SUBSTITUENT EFFECTS OF H-1-NMR PARAMETERS OF CHLORINATED DIPHENYL ETHERS - A STATISTICAL APPROACH

The H-1 NMR spectra of 64 polychlorinated diphenyl ethers (PCDEs) were measured and assigned. Multiple linear regression analysis was used t o estimate the effects of chlorine atoms on the H-1 NMR chemical shift s and coupling constants. The 'simple sum rules' were found to be inad equate for the prediction of H-1 NMR chemical shifts of PCDEs. Therefo re, corrective terms of two chlorine atoms were taken into account. Th e most important effects on chemical shifts were shown to be the steri c interactions of two adjacent chlorine atoms and the intramolecular r ing current effect observed in the ortho-proton of tri-ortho-substitut ed PCDEs. The substituent effects on J(HH) coup ling constants were fo und to be approximately additive. An interannular coupling between ort ho-protons [(6)J(HH) = 0.05-0.15 Hz] of adjacent rings was observed.