Understanding the local reactivity in polar organic reactions through electrophilic and nucleophilic Parr functions

Building upon our recent studies devoted to the bonding changes in polar reactions RSC Advances, 2012, 2, 1334 and Org. Biomol. Chem., 2012, 10, 3841, we propose herein two new electrophilic, P+k, and nucleophilic, P−k, Parr functions based on the spin density distribution at the radical anion and at the radical cation of a neutral molecule. These local functions allow for the characterisation of the most electrophilic and nucleophilic centres of molecules, and for the establishment of the regio- and chemoselectivity in polar reactions. The proposed Parr functions are compared with both, the Parr–Yang Fukui functions J. Am. Chem. Soc. 1984, 106, 4049 based on frontier molecular orbitals, and Yang–Mortier condensed Fukui functions J. Am. Chem. Soc. 1986, 108, 5708 based on Mulliken charges.