Synthesis and Characterization of Surface-Active Ionic Liquids Used in the Disruption of Escherichia Coli Cells.

Twelve surface-active ionic liquids (SAILs) and surface-active derivatives, based on imidazolium, ammonium, and phosphonium cations and containing one, or more, long alkyl chains in the cation and/or the anion, were synthetized and characterized. The aggregation behavior of these SAILs in water, as well as their adsorption at solution/air interface, were studied by assessing surface tension and conductivity. The CMC values obtained (0.03-6.0 mM) show a high propensity of these compounds to self-aggregate in aqueous media. Their thermal properties were also characterized, namely the melting point and decomposition temperature by using DSC and TGA, respectively. Furthermore, the toxicity of these SAILs was evaluated using the marine bacteria Aliivibrio fischeri (Gram-negative). According to the EC50 values obtained (0.3-2.7 mg L-1 ), the surface-active compounds tested should be considered "toxic" or "highly toxic". Their ability to induce cell disruption of Escherichia coli cells (also Gram-negative), releasing the intracellular green fluorescent protein (GFP) produced, was investigated. The results clearly evidence the capability of these SAILs to act as cell disruption agents.

Ionic Liquids Derived from Proline: Application as Surfactants.

Ionic liquids derived from prolinium esters, previously described as fully green and stable, were found to decompose in the presence of water by ester hydrolysis. To avoid this problem, a new family of these biodegradable salts incorporating an alcohol instead of the ester group is proposed. From this family, two novel ionic liquids that incorporate the prolinolium cation [HOPro] and the [DS] or [DBS] anion were selected (DS=dodecylsulfate; DBS=dodecylbenzenesulfonate). Both salts are liquid at room temperature, a property not usually found in ionic surfactants, and are also chemically and thermally stable. Moreover, they are more effective in reducing the surface tension of water than the corresponding traditional surfactants in the form of sodium salts, being useful for applications related to their aggregation capacity. They were tested for surfactant enhanced oil recovery and an optimal formulation for reservoirs at high salinity and temperature, able to produce ultra-low interfacial tension, was found with [HOPro][DBS].

Novel 2-alkyl-1-ethylpyridinium ionic liquids: synthesis, dissociation energies and volatility.

This work presents the synthesis, volatility study and electrospray ionization mass spectrometry with energy-variable collision induced dissociation of the isolated [(cation)2(anion)](+) of a novel series of 2-alkyl-1-ethyl pyridinium based ionic liquids, [(2)CN-2(1)C2Py][NTf2]. Compared to the imidazolium based ionic liquids, the new ionic liquid series presents a higher thermal stability and lower volatility. The [(cation)2(anion)](+) collision induced dissociation energies of both [(2)CN-2(1)C2Py][NTf2] and [CNPy][NTf2] pyridinium series show an identical trend with a pronounced decrease of the relative cation-anion interaction energy towards an almost constant value for N = 6. It was found that the lower volatility of [(2)CN-2(1)C2Py][NTf2] with a shorter alkyl chain length is due to its higher enthalpy of vaporization. Starting from [(2)C3(1)C2Py][NTf2], the lower volatility is governed by the combination of slightly lower entropies and higher enthalpies of vaporization, an indication of a higher structural disorder of the pyridinium based ionic liquids than the imidazolium based ionic liquids. Dissociation energies and volatility trends support the cohesive energy interpretation model based on the overlapping of the electrostatic and van der Waals functional interaction potentials.

Knoevenagel reaction in [MMIm][MSO4]: synthesis of coumarins.

The ionic liquid 1,3-dimethylimidazolium methyl sulfate, [MMIm][MSO4], together with a small amount of water (the amount taken up by the ionic liquid upon exposure to air), acts efficiently as both solvent and catalyst of the Knoevenagel condensation reactions of malononitrile with 4-substituted benzaldehydes, without the need for any other solvent or promoter, affording yields of 92%-99% within 2-7 min at room temperature. When L-proline is used as an additional promoter to obtain coumarins from o-hydroxybenzaldehydes, the reaction also proceeds in high yields. Work-up is very simple and the ionic liquid can be reused several times. Some of the coumarins obtained are described for the first time.

Design and Characterization of Naphthalene Ionic Liquids.

Surfactants have a great number of applications. Among these chemicals, petroleum sulfonates have been widely used due to their effectiveness in reducing interfacial tension. This is the case of sodium octylnaphthalene sulfonate which is a solid with a very low solubility in water. To overcome these drawbacks, this work aimed to synthesize new surface active ionic liquids based on a naphthalene sulfonate anion and traditional cations of these salts (imidazolium, pyrrolidinium, and pyridinium). The new chemicals showed high thermal stability, ionic liquid nature, and a stronger surfactant character than the original naphthalene. Moreover, they were found to be water soluble which greatly facilitates their application in the form of aqueous formulations. 1-Hexyl-3-methylimidazolium 4-(n-octyl)naphthalene-1-sulfonate showed the best capacity to reduce water-air and water-oil interfacial tension.