Organophosphorus compounds. VII. Electron-impact fragmentations of esters of phosphonic acids

Abstract

The mass spectra of some dialkyl and diaryl esters of a variety of alkyl-, alkenyl-, alkynyl-, and aryl-phosphonic acids are discussed. The spectra are in many cases similar to those observed for simple dialkyl alkylphosphonates, but with some important differences depending on the nature of the hydrocarbon group attached directly to the phosphorus atom. Some unusual rearrangements are observed, involving migration of a hydro-carbon fragment from the ester group to the hydrocarbon moiety attached to phosphorus, with simultaneous expulsion of a phosphinyl radical. Thus diethyl vinylphosphonate gives an ion [C₄H₇]⁺; diethyl 2-phenylvinylphosphonate gives a base peak at m/e 131 due to PhCH=CHCHCH₃; diphenyl 2-phenylvinylphosphonate gives an ion [C₁₄H₁₂O]⁺', and from this, an ion [C₁₄H₁₀]⁺ which can be formulated as the molecular ion of phenanthrene.