Endor study of γ-irradiated ammonium hydrogen 2,2′-oxydiacetate single crystals

Abstract

EPR and ENDOR spectroscopy were used to determine the effects of radiation on single crystals of ammonium hydrogen 2,2′-oxydiacetate that had been γ-irradiated at room temperature. Hyperfine tensors of the α, γ and hydrogen-bonded protons were determined from the ENDOR data for the two radicals of the type OOC–CH₂–O–Ċ H–CO₂H. The proton couplings were compared with the calculated values, taking into account spin distribution over the carboxylic group and the ether oxygen. In addition, two more radicals characterized by typical α-proton couplings were observed. These radicals could not be associated with the parent hydrogen oxydiacetate ion. It is suggested that the radicals are formed by the separation of the ligand halves of the hydrogen 2,2′-oxydiacetate ion.