GAS-PHASE PROTONATION OF ALLENE AND PROPYNE. REMARKABLY SELECTIVE FORMATION OF 2-PROPENYL IONS.

Article abstract of DOI:10.1021/ja00321a600

The structure of C//3H//5** plus ions, obtained in the dilute gas state from the protonation of propyne and allene by radiolytically formed H//3** plus and C//nH//5** plus (n equals 1,2) ions, has been investigated in the pressure range from 150 to 760 torr. The C//3H//5** plus ions have been trapped with two gaseous nucleophiles, i. e. , benzene and 1,4-dibromobutane, and their structure has been inferred from the nature of the neutral products isolated. The results, in particular those from the systems containing 1,4-dibromobutane, show that 2-propenyl ions are formed almost exclusively in the kinetically significant step of the protonation from both propyne and allene, a partial isomerization to the allyl structure being observed in the systems containing benzene.