NMR spectroscopy in environmental chemistry: H-1 and C-13 NMR chemical shift assignments of chlorinated dibenzothiophenes based on two-dimensional NMR techniques and ab initio MO and DFT/GIAO calculations

H-1 and C-13 NMR spectra for seven chlorinated dibenzothiophenes (DBTs) wer e measured. Complete H-1 and C-13 NMR chemical shift assignments for 2,8- a nd 3,7-dichloro- and 2,3,6,8-, 2,3,7,8- and 2,4,6,8-tetrachloro congeners a re based on z-gradient selected inverse (proton detected) two-dimensional h eteronuclear chemical shift correlation experiments, H-1, C-13 HMQC and HMB C. For 1,2,3,4,6,7,8-heptachloro-DBT and octachloro-DBT, where polarization transfer techniques from proton to (all) carbons are not possible, the C-1 3 NMR chemical shift assignments are based on theoretical calculations usin g ab initio MO and DFT/GIAO methods at the HF/6-311G* and BPW91/6-311G* lev els. The observed HMBC correlations for the heptachloro congener are in goo d agreement with a theoretically predicted shift order, providing evidence for the reliability of the theoretical method. Copyright (C) 1999 John Wile y & Sons, Ltd.