Question

Is there a molecule which behaves as both nucleophile and electrophile?

Answer 1

Not at the same time, but I can think of benzene as one example. I can't imagine any other examples, though.

Two major types of reactions that involve benzene are electrophilic aromatic substitution reactions (EAS) and nucleophilic aromatic substitution reactions (NAS).

One example of EAS is the Friedel-Crafts Acylation, in which benzene acts as a nucleophile in the presence of an acyl chloride and `"AlCl"_3`:

and one example of NAS is the `"S"_"N" "Ar"` reaction (which is generally rare), in which benzene acts as an electrophile due to a strongly-deactivating group (good electron-withdrawing group) such as the `"NO"_2^(-)` group (which is neutral when bonded to a cation), in the presence of base:

You might say, "well wait a minute, can we do that?" Yes, we can; this can be justified by the resonance stabilization this molecule has: