The purpose of this work was to analyze the microscopic feature of binary solvent systems formed by a molecular solvent (acetonitrile or dimethylformamide or methanol) and an ionic liquid (IL) cosolvent [1‐(1‐butyl)‐3‐methylimidazolium tetrafluoroborate or 1‐(1‐butyl)‐3‐methylimidazolium hexafluorophosphate]. The empirical solvatochromic solvent parameters ET(30), π*, α, and β were determined from the solvatochromic shifts of adequate indicators. The behavior of the solvent systems was analyzed according to their deviation from ideality. The study focused on the identification of solvent mixtures with relevant solvating properties in order to select mixed solvents with particular characteristics. The comparison of the molecular–microscopic solvent parameters corresponding to the selected binary mixtures with both ILs considered at similar mixed‐solvent composition revealed that the difference is centered on the basic character of them. A kinetic study of a nucleophilic aromatic substitution reaction between 1‐fluoro‐2,4‐dinitrobenzene (FDNB) and 1‐butylamine (BU) developed in (acetonitrile or dimethylformamide + IL) solvent mixtures is presented in order to investigate and compare the solvent effects on a chemical process. For the explored reactive systems the solvation behavior is dominated by both the dipolarity/polarizability and the basicity of the media, contributing these solvent properties to accelerating the chemical process. Copyright © 2007 John Wiley & Sons, Ltd.

The main purpose of this work is to analyze the microscopic feature of solvent systems resulting from the basis of binary mixtures formed by a protic molecular solvent (methanol, ethanol, propan-1-ol, propan-2-ol, and 2-ethoxyethanol) and a 1-butyl-3-methylimidazolium (bmim)-based ionic liquid (IL) cosolvent composed of different anions (tetrafluoroborate, hexafluorophosphate, chloride, and bromide). At the same time, a complementary aim is to evaluate the incidence of anion type on the solvation pattern. The empirical solvatochromic parameters E(T)(N), π*, β, and α were determined from the UV-vis solvatochromic shifts of adequate probes. The behavior of the solvent systems was analyzed according to their deviation from ideality. E(T)(N) polarity and π* dipolarity/polarizability exhibit positive deviation from ideal behavior in all binary mixtures at the explored compositions. Moreover, E(T)(N) and α parameters display synergetic effects in some binary mixtures composed of tetrafluoroborate and hexafluorophosphate anions. The influence of anion nature on the response patterns is clearly manifested in the basicity β and acidity α of the media. This is connected with the degree and type of interaction between the anions and the 1-butyl-3-methylimidazolium cation. The ion-pair character of the ionic liquids affects their interactions with a solute or a molecular solvent. The application of an appropriate preferential solvation model allowed us to obtain valuable information about solute-solvent and solvent-solvent interactions of the selected ionic liquid mixtures. It is possible to identify relevant mixtures paying particular attention to the most remarkable microscopic properties, the acidity and the basicity, in order to propose "new solvents". Thus, the solvating feature can be tailored selecting the molecular and/or the ionic component at a particular composition. A simplified combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) equation is shown to satisfactorily predict the solvatochromic parameters within [protic molecular solvent + bmim-based IL].

A study was made of the influence of temperature on the reactions between 1‐fluoro‐2,6‐dinitrobenzene and each of the secondary amines pyrrolidine, piperidine and homopiperidine (hexahydro‐1H‐azepine), carried out in ethyl acetate–chloroform binary solvent mixtures. It involved the analysis of both global activation parameters and the corresponding Arrhenius plots from the kA values at three amine concentrations. These values were obtained by carrying out the reactions at 5, 15, 25, 40 and 50°C over the whole range of chloroform mole fraction. The analysis of Arrhenius lines allowed us to prove the existence of isokinetic relationships, which were used as a diagnostic tool in order to infer a changeover in the nature of the rate‐determining transition state as a function of solvent composition. The experimental evidence together with theoretical quantum mechanical calculations suggest that the reactions with the secondary amines explored carried out in pure ethyl acetate and ethyl acetate–chloroform solvent mixture at X = 0.1 and in some cases also at X = 0.3 proceed via the formation of a six‐membered orientated dipolar aggregate in which the specific base–general acid (SB–GA) mechanism may take place. The reactions carried out in the remaining solvent mixtures evolve towards the classical SB–GA mechanism. Copyright © 2004 John Wiley & Sons, Ltd.

New cationic surface‐active ionic liquids (SAIL) were synthesized using 1‐alkylimidazolium cations [CnHim] (n = 8, 10, 12, 14, and 16) with trifluoroacetate ([CF3CO2]) and methanesulfonate ([CH3SO3]) anions as counterions. Their self‐aggregation behavior in water was investigated using electrical conductivity and fluorescence measurements. Based on the obtained results, the critical micellar concentration (CMC), the degree of counterion dissociation, α, the Gibbs free energy of micelle formation, normalΔGmic0, and the mean aggregation number (Nagg) were determined. The analysis of these parameters indicates that these new SAIL exhibit certain improved properties with respect to traditional cationic surfactants. Furthermore, SAIL with [CF3CO2] counterions exhibit lower CMC values than alkyltrimethylammonium bromide (CnTAB)‐type surfactants and their dialkylimidazolium counterparts with the same alkyl chain length. It was demonstrated that, in the studied SAIL, the hydrophobic probe pyrene resides deeper inside the palisade layer of the micelle and the estimated E T(30) polarity values of micellar pseudophase confirm this result. The abovementioned outcomes demonstrate that the 1‐alkylimidazolium cation is suitable to promote aggregation when it is accompanied by the appropriate counterions. Consequently, this contribution becomes a valuable first step toward the potential application of these compounds as a new class of “designed cationic surfactants.”