Brønsted Ionic Liquids for Sustainable Processes: Synthesis and Physical Properties

Abstract

This report describes the synthesis of ionic liquids that incorporate the N-methyl-2-hydroxyethylammonium cation with various carboxylic acid anions and the study of some of their physical properties, including self-diffusion coefficients, density, speed of sound, viscosity, and refractive index. 1 H and 13 C NMR spectra were used to characterize the chemical structure of the species in concordance with FT-IR spectra. DOSY NMR spectra was used to determine the self-diffusion coefficients of the components, which were consistent with the formation of a lamellar or micellar liquid-crystal phase in samples containing an alkyl chain in the anion species. Thermoacoustic parameters showed that anion alkyl chain has an influence on the molecular packing of these ionic liquids. In addition, the effect of temperature on the properties seems to be related to the size and the type of aliphatic chain of the ionic liquid.

Protic Ionic Liquids Used as Metal-Forming Green Lubricants for Aluminum: Effect of Anion Chain Length

“…Their properties of extremely low vapor pressure, high viscosity, high thermal and ionic conductivity, non-flammability, thermal and chemical stability, and low toxicity make them suitable in many fields of applications, such as catalysis, electrochemical devices and separation processes. Protic ionic liquids can be tailored for a specific application taking into account that a small change whether in anion structure whether in cation structure or in both, modifies their corresponding physicalchemical properties [1][2][3][4][5][6][7] . Among the promising uses of ionic liquids, lubrication for metal-metal, metal-ceramic and ceramic-ceramic contacts has been a new trend since the authors Ye et al 8 showed a significant reduction in the average coefficient of friction for some of the aforementioned tribopairs using two different alkylimidazolium tetrafluoroborates.…”

Physicochemical and Acid-base Properties of a Series of 2-Hydroxyethylammonium-based Protic Ionic Liquids

“…[33][34][35][36][37] In order to clarify solvent natures, one must have extensive knowledge of physicochemical and Brønsted and/or Lewis acid-base properties of ionic liquids. Experimental results for the physicochemical properties [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] and solvatochromic parameters [53][54][55] of ionic liquids with the hydroxyl groups have been reported.…”

Structural Effects on the Physico‐Chemical and Catalytic Properties of Acidic Ionic Liquids: An Overview

“…[63] Subsequently, a series of substituted amine-based ILs with the aliphatic linear pentanoic acid as counter anion was prepared. [64] In particular, (2-hydroxyethyl)ammonium pentanoate [HOH 4 COO] were synthesized and the influence of their structural variations on their thermodynamic properties (density, ultrasonic velocity, ionic conductivity, refractive index, viscosity, and surface tension) was investigated as a function of temperature.…”

“…[63] The sizes and types of alkyl chain also determine the effect of temperature on some physico-chemical properties; local structure models should be applied to explain the macroscopic behavior in terms of the molecular arrangement.…”