chiroptical properties in the intrinsically dissymmetric amide chromophore of n-acylaziridines are investigated experimentally and by ab initio molecular orbital calculations. computations on n-formylaziridine (1a) and measurements of the cd spectra of (1r, 2r)-1-acetyl-2-methylaziridine (1b), (1r,2r)-1-( alpha -hydrohexafluoroisobutyryl)-2-methylaziridine (1c), (2's)-1-(2'-methylbutyryl)aziridine (1d), and (2's)-1-(2'-methylbutyryl)-2,2-dimethylaziridine (1e) suggest that the cotton effect (ce) for the long wavelength absorption (band i) obeys a spiral rule' a right-handed twist of the o=c-n-c(ring) bonds corresponds to a negative ce for band i. band i is assigned to the valence n/sub o/- pi */sub co/ transition. the next four higher energy absorptions are due to transitions to rydberg states, n/sub n/-3s and n/sub n/-3p. experimental cd spectra are also reported for the related compounds, (2's)-1,2-bis(2'-methylbutyryl)-3,3-dimethyldiaziridine (2a), ( alpha s)-1,2-diacetyl-3-sec-butyldiaziridine (2b), (2's)-2-(2'-methylbutyryl)-3,3-dimethyloxaziridine (3a), (5s)-2-acetyl-5-methyl-1-oxa-2-azaspiro(2.5)octane (3b), (s)-n,n-dimethyl-2-methylbutyramide (4), and (2s)-1-( alpha -hydrohexafluoroisobutyryl)-2-methylazetidine (5)