The deuterium distribution observed in isobutane recovered after short contact times with the DF-SbF5 superacid at 0° C shows that a very fast reversible protonation of all CH bonds occurs before ionization of the alkane, in accord with the Olah σ-basicity concept. Comparison of the amounts of hydrogen with the amount of tert-butyl ions generated during ionization shows that the reaction is purely protolytic in HF containing up to 20 mol% SbF5 ...
