Methyl Cation Affinities of Canonical Organic Functional Groups.

Methyl cation affinities are calculated for the canonical nucleophilic functional groups in organic chemistry. These methyl cation affinities, calculated with a solvation model (MCA*), give an emprical correlation with the term from the Mayr equation under aprotic conditions when they are scaled to the Mayr reference cation (4-MeOCH)CH (Mayr = 0). Highly reactive anionic nucleophiles were found to give a separate correlation, while some ylides and phosphorus compounds were determined to give a poor correlation. MCA*s are estimated for a broad range of simple molecules representing the canonical functional groups in organic chemistry. On the basis of a linear correlation, we estimate the range of nucleophilicities of organic functional groups, ranging from a C-C bond to a hypothetical -butyl carbanion, toward the reference electrophile to be about 50 orders of magnitude.