Substituent effects of 1H NMR parameters of chlorinated diphenyl ethers. A statistical approach

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Abstract
The 1H NMR spectra of 64 polychlorinated diphenyl ethers (PCDEs) were measured and assigned. Multiple linear regression analysis was used to estimate the effects of chlorine atoms on the 1H NMR chemical shifts and coupling constants. The ‘simple sum rules’ were found to be inadequate for the prediction of 1H NMR chemical shifts of PCDEs. Therefore, corrective terms of two chlorine atoms were taken into account. The most important effects on chemical shifts were shown to be the steric interactions of two adjacent chlorine atoms and the intramolecular ring current effect observed in the ortho‐proton of tri‐ortho‐substituted PCDEs. The substituent effects on J(HH) coupling constants were found to be approximately additive. An interannular coupling between ortho‐protons [6J(HH) = 0.05–0.15 Hz] of adjacent rings was observed.