Free radicals in pyrimidines. ESR of x-irradiated single crystals of phenobarbital
Two crystal polymorphs of phenobarbital, of melting points 175 deg C and 17# deg C, were x-irradiated in air at room temperature with doses of 10 Mrads. ESR spectra were recorded at 5 deg intervals about each of 3 orthogonal axes at both 9.3 GHz and 22.5 GHz. A comparative table is preserted of the ESR data obtained from the two crystal structures. The results were essentially the same, except that the relative values of the proton hyperfine couplings were different because of the different ethyl group rotations about the bond to C(5). It is tentatively suggested that one factor important to the mechanism of radical formation in this group of compounds is the difficulty in reorienting a large group into the plane of the pyrimidine ring when the electronic configuration of C(5) goes from sp/sup 3/ in the undamaged molecule, to sp/sup 2/ in the free radical. It is also suggested that another factor to be considered is the relative stability of alternate radical structures. (UK)
- Research Organization:
- Southern Illinois Univ., Carbondale
- NSA Number:
- NSA-29-012576
- OSTI ID:
- 4382382
- Journal Information:
- Int. J. Radiat. Biol., v. 24, no. 4, pp. 427-431, Journal Name: Int. J. Radiat. Biol., v. 24, no. 4, pp. 427-431; ISSN IJRBA
- Country of Publication:
- United Kingdom
- Language:
- English
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