Search results for "aqueous solution"

Umsetzung von amino-aziminen mit basen

1980

Abstract Amino-azimines of type (1) react at room temperature with bases (ammonia, aliphatic amines, hydrazine and methyl-hydrazine, aqueous/ethanolic sodium hydroxide) by cleavage of the to the and the NNN moieties (azide).

Formation of α-ω(4,7,10,13-pentaoxa-16-azacyclooctadecane) hexadecane micelles in aqueous solution – effect of HCl addition

2003

The structure of aggregates of a new bolaform surfactant [α-ω (4,7,10,13-pentaoxa-16-azacyclooctadecane) hexadecane] in neat aqueous solution has been investigated by small-angle neutron scattering. Preliminary data analysis unequivocally indicates that globular micelles are formed. This finding has been confirmed by the analysis of data obtained upon addition of hydrochloric acid. The observed significant reduction of micelle aggregation number has been attributed to the peculiar complexing ability of the two aza-crown ether units in the surfactant molecule; this is in line with information inferred from the complexation of ions into the non alkylated azacrown ethers. As a consequence of h…

Effects of non-ionic micelles on transient chaos in an unstirred Belousov-Zhabotinsky reaction.

2001

The behaviour of the Ce(IV)-catalyzed Belousov-Zhabotinsky (BZ) system has been monitored at 20.0 degrees C in unstirred batch conditions in the absence and presence of different amounts of the non-ionic micelle-forming surfactants hexaethylene glycol monodecyl ether (C10E6) and hexaethylene glycol monotetradecyl ether (C14E6). The influence of the non-ionic surfactants on both the kinetics of the oxidation of malonic acid (MA) by Ce(IV) species and the behaviour of the BZ reaction in stirred batch conditions has also been studied over a wide surfactant concentration range. The experimental results have shown that, in unstirred batch conditions, at surfactant concentrations below the critic…

Organocatalytic α-Methylenation of Aldehydes: Preparation of 3,7-Dimethyl-2-Methylene-6-Octenal

2010

4-(Dimethylamino)benzoic acid Pyrrolidine Citronellal 3,7-Dimethyl-2-methylene-6-octenal Formaldehdye, aqueous Keywords: Aldehydes. Methylenation; Organo catalytic reaction; Alpha-substituted acroleins; Intermediates; Rapid synthesis; Functionalities; Waste disposal

Electrochemical synthesis of diaryl dichalcogenides in acetonitrile, with two sacrificial electrodes: diseleno and ditelluro derivatives of quinolones

1993

Influence of operational variables on the photodegradation kinetics of Monuron in aqueous titanium dioxide dispersions

1994

The degradation of Monuron [N′—(4-chlorophenyl)—N, N dimethyl urea] in aqueous TiO 2 dispersions irradiated in the near-UV region has been investigated using a Pyrex batch photoreactor. The influence on the degradation kinetics of pH, initial Monuron concentration and catalyst concentration has been studied. The mineralization of the pollutant was also investigated. Measurements of photon absorbed flows allowed to determine the quantum yield values; they were found to increase by increasing the initial pH of the dispersion.

Green Solvents for Analytical Separation and Analyses

2010

The alternatives to the use of organic solvents that have been offered by the scientific literature reviewed. In order to look at the best solvents from both analytical and sustainable view points, the use of water under superheated conditions, supercritical fluids, renewable organics, ionic liquids, and aqueous solutions of amphiphillic compounds, have been evaluated. As a general conclusion, it can be seen that, at present, green alternatives to the traditional organic solvents employed in analytical separations and analysis that are being well explored are the capabilities of the use of alcohols, supercritical fluids, and superheated water; and remain unexplored tremendous possibilities …

Binding of acrylic and sulphonic polyanions by open-chain polyammonium cations

2000

Abstract The interactions between some acrylic and sulphonic polyanions and some protonated amines (diamines NH 2 -(CH 2 ) x -NH 2 , x =2,…,10; linear tri-, tetra-, penta- and hexa-amines) were studied potentiometrically in aqueous solution, at 25°C. For both types of polyanions AL 2 H i (L − , monomer of polyanion, A, amine) species are formed, with i =1,…, n ( n =number of amino groups in the amine). The stability of these species is strictly dependent on the polyammonium cation charge, and fairly independent of the type of amine (in diamine species maximum stability is observed for x =4, 5). Acrylic and sulphonic polyanion complexes are considerably stronger than analogous species formed…

Investigating self-assembly and metal nanoclusters in aqueous di-block copolymers solutions

2002

Self-assembling properties of di-block copolymers/ surfactant hybrids in aqueous solution can be exploited to obtain metal nanoparticles stable dispersion. Results will be presented here for polystyrene-block-poly(ethylene oxide) solutions. A SANS structural investigation has been performed over different molecular weights of both hydrophilic and hydrophobic block, by varying temperature and concentration of the copolymer. A SAXS characterization of micellar systems containing Pt nanoparticles is reported.

How do different surface modification strategies affect the properties of MnO nanoparticles for biomedical applications? Comparison of PEGylated and …

2011

ABSTRACTMnO nanoparticles (NPs) were surface functionalized by two different approaches, (1) using a dopamine-poly(ethylene glycol) (PEG) (DA-PEG) ligand and (2) by encapsulation within a thin silica shell applying a novel approach. Both MnO@DA-PEG and MnO@SiO2 NPs exhibited excellent long-term stability in physiological solutions. In addition, the cytotoxic potential of both materials was comparatively low. Furthermore, owing to the magnetic properties of MnO NPs, both MnO@DA-PEG and MnO@SiO2 lead to a shortening of the longitudinal relaxation time T1 in MRI. In comparison to the PEGylated MnO NPs, the presence of a thin silica shell led to a greater stability of the MnO core itself by pre…