On the basis of the results of IR and UV spectroscopy, a considerable decrease in the efficacy of the conjugation of the unshared pair of the nitrogen atom with a carbonyl group in ynaziridines as compared with ynamines has been shown.The difference in the electronic structures of these compounds finds its reflection in their chemical behavior: the electrophilicity of the triple bond in an ynaziridine is higher than that in the analogous ynamine in reaction with amines.