| Résumé | The EPR spectroscopic parameters for a number of acyclic N-alkylcarboxamidyls, RṄC(O)Ŕ, have been measured over a wide range of temperatures. The results can only be interpreted in terms of a π-electronic configuration in which the unpaired electron resides mainly in an N 2p orbital perpendicular to the RNC plane. Measurements of the 13C hyperfine splittings (hfs) for some RṄC(O)13CH3 demonstrate that the O and 13C atoms lie in or near the RNC plane except when R is tert-butyl, in which case steric forces twist these atoms out of this plane by 20° or more. There is less conjugative delocalization of the unpaired electron from N to O in the Me3CṄC(O)R′ radicals because they are twisted and hence these radicals have a larger N hfs and a smaller g value than amidyls which have R = primary or secondary alkyl. The first cyclic amidyl, 5,5-dimethyl-2-oxopyrrolidin-1-yl, has been detected. This radical has a smaller N hfs (11.2 G) and a higher g value (2.0063) than the acyclic radicals. © 1981 American Chemical Society. |
|---|
