A Substituent Steric Effect Index Based on the Molecular Graph
Lemont B. Kier · Quantitative Structure-Activity Relationships · 1987
Abstract Three graph‐based indexes of molecular shape have been found to correlate well with the Taft steric indexes, Es, for electron influence‐free alkyl groups and ten symmetric‐top groups used by Charton to compute a Van der Waals radius‐based index, v. The equation model includes the 1kα, and 3Kα, shape indexes and the 0k index equivalent to the Shannon information content per molecule. This later index encodes the group symmetry. The equation model is simplified to the expression ≈︁ = 2k ‐ 3kα ‐ 0k where Xi (≈︁) is proposed as a graph‐based shape index encoding the steric influence of a group.