Vapors from Ionic Liquids: Reconciling Simulations with Mass Spectrometric Data

Abstract

The species involved in the distillation of aprotic ionic liquids are discussed in light of recent simulations and mass spectrometric data obtained by various techniques. New mass spectrometric data collected via laser-induced acoustic desorption and the thermal desorption of ionic liquids are also presented as well as additional DFT calculations. The available evidence of theoretical simulations and mass spectrometric data suggests that the distillation of ionic liquids occurs mainly via neutral ion pairs of composition C_<i>n</i>A_<i>n</i> [C⁺ = cation and A^– = anion], followed by gas-phase dissociation to lower order ion pairs and then dissociation of hot CA to C⁺ and A^–, followed by ion/molecule association events to give [C_<i>n</i>A_<i>n</i>–1]⁺ or [C_<i>n</i>–1A_<i>n</i>]⁻ ions to a degree that depends on the amount of internal energy deposited into the neutral C_<i>n</i>A_<i>n</i> clusters upon evaporation