E.S.R. spectra of X-irradiated methylene diphosphonic acid

Abstract

X-irradiation of single crystals of methylene diphosphonic acid gives rise to E.S.R. spectra which have been assigned to (OH)₂(O)P-ĊH₂ and

The former species is the more abundant of the two and the methylene group undergoes rapid re-orientation about a two-fold axis at room temperature but is stationary at 77 K. The ¹H and ³¹P coupling constants in this radical are very similar to those in Ph₃P⁺CH₂, and support the previous conclusions [1] that there is little delocalization of the unpaired electron to the phosphorus atom.