H/D exchange between light alkanes and deuterated strong acids. Competition between regiospecific isotope exchange and skeletal rearrangement: an 1H/2H NMR study Original Research Article

The deuterium distribution observed in 3-ethylpentane when it is in contact with D2O-exchanged USY zeolite at temperatures as low as 70°C shows that for some alkanes the skeletal rearrangement of the intermediate tertiary carbenium ion can be much faster than the de- and reprotonation reaction which is at the origin of the observed, generally regiospecific, isotope exchange. This behavior is notably increased when the solid acid is replaced by D2SO4 in which the hydride transfer is less efficient.