Isolation, X-ray structures, and electronic spectra of reactive intermediates in Friedel-Crafts acylations

Reactive intermediates in the Friedel-Crafts acylation of aromatic donors are scrutinized upon their successful isolation and X-ray crystallography at very low temperatures. The X-ray-structure examinations of aliphatic and aromatic acylium electrophiles isolated as crystalline salts that indicate the origins of their electrophilic reactivity are analyzed.