The effect of imidazolium salts with amino acids as counterions on the reactivity of 4-nitrophenyl acetate: A kinetic study

As a first approach to improve the "green character" of the surfactants based on imidazolium cations, three surfactants using 1-tetradecyl-3-methylimidazolium [C(14)mim](+) as cation and different amino acids (AA) as counterion, were synthetized [C(14)mim][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 [C(14)mim][Br] was including as well. We present the application of the micellar solutions (formed with this surfactants), as reactionmedia for the reaction of 4-nitrophenyl acetate (NPA) and found that reaction rates (k(obs)) increase significantly compared to the reaction in water. Additionally, a novel reactivity modulation of NPA in these micellar systems was found. (C) 2020 Elsevier B.V. All rights reserved.