858-11-7Relevant academic research and scientific papers
Studies of Primary Alkyl and Aralkyl Radicals Using Electron Spin Resonance Spectroscopy and Intermediate Neglect of Differential Overlap Calculations
Brumby, Steven
, p. 1917 - 1924 (2007/10/02)
It is argued that a published ESR spectrum due to n-propyl radicals in solution does not, as has been claimed, exhibit selective broadening of the lines with M = 0 for the α protons, but, rather, a broadening of the lines with M = +/- 1 for the β protons.Based on INDO calculations for the n-propyl radical, and an analysis of the restricted internal rotation, the reported variations in aγ with temperature are rationalized.ESR spectra of 2-hydroxyethyl radicals in solution have been analyzed, and no line width alternation was detected at temperatures of -50 deg C and above.The well-known line width alternation in the ESR spectrum on n-butyl radicals is discussed and it is suggested, partly on the basis of INDO calculations, that the preferred orientations about the Cα-Cβ bond are dependent, to some extent, on the configuration with respect to the Cβ-Cγ bond.The ESR spectra of the species Me3CCH2CH2., Me3CCH2CH2CH2., and Ph3CCH2CH2. are reported and discussed.The spectrum of the former species shows no line width alternation, but the spectrum of the latter species shows a pronounced alternation, which is attributed to the chiral nature of the trityl group.ESR spectra of the species Me(CH2)nCH2. and Ph(CH2)nCH2., with n = 2,3, and 4, display particularly marked line width alternation in the latter series when n = 3 and 4.This observation, together with the results of INDO calculations, may possibly indicate that these radicals prefer conformations with the plane of the trigonal carbon atom parallel to the phenyl-group plane.
