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Article ID: 1614 - Last Modified: December 2, 2013

How do I find the most reactive sites for electrophilic or nucleophilic attack on my substrate, and what are the electrophilic and nucleophilic atoms on the attacking species?

You can use Jaguar to calculate the f and f+ Fukui functions (using Applications → Jaguar → Fukui Functions). The maximum values of these functions on the molecular surface indicate the most reactive sites. Highly nucleophilic atoms are those with large, negative values of f. These are atoms that are most likely to act as Lewis bases. Conversely, highly electrophilic atoms are those with large, positive values of f+. These are atoms that are most likely to act as Lewis acids.

Another way of doing this is to use the atomic Fukui indices (also known as condensed-to-atoms Fukui functions), which can be requested in the Properties tab of the Jaguar panel or the QSite panel. The interpretation of the Fukui indices depends on whether the atom of interest is considered to be nucleophilic (or Lewis basic) or electrophilic (or Lewis acidic). For an electrophile, the atoms that are most susceptible to attack by a nucleophile are indicated by high positive values of f_NN for the LUMO. For a nucleophile, atoms with the highest positive values of f_NN for the HOMO are most nucleophilic and thus most likely to attack an electrophile. Note that atomic Fukui indices are not reliable for identifying the most reactive nucleophilic or electrophilic site within a particular molecule. They are more useful in finding trends in reactivity for a chosen atomic site in a series of related molecules.

More information can be found in Chapter 5 of the Jaguar User Manual.

We do not recommend using atomic charges for the prediction of reactivity.

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