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Characterizing Ionic Liquids as Reaction Media through a Chemical Probe
Author(s) -
Dichiarante Valentina,
Betti Cecilia,
Fagi Maurizio,
Maia Angelamaria,
Landini Dario,
Albini Angelo
Publication year - 2007
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.200601078
Subject(s) - ionic liquid , chemical reaction , ionic bonding , chemistry , computer science , chemical engineering , materials science , nanotechnology , ion , organic chemistry , engineering , catalysis
The triplet N , N ‐dimethylaminophenyl cation, a highly reactive but chemospecific electrophile, has been used as a probe for characterizing the properties of reaction media for a series of imidazolium ILs. With the N ‐hexyl‐ N ‐methyl imidazolium derivatives ( not with the N ‐butyl analogues), hydrogen transfer leading to the aniline was the main process. Trapping by iodide occurred with an inverse dependence on viscosity. Trapping by π nucleophiles exhibited a more complex behavior. This was explained by the effect of both the bulk viscosity and the structure of the IL cation on both steps of the reaction, namely, initial electrophilic attack and ensuing cation elimination or nucleophile addition. However, with an excellent nucleophile, such as thiophene, or when the latter step was intramolecular, as with 4‐pentenol, the difference was obliterated and trapping became uniform. Incorporation of the probe into the IL cation (through insertion into the CH bond α to the imidazolium ring) was demonstrated, while no addition to the anion tested (including bis(trifluoromethanesulfonimide)) took place.