Enthalpies of Formation of Dibenzo-<i>p</i>-dioxin and Polychlorinated Dibenzo-<i>p</i>-dioxins Calculated by Density Functional Theory

Дорофеева, О. В.; Yungman, V. S.

doi:10.1021/jp026973y

Cited by 13 publications

(20 citation statements)

References 24 publications

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“…For approximate treatment of molecules with low-frequency internal rotations, Radom and co-workers , recommended to calculate the ZPE (zero-point energy) and thermal contribution to enthalpy associated with the frequencies below 260 cm –1 using a free rotor approximation. Even in the isodesmic reaction scheme, this procedure leads to the better agreement between the experimental and calculated enthalpies of formation when the reactants and products have different number of low-frequency modes, however, an error is usually minor when the reactants and products have similar internal rotations …”

Section: Results and Discussionmentioning

confidence: 99%

Gas-Phase Enthalpies of Formation and Enthalpies of Sublimation of Amino Acids Based on Isodesmic Reaction Calculations

Дорофеева

Ryzhova

2014

J. Phys. Chem. A

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Accurate gas-phase enthalpies of formation (ΔfH298°) of 20 common α-amino acids, seven uncommon amino acids, and three small peptides were calculated by combining G4 theory calculations with an isodesmic reaction approach. The internal consistency over a set of ΔfH298°(g) values was achieved by sequential adjustment of their values through the isodesmic reactions. Four amino acids, alanine, β-alanine, sarcosine, and glycine, with reliable internally self-consistent experimental data, were chosen as the key reference compounds. These amino acids together with about 100 compounds with reliable experimental data (their accuracy was supported by G4 calculations) were used to estimate the enthalpies of formation of remaining amino acids. All of the amino acids with the previously established enthalpies of formation were later used as the reference species in the isodesmic reactions for the other amino acids. A systematic comparison was made of 14 experimentally determined enthalpies of formation with the results of calculations. The experimental enthalpies of formation for 10 amino acids were reproduced with good accuracy, but the experimental and calculated values for 4 compounds differed by 11–21 kJ/mol. For these species, the theoretical ΔfH298°(g) values were suggested as more reliable than the experimental values. On the basis of theoretical results, the recommended values for the gas-phase enthalpies of formation were also provided for amino acids for which the experimental ΔfH298°(g) were not available. The enthalpies of sublimation were evaluated for all compounds by taking into account the literature data on the solid-phase enthalpies of formation and the ΔfH298°(g) values recommended in our work. A special attention was paid to the accurate prediction of enthalpies of formation of amino acids from the atomization reactions. The problems associated with conformational flexibility of these compounds and harmonic treatment of low frequency torsional modes were discussed. The surprisingly good agreement between the ΔfH298°(g) values calculated from the atomization and isodesmic reactions is largely the result of a fortuitous mutual compensation of various corrections used in the atomization reaction procedure.

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Section: Results and Discussionmentioning

confidence: 99%

Gas-Phase Enthalpies of Formation and Enthalpies of Sublimation of Amino Acids Based on Isodesmic Reaction Calculations

Дорофеева

Ryzhova

2014

J. Phys. Chem. A

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“…As already noted, in the recent years the enthalpies of formation of different polychlorinated aromatic compounds were predicted from B3LYP calculations using isodesmic reactions [8][9][10][11][12][13][14][15]. To estimate the f H • 298 values of PCDDs, the following reactions may be considered as the most appropriate:…”

Section: Polychlorinated Aromatic Compoundsmentioning

confidence: 99%

“…The thermodynamic properties of chlorinated aromatic species are important in the kinetic modeling their formation during the processes of pyrolysis and oxidation. A large number of studies on the estimation of thermochemical properties of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans, naphthalenes, and biphenyls has been published last years (see [8][9][10][11][12][13][14][15], and references cited therein). In these works, the enthalpies of formation were calculated using the B3LYP total energies and isodesmic reactions.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Gaussian-3X theory for chlorinated organic molecules. Enthalpies of formation of chlorobenzenes and predictions for polychlorinated aromatic compounds

2006

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The enthalpies of formation of chlorinated methanes, ethanes, ethylenes, phenols, and benzenes have been calculated at the G3X level of theory using the atomization energy procedure and the method of isodesmic reactions. By comparing the most reliable experimental data on chlorinated hydrocarbons recommended by Manion [Manion JA (2002) J Phys Chem Ref Data 31:123] with the G3X results, the accuracy of theoretical enthalpies of formation is estimated as ranging from ± 4 to ± 10 kJ/mol. Only for hexachloroethane, the difference between the experimental value and G3X result was outside this range and the experimental enthalpy of formation of hexachloroethane was called into question by theory. The G3X enthalpies of formation of all chlorobenzenes agree well with experimental data which were partly reanalyzed using recent experimental data on enthalpies of sublimation. Based on the G3X results, a set of self-consistent experimental data for chlorobenzenes is recommended. The enthalpies of formation of some polychlorinated dibenzo-p-dioxins were estimated using improved enthalpies of formation for chlorobenzenes. The possible inaccuracy of previously estimated values for polychlorinated aromatic compounds is discussed.

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“…Therefore, theoretical studies can be relevant for understanding the mechanisms of PCDD formation in combustion processes. Most of the theoretical studies have focused on the determination of thermodynamic properties, [4,35,[40][41][42][43][44][45][46][47][48] while the remainder have analyzed the molecular geometry, [49][50][51] vibrational frequencies, [50] mechanisms of formation [35,[52][53][54][55] and decomposition, [56] and reactivity with OH radicals. [57] The mechanisms of formation of PCDDs involving anionic species have been studied less than those involving radicals and focusing only on the closure step of the central ring for PCDD formation.…”

Section: Introductionmentioning

confidence: 99%

Formation of Trichlorinated Dibenzo‐p‐dioxins from 2,4‐Dichlorophenol and 2,4,5‐Trichlorophenolate: A Theoretical Study

Suárez

Menéndez

et al. 2006

ChemPhysChem

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The reaction of the 2,4,5-trichlorophenolate anion with 2,4-dichlorophenol to afford trichlorinated dibenzo-p-dioxins (T3CDDs) is investigated at the B3LYP/6-31+G(d) and B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G(d)+ZPVE(B3LYP/6-31+G(d)) levels of theory. The first stage of the process corresponds to the formation of a predioxin, which can evolve through four different routes. Two of them lead directly to the products 2,3,7-T3CDD and 1,3,8-T3CDD, and the other two afford different predioxin-type intermediates, which in turn can evolve through all or some of the four routes to give new predioxins or T3CDD. Consequently, the theoretical results obtained show plainly the complex chemistry implied in the formation of dioxins from chlorophenols via anionic mechanisms by disclosing all the critical structures through which the system evolves, thus allowing assessment of the viability of the different mechanistic routes and the accessible products. The statistical thermodynamics treatment at 1 atm and 298.15, 600, 900, and 1200 K indicates that at higher temperatures, the Gibbs energy barrier for the formation of the initial predioxin is clearly the rate-determining step for the whole process, but at lower temperatures the Gibbs energy barrier for this step is similar to those for its evolution into 2,3,7-T3CDD. This result is in contrast with previous proposals that the closure of the central ring is the rate-limiting step. Finally, according to our results the rate constant for the formation of polychlorinated dibenzo-p-dioxins increases with the temperature, in agreement with the experimental observation that the conversion of trichlorophenols increases when going from 600 to 900 K in the gas phase in the absence of catalysts, and with DFT molecular dynamics results.

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Enthalpies of Formation of Dibenzo-p-dioxin and Polychlorinated Dibenzo-p-dioxins Calculated by Density Functional Theory

Cited by 13 publications

References 24 publications

Gas-Phase Enthalpies of Formation and Enthalpies of Sublimation of Amino Acids Based on Isodesmic Reaction Calculations

Gas-Phase Enthalpies of Formation and Enthalpies of Sublimation of Amino Acids Based on Isodesmic Reaction Calculations

Assessment of Gaussian-3X theory for chlorinated organic molecules. Enthalpies of formation of chlorobenzenes and predictions for polychlorinated aromatic compounds

Formation of Trichlorinated Dibenzo‐p‐dioxins from 2,4‐Dichlorophenol and 2,4,5‐Trichlorophenolate: A Theoretical Study

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