Identification of Active Surface Species for Friedel–Crafts Acylation and Koch Carbonylation Reactions by in situ Solid‐State NMR Spectroscopy

Finding the culprits: In situ NMR spectroscopy combined with theoretical calculations show the formation of acetyl species covalently bound to framework oxygen atoms in acid zeolites. These species, and not the usually assumed acylium cations, are the reactive intermediates in Friedel–Crafts acylation and Koch carbonylation reactions on zeolites.