Consecutive ionic reactions in gaseous butenes

Abstract

Ion-molecules reactions occurring in the four isomeric butenes have been studied up to a pressure of 0.5 torr inside a mass spectrometric source, where ionization is produced by tritium β-rays. Long-chain processes have been recognized, leading to the formation of polymeric ions. In isobutene, the predominant chain, which involves alkyl carbonium ions, has been followed up to C₁₆H⁺₃₃. This chain, although with a lower yield, has also been found in the other isomers. Minor chains and branching reactions complicate the mass-spectra at the highest pressures investigated, and lead mainly to C_nH⁺_2n–1 and C_nH⁺_2n–3 ions. Peculiar to the 2-butenes are extensive chains of odd-electron C_nH⁺_2n ions.