![]() There are also electron donors serving as meta directing groups. Anionic systems are always electron donors. Most neutral species we studied here are electron withdrawal in nature. Our results do not support that ortho/ para directing groups are electron donors and meta directing groups are electron acceptors. Ortho/ para directing groups have most negative charges on the ortho/ para positions, while meta directing groups often possess the largest negative charge on the meta position. We find that regioselectivity of electrophilic attacks is determined by the Hirshfeld charge distribution on the aromatic ring. Here, based on the theoretical framework we recently established in density functional reactivity theory (DFRT), where electrophilicity and nucleophilicity are simultaneously quantified by the Hirshfeld charge, the nature of ortho/ para and meta group directing is systematically investigated for a total of 85 systems. Though resonance and inductive effects have been employed in textbooks to explain this phenomenon, no satisfactory quantitative interpretation is available in the literature. ![]() The groups that promote substitution at the ortho/ para or meta positions are, respectively, called ortho/ para and meta directing groups, which are often characterized by their capability to donate electrons to or withdraw electrons from the ring. Electrophilic aromatic substitution as one of the most fundamental chemical processes is affected by atoms or groups already attached to the aromatic ring.
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