The physicochemical characterization of six alkylammonium-based protic ionic liquids (PILs) is presented. These compounds were prepared through a simple and atom-economic neutralization reaction between a tertiary amine and a Brønsted acid, HX, where X- is HCOO-, CH3COO-, HF2-. The temperature dependency and the effect of added water on properties such as density, viscosity, ionic conductivity, and the thermal comportment of these PILs were measured and investigated. The results allowed us to classify them according to a classical Walden diagram and to appreciate their great "fragility". PILs have applicable perspectives in replacements of conventional inorganic acids for fuel cell devices and thermal transfer fluids.
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http://dx.doi.org/10.1021/jp803489n | DOI Listing |
J Chem Phys
May 2018
Mulliken Center for Theoretical Chemistry, Universität Bonn, Beringstr. 4, D-53115 Bonn, Germany.
We applied the binary Quantum Cluster Equilibrium (bQCE) method to a number of alkylammonium-based protic ionic liquids in order to predict boiling points, vaporization enthalpies, and proton activities. The theory combines statistical thermodynamics of van-der-Waals-type clusters with quantum chemistry and yields the partition functions (and associated thermodynamic potentials) of binary mixtures over a wide range of thermodynamic phase points. Unlike conventional cluster approaches that are limited to the prediction of thermodynamic properties, dissociation reactions can be effortlessly included into the bQCE formalism, giving access to ionicities, as well.
View Article and Find Full Text PDFPhys Chem Chem Phys
April 2018
Grupo de Nanomateriales, Fotónica y Materia Blanda, Departamento de Física de Partículas, Facultade de Física, Universidade de Santiago de Compostela, Campus Vida s/n, E-15782 Santiago de Compostela, Spain.
Mixtures of alkylammonium based protic ionic liquids and alkylmethylimidazolium based aprotic ionic liquids were studied by means of molecular dynamics simulations. Close to ideal mixing is observed in most studied magnitudes; however, the effect of increasing alkyl chain length in each of the cations is markedly different, with longer protic cations showing larger deviations, especially with regards to mixing enthalpy, which exhibits a strong compound forming tendency. The compound forming nature of these protic ionic liquids is shown to induce sharp changes in their local environment upon mixing.
View Article and Find Full Text PDFJ Phys Chem A
October 2017
G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, 1 Akademicheskaya Street, Ivanovo 153045, Russia.
The structural and energetic characteristics of protic ionic liquids (PILs) based on ethyl-, diethyl-, or triethylammonium cations with anions of phosphorus, trifluoroacetic, or p-toluenesulfonic acids have been investigated by density functional theory calculations at the B3LYP/6-31++G(d,p) level of theory. As a result of the interaction between acid and alkylamine, the H-bonded molecular complexes or H-bonded ion pairs have been obtained. The increasing number of ethyl groups attached to the nitrogen atom of amine and H-bond donor ability of acid causes a stronger H-bonding interaction leading to the formation of ion pairs.
View Article and Find Full Text PDFJ Am Chem Soc
May 2017
School of Chemistry, WestCHEM, University of Glasgow, Glasgow G12 8QQ, U.K.
Gigahertz- to terahertz-frequency infrared and Raman spectra contain a wealth of information concerning the structure, intermolecular forces, and dynamics of ionic liquids. However, these spectra generally have a large number of contributions ranging from slow diffusional modes to underdamped librations and intramolecular vibrational modes. This makes it difficult to isolate effects such as the role of Coulombic and hydrogen-bonding interactions.
View Article and Find Full Text PDFJ Phys Chem B
February 2015
Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India.
Hydrogen bonding in alkylammonium based protic ionic liquids was studied using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. Normal-mode analysis within the harmonic approximation and power spectra of velocity autocorrelation functions were used as tools to obtain the vibrational spectra in both the gas phase and the crystalline phases of these protic ionic liquids. The hydrogen bond vibrational modes were identified in the 150-240 cm(-1) region of the far-infrared (far-IR) spectra.
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