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2- and 3-Acetylpyrroles: A Combined Calorimetric and Computational Study

2009; American Chemical Society; Volume: 113; Issue: 15 Linguagem: Inglês

10.1021/jp810407m

1520-5215

Ana Filipa L.O.M. Santos, José R. B. Gomes, Manuel A. V. Ribeiro da Silva,

Chemical and Physical Properties in Aqueous Solutions

A combined experimental and computational study on the thermochemistry of 2- and 3-acetylpyrroles was performed. The enthalpies of combustion and sublimation were measured by static bomb combustion calorimetry and Knudsen effusion mass-loss technique, respectively, and the standard (p° = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, were determined. Additionally, the gas-phase enthalpies of formation were estimated by G3(MP2)//B3LYP calculations, using several gas-phase working reactions, and were compared with the experimental ones. N−H bond dissociation enthalpies, gas-phase acidities and basicities, proton and electron affinities and ionization enthalpies were also calculated. Experimental and theoretical results are in good agreement and show that 2-acetylpyrrole is thermodynamically more stable than the 3-isomer. The substituent effects of the acetyl group in pyrrole, thiophene and pyridine rings were also analyzed.