REACTIONS OF HEXYL CATIONS WITH BENZENE IN HF-TAF5 - MECHANISM STUDY

Tertiary hexyl cations (1) generated by the protonolysis of methylcyclopentane in HF-TaF5 are effectively trapped by benzene. The protonated phenylhexane isomers (4-H+) thus formed are kinetically unstable and undergo hydride transfer reactions with the small amount of 1 existing in equilibrium with 4-H+. This converts the reactants completely to hexanes and 1, 3, 3-trimethylindanyl cation (9). The latter remains the main component of the mixture, while slowly rearranging to other cations with indan and tetralin skeletons. The formation of 9 is reversible; its treatment with an excess of alkane generates benzene. A consecutive reaction observed on longer standing is the irreversible cracking of 9 or 4-H+ to ethylbenzene. This degradation reaction also requires the presence of an alkane as a source of hydride ions. Disproportionation of ethylbenzene led to 1, 3-di-and 1, 3, 5-triethylbenzene. © 1979, American Chemical Society. All rights reserved.