E-BASED AND C-BASED DUAL PARAMETER SUBSTITUENT CONSTANT CORRELATIONS

Previously reported Delta E(X) and Delta C-X values for E- and C-based dual parameter substituent constant correlations are refined by extending the treatment to several new series of reactions that do not correlate well with Hammett or Taft substituent constants. The additivity of substituent constants for multiple substituents on a parent compound is tested. Saturation of the pi contribution is proposed for conjugative substituents that are effective pi bonding groups. A new series of two- or three-bond substituent constants, 2-X, are developed. The reactions of substituted acetic acids and esters are treated as 2-X, XCH(2) substituents in constrast to prior analyses which treated these systems with localized 3-X parameters. The consistency of the Delta E-Delta C approach with the E and C model is shown by testing the use of the Delta E(X) and Delta C-X substituent parameters to calculate the E(A) and C-A values of substituted phenols.