Electron‐impact‐induced rearrangements in the mass spectra of phosphinyl stabilized triphenylphosphonium ylides

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Abstract
Examination of the mass spectra of some methyl and phenyl phosphonate stabilized triphenylphosphonium ylides revealed that these compounds are quite stable to electron‐impact and provided valuable structural information. They exhibit strong molecular and [M ‐ H]+ ions, and fragment ions which are characteristic for the phosphonium or the phosphonate portion of the molecules. Numerous rearrangement ions were detected, however, the most prominent of which involves the migration of a phosphonate phenyl to the ylide carbon, leading to the base peak (m/e 352) in the spectrum of diphenyl triphenylphosphoranylidenemethylphosphonate. The mechanism of these fragmentations has been studied with the aid of high resolution analysis and deuterium labeled analogs whose preparation is reported.