ESR studies on hydroxyl radical reactions with glycine

Radicals H₂N? ?H? COOH and H₂N? ?H? COO^? which have different ESR. spectra are observed during the reaction of hydroxyl radicals with glycine in aqueous solution. Rapid and reversible exchange between the different dissociated radicals is induced by addition of phosphoric acid. The pH dependence of the ESR. spectra yields the pK value and rate constants for proton transfer reactions between the radicals and phosphoric acid.