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It is well-known that for a fixed ionic liquid cation, variation of the anion determines the physicochemical properties and the activity as solvent or catalyst. Although ion exchange is an acknowledged phenomenon, it is often overlooked in ionic liquid applications due to a lacking framework. We propose here a framework to describe and predict ionic liquid ion exchange with a gain in interaction energy as driving force. The low charge density ionic liquid cations display low interaction energies and are condemned to pair with the most weakly interacting anions in the system, after all stronger interactions have formed. This is demonstrated both for phosphonium and imidazolium ionic liquids, with and without hydration effects. The importance on processing is exemplified by esterification, in which the degree of exchange of carboxylic acid for carboxylate and the availability of protons determines the conversion. [ABSTRACT FROM AUTHOR]

Ionic liquids can both act as a solvent and mediate esterification to valorize low-titer volatile fatty acids and generate organic solvents from renewable carbon sources including biowaste and CO2. In this study, four phosphonium ionic liquids were tested for single-stage extraction of acetic acid from a dilute stream and esterification to ethyl acetate with added ethanol and heat. The esterification proceeded with a maximum conversion of 85.9±1.3 % after 30 min at 75 °C at a 1:1 stoichiometric ratio of reactants. Extraction and esterification can be tailored using mixed-anion ionic liquids; this is demonstrated herein using a common trihexyl(tetradecyl)phosphonium cation and a mixed chloride and bis(trifluoromethylsulfonyl)imide anion ionic liquid. As a further proof-of-concept, ethyl acetate was generated from an ionic liquid-driven esterification of an acetic acid extractant generated using CO2 as the only carbon source by microbial electrosynthesis. [ABSTRACT FROM AUTHOR]

Bromination reactions are crucial in today's chemical industry since the versatility of the formed organobromides makes them suitable building blocks for numerous syntheses. However, the use of the toxic and highly reactive molecular bromine (Br2) makes these brominations very challenging and hazardous. We describe here a safe and straightforward protocol for bromination in continuous flow. The hazardous Br2 or KOBr is generated in situ by reacting an oxidant (NaOCl) with HBr or KBr, respectively, which is directly coupled to the bromination reaction and a quench of residual bromine. This protocol was demonstrated by polybrominating both alkenes and aromatic substrates in a wide variety of solvents, with yields ranging from 78% to 99%. The protocol can easily be adapted for the bromination of other substrates in an academic and industrial environment. [ABSTRACT FROM AUTHOR]