Proton nuclear magnetic resonance studies of dibenzo‐p‐dioxins: Substituent effects

High‐resolution proton nuclear magnetic resonance through heptachlorinated dibenzo‐p‐dioxins are presented. Chemical shifts from dioxins that were synthesized separately are used to assign congeners formed in mixtures. Linear multiple regression analysis was applied to the chemical shift results and the model yielded excellent shift predictability once substituent interactions had been included in the analysis. The average deviation from experimental values was 0.004 ppm. The intra‐ring substituent effects can be explained by a combination of through‐space and ring current effects. Inter‐ring substituent effects showed a dependence on distance, but the reason for this trend is not clear. These measurements demonstrate a reproducible chemical shift effect over nine bonds.