Calorimetric and Computational Study of 2- and 3-Acetyl-1-methylpyrrole Isomers

This work reports the enthalpies of formation in the condensed and gas phases of 2-acetyl-1-methylpyrrole and 3-acetyl-1-methylpyrrole, derived from the standard (p o = 0.1 MPa) molar enthalpies of combustion, in oxygen, Δc H m o, measured by static bomb combustion calorimetry and the standard molar...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2010-03, Vol.114 (8), p.2846-2851
Main Authors: Ribeiro da Silva, Manuel A. V, Santos, Ana Filipa L. O. M
Format: Article
Language:English
Subjects:
B: Statistical Mechanics, Thermodynamics, Medium Effects
Calorimetry
Computer Simulation
Isomerism
Models, Chemical
Pyrroles - chemistry
Quantum Theory
Thermodynamics
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Summary:This work reports the enthalpies of formation in the condensed and gas phases of 2-acetyl-1-methylpyrrole and 3-acetyl-1-methylpyrrole, derived from the standard (p o = 0.1 MPa) molar enthalpies of combustion, in oxygen, Δc H m o, measured by static bomb combustion calorimetry and the standard molar enthalpies of vaporization, Δl g H m o, at T = 298.15 K, obtained by high-temperature Calvet microcalorimetry. The theoretically estimated gas-phase enthalpies of formation were calculated from high-level ab initio molecular orbital calculations at the G3(MP2)//B3LYP level; the computed values compare very well with the experimental results obtained in this work and show that the 2-acetyl-1-methylpyrrole is thermodynamically more stable than the 3-isomer. Furthermore, this composite method was also applied in the calculation of bond dissociation enthalpies, gas-phase basicities, proton and electron affinities, and adiabatic ionization enthalpies.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp911323c