RESUMEN
The formation in solution of supramolecular complexes type zwitterion-cation have been shown. The industrial grade zwitterion surfactants cocamidopropyl hydroxysultaine and cocamidopropyl betaine with sodium ion were studied. A combined experimental and theoretical point of view was performed, through the use of Ultra-Performance Liquid Chromatography/Mass Spectrometry/ElectroSpray Ionization with positive mode (UPLC/MS/ESI+) analytic technique and Density Functional Theory (DFT) theoretical approach. Then, the supramolecular complex zwitterion-cation-anion triplets are shown to be viable. Mass/Charge (m/z) relationships have been determined through MS/ESI using positive mode as an ionization source, obtaining five and four molecular species for industrial grade sultaine and betaine chemical products, respectively. Also, molecular zwitterion-NaCl complexes were theoretically studied in three different dielectric constants corresponding to water, methanol, and acetone solvents. It was found that acetone, the lower dielectric constant solvent studied, shows the higher interaction energy. In both vacuum neutral, zwitterion-NaCl, and vacuum positive, zwitterion-Na+, molecular complexes the interaction of the cocamidopropyl hydroxysultaine pairs is less strong than cocamidopropyl betaine ones.
Asunto(s)
Teoría Funcional de la Densidad , Sodio/química , Espectrometría de Masa por Ionización de Electrospray , Tensoactivos/química , Cationes , Cromatografía Líquida de Alta Presión , Conformación Molecular , Peso Molecular , Cloruro de Sodio/químicaRESUMEN
Herein is presented a new methodology to determine the static adsorption of a zwitterionic surfactant on limestone in three different aqueous media [high-performance liquid chromatography (HPLC) water, seawater, and connate water] with the use of HPLC at room temperature and 70 °C. The results showed that, in both HPLC water and seawater, the surfactant adsorption followed a monolayer Langmuir tendency. In contrast, for connate water, the surfactant presented a new adsorption profile, characterized by two regions: (i) At surfactant concentrations below 1500 mg L(-1), an increase of adsorption is observed as the amount of divalent cations increases in the aqueous media. (ii) At surfactant concentrations above 1500 mg L(-1), the adsorption decreases because the equilibrium, monomer â micelle â vesicle, is shifted to the formation of vesicles, giving as a result a decrease in the concentration of monomers, thus reducing the interaction between the surfactant and the rock, and therefore, lower adsorption values were obtained. The behavior of the surfactant adsorption under different concentrations of divalent cations was well-described by the use of a new modified Langmuir model: (dΓ/dt)ads = k(ads)c(Γ∞ - Γ) - k(cmc)(c - c(cmc))(n)ΓH(c - c(cmc)). It was also observed that, as the temperature increases, the adsorption is reduced because of the exothermic nature of the adsorption processes.
RESUMEN
A novel tetrahydroxypyrrolizidine alkaloid (6) was obtained from rosmarinine degradation in 23% yield (isolated from Senecio callosas).