By means of 1H NMR spectroscopy it was demonstrated that 2-(2-thienyl)pyrrole and its 1-vinyl-substituted derivatives are protonated by adds (HSO3F, CF3CO2H, HCl, and HBr) at the C5 atom of the pyrrole ring. The reaction with the superacid system HSO3F/SbF5/SO2 leads to an equilibrium mixture of pyrrolium and thiophenium ions. The MNDO method was used to calculate the heats of formation (δH), charges, and partial electron densities of the highest occupied molecular orbitals (HOMO) of 2-(2-thienyl)pyrrole and its protonated forms. The calculated δH values of the thienylpyrrolium and pyrrolylthiophenium ions are in agreement with the experimentally established relationship.
ASJC Scopus subject areas
- Organic Chemistry