Theoretical Calculations and Superacidity in the Gas Phase

Subsequently, the development of both theoretical DFT methods and more sophisticated ab initio high-level MP2-type calculations has also spurred investigations in the superacid field. 

AG values of deprotonation are as low as 249-250 kcal mol 1 for HS03F or HF associated with SbF5 or S03. The strongest superacid was found to be dodeca-fluorocarborane acid CBnF12H with a AG of 209 kcal mol 1 even suggesting that the dodeca(trifluoromethyl)carborane acid CBnlCF l H would be below the 200 kcal moL1 level  

Mota and co-workers have investigated the nature of superacid electrophilic species in HF-SbF5 by density functional theory63 and measured the ability of the system to protonate light alkanes (methane, ethane, propane, and isobutane).64 

More recently, Gutowski and Dixon65 have recalculated [G3(MP2) theory] the intrinsic gas-phase acidities of a series of 21 Brpnsted acids. The computed results are in excellent agreement with experimental gas-phase acidities in the range 342-302 kcal moP1 to within lkcal/molfor 14 out of 15 acids. However, acids with experimental acidities lower than 302 kcal mol 1 were found to have large deviations compared to the G3(MP2) results. 

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