The Alkyl Inductive Effect. I. Relations between σI σ*, QI, and Q* for H and Alkyl Groups; σI Values from the Size and Branching of R

Abstract

For alkyl groups it is shown that new inductive substituent constants, σI(R), can be calculated accurately from previously obtained polar substituent constants, σ*(R), from the simple relation σI(R) = σI(Me)[I-2σ*(R)]. In similar fashion, the two reaction constants are related by QI/Q* = σ*(H)/σI(Me) = 10.6. Many new a\ values are presented for groups for which no previous estimate has been available. The attentuation of σI (R) with alkyl size for n-alkyl groups is shown to be a function of the number of C atoms, nc: σI(R) = —0.137 nc/(2nc + 1). The effect of branching of R is also discussed. © 1979, Walter de Gruyter. All rights reserved.