Easy and accurate computation of energy barriers for carbocation solvation: an expeditious tool to face carbocation chemistry.

An expeditious procedure for the challenging computation of the free energy barriers (Δ G ≠ ) for the solvation of carbocations is presented. This procedure is based on Marcus Theory (MT) and the popular B3LYP/6-31G(d)//PCM method, and it allows the easy, accurate and inexpensive prediction of these barriers for carbocations of very different stability. This method was validated by the fair mean absolute error ( ca. 1.5 kcal mol -1 ) achieved in the prediction of 19 known experimental barriers covering a range of ca. 50 kcal mol -1 . Interestingly, the new procedure also uses an original method for the calculation of the required inner reorganization energy ( Λ i ) and free energy of reaction (Δ G ). This procedure should pave the way to face computationally the pivotal issue of carbocation chemistry and could be easily extended to any bimolecular organic reaction.