Thermodynamic Properties of Polybrominated Dibenzo-p-dioxins and Dibenzofurans Calculated by Density Functional Theory

Abstract

Heat capacities and entropies for 76 polybrominated dibenzo-p-dioxins (PBDDs) and 136 polybrominated dibenzofurans (PBDFs) in the gas state have been computed using the density functional theory. Based on the output data of Gaussian, three methods were employed to calculate enthalpies and Gibbs energies of formation of PBDDs and PBDFs in the gaseous state at 298.15 K and 101.325 kPa. To assess the three methods, thermodynamic properties of 16 brominated arenes compounds were first calculated and compared with experimental values. Among the three methods used, method 2 has the smallest average absolute deviation from the experimental data. All values for the heat capacity, entropy, enthalpy and energy of formation of the 76 PBDDs increase, as the number of substituted bromines increases. For isomers of tetrabromodibenzo-p-dioxins, 1, 3,6,1,3,7,1,3,7,9-TeBDD and the most toxic compound 2,3,7,8-TeBDD are more stable than the others, and easier to form during formation process. Comparing with PBDDs, the formation enthalpies and Gibbs energies of PBDF isomers are more variable. The formation enthalpies and Gibbs energies of isomers which have bromine substitutions in 1 and 9 positions are much higher than those of the others.

The enthalpies of formation of brominated benzenes and phenols: A theoretical prediction

“…Therefore, none of the DFT methods tested here is suitable for prediction of D f H 298K (g) for PBDD/DF/DEs even with homodesmic reaction corrections, and the pragmatic methods would be G3XMP2-CC/QCI or MP2 with a large basis set such as G3MP2Large. The tests on DFT methods cast doubt on the previous B3LYP/6-31G(d) predictions on the thermodynamic properties of highly brominated PBDD/DF/DEs even with the similar homodesmic reactions [22][23][24], especially for the species with ortho-BrBr-substitutions. D f H 298K (g) of BrPhs are predicted here using HR2.…”

“…Cox and Pilcher [20] suggested D f H 298K (g, C 6 H 5 Br) $105.4 kJ/mol from the combustion and heat of vaporization measurements, and recently Ribeiro da Silva and Lobo Ferreira measured the enthalpies of 2-and 4-bromophenols using combustion studies [21]. On the other hand, there have been two theoretical predictions on the thermodynamic properties of PBDD/Fs [22,23] and PBDEs [24] using density functional theory (DFT) at B3LYP/6-31G(d) level. Our previous theoretical studies on PCDD/DF/Ns showed that DFT methods greatly over-estimated the Cl-Cl repulsions when comparing to Gaussian-3X (G3X) method, and the discrepancy of DFT-B3LYP to G3X was as large as 30 kJ/mol for C 6 Cl 6 even after homodesmic reaction correction [25][26][27].…”

DFT Study of Structural and Thermodynamic Properties for Polybrominated 5,10-Dihydrophenazines

“…The following equations are employed to calculate the absolute internal energy (U ), enthalpies (H ), and Gibbs energies (G) of the molecule at 0 K and the specified temperature (T ) [13]:…”

Efficient Synthesis of Novel Tricyclic Benzoxazine Derivative via Ring Opening of Epoxide Along the Mp and DFT Studies of Structural, Spectroscopic (Ir, Raman, Uv-Vis), Thermodynamic, Orbitals and Nlo Properties of Desired Tricyclic Benzoxazine Derivative

“…The increase of temperature resulting in the increase of thermodynamic energies. This thermodynamic data is useful to predict direction of chemical reactivity in accordance with laws of thermodynamics [62]. Tricyclic compounds are known for their biological activities and this statistical thermodynamic data can be useful for further investigations of biological interactions as function of temperature.…”