Collect. Czech. Chem. Commun. 1999, 64, 1877-1892

Kinetic Study of the Reactions of Some 5-Nitro-2-(4-nitrophenoxy)-3-X-thiophenes with Aniline and 4-Methoxyaniline in Methanol

Vincenzo Frennaa, Gabriella Macalusoa, Giovanni Consigliob, Susanna Guernellib and Domenico Spinellib,*

a Dipartimento di Chimica Organica "E. PaternĂ²", 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


The rate constants of the title reactions have been measured at various amine concentrations. The second-order kinetic constant for the amino substitution increases in a hyperbolic way as a function of the nucleophile concentration. The k3Am/k-1 ratio for each catalysed system is not a monotonic function of the X substituent. This result has been rationalized in the framework of the SB-GA (Specific Base-General Acid) mechanism of base catalysis.

Keywords: Aromatic nucleophilic substitutions; Thiophenes; Base catalysis; SB-GA mechanism; Reaction kinetics.