An Eco-Friendly Friedel–Crafts Acylation Experiment for the Undergraduate Laboratory Using BMIMBF4 and BMIMMeSO4 with MgBr2·OEt2 as a Safer Alternative to AlCl3 and DCM

This article presents a greener, safer undergraduate laboratory experiment for the Friedel–Crafts acylation of ferrocene. The conventional aluminum chloride/dichloromethane (AlCl3/DCM) protocol is replaced by the ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) and 1-butyl-3-methylimidazolium methyl sulfate (BMIMMeSO4), with magnesium bromide diethyl etherate (MgBr2·OEt2) used as a milder Lewis acid . Under instructional conditions, the BMIMBF4/MgBr2·OEt2 system affords 67% ± 2% (n = 3) acetylferrocene, exceeding a DCM control (59% ± 3%, n = 3) while reducing volatile organic compounds and corrosive waste. The experiment fits a standard three-hour lab by using a pre-lab start or a two-week format and emphasizes learning objectives in electrophilic aromatic substitution, safer solvent/catalyst selection, and spectroscopic analysis (IR, 1H NMR; optional GC-MS). A brief classroom implementation with student feedback is reported.