Figure 10.

(A) Reaction via the equilibrium formation of some isobutylene by the depolymerization of the polyisobutyl cation. Reaction of this isobutylene with a Brønsted acid to form tert-butyl carbenium ions that, in a more enthalpically favorable step, form tert-butylbenzene by Friedel–Crafts chemistry. (B) Qualitative ¹H NMR spectroscopic studies showing the extent of depolymerization of polyisobutylene oligomers with various end groups in toluene in the presence of 2.2 equiv of CF₃SO₃H at 25 °C for 20 h. Figure adapted from ref (76). Copyright 2019 American Chemical Society.