CHEMISTRY IN SUPER ACIDS .3. PROTONATION OF ALKANES AND INTERMEDIACY OF ALKANONIUM IONS PENTACOORDINATED CARBON CATIONS OF CH5+ TYPE . HYDROGEN EXCHANGE PROTOLYTIC CLEAVAGE HYDROGEN ABSTRACTION AND POLYCONDENSATION OF METHANE ETHANE 2,2-DIMETHYLPROPANE (NEOPENTANE) AND 2,2,3,3-TETRAMETHYLBUTANE IN FSO3H-SBF5 (MAGIC ACID) SOLUTION

Alkanes undergo hydrogen exchange, protolytic cleavage, and hydrogen abstraction followed by polycondensation in the super acid system, FSO3H-SbF5. Methane and ethane undergo both hydrogen exchange and polycondensation to produce t-butyl cation, t-hexyl cations, or higher analogous tertiary alkylcarbonium ions. Neopentane undergoes hydrogen exchange, protolytic fragmentation to trimethylcarbonium ion and methane, and hydrogen abstraction followed by fast rearrangement of the t-amyl cation. 2,2,3,3-Tetramethylbutane cleaves to produce the trimethylcarbonium ion. Structures of the intermediate protonated alkane ions (alkanonium ions, of the CH5+ type) formed in these reactions were calculated using an all-valence-electron SCF method.