Ion—Molecule Reactions by a Photoionization Mass Spectrometer. II. Butene−1, Butene−2, and Isobutylene

Ion—molecule reactions of the parent ions of butene−1, butene−2 (cis and trans), and isobutylene with their corresponding neutral molecules have been studied by a photoionization mass spectrometer. Seven reactions of butene−1 parent ions, three of butene−2, and three of isobutylene have been identified and their cross sections determined. Parent-plus-one and parent-minus-one reactions occurred more or less in all olefins studied, among which C4H9+ formation in isobutylene had a much larger cross section than others. Butene−2 parent ions were highly unreactive compared with the other two olefin ions, and their cis and trans isomers showed the same reactions with exactly the same cross sections.