Characterization of gem-difluoropropargyl synthons through HF loss from protonated molecules in methane chemical ionization mass spectra

Electron impact and methane chemical ionization mass spectra were obtained following gas chromatography/mass spectrometry for several gem-difluoropropargyl compounds, which had been synthesized as potential intermediates for synthesis of gem-difluoromethylene-containing C-3 acetylenes. El spectra were variable with respect to the presentation of molecular ions, depending on substituent functional groups present. Methane-CI spectra were characterized by loss of 19 mass units from molecular weight with all compounds examined. These [M - 19](+) ions often presented as base peaks of the CI spectra, and were more reliably present and abundant than [M + I](+) ions for these compounds. These ions could have been formed by elimination of HF from the protonated molecules under conditions of methane chemical ionization. (C) 2005 Elsevier B.V. All rights reserved.