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

摘要

The deuterium distribution observed in 3-ethylpentane when it is in contact with D_2O-exchanged USY zeolite at temperatures as low as 70 deg 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 D_2SO_4 in which the hydride transfer is less efficient.