ELECTRON SPIN RESONANCE OF FREE RADICALS IN X-IRRADIATED CHOLESTEROL AND 5,6-DIHYDRO-CHOLESTEROL

A new interpretation of the electron spin resonance spectrum [2, 5] of X-irradiated pure cholesterol powder was established because in Gordy's former interpretation [5] the difference between the hyperfine splittings of the ESR spectrum from axially and equatorially oriented H atoms in the cyclic part of the cholesterol molecule was neglected. The new interpretation (Cholesteryl-7) was found with regard of data from Onishi and Nitta measured on the cyclohexenyl radical [10], by identifying the triplet splitting (a=26 Oe) in the ESR spectrum of irradiated cholesterol with both axial Hβ1 resp. H′β1 atoms and correlating the doublet splitting (a=15 Oe) with the Hα2 atom and by accepting the hyperfine splittings of the Hα1 atom and of the equatorial Hβ2 atom not exceeding 6 Oe and therefore not being resolved because of the considerable line width of about 10 Oe. The unpaired electron's localisation near the double bond was shown by a control experiment with 5,6-dihydrocholesterol. © 1969 Springer-Verlag.