Premium
Proton Thermodynamics in a Protic Ionic Liquid, Ethylammonium Nitrate
Author(s) -
Kanzaki Ryo,
Kodamatani Hitoshi,
Tomiyasu Takashi
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201903485
Subject(s) - ionic liquid , proton , nitrate , chemistry , thermodynamics , physics , organic chemistry , nuclear physics , catalysis
In order to investigate the proton solvation state in protic ionic liquids (PILs), ten acid dissociation enthalpies and entropies of eight compounds were determined in ethylammonium nitrate (EAN). Regardless of the nature of the compound, 24 kJ mol −1 larger enthalpy and 65 J mol −1 K −1 larger entropy than those in water, respectively, were observed. These values were reasonably explained by the differences in the proton solvation structure in EAN and water. Namely, protons in EAN exist as HNO 3 , having a higher reaction energy than that of H 3 O + in water, undergo entropic stabilization as a result of the less‐structured solvation. As such, the entropic effect of the proton solvation structure on the acid–base property is possibly applicable to all PILs. In addition, based on these proton thermodynamics, enthalpy and entropy windows were proposed as a novel perspective for the characterization of solvents. Use of this concept enabled the visualization of similarities and differences between EAN and water.