Résumé
There are typically signs of light degradation of ionic liquids by pyrolysis when used in electrochemistry or when submitted to high heat or to ultrasound irradiation for chemical reactions. Cavitation observed through sonoluminescence from dry hydrophobic ionic liquids under sonication leads to degradation by pyrolysis at the level of traces. The degradation products can hinder recycling ionic liquids and, in turn, hinder the beneficial of their use and development of efficient large-scale processes. Unfortunately, various experimental limitations have prevented structural determination. The problems include the following: ionic liquids are almost non-volatile, which excludes the use of classical analytical techniques, and degradation products are produced at very low concentrations, which complicates extraction and analysis. Reported here is the first structural determination of the degradation products of a hydrophobic bis(trifluoromethylsulfonyl)imide-based ionic liquid under ultrasonic irradiation.