abstract
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 degrees = 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.
keywords
CHEMICAL THERMODYNAMIC PROPERTIES; KNUDSEN EFFUSION APPARATUS; BOND-DISSOCIATION ENERGIES; STANDARD MOLAR ENTHALPIES; GAS-PHASE; ELECTRONIC-STRUCTURE; PROTON AFFINITIES; N-H; THERMOCHEMISTRY; AROMA
subject category
Chemistry; Physics
authors
Santos, AFLOM; Gomes, JRB; da Silva, MAVR
our authors
José R. B. Gomes
Principal Researcheracknowledgements
Thanks are due to Fundacao para a Ciencia e a Tecnologia, FCT, Lisbon, Portugal, and to FEDER for financial support to Centro de Investigacao em Quimica, University of Porto. A.F.L.O.M.S. thanks FCT and the European Social Fund (ESF) under the Community Support Framework (CSF) for the award of the postdoctoral fellowship (SFRH/BPD/41601/2007).