Abstract
Thermodynamic functions, including enthalpy (Hθ) and entropy (Sθ) for 76 polychlorophenazines (PCPZs) in the gas state at 298.15 K and 101.325 kPa, have been calculated using the B3LYP/6-31G∗level with Gaussian 03 program, and considered on solvation affects. Total free energy in water (Gw) was calculated with the same program. Based on these data, the isodesmic reactions were designed to calculate the standard formation heat (ΔfHθ) and standard free energy of formation in water(ΔfGwθ). The dependences of these thermodynamic parameters on the numbers and positions of chlorine substitution (NPCS) were discussed. It is suggested thatSθ, ΔfHθ, andΔfGwθof PCPZs varied greatly withNPCS. Moreover, the values of molar heat capacity at constant pressure (Cp,m) from 200 to 1800 K for PCPZ congeners were calculated using a statistical thermodynamics calculation program based on Gaussian output files, and the temperature-dependence relation ofCp,mwas obtained using the least-squares method. In addition, according to the relative magnitude of theirΔfGwθ, the relative stability order of PCPZ congeners was theoretically proposed.
Highlights
Phenazine (PZ) shows properties of a wide range in significant applications [1, 2]
It is suggested that Δ f Hθ and Δ f Gθw of PCPZs varied greatly with the positions of chlorine substitution, with an order of decrement for these parameters being position β> position α
76 PCPZs were fully optimized at B3LYP/6-31G∗ level, and their Hθ, Sθ, and Gw were obtained
Summary
Phenazine (PZ) shows properties of a wide range in significant applications [1, 2]. Natural and synthetic phenazines have attracted considerable attention because of their interesting biological activities [3], that is, antibiotic and anticancer agents [4, 5]. Halosubstituted phenazines are useful as herbicides [6]. Using the in vitro bioassay for dioxin-like activity showed that TBPZ has an ED50 of 10−7 M [7]. It can draw the conclusion that polychlorophenzines have dioxin-like activity. For studying their generation, degradation, and environmental risk, it is important to know the thermodynamic properties of PCPZs. In addition, solvation has huge effect on organic reactivity/stability, and these studies were reported previously. Warshel [8] studied computer modeling of chemical reactions in enzymes and solutions; Bren et al
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