Electron spin resonance studies of irradiated succinamic acid. II. Monoclinic single crystals

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Abstract
The radiation products and decay mechanisms have been studied in single crystals of monoclinic succinamic acid using electron spin resonance spectroscopy over the temperature range from 77° through 300°K. At 77°K the primary radical observed is the anion radical COOHCH2CH2(ĊONH2)− where the unpaired electron is delocalized throughout the entire amide group. This radical decays at about 180°K to a nonparamagnetic species. The minor product at 77°K is the cation product and decays at about 157°K by intermolecular hydrogen abstraction to two radicals which are stable at room temperature, COOHĊHCH2CONH2, and COOHCH2ĊHCONH2. The spectra observed at 300°K are identical in crystals irradiated at 77°K and warmed to 300°K. The differences in the radiation products and mechanisms for the monoclinic and triclinic forms are discussed.