Search results for "ethanol"

Phase Behavior of the System Linear Polyglycerol + Methanol + Carbon Dioxide

2011

To compare the phase behavior of linear and hyperbranched polymers, the phase envelopes of the ternary system linear polyglycerol + methanol + carbon dioxide were determined for polymers of varying molar mass. Phase changes were detected by a static synthetic method using the Cailletet setup for temperatures between 331 K and 421 K and pressures up to 13.1 MPa. Besides the vapor–liquid and liquid–liquid equilibria, also the vapor–liquid to vapor–liquid–liquid and vapor–liquid–liquid to liquid–liquid phase boundaries are reported. The experimental results are similar to systems with hyperbranched polymers (rather than linear polymers). For the systems with linear polymers, however, the bubbl…

A new ceramide from the leaves of Lannea schimperi (Hochst. ex A.Rich.) Engl.

2020

A new ceramide is being reported herein together with six known compounds from the methanol extract of the leaves of Lannea schimperi (Hochst. ex A.Rich.) Engl. The metabolites were obtained through repeated open column chromatography and were characterized by spectroscopic and spectrometric techniques. The radical-scavenging activity of the crude extract and isolated compounds was evaluated using the DPPH radical. The obtained results suggest the studied species as prominent candidate to fight reactive oxygen species (ROS).

Use of reversed-phase C18 Sep-Pak cartridges for the purification and concentration of sepiapterin and other pteridines

1985

Abstract Several pteridines have been tested for their ability to bind to C 18 Sep-Pak. Riboflavin, sepiapterin, deoxysepiapterin, 6-acetyl-7,8-dihydropterin, 6-acetyldihydrohomopterin and 3′-hydroxysepiapterin were strongly retained and all but 6-acetyldihydrohomopterin quantitatively recovered upon elution with 2 ml of methanol. The effect of the concentration and volume of the sample, pH and salt concentration on the retention of sepiapterin have been studied. The procedure was very useful for the purification, desalting, solvent exchange and concentration of pteridines having high affinity for the cartridge. C 18 Sep-Pak has been applied succesfully to sample clean-up prior to high-perf…

Aqueous selective photocatalytic oxidation of salicyl alcohol by TiO2 catalysts: Influence of some physico-chemical features

2021

Abstract Partial photocatalytic oxidation of salicyl alcohol (2-hydroxybenzyl alcohol) to salicylaldehyde in water was investigated under environmental friendly conditions in the presence of home-prepared and commercial TiO2 (Merck and Aeroxide P25) samples under UVA irradiation. The photocatalysts were characterized by using BET, XRD, SEM and/or TEM techniques. The effects of crystallinity degree, pH (3–11) and presence of a hole trap (ethanol) on the photocatalytic activity and product selectivity were investigated. 4-Hydroxybenzyl alcohol was also used to study the influence of the position of the substituent group in the aromatic ring. High alcohols conversion and product selectivity va…

On the determination of underivatised fatty alcohol ethoxylates by electrospray ionisation–mass spectrometry

2006

Abstract The oligomers of fatty alcohol ethoxylates (FAEs) exhibit large sensitivity differences in mass spectrometry with electrospray ionisation (ESI–MS) and atmospheric pressure chemical ionization (APCI). Standards of the oligomers from m = 1 to 7 ethylene oxide units (EOs) and linear alkyl chains from n = 10 to 18 carbon atoms were infused to examine the relative sensitivities or response factors in several media. The response factors of the [M + H]+ and [M + Na]+ peaks in 9:1 acetonitrile/water and methanol/water media containing acid buffers increased following irregular patterns when n and m increased. In methanol/water the response factors depended on the parity of m, being larger …

Structure and Dynamics of NaCl in Methanol. A Molecular Dynamics Study

1991

Abstract A recently developed flexible three-site model for methanol was employed to perform a Molecular Dynamics simulation of a 0.6 molal NaCl solution. The ion-methanol and ion-ion potential functions were derived from ab initio calculations. The structural properties of the solution are discussed on the basis of radial and angular distribution functions, the orientation of the methanol molecules, and their geometrical arrangement in the solvation shells of the ions. The dynamical properties of the solution - like self-diffusion coefficients, hindered translations, librations, and internal vibrations of the methanol molecules - are calculated from various autocorrelation functions.

Vergleichende Untersuchung zur Diastereoselektivität derO-Methylierung von sterisch behinderten β-Ketocarbonsäureestern und ihren Enolen

1990

Diastereoselectivity of the O-Methylation of Sterically Hindered β-Ketocarboxylates and Their Enols The enols 1a, b, and 1c, which exists almost completely in the keto form, have been methylated at the oxygen atom with diazomethane. The regioselective reaction can be catalyzed by methanol, but may loose in that case the diastereoselectivity. A comparison with the methylation of the enolates by iodomethane is discussed.

Ethanol production improvement in Zymomonas mobilis by supplementation of fructan-cleaving enzymes on sucrose containing substrates

2010

Fluorous (Trimethylsilyl)ethanol:  A New Reagent for Carboxylic Acid Tagging and Protection in Peptide Synthesis

2006

Starting with a fluorous analogue of 2-(trimethylsilyl)ethanol, we have designed an easy method for preparing a new fluorous tag ((F)TMSE) for the protection of carboxylic acids. Because mild conditions are employed in the tag cleavage (TBAF in the presence of 4 A molecular sieves, which prevent racemization), this tag can be advantageously used in the synthesis of peptides and modified peptides, as we have demonstrated with several examples, including the fluorous synthesis of short alpha- and beta-peptides as well as of modified fluorinated retropeptides.

Synthesis, characterization and magnetic properties of mixed-valence iron complexes with 2-pyridyl oximes

2018

Two new mixed-valence iron complexes with 2-pyridyl oximes, [Fe(mpko)3Fe(H2O)2(NO3)](NO3)·2H2O (1) (mpko− = methyl(2-pyridyl)ketone oximate) and [{Fe(dpko)3}2Fe](ClO4)·4H2O (2) (dpko− = bis(2-pyridyl)ketone oximate), have been prepared by reaction of FeIII with mpkoH in methanol (1) and FeII with dpkoH in methanol/water (2). Dinuclear FeII(low-spin)FeIII(high-spin) and trinuclear FeII(low-spin)FeIII(high-spin)FeII(low-spin) cations are present in the crystal structure of 1 and 2, respectively. Intermolecular hydrogen bonds in 1 lead to weak antiferromagnetic interactions between pairs of neighboring FeIII centers, which allows observation of single-ion zero-field splitting effects.