A theoretical analysis of substituted aromatic compounds

The substituents CH3, F, NO2, OCH3, and CH2CH2 were placed at the ortho, meta, and para positions on the aromatic molecules aniline, benzaldehdye, nitrobenzene, and phenol. MMFF94, AM1, B3LYP, M06, M06-2X, ωB97X, ωB97X-d, and RI-MP2 using cc-pVDZ and cc-pVTZ and CCSD(T) with cc-pVDZ basis sets were used to calculate the geometries and energies of all regiomers of the molecules. Relative energies of the ortho and meta regiomers relative to the para regiomers were calculated and compared to the CCSD(T) values. A good basis set correlation between cc-pVDZ and cc-pVTZ was observed in RI-MP2. Overall, RI-MP2 gave the best correlation with the CCSD(T) results. All of the hybrid functionals showed similar accuracy and could effectively describe the intramolecular hydrogen-bonding interactions of these compounds. The methoxy group at the para position in methoxyaniline, methoxyphenol, methoxynitrobenzene, and methoxybenzaldehyde was rotated around the phenyl-O bond. HF, along with the cc-pVDZ basis with the other methods, generated inaccurate energy profiles for p-methoxyphenol. For the density functional theory methods, it was necessary to use improved grids to get smooth curves. © 2013 Wiley Periodicals, Inc.