020
Aims Explore the efficacy, safety and tolerability of the dual sodium-glucose cotransporter (SGLT) 1 and 2 inhibitor, licogliflozin in patients with type-2 diabetes mellitus (T2DM) and heart failure. Methods This multicentre, parallel-group phase IIA study randomized 125 patients with T2DM and heart failure (New York Heart Association II-IV; plasma N-terminal pro b-type natriuretic peptide [NT-proBNP] >300 pg/mL) to licogliflozin (2.5 mg, 10 mg, 50 mg) taken at bedtime, empagliflozin (25 mg) or placebo (44 patients completed the study). The primary endpoint was change from baseline in NT-proBNP after 12 weeks. Secondary endpoints included change from baseline in glycated haemoglobin, fas…
Cationic and Zwitterionic Polymerizable Surfactants: Quaternary Ammonium Dialkyl Maleates. 1. Synthesis and Characterization
1999
Cationic and zwitterionic reactive dialkyl maleates with different hydrophobic chain lengths (R = C10H21, C12H25, C16H33, and C18H37), and some similar surfactants without double bonds were synthesized with an aim to use them as stabilizers in the batch and seeded emulsion copolymerization of styrene and butyl acrylate (part 2 of this series). Surfactants are obtained in a three-step synthesis, starting from ring opening of maleic anhydride, followed by O alkylation with an aminoalkyl compound, and finishing with quaternization of the amino group in the hydrophilic part of the molecule. The chemical structure of surfactants was confirmed by 1H NMR. Melting points and critical micelle concen…