Thermochemistry of ammonium based ionic liquids: Tetra-alkyl ammonium nitrates – Experiments and computations

In this work data of the molar enthalpies of formation of the ionic liquids [R4N][NO3] were measured by means of combustion calorimetry. The thermal behavior of [R4N][NO3] was studied using differential scanning calorimetry. First-principles calculations of the enthalpy of formation in the gaseous phase have been performed for the ionic species using the G3(MP2) theory. Enthalpies of formation of aqueous tetra-alkyl ammonium ions ΔfHm° ([R4N]+(aq)) derived in this work are useful for prediction thermochemical properties of the ammonium based ionic liquids.

► Gaseous enthalpies of formation of [R4N][NO3] were derived from experiment.
► We used combustion, solution, and differential scanning calorimetry.
► First-principles calculations used to test consistency of experimental data.
► Enthalpies of formation of aqueous alkylammonium cations were derived.
► The latter suggested for prediction thermochemistry of ammonium based ionic liquids.