Abstract
The 13C N.M.R. spectra of a series of 5,5-dimethyl 2,4-dichalcogeno substituted imidazolidines are reported. The 13C chemical shifts are assigned by means of a CNDO/S calculation. On the whole the shielding effect of the di-homochalcogeno atoms on C-2 and C-4 increases in the order Se ≤ S ≪ O while for the di-hetero atoms no regular trends have been found. On the contrary the resonance of C-5 inside the ring moves downfield keeping one chalcogen atom constant and substituting the oxygen with sulphur and selenium.