Isolation and X-ray Structures of Labile Benzoic- and Acetic-Acidium Carbocations

New carbocationic salts (via O-protonation of substituted
benzoic acids) are prepared for the first time by controlled
hydration of the corresponding benzoylium salts and isolated
in pure crystalline form. Precise X-ray structural analyses
reveal the rather unexpected (electronic) structure of the
carboxylic-acidium functionality.