Addition radicals formed by hydroxyl radical bombardment of uracil.

Direct addition of O-H radicals at room temperature to the carbon No.5 of the uracil ring has been proved by measurement of the proton hyperfine structure in the electron spin resonance of the resulting uracil + O-H radicals. Upon addition of the OH, the H originally bound to carbon No. 5 shifts to No. 6, thus forming a methylene group at carbon No. 6, with the two protons having equivalent coupling of 28 gauss. The spin density on carbon No. 5 is O.64. The radicals were produced when powdered samples of uracil were subjected to a low-velocity beam of O-H radicals coming from either hydrogen peroxide or water vapor under reduced pressure and subjected to an electric discharge.