Investigations of structure and conformation. Part IV. An electron spin resonance and INDO molecular orbital study of the influence of electronic interactions upon radical geometry

Abstract

INDO MO Calculations provide support for conclusions based on e.s.r. hyperfine splittings that α-hydroxyalkyl radicals are bent at the radical centre and that α,β-dihydroxy- and α-hydroxy-β-ammonio-ethyl radicals preferentially adopt an almost eclipsing conformation; evidence is also obtained that in this conformation there is distortion from tetrahedral geometry at the β-carbon (this explains the unusually low β-hydrogen splittings observed). In contrast, the radical ·CH₂·CH₂OH is planar at the radical centre and prefers a conformation in which the β-C–O bond subtends an angle of 90° with the orbital of the unpaired electron.