Doubly charged ion mass spectra: IV—chlorinated and brominated alkanes

Abstract

AbstractDoubly charged ion mass spectra have been obtained for 42 chlorinated and brominated n‐alkane (methyl through octyl) hydrocarbons. A double focusing Hitachi RMU‐7L mass spectrometer, operated at 1.6kV accelerating voltage, has been used to measure the spectra. Molecular doubly charged ions have not been observed. Intense fragment ions have been produced from extensive H and halogen loss as well as CC bond rupture of the parent molecule. The most abundant ions in the doubly charged ion spectra observed in this investigation resulted from reactions of [Cl]2+˙, [Br]2+˙, [CCL2]2+, [C2H2Cl]2+˙, [C3H2]2+, [C3HCl]2+, [C3HBr]2+, [C4H3]2+˙, [C4H4]2+, [C4H6Br]2+˙, [C4H8Br]2+˙, [C5H2]2+, [C6H6]2+, [C6H8]2+ and [C7H8]2+. The prominent doubly charged fragment ions formed by electron impact of the smaller halogenated alkanes generally contained halogen, whereas ions of the type [CnHx]2+ were dominant in the spectra of higher molecular weight mono‐ and dihalogenated alkanes. Appearance energies of several ions have been measured. A geometry optimized quantum mechanical SCF treatment has been used to compute energies, charge densities and structures of doubly charged halogenated alkane ions.