Radical cation of HP(O)(OMe)2: electron paramagnetic resonance evidence for competition between bonding to solvent, a 1,2-hydrogen shift, and a 1,4-hydrogen shift

Abstract

Exposure of dilute solutions of dimethylphosphonate in fluorotrichloromethane to ⁶⁰Co γ-rays at 77 K gave EPR features characteristic of three types of radical cations. One is the parent cation which has formed a weak σ* bond between oxygen and chlorine, with A_max(³⁵Cl)= 78 G. The second is the rearranged distonic cation H₂ĊOPH(OMe)(OH)⁺ and the third is identified as the phosphoryl radical, (MeO)₂P(OH)⁺.

In more concentrated solutions (MeO)₂PO radicals were also observed, and exposure to visible light converted the chlorine adducts into the carbon-centred radicals.