N.M.R. spectra of the carbolines. II. ¹⁴N quadrupolar and exchange broadening of spectral lines

Abstract

The n.m.r, spectra of carbazole and the carbolines were previously reported to show unusual line broadening effects under certain conditions. It is found that for the proton in position 9 both chemical exchange and ¹⁴N quadrupolar relaxation are responsible for the large line widths observed, while for protons in the ?pyridine? ring chemical exchange is the more important effect. The nature of this exchange is still uncertain, the rate being critically dependent on solvent and sample purity as well as temperature.