Fukui function regioselectivity indicators

When a molecule accepts electrons, the electrons tend to go to places where/1 (r) is large because it is at these locations that the molecule is most able to stabilize additional electrons. Therefore a molecule is susceptible to nucleophilic attack at sites where/ "(r) is large. Similarly, a molecule is susceptible to electrophilic attack at sites where f (r) is large, because these are the regions where electron removal destabilizes the molecule the least. In chemical density functional theory (DFT), the Fukui functions are the key regioselectivity indicators for electron-transfer controlled reactions. 

All of these regioselectivity indicators are called Fukui functions, in honor of Kenichi Fukui, who pioneered the analogous frontier orbital reactivity descriptors in the early 1950s [12-14]. The Fukui function and its twin, the local softness [15]. 

Besides the global descriptors of reactivity, there are a number of local indices that describe the active sites within a molecnle. Among them, of special interest is the Fukui function [48, 53, 57-60]. This index, besides being a local descriptor of reactivity by itself (i.e., regioselectivity), may act as a convenient distribution function for global quantities. The original definition is as follows [59, 61] ... 

Although Parr and Yang proposed this Fukui function for describing the regioselectivity of radical reagents and has heen used as such in early-literature conceptual DFT applications, this reactivity indicator has recently been found to be rather incapable of describing the broad scope of radical reactions, e.g. the distinction between electrophilic, nucleophilic and neutral radicals. ... 

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