MECHANISM OF SUPERACID CATALYZED ALKANE ACTIVATION - THEORETICAL AB-INITIO STUDIES OF PENTACOORDINATED CARBONIUM-ION REARRANGEMENT

A theoretical ab initio study of the interconversion of pentacoordinat ed carbonium ions was carried out. For the isobutonium cations it was found that the respective C-carbonium ions were lower in energy than t he H-isobutonium ions. Nevertheless, the interconversion of the 1-H-is obutonium cation in the C-isobutonium ion is a barrierless process. Th is suggests that product arisen from C-C protonation in liquid superac id and zeolite catalyzed alkane activation may be formed by protonatio n in the outer and more accessible primary C-H bonds of isobutane, rat her than by direct protonation of the inner and more steric demanding C-C bonds.