A multi-descriptor analysis of substituent effects on the structure and aromaticity of benzene derivatives:
Julio C V Chagas1, Bruno D Milanez1, Vytor P Oliveira1
1Department of Chemistry, Aeronautics Institute of Technology, São José dos Campos, São Paulo, Brazil.
Abstract:
This work provides a detailed multi-component analysis of aromaticity in monosubstituted (X = CH3, C , C , NH2, NH-, NH+, OH, O-, and O+) and para-homodisubstituted (X = CH3, CH2, NH2, NH, OH, and O) benzene derivatives. We investigate the effects of substituents using single-reference (B3LYP/DFT) and multireference (CASSCF/MRCI) methods, focusing on structural (HOMA), vibrational (AI(vib)), topological (ELFπ), electronic (MCI), magnetic (NICS), and stability (S0-T1 splitting) properties. The findings reveal that appropriate π-electron-donating and π-electron-accepting substituents with suitable size and symmetry can interact with the π-system of the ring, significantly influencing π-electron delocalization. While the charge factor has a minimal impact on π-electron delocalization, the presence of a pz orbital capable of interacting with the π-electron delocalization is the primary factor leading to a deviation from the typical aromaticity characteristics observed in benzene.
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