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Papers Published

1. Johnson, GA, Free radicals formed by exposure of pyrimidine solids to sodium atoms: an electron spin resonance study., Proc Natl Acad Sci U S A, vol. 72 no. 3 (March, 1975), pp. 974-978 [165496], [doi] .
   (last updated on 2025/02/12)

   Abstract:
   Sodium atoms have been deposited on various pyrimidine powders under high vacuum at 77 degrees K and the electron spin resonance spectra of the resulting free radicals have been observed. Generally, the spectra show that the electron of the Na goes into a molecular orbital of the pyrimidine ring and the Na+ ions become attached to a carbonyl oxygen of the resulting pyrimidine anion. In 5-fluorouracil and 5-chlorouracil, however, the halogen is evidently abstracted by the Na to form NaF or NaC1 and the neutral uracil radical. Thymine shows evidence for H-addition radicals as well as the Na+-[thymine]-complex. The H source for the addition radicals may be an H-2-0 impurity in the sample, with which the Na atoms combine to release the H atoms. In addition to a resonance with g equals 2.00 from the pyrimidine anion radical, broad resonances with g greater than 2 were observed for 5-bromouracil, 5-chlorouracil and 5-iodouracil, as well as for alloxan and cytosine. These resonances, generally unstable at room temperature, are believed to arise from electrons trapped in interstitial sties or vacancies in the lattice.

   Keywords:
   Alloxan • Bromouracil • Cytosine • Electron Spin Resonance Spectroscopy • Fluorouracil • Free Radicals • Pyrimidines* • Sodium* • Thymine • Uracil • analogs & derivatives