Unraveling Interactions and Catalytic Mechanisms of Ionic Liquid[Bmim][BF4]and Styrene Oxide Using Sum Frequency Spectroscopy
The utilization of ionic liquids as versatile reaction media and catalysts has garnered signifi-cant attention in the field of green and sustainable chem-istry.In this study,sum fre-quency generation vibrational spectroscopy(SFG-VS)is em-ployed to investigate the inter-actions between 1-butyl-3-methylimidazolium tetrafluo-roborate([Bmim][BF4])and styrene oxide(SO)at the air/liquid interface.Spectral analysis in the range of 1000 cm-1 to 3700 cm-1 reveals that on-ly vibrational modes of C-H bonds are observed.Notably,the orientation of the epoxy ring of SO is found to be towards the bulk phase,while the three C-H groups on the imidazolium ring of the cation are parallel to the surface.Consequently,there are no observed interactions be-tween the cation and SO.However,in the vibrational spectra of C-H bonds,interactions be-tween the anion BF4-and the CH2 group of the epoxy ring result in blue shifts in the vibra-tions of CH(SO)and CH3(cation).These findings support a proposed reaction mechanism where the ionic liquid catalyzes SO first and subsequently reacts with CO2,providing valu-able insights into intermolecular interactions and molecular orientations at reaction inter-faces.
Sum frequency generationIonic liquidMolecular interactionCatalytic mecha-nisms
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