Unimolecular Decompositions of 2, 2, 2-Trifluoroethyl Acetate, 2, 2, 2-Trifluoroethyl Trifluoroacetate, and S-Ethyl Trifluorothioacetate upon Electron Impact

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The unimolecular decompositions of the metastable ions produced from 2,2,2-trifluoroethyl acetate, CH3COOCH2CF3, 1, (Mw: 142), 2,2,2-trifluoroethyl trifluoroacetate, CF3COOCH2CF3, 2, (Mw: 196), and S-ethyl trifluorothioacetate, CF3COSCH2CH3, 3, (Mw: 158) upon electron ionization have been investigated by means of mass-analyzed ion kinetic energy (MIKE) spectrometry and D-labeling. The metastable ions 1+ decompose exclusively to give the ion at m/z 122 by losing HF via an 1,2-elimination.In the normal mass spectrum of 2, no molecular ion is observed, while the ion corresponding to the loss of CF3 gives rise to an intense peak at m/z 127 (about 90% of the base peak) and the ion corresponding to the loss of F gives the peak at m/z 177 with moderate intensity (about 20%). Both ions consist of two isomeric ions. Some interesting rearrangement processes, such as CF3 or OCH2CF3 migration followed by the loss of a CO molecule, occur during the metastable fragmentations of these ions.The molecular ion of 3, which is a base peak, decomposes into the ions at m/z 89 and 61 by losing CF3 and CF3CO, respectively, in the metastable time region. The relative abundance of ions in the MIKE spectrum are rationalized with the thermochemical data estimated by the PM 3 method.
日本質量分析学会の論文
1998-09-01