EPR INVESTIGATIONS CONCERNING THE STRUCTURE OF THE ASCORBIC ACID RADICAL IN WATER, ALCOHOL, AND DIMETHYLSULFOXIDE

Abstract— Electron paramagnetic resonance (EPR) spectra of the ascorbic acid radical in water, methanol, ethanol, n -propanol, and dimethylsulfoxide are reported. The radical was produced by photolyzing ascorbic acid solutions containing acetone. Lines from ¹³C in natural abundance are observed. Four different ¹³C-coupling constants can be distinguished. A comparison of the experimental ¹H-coupling constants with values calculated by the INDO method allows assignment to specific protons in the radical. An effect of solvent on the spectrum is observed and is interpreted in terms of intramolecular hydrogen bonding. Data are presented which indicate that ascorbic acid is able to scavenge alcohol radicals by H-atom transfer.