Deceptive simplicity in ABMX N.M.R. spectra. I. Dibenzothiophen and 9,9'-dicarbazyl

Abstract

Analyses of the spectra of dibenzothiophen and 9,9?-dicarbazyl in several solvents are reported. It is found that most of these spectra are partly or wholly deceptively simple. The criteria for deceptive simplicity in ABMX spectra are discussed in some detail and it is shown that the parameters given by a LAOCN3 analysis have a much larger uncertainty for these spectra than the probable errors suggested by the program. As in the case for deceptively simple three-spin spectra, an accurate analysis is not possible because the results depend on the methods used to estimate the positions of weak and overlapping lines. By using solvent shifts to break the deceptive simplicity, accurate analysis became possible, and the results were confirmed by examination of 13C-H satellite spectra. The relative signs of the coupling constants of dibenzothiophen were determined by tickling experiments.