Abstract: | The mass spectra of the fluorinated β-diketones RCOCH2COCF3 (R = Ph, p-FC6H4, p-ClC6H4, p-BrC6H4, p-MeC6H4 and 2-thienyl) and their monothio analogues RC(SH)?CHCOCF3 have been obtained. The replacement of one oxygen by sulphur in the β-diketones brings about a greater complexity in the mass spectra. The β-diketones fragment by first losing a ·CF3 radical and then successively lose CH2?C?O and CO to yield \documentclass{article}\pagestyle{empty}\begin{document}${\rm R}\mathop {\rm C}\limits^{\rm + } {\rm = O]} $\end{document} and R]+. The monothio-β-diketones also fragment by an analogous reaction pathway: viz. the initial loss of ·CF3 is followed by the successive loss of CH2?C?O and CS to yield \documentclass{article}\pagestyle{empty}\begin{document}${\rm R}\mathop {\rm C}\limits^{\rm + } {\rm = S]} $\end{document} and R]+. However, they also fragment by two other pathways involving the initial loss of ·H and ·X (X=F, Cl, Br, Me), the latter occurring only with those monothio-β-diketones having R=p-XC6H4. |