Experimental and computational energetic study of two halogenated 2-acetylpyrrole derivatives: 2-Trichloroacetylpyrrole and 2-trifluoroacetylpyrrole

Santos, Ana Filipa L.O.M.; Silva, Manuel A.V. Ribeiro da

doi:10.1016/j.jct.2010.04.001

Cited by 18 publications

(3 citation statements)

References 46 publications

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“…The enthalpic increment for the insertion of a −COOH group in position 2 of the pyrrolidine ring is between −385.2 ± 2.4 kJ•mol −1 for L-proline and −388.5 ± 2.2 kJ•mol −1 for D-proline, as shown in Figure 3. This large enthalpic stabilization may be due to an intramolecular hydrogen bond, which was already reported for 2-acetylpyrrole, 55 2pyrrolecarboxylic acid, 56 2-trichloroacetylpyrrole and 2-trifluoroacetylpyrrole, 74 and 2-pyrrolecarboxaldehyde. 75 However, the stabilization is lower than that observed when a hydrogen atom is substituted by a −COOH group in the 2-position of pyrrole and 1-methylpyrrole (see Figure 3), which can be explained by a more favorable electronic delocalization in the aromatic rings, since the pyrrole ring is planar and the pyrrolidine ring is puckered.…”

Section: Resultssupporting

confidence: 63%

Thermodynamic and Conformational Study of Proline Stereoisomers

2014

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Amino acids play fundamental roles both as building blocks of proteins and as intermediates in metabolism. Proline, one of the 20 natural amino acids, has a primordial function in enzymes, peptide hormones, and proteins. The energetic characterization of these molecules provides information concerning stability and reactivity and has great importance in understanding the activity and behavior of larger molecules containing these structures as fragments. In the present work, parallel experimental and computational studies have been performed. The experimental studies have been based on calorimetric and effusion techniques, from which the enthalpy of formation in the crystalline phase and the enthalpy of sublimation of the sterioisomers L-, D-, and the DL-mixture of proline have been derived. Additionally, vapor pressure measurements have also enabled the determination of the entropies and Gibbs energies of sublimation, at T = 298.15 K. From the former results, the experimental standard (p(o) = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, of L-proline, D-proline, and DL-proline have been calculated as -388.6 ± 2.3, -391.9 ± 2.0, and -391.5 ± 2.4 kJ·mol(-1), respectively. A computational study at the G3 and G4 levels has been carried out. Conformational analysis has been done and the enthalpy of formation of proline as well as other intrinsic properties such as acidity, basicity, adiabatic ionization enthalpy, electron and proton affinities, and bond dissociation enthalpies have been calculated. There is a very good agreement between calculated and experimental values, when they are available.

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Section: Resultssupporting

confidence: 63%

Thermodynamic and Conformational Study of Proline Stereoisomers

2014

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“…For M2PC and E2PC, the N−H,O-syn is the most stable conformation adopted by both molecules, in agreement with studies from other researchers 56−59 as well as with other 2-pyrrole-substituted analogues. 40,41,45,49 The N−H,O-anti conformation is 4.4 and 4.2 kJ•mol −1 less stable than the N− H,O-syn, for M2PC and E2PC, respectively. For M2PC, this enthalpic difference is in perfect accordance with the values found by Dubis and Grabowski, determined at RHF/6-31G(d,p) and RHF/6-311++G(d,p) levels, 5.4 kJ•mol −1 , 57 and with the B3LYP/6-311++G(d,p) approach, 4.4 kJ•mol −1 .…”

Section: The Journal Of Physical Chemistry Amentioning

confidence: 97%

“…Following our studies on the thermodynamic and thermochemical properties of several substituted pyrroles and their relationship with the corresponding molecular structures, − which are intended to be used as a building blocks of porphyrins, polypyrroles, and drugs with high therapeutical potential, we report, in the present work, an experimental and computational study on the energetic and structural properties of several alkyl pyrrolecarboxylates (alkyl = methyl or ethyl). It is of great importance for the understanding of the activity and behavior of large molecules to know the molecular energetics of its fragments.…”

Section: Introductionmentioning

confidence: 99%

Molecular Energetics of Alkyl Pyrrolecarboxylates: Calorimetric and Computational Study

Santos

Silva

2013

J. Phys. Chem. A

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The pyrrole subunit plays an important role in material science as the building block of polypyrroles, an important representative class of conducting polymers, which found widely applications in the area of new materials due to their chemical, thermal, and electrical properties associated with their easiness and low cost of production, making them especially promising for commercial applications. The energetic characterization of this kind of molecules provides information concerning stability, reactivity, and biodegrability of chemical compounds in environment being, for example, helpful in choosing the most adequate method for their elimination by converting the waste into harmless compounds or even decreasing the production of toxic substances in industrial processes. This work reports a combination of calorimetric and computational determinations of several alkyl pyrrolecarboxylates (alkyl = methyl or ethyl) whose main purpose is the calculation of their standard (p° = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T = 298.15 K. Experimentally, for methyl 1-pyrrolecarboxylate (M1PC), methyl 2-pyrrolecarboxylate (M2PC), and ethyl 2-pyrrolecarboxylate (E2PC), these values were derived from the standard (p° = 0.1 MPa) molar enthalpies of formation, in the condensed phase, ΔfHm° (cr,l), at T = 298.15 K, obtained by static bomb combustion calorimetry, and from the standard molar enthalpies of phase transition, Δcr,l(g)Hm°, at T = 298.15 K, determined by high-temperature Calvet microcalorimetry. Standard ab initio molecular calculations, at the G3(MP2)//B3LYP level, were performed, and the standard enthalpies of formation of these three compounds were estimated. A very good agreement between the calculated and the experimental data was obtained. Thereby, we have extended these calculations to other alkyl pyrrolecarboxylates, namely, ethyl 1-pyrrolecarboxylate (E1PC), methyl 3-pyrrolecarboxylate (M3PC), and ethyl 3-pyrrolecarboxylate (E3PC), whose study was not performed experimentally. The computational analysis, at the B3LYP/6-31G(d) level of theory, of the six molecules allowed a detailed inspection and a better knowledge about their molecular structure and geometrical parameters.

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The influence of methyl groups on the torsion angle and on the energetics of 1-phenylpyrrole derivatives: a thermodynamic and computational study

Santos

Silva

2013

Struct Chem

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Experimental and computational energetic study of two halogenated 2-acetylpyrrole derivatives: 2-Trichloroacetylpyrrole and 2-trifluoroacetylpyrrole

Cited by 18 publications

References 46 publications

Thermodynamic and Conformational Study of Proline Stereoisomers

Thermodynamic and Conformational Study of Proline Stereoisomers

Molecular Energetics of Alkyl Pyrrolecarboxylates: Calorimetric and Computational Study

The influence of methyl groups on the torsion angle and on the energetics of 1-phenylpyrrole derivatives: a thermodynamic and computational study

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