AN ELECTRON-SPIN-RESONANCE STUDY ON THE GAMMA-IRRADIATION OF UREA, UREA-D(4), 1,3-DIMETHYLUREA, 1,3-DIETHYLUREA AND 1,1',3,3'-TETRAMETHYLUREA

Urea, urea-d4, 1,3-dimethylurea, 1,3-diethylurea powder and 1,1',3,3'-tetramethylurea, and their solutions in D2O Were gamma-irradiated with 0.0882 kGy both at room temperature and at 77 K. The product radicals were identified with X-band electron spin resonance, based on the g-factor and hyperfine coupling constants. The radicals formed from urea and urea-d4 were identified as nitrogen-centered and resulted from N-H bond dissociation. The radicals produced from 1,3-dimethylurea, 1,3-diethylurea and 1,1',3,3'-tetramethylurea were identified as carbon-centered and resulted from C-H bond cleavage. The electron spin resonance signals of 1,3-dimethylurea, 1,3-diethylurea and 1,1',3,3'-tetramethylurea are similar in both the powder and D2O solution. The radicals observed from 1,3-dimethylurea, 1,3-diethylurea and 1,1',3,3'-tetramethylurea were identified as .NH-CH2, .NH-CHCH3 and .N(CH3)(CH2), respectively.