A NEW APPROACH TO THE THEORETICAL ESTIMATION OF INDUCTIVE CONSTANTS

A new model of the inductive effect is proposed, allowing highly accur ate theoretical calculations of inductive constants for a diversity of substituents, using a simple and readily available system of mathemat ics. According to this approach, the inductive effect of a substituent is considered in terms of the additive influence of its constituent a toms. A constant inherent capacity for inductive interaction with a re active center (with a four-coordinate carbon atom chosen for such a ce nter), represented by an atomic constant sigma(A), is ascribed to each atom. Values of sigma(A) for a wide variety of atoms are determined, and their physical meaning is revealed to elucidate to a certain exten t the physical nature of the inductive effect. In addition, the propos ed model permits the convenient use in calculations of group constants sigma(G) characterizing the inductive power of groups. Values of sigm a(G) are determined for molecular fragments that are most widely dealt with in organic chemistry, and the use of sigma(A) or sigma(G) consta nts and of their superposition is shown to have, in most cases, little or no effect on the accuracy and reproducibility of the results obtai ned. It is also shown that, in terms of the developed approach, the in ductive effect of a substituent is closely associated with its conform ation. Theoretical inductive constants were calculated for 427 organic , aromatic, organometallic and charged substituents, and they showed p erfect correlation with the corresponding experimental values. (C) 199 8 John Wiley & Sons, Ltd.