Collect. Czech. Chem. Commun. 1999, 64, 1893-1901

Protonation of Some 5-Substituted Di(2-thienyl) Ketones in Sulfuric Acid. A Comparison with Other 2-Thienyl and Phenyl Ketones

Renato Notoa,*, Michelangelo Gruttadauriaa, Paolo Lo Meoa and Domenico Spinellib

a Dipartimento di Chimica Organica "E. Paternò", Viale delle Scienze, Parco d'Orleans 2, I-90128 Palermo, Italy
b Dipartimento di Chimica Organica "A. Mangini", Via S. Donato 15, I-40127 Bologna, Italy


Protonation equilibria of some 5-substituted di(2-thienyl) ketones have been investigated spectrophotometrically in aqueous solutions of sulfuric acid at 298 K. The experimental pKBH+ values have been analyzed by means of the Hammett equation. The calculated ρ as well as the pKBH+ and m* values have been compared with those for substituted 2-acetyl- thiophenes and phenyl 2-thienyl ketones.

Keywords: Acidity constants; Heterocyclic ketones; Linear free energy relationships; Thiophenes; Substituent effects; Hammett equation.