STUDIES ON ELECTRONEGATIVITY II. GROUP ELECTRONEGATIVITIES

An empirical formula based on the method for calculating the atomic electronegativity is extended to the calculation of group electronegativities, that is, x=n~*/r~* (1) where r~* is the effective radius (in A) of the central atom A in group-ABy, and n~*, the number of effective valence electrons on the atom A. For calculating x, r~* can be determined by Sanderson's method, and n~* can be estimated by n~*=n+2∑m(X_A/(X_A+X_B))+(1/a)∑p((X_B-XA)/(X_A-X_B)) (2) where n is the number of valence electrons on the free atom A less the number taking part in the bonding to B, X_A and X_B are the electronegativities of the atoms A and B respectively, m and p represent the number of bonded electrons and nonbonded electrons of atom B respectively, and α is a constant which represents the decrease of the inductive effect upon propagation along the chemical bond. The quantity n~*/r~* represents the absolute group electronegativity which is related to Pauling's unit by the following equation: x_((Pauling))=0.34(n~*/r~*)+0.67 (3) The electronegativities for various type of groups have been calculated and the values found are dose to those obtained by other authors. It is also found that, when arranged in order of decreasing group electronegativities, the sequence is identical with Kharasch's relative group electronegativity series and the relative magnitudes of the group electronegativities are in line with Taft's polar substituent constant σ~* as well as with Chiang-Tai's inductive effective index Ⅰ.