The Structure of Amidyl Radicals. Evidence for the ?-Electronic Ground State and for Twist about the Acyl-Nitrogen Bond by Electron Paramagnetic Resonance Spectroscopy

Article abstract of DOI:10.1021/ja00393a021

The EPR spectroscopic parameters for a number of acyclic N-alkylcarboxamidyls, R<*>C(O)R', have been measured over a wide range of temperatures.The results can only be interpreted in terms of ?-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 R<*>C(O)(13)CH3 demonstrate that the O and 13C atoms lie in or near the RNC plane except when R ist tert-butyl, in which case steric forces twist these atoms out of this plane by 20 deg or more.There is less conjugative delocalization of the unpaired electron from N to O in the Me3C<*>C(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.