Theoretical Study of the Orientation Rules in Photonucleophilic Aromatic Substitutions.

The photonucleophilic aromatic substitution reactions of nitrobenzene derivatives Were studied by ab initio and Density Functional Theory methods. The photohydrolysis is shown to proceed via an addition—elimination mechanism with two intermediates, except in the case of a chlorine leaving group. Depending on the substituents, the addition step, the elimination step, or the radiationless transition is the rate-determining process. The solvent effect on the SN2 Ar* reactions was evaluated by a continuum model. Next, the regioselectivity of the addition step is investigated within the framework of the so-called spin-polarized conceptual density functional theory. It is shown that the preference observed for the meta or para (with respect to the NO2 group) pathways in the addition step can be predicted by using the spin- polarized Fukui functions applied for the prereactive π-complex. [ABSTRACT FROM AUTHOR]