Thermodynamic Properties of Dibenzo-p-dioxin, Dibenzofuran, and Their Polychlorinated Derivatives in the Gaseous and Condensed Phases. 1. Thermodynamic Properties of Gaseous Compounds

Abstract

Gas-phase thermodynamic properties (enthalpy of formation, entropy, and heat capacity) are estimated for dibenzo-p-dioxin (DD), dibenzofuran (DF), 75 possible isomers of polychlorinated dibenzo-p-dioxins (PCDDs), and 135 of polychlorinated dibenzofurans (PCDFs). To estimate the enthalpy of formation values, the difference method is used that is completely consistent with the group additivity approach. Entropies and heat capacities are calculated by statistical thermodynamics using evaluated structural parameters and vibrational frequencies. Normal coordinate analysis is carried out for all isomers of PCDDs and PCDFs by transferring the force constants from polycyclic aromatic hydrocarbons, dibenzofuran, and chlorinated benzenes. The group additivity scheme with 10 parameters is developed to approximate calculated thermodynamic properties. Results obtained in this work are compared with published experimental and theoretical data.

Mechanisms for formation, chlorination, dechlorination and destruction of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs)

“…Group additivity (GA) methods were used by Dorofeeva et al [218] to obtain a value of 13.2 kcal/ mol for the enthalpy of formation of dibenzofuran. Shaub [60,219] and Thompson [220] have used GA methods to estimate enthalpies of formation of dibenzo-p-dioxin, (À15, À13.1 kcal/mol), 1-MCDD (À22.7, À20.2 kcal/mol), 2-MCDD (À32.9, À20.5 kcal/mol) and 2,3-DCDD (À48.4, À25.5 kcal/mol), respectively by means of comparisons with other similar organic structures.…”

“…Each ortho-or meta-Cl/Cl interaction is assumed to reduce the enthalpy of formation by 1.8 kcal/mol and 0.60 kcal/mol respectively. These GA rules of Dorofeeva et al [218] were reviewed by Zhu and Bozzelli [221]. They recommended adding 2.6 and 3.6 kcal/mol for each ortho-and meta-chlorine interaction in dibenzo-p-dioxin, respectively.…”

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

“…[1][2][3][4] Most of the emissions of PCDDs stem from anthropogenic activities such as waste incineration, [5][6][7][8][9][10][11] metallurgical processes, [12][13][14][15][16] chemical manufacturing, or the papermaking process. [17] To a small extent, PCDDs are also discharged into the environment from natural processes by volcanic eruptions and forest and brush fires, [18][19][20] or even by plants, insects, bacteria, etc.…”

“…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.…”

Thermodynamics of dibenzo-p-dioxin and 1,2,3,4-tetrachlorodibenzo-p-dioxin fromT= 5 K toT= 490 K

“…These quantities were used as a basis to estimate the enthalpy of formation of other PCDDs. In subsequent work, (12) the authors developed, based on the additivity of group contributions, a scheme with 10 parameters that was employed in the calculation of the thermodynamic characteristics of dioxins; they calculated the heat capacities and entropies of the gaseous substances by the method of statistical thermodynamics on the basis of estimate structural parameters and vibration frequencies.…”