Electrophilicity Index

TLDR

Prompted by a recent paper by Maynard and co‑workers, the authors introduce a new property of chemical species. The study proposes that the square of electronegativity divided by chemical hardness defines an electrophilicity index. The authors define this index and tabulate it for various atomic and molecular species using two models of the energy–electron number relationship. They demonstrate that the index quantifies the second‑order energy change of an electrophile as it is saturated with electrons. Published in the National Academy of Sciences, USA.

Abstract

Prompted by a recent paper by Maynard and co-workers (Maynard, A. T.; Huang, M.; Rice, W. G.; Covel, D. G. Proc. Natl. Acad. Sci. U.S.A. 1998, 95, 11578), we propose that a specific property of a chemical species, the square of its electronegativity divided by its chemical hardness, be taken as defining its electrophilicity index. We tabulate this quantity for a number of atomic and molecular species, for two different models of the energy−electron number relationships, and we show that it measures the second-order energy change of an electrophile as it is saturated with electrons.