The 13C NMR spectra and structure of 2,1,3-benzoxadiazole,-benzothiadiazole and -benzoselenadiazole

The ¹³C NMR chemical shifts and one-bond carbon–hydrogen coupling constants have been obtained for the title compounds in carbon disulphide as solvent. There appears to be little solvent effect on the ¹³C chemical shifts. The results suggest the order of release of electrons into the ring is O ? S > Se.