Protosolvation acetyl cation

Volpin called the CH3COCI lAlCk complex an aprotic superacid. The results indicate that the acetyl cation is activated by further 0-complexation with a second molecule of AIX3 (the equivalent of protonation or protosolvation). 

Scheme 1. Protosolvation of the acetyl cation and its reaction with isobutane.

As noted previously in Chapter 1, the electrophilic reactivities of acetyl salts increase dramatically as the acidity of the reaction medium increases. This was one of the observations that lead Olah and co-workers to first propose the concept of superelectrophilic activation, or protosolvation of the acetyl cation, in 1975.2 This seminal paper described the chemistry of acetyl hexafluoroantimonate (CHsCO+SbFg-) and the reaction with alkanes in various solvents. In aprotic solvents such as SO2, SO2CIF, AsF3, and CH2CI2, there was no reaction. However in HF-BF3, acetyl salts react with Ao-alkanes and efficient hydride abstraction is observed.27 This was interpreted by Olah as evidence for protonation of the acetyl... 

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