CONTRASTING BEHAVIOR OF PENTAFLUOROPHENOXYACETONE AND PENTAFLUOROBENZYLOXYACETONE IN ELECTRON-IMPACT AND ELECTRON-CAPTURE MASS-SPECTROMETRY

Towards the goal of finding new ketone electrophores suitable as molec ular labels for electrophoric release tags, pentafluorophenoxyacetone (1) and pentafluorbenzyloxyacetone (2) were prepared Both ketones were evaluated by electron capture (EC) and electron impact (EI) modes of mass spectrometry (MS). By EC-MS, 1 nearly gave a single ion (as desir ed), whereas 2 gave many ions. This behavior was completely reversed i n EI-MS. To account for certain ion fragments in the EC mass spectrum of 2, an anion radical McLafferty-type rearrangement and loss of a car bene neutral were postulated. Electron impact of 1 gave an abundant io n at m/z 117 ((CF3+)-F-5), which was suggested to be a diyne cation. ( C) 1998 John Whey & Sons, Ltd.