QSAR of aromatic substances: Toxicity of polychlorodibenzofurans

The flip regression procedure for handling substituted symmetric congeners described previously with regard to benzenoid aromatics has been applied to the dibenzofuran system that has similar symmetry. Polychlorodibenzofurans are important, highly toxic environmental contaminants that bind to the aryl hydrocarbon receptor (AhR). Their toxicity is known to correlate with their Pearson-Parr softness, and in this contribution it is shown that the orientation of nodes in their occupied π orbitals explains a further large portion of the variance in their toxicity, the two together accounting for up to 95% of this variance.