Organocatalyzed One-Step Synthesis of Functionalized <i>N-</i>Alkyl-Pyridinium Salts from Biomass Derived 5‑Hydroxymethylfurfural

An efficient and scalable method has been developed for the synthesis of <i>N-</i>alkylpyridinium salts from biomass derived 5-hydroxymethyl­furfural and alkyl amines using a catalytic amount of formic acid. This protocol is also extended to various diamines providing the exclusive formation of mono-<i>N-</i>alkylpyridinium salts. In addition, the mechanism for the formation of pyridinium salts was studied by DFT and using H₂¹⁸O isotope labeled experiments showing no incorporation of ¹⁸O in the product

Using ¹²⁹Xe NMR to Probe the Structure of Ionic Liquids

The mesoscopic structure of 30 distinct ionic liquids was probed by ¹²⁹Xe NMR spectroscopy. The interpretation of the experimental data was complemented using molecular dynamics results. The results clearly show that xenon can effectively probe the various environments characteristic of different ionic liquids (ILs) and is thus able to distinguish between distinct ionic liquid families, including different types of interactions with diverse types of anion/polar networks. A finer analysis of the NMR data also confirmed that the xenon probes can also provide information on how the complex structure of an IL evolves along a homologous series

Liquid–Liquid Equilibrium of Cholinium-Derived Bistriflimide Ionic Liquids with Water and Octanol

The liquid–liquid equilibria of mixtures of cholinum-based ionic liquids (<i>N</i>-alkyl-<i>N,N</i>-dimethylhydroxyethylammonium bis­(trifluoromethane)­sulfonylimide, [N_{11<i>n</i>2OH}]­[Ntf₂], <i>n</i> = 1, 2, 3, 4, and 5) plus water or 1-octanol were investigated at atmospheric pressure over the entire composition range. The experiments were conducted between 265 and 385 K using the cloud-point method. The systems exhibit phase diagrams consistent with the existence of upper critical solution temperatures. The solubility of [N_{1 1 <i>n</i> 2OH}]­[Ntf₂] in water is lower for cations with longer alkyl side chains (larger <i>n</i> values). The corresponding trend in the octanol mixtures is reversed. The ([N_1 1 1 2OH]­[Ntf₂] + water + octanol) ternary system shows triple liquid–liquid immiscibility at room temperature and atmospheric pressure. A combined analytic/synthetic method was used to estimate the corresponding phase diagram under those conditions. Auxiliary molecular dynamics simulation data were used to interpret the experimental results at a molecular level

Generating Ionic Liquids from Ionic Solids: An Investigation of the Melting Behavior of Binary Mixtures of Ionic Liquids

Mixtures of ionic liquids (ILs) allow enlarging the plethora of the physical and chemical properties of these materials in addition to the well-known tunable character associated with pure compounds. It is shown here that mixtures also induce a significant decrease of the melting points of the mixture to values well below those of the original compounds allowing the tuning of the melting point of an ionic liquid mixture and the generation of novel ionic liquids from mesotherm salts. This work evaluates the melting behavior of mixtures of seven hexafluorophosphate-based compounds combined with imidazolium-, pyridinium-, pyrrolidinium-, piperidinium- ammonium-, or phosphonium-based cations. The solid–liquid equilibrium phase diagrams of nine of their binary mixtures were measured using optical microscopy and differential scanning calorimetry. The pure ILs’ melting profile reveals the presence of polymorphs with highly energetic solid–solid transitions that are relevant for the evaluation of these systems. The phase diagrams reported here also allow an investigation on the nonideality of the mixtures of ionic liquids. A classical thermodynamic approach shows that while most of the mixtures investigated present an ideal liquid behavior, others show slight or even marked nonideal profiles. One particular system, [C₃mpyr]­[PF₆] (1-methyl-1-propylpyrrolidinium hexafluorophosphate) + [C₃mpip]­[PF₆] (1-methyl-1-propylpiperidinium hexafluorophosphate), displays a continuous solid solution as established by differential scanning calorimetry, powder X-ray diffraction, and crystallographic data being one of the few ionic liquid alloys ever reported