Comparative Study of the Effects of Aqueous Micellar Media Formed by Amphiphilic Ionic Liquids and Conventional Surfactants on Reactions of Synthetic Interest (original) (raw)
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In the present work, our objective is to take advantage of the property presented by Ionic Liquids (ILs) based on 1-alkyl-3-methylimidazolium cations by having amphiphilic character when the alkyl group is a long hydrocarbon chain. These ILs can act as surfactants forming micelles in aqueous solution. In this sense, the micellar effect on a Diels-Alder reaction (DA) was analyzed taken as a reference. The reactive system studied consists of maleic anhydride and isoprene, variables such as diene:dienophile ratio and reaction temperatura among the most important were optimized. N,N-dodecylmethylimidazolium bromide was used at the critical micellar concentration (CMC) of 1 × 10−2 M. These “new systems” microheterogeneous would allow, in addition to better solubilization of non-polar substrates, to adopt milder reaction conditions.
Aqueous micellary systems formed by surfactant ionic liquids. Application in Diels-Alder reactions
Proceedings, 2019
In the present work, our objective is to take advantage of the property presented by Ionic Liquids (ILs) based on 1-alkyl-3-methylimidazolium cations by having amphiphilic character when the alkyl group is a long hydrocarbon chain. These ILs can act as surfactants forming micelles in aqueous solution. In this sense, the micellar effect on a Diels-Alder reaction (DA) was analyzed taken as a reference. The reactive system studied consists of maleic anhydride and isoprene, variables such as diene:dienophile ratio and reaction temperatura among the most important were optimized. N,N-dodecylmethylimidazolium bromide was used at the critical micellar concentration (CMC) of 1 × 10 −2 M. These "new systems" microheterogeneous would allow, in addition to better solubilization of non-polar substrates, to adopt milder reaction conditions.
Chemistry Proceedings
The micellar effect on Diels–Alder (DA) reaction was analyzed taking advantage of the property presented by ionic liquids (ILs) based on 1-alkyl-3-methylimidazolium cations by having amphiphilic character when the alkyl group is a long hydrocarbon chain-12 carbon atoms [C12mim]. These ILs can act as surfactants forming micelles in aqueous solution. The reactive system studied consists of nitrofuran and isoprene which allows obtaining benzofuran through green synthetic strategies. These “new microheterogeneous systems” would allow a better solubilization of non-polar substrates and to adopt reaction conditions softer than the traditional thermal.
Коллоидный журнал, 2014
Here, we review two recent theoretical models in the field of ionic surfactant micelles and discuss the comparison of their predictions with experimental data. The first approach is based on the analysis of the stepwise thinning (stratification) of liquid films formed from micellar solutions. From the experimental step wise dependence of the film thickness on time, it is possible to determine the micelle aggregation number and charge. The second approach is based on a complete system of equations (a generalized phase separation model), which describes the chemical and mechanical equilibrium of ionic micelles, including the effects of electrostatic and non electrostatic interactions, and counterion binding. The parameters of this model can be determined by fitting a given set of experimental data, for example, the dependence of the critical micel lization concentration on the salt concentration. The model is generalized to mixed solutions of ionic and nonionic surfactants. It quantitatively describes the dependencies of the critical micellization concentration on the composition of the surfactant mixture and on the electrolyte concentration, and predicts the concen trations of the monomers that are in equilibrium with the micelles, as well as the solution's electrolytic con ductivity; the micelle composition, aggregation number, ionization degree and surface electric potential. These predictions are in very good agreement with experimental data, including data from stratifying films. The model can find applications for the analysis and quantitative interpretation of the properties of various micellar solutions of ionic surfactants and mixed solutions of ionic and nonionic surfactants.
Molecules, 2019
The paper analyses influences of the temperature and hydrophilic groups on micellar properties of ionic surfactants with 12-carbonic hydrophobic chains. The aim is to assess the impact of hydrophilic groups and temperature on thermodynamic parameters and micellization. This knowledge is indispensable for the formulation of new dosage forms. The method uses conductometric measurements. The following hydrophilic groups are analyzed: trimethylammonium bromide, trimethylammonium chloride, ethyldimethylammonium bromide, didodecyldimethylammonium bromide, pyridinium chloride, benzyldimethyl-ammonium chloride, methylephedrinium bromide, cis and trans-[(2-benzyloxy)-cyclohexyl-methyl]-N, N-dimethylammonium bromide, sodium sulphate and lithium sulphate. Except for a few cases, there is a good agreement between values of critical micellar concentrations (CMC) and critical vesicle concentration (CVC) obtained here and those which were obtained by other authors and/or by other physicochemical m...
Journal of Surfactants and Detergents, 2013
Various micelle parameters viz., critical micelle concentration (CMC), counter-ion binding (b), aggregation number (N), hydrodynamic radius (R h ), micelle zeta potential (f) and energetic parameters, free energy of micellization (DG 0 m ), enthalpy of micellization (DH 0 m ) and entropy of micelle formation (DS 0 m ) were determined for sodium dodecylsulfate, and dodecyltrimethylammonium bromide in the presence of NaCl for the former and NaBr for the latter. Conductometry and calorimetry methods were used for the measurements of CMC and energetic parameters. The fluorimetric (static quenching) method was employed to determine N and dynamic light scattering to estimate R h and f. The conductometrically determined b was verified from the CMC values by calorimetry using the Corrin-Harkins equation. The results found for the two surfactants of identical tails but different head groups have been presented and discussed. A detailed report on the salt effect using salts containing counter-ions the same as those in the surfactant is found only limitedly in the literature.
Formation of Reverse Micelles in a Room-Temperature Ionic Liquid
ChemPhysChem, 2008
Reverse micelles (RMs) or water-in-oil microemulsions are water droplets stabilized in non-polar solvents by a layer of surfactant molecules. [1] At certain concentrations, amphiphilic surfactants self-assemble to form thermodynamically stable spherical RMs. [1c] The macroscopic homogeneity and transparency of this system permits the use of continuous spectrophotometric techniques. The tremendous potential of RMs as media for biocatalysis, [2] drug delivery, [3] separation, [4] protein refolding, nanomaterial synthesis, [6] and other dispersant technologies are well recognized. However, the frequently used organic solvents are highly volatile, irritating and quite toxic. The industrial application of micellar technology in food, cosmetic and pharmaceutical industries thus requires a green solvent to minimize the problems inherent in conventional solvent disposal into the environment.