2‐(2‐Thienyl)pyrrole and its 3‐alkyl‐1‐vinyl derivatives have been shown (1H NMR) to be protonated by HSO3F, CF3COOH, HCl and HBr at the pyrrole C‐5 atom. Reaction with the superacid system HSO3FSbF5–SO2 results in the equilibrium between pyrrolium and thiophenium ions. The heats of formation (ΔH), charges and HOMO partial electron densities for 2‐(2‐thienyl)pyrrole and its protonated forms have been calculated by the MNDO method. The calculated ΔH values of thienylpyrrolium and pyrrolythiophenium ions are in agreement with the experimentally observed ratio.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry