The kinetics of the conversion of C-13-labeled n-butane adsorbed on sulfated zirconia (SZ) were monitored by in situ C-13 MAS NMR spectroscopy. Rate constants of n- to isobutane isomerization and of the C-13-isotope scrambling from the primary to the secondary carbon atoms in n-butane were determined. The monomolecular scrambling of the C-13-label in adsorbed n-butane has an activation energy of 17 ± 3 kcal mol(-1) and occurs faster than the bimolecular process of n-butane isomerization which has an activation energy of 15.1 ± 0.2 kcal mol(-1). The transfer of the selective C-13-label from the primary to the secondary carbon atom in the adsorbed n-butane seems to consist of two reaction steps: (i) a hydride abstraction by SZ leading to the formation of sec-butyl cations and (ii) a label scrambling in the sec-butyl cations. This two-step process with the formation of sec-butyl cations as intermediate increases the apparent activation energy for the C-13-label scrambling, which is almost twice as large compared with the activation energy for carbon scrambling of sec-butyl cations in a superacidic solution.