Electron spin resonance of γ-irradiated alkyl phosphates: The C2H5 radical in magnesium diethyl phosphate (MgDEP)

The major free radical product trapped at 77°K in γ-irradiated magnesium diethyl phosphate [((C2H5O)2PO2)2Mg] is the ethyl radical. The following principal values for the α and β proton hyperfine tensors were determined from ESR data obtained at the Q band: Axα=15.9, Ayα=20.6, Azα=25.5; and Axβ=26.0, Ayβ=26.5, Azβ = 27.6± 0.5 G. Significant reorientation of the ethyl radical occurs upon cleavage of the carbon oxygen bond. The assymetry in the α hyperfine tensor has been interpreted in terms of a twofold potential barrier to the rotation of the methylene group. Hindrance to the rotation of the methyl group, relative to the methylene, is apparent from differential line broadening within the spectrum at 77°K.