The AM1 calculation was done for ortho‐substituted toluenes (o‐X‐C6H4‐CH3) and ortho‐substituted tert‐butylbenzenes (o‐X‐C6H4‐t‐Bu). The difference in the calculated heat of formation between o‐X‐C6H4‐CH3 and o‐X‐C6H4‐t‐Bu was used as a theoretical steric index for ortho‐X. The correlation of this theoretical steric index with the empirical steric parameter sets such as our recently defined Es(AMD) and the Taft–Kutter–Hansch (TKH) Es was examined. In spite of the simplicity of the model system, the theoretical index was linear with the Es(AMD) constant with a correlation coefficient of r = 0.972 for 17 substituents of various structures. Including the phenyl group, the correlation with the TKH Es constant was r = 0.948. The theoretically calculated index was shown to serve as a measure of the ortho steric effect.
ASJC Scopus subject areas
- Computational Mathematics