One colorimetric and one fluorescent-indicator displacement assay (IDA) were studied to assess their interaction with methyl viologen (MV), an herbicide commercially known as paraquat. The host-guest complexes formed by cucurbit[7]uril (CB[7]) and the 4-nitroaniline (NA) or Berberine (Be) dyes function as colorimetric- and fluorescent-IDA for MV, respectively. The CB[7]@NA and CB[7]@Be complexes were characterized by UV-vis, fluorescence spectroscopy, and dynamic simulations. Isothermal titration calorimetry (ITC) experiments and dynamic simulations were employed to obtain thermodynamic data for the formation of the 1:1 inclusion complexes. Finally, NA is proposed as a reference colorimetric dye for determining CB[7]-binding affinities using competitive host-guest titrations, and the fluorescent-IDA as the best assay proposed, as it exhibits a high binding constant, a good detection limit of 2.7 x 10-6 mol L-1, good linearity in the range from 4 x 10-6 mol L-1 to 3.5 x 10-5 mol L-1, in aqueous solution. One colorimetric- and one fluorescent-IDA were tested to determine methylviologen. 4-Nitroaniline is tested as the reference colorimetric dye for determining CB[7]-binding affinities. The proposed IDA assays were selectives to MV over the other pesticides.image

Surface distribution and particle size play a key role in the catalytic activity of substituted La1−xAxCoO3 (A = Ca/Sr, x = 0.2–0.4) perovskites.

Propylene carbonate is becoming a suitable green alternative to volatile organic solvents in the study of chemical reactions. In this study, an efficient method for nucleophilic degradation of five organophosphorus pesticides, fenitrothion, malathion, diazinon, parathion, and paraoxon, using propylene carbonate as a solvent is proposed. The effect of changing the nature of the nucleophile and the influence of microwave (MW) heating were investigated. A screening of temperatures (50 °C-120 °C) was performed under microwave heating. The pesticide degradation was followed by 31P NMR, and the extent of conversion (%) was calculated by the integration of phosphorus signals. Keeping in mind that recently it has been reported that some ionic liquids play a nucleophilic role, in this work we report for the first time the degradation of organophosphorus pesticides by using an amino acid-based ionic liquid such as Bmim[Ala] as a nucleophile and a bio-based solvent (propylene carbonate) as a reaction medium in combination with microwave heating.

Liquid-phase hydrogenation of succinic acid (SA) over supported Ni and Co catalysts was investigated at 200 degrees C and 6 MPa of H-2. Reduced and passivated catalysts with the same surface metal density (2.5 atoms of metal per nm(2) of support) were prepared by incipient wetness impregnation. The catalysts were characterized by X-ray diffraction (XRD), N-2 adsorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), CO-chemisorption, and temperature-programmed desorption of NH3 (TPD-NH3). The Ni and Co catalysts supported over SiO2 showed different product distribution, due to the adsorption of the SA over the surface of catalysts, determined by DFT calculations. The Co/SiO2, Co/SiO2-Al2O3, and Co/Al2O3 catalysts showed different product distribution, which was correlated with total acidity from TPD-NH3 results. In general, the Co catalysts promoted the hydrogenation process; however, the highest total acidity showed by Co/Al2O3 also promoted the dehydration process. Finally, the initial rate follows the trend according to the dispersion determined by COchemisorption.

As a first approach to improve the “green character” of the surfactants based on imidazolium cations, three surfactants using 1-tetradecyl-3-methylimidazolium [C14mim]+ as cation and different amino acids (AA) as counterion, were synthetized [C14mim][AA], where AA: L-alanine (L-Ala); L-phenylalanine (L-Phe) or L-proline (L-Pro). The aggregation behavior of these surfactants in water was characterized by surface tension, conductivity measurements and ITC, in order to determine the critical micelle concentration (CMC) and to provide aggregation parameters. In other to evaluate the replacement of a simple inorganic anion [Br]− by AAs in the structure of these surfactants, the characterization of [C14mim][Br] was including as well.We present the application of the micellar solutions (formed with this surfactants), as reaction media for the reaction of 4-nitrophenyl acetate (NPA) and found that reaction rates (kobs) increase significantly compared to the reaction in water. Additionally, a novel reactivity modulation of NPA in these micellar systems was found.

The effect of 3 amino acids on the self-assembly properties of the surface-active ionic liquid: 1-tetradecyl-3-methyl imidazolium bromide, [C(14)mim][Br], was studied in neutral and basic aqueous solution. The critical micelle concentrations were determined by different techniques, and the thermodynamic parameters of micellization (Delta G(mic)(0), Delta H-mic(0), and Delta S-mic(0)) were measured by isothermal titration calorimetry. The critical micelle concentration values decrease in the presence of all the amino acids used in this study. The most substantial effect was observed in the presence of L-tryptophan at pH 12, due to the electrostatic and pi-pi interactions with the imidazolium headgroup of the surfactant. Always entropy-driven micellization occurred. Both the enthalpy and entropy changes upon association to micelles increased when the pH was enhanced from 7 to 12. H-1 NMR measurements demonstrated that among the used amino acids, L tryptophan interacts most strongly with the headgroup of the surfactant cation. The knowledge on the surfactant-amino acid interactions significantly contributes to the deeper understanding of the effect of surfactants on the properties of peptides.

The synthesis of a series of ionic liquids using 1-butyl 3-methylimidazolium (Bmim+) as a cation and different amino acids (AA) as anions (Bmim[AA]) is described. These ILs were used for the first time as reaction media to achieve more eco-friendly Paraoxon degradation. The results show that the degradation of Paraoxon in these Bmim[AA]s is accomplished with great efficiency and without an extra nucleophilic agent. Therefore, we propose that all the Bmim[AA]s used in this study have a dual role in the outcome of this reaction; as a nucleophile and a solvent to carry out degradation of the organophosphorous pesticide, Paraoxon. Both kinetics and product distribution results found in this study for Paraoxon degradation turned out to be promising, because this process is achieved in a reaction medium with a better environmental profile.

In this work, we report a kinetic study of the reactions of the title compound with secondary alicyclic amines at different temperatures in acetonitrile and several ionic liquids (ILs). From this study, we have described that the reactions in MeCN and in the studied ILs occur by a concerted mechanism and that the activation parameters are sensitive to the structural properties of the ILs. The pKa values of all amines used in both MeCN and ILs were determined.

Correction for ‘Reaction mechanisms in ionic liquids: the kinetics and mechanism of the reaction of O,O-diethyl (2,4-dinitrophenyl) phosphate triester with secondary alicyclic amines’ by Paulina Pavez et al., Org. Biomol. Chem., 2016, DOI: 10.1039/c5ob02128f.

The reactions of O,O-diethyl 2,4-dinitrophenyl phosphate triester (1) with secondary alicyclic (SA) amines in the ionic liquids [Bmim]BF4 and [Bmim]DCA were subjected to a kinetic study. Eyring plots were obtained for the title reactions in the above ionic liquids (ILs) and also in aqueous ethanol (44 wt% ethanol). Two different reaction pathways were observed in [Bmim]BF4: nucleophilic attack at the phosphoryl center, SN2(P), and at the C-1 aromatic carbon, SN(Ar), where the product distribution remained constant and independent of the amine nature. In contrast, in [Bmim]DCA only the SN2(P) pathway was found. From the kinetic analysis of the SN2(P) pathway in both ILs, curved upwards plots of kobsdvs. 1-formylpiperazine concentration were obtained. Based on the kinetic behavior, a change in the mechanism of the SN2(P) pathway is proposed for the aminolysis of 1, from a concerted process in aqueous ethanol to a stepwise mechanism, through a zwitterionic pentacoordinate intermediate, when [Bmim]BF4 and [Bmim]DCA are used as the solvents of the reaction.

An electrochemical technique was used to investigate pKa values of some substituted secondary alicyclic (SA) amines, pyridines (py), anilines (AN), and triethylamine (Et3N) in different ionic liquids. The method involves cyclic voltammetry at a platinized Pt electrode. The experimental data were correlated with pKa values reported previously in aqueous solution, and Hammett parameters were correlated with pKa values in ionic liquids to determine ρ values in these media.

The reaction of p-nitrophenyl acetate (1) with piperidine was studied in nine organic solvents and in nine ionic liquids. The aminolysis of 1 by four different secondary amines was also studied in [Bmim]BF4 and their basicities were determined in this solvent using two different methods. Medium effects were analysed and interpreted by comparing the rate constants of aminolysis for the two sets of solvents.