Studies of Fragment Ion Distribution and Reaction with a Charge Spectrometer. VIII. Fragmentation Processes of Various Alkyl Halides

Abstract

Abstract The breakdown curves for C2H5X, n-C3H7X, and n-C4H9X (X=Cl, Br, and I) were obtained by the use of a double mass spectrometer of the perpendicular type. The charge exchange mass spectra for alkyl bromide and alkyl iodide are found to be similar, although those for alkyl chloride are somewhat different from these for bromide and iodide. According to the molecular orbital calculation, the difference of the electronic configuration between chloride and bromide or iodide is found to correspond to the difference of the breakdown curves. The results obtained in this study using larger molecules support our previous analysis on the breakdown processes in smaller molecules: (1) direct scission of the bond which has lost one electron by the charge exchange reaction, (2) electron redistribution, and (3) secondary decomposition (and those of higher order) from the primary fragments. In the case of alkyl chloride, formation of the ion CnH2n+ is ascribed to the elimination of HX from the molecular ion in its electronically ground but vibrationally excited state.