FIELD AND RESONANCE COMPONENTS OF SUBSTITUENT EFFECTS

F and R, field and resonance constants, are calculated for 42 substituents from Hammett σm and σsGpvalues by assuming that any set of substituent constants (σsGm, σsGp, σsG′, etc.) may be expressed as f * + K*, that r = 0 for σsG′ (from ionization of 4-substituted bicyclo[2.2.2]octanecarboxylic acids), and that (R = 0 for the (CH3)3N+ substituent, * and * are proposed as moee accurately defined and more physically significant independent variables for correlating or predicting substituent effects on all kinds of rates, equilibria, and physical properties than any other pair out of 43 sets (reaction series) considered, including σsGm, σsGp, σsGp-, σsGp+, βsGp - σsGm, σsG*, σsGI, and σsGR0. For all 43 sets, the weighting factors f and r are evaluated, the average correlation coefficient is 0.967 (and not significantly increased by the use of the three independent variables *, σsGp-, σsGp- instead of the two ββ and (R), and the importance of resonance, % ββ, is calculated from f and r, e.g., as 22% for σsGm, 53% for σsGP, 66% for σsGp+, and 92% for σsGp - σsGm. © 1968, American Chemical Society. All rights reserved.