Stability, acidity and interaction properties of [Bmim][SbF6] coupled with concentrated sulfuric acid

Ionic liquid coupled with strong acid systems presents considerable promise in some catalytic fields. In the present work, the multiple complex systems composed by 98 wt% concentrated sulfuric acid and [Bmim][SbF6] were investigated in the terms of stability, acidity and interaction properties. It was found that acidolysis of [Bmim][SbF6] occurred in the 98 wt% concentrated sulfuric acid accompanied by HF releasing and SbF6− degrading to [SbF6−y(HSO4)y]−. The species after acidolysis in the multiple complex systems were checked and confirmed by electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared spectroscopy (FT-IR), 1H NMR and 19F NMR. Acidity increased slightly with less than 1 wt% [Bmim][SbF6] addition, while decreased with more proportion, which was determined based on the Hammett acidity functions H0, using 13C NMR. The strong hydrogen bond S–O–H···F of interaction among the multiple complex systems was confirmed by molecular dynamic simulation.