ELECTRON-PARAMAGNETIC RESONANCE-SPECTRA OF ALIPHATIC KETYL RADICAL-ANIONS IN FLUID SOLUTION

Improved methods have been developed for generating aliphatic ketyl radical anions in solution for study by EPR spectroscopy. These methods involve either photolysis of a solution of potassium in the corresponding alcohol (which probably proceeds by initial electron transfer to the solvent), or abstraction of a hydrogen atom from the corresponding alcohol by photolytically generated tert-butoxyl radicals under strongly basic conditions. The EPR spectra of a number of new aldehyde and ketone radical ions are described, and compared with the spectra of their conjugate acids. The value of a(C-13-alpha) in the acetone radical anion is found to be 52.2 G confirming that it is non-planar. The Arrhenius parameters for the inversion of the ring in the cyclohexanone radical anion are E(a) = 6.6 kcal mol-1,dagger and log (A/s-1) = 13.2.