The bonding in benzene, phenol and phenyl halides

The V(Ci, Cj) basin populations, their variance and the electrophilic substitution positional indices of the studied CeHsX molecules are fisted in Table 21. The V(C, X) populations and their variance are close to their values in the CH3X series. As expected the V(C, C) basin populations are intermediate between those inherent to a single and a double C—C bond and subject to a large fluctuation of the charge density. The classical meaning of the variance is the square of the standard deviation though the standard deviation cannot be defined for a quantum system, the classical limit provides at least qualitative information about the delocalization. In the present case a 1.16, which is consistent with the resonance picture involving the Kekule structures. 

FIGURE 14 (PLATE 3). Localization domains of mono-X-substituted benzenes C6H5X (from left to right top X = H, OH, F, bottom X = Cl, Br, I). The ELF value defining the boundary isosurface, t (r) = 0.659 corresponds to the critical point of index 1 on the separatrix between adjacent V(C, C) basins of benzene. Colour code magenta = core, orange = monosynaptic, blue = protonated disynaptic, green = disynaptic. Adapted from Reference 220 with permission 

TABLE 21. Basin populations N(V), variance of the basin populations a (V) and electrophilic substitution positional indices RIc of the C6H5X molecules 

Values taken from Reference 220 with permission. 

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