Natalia F. Moiseeva

Density functional theory study of conformations, barriers to internal rotations and torsional potentials of polychlorinated biphenyls

Abstract Torsional barriers, potential energy curves, structural parameters and vibrational frequencies were calculated for 119 polychlorinated biphenyls (PCBs) at the B3LYP/6-31G(d,p) density functional theory level. From these calculations, the molecular parameters of remaining 90 PCB congeners can be estimated with reasonable accuracy. The conformations and torsional barriers of PCBs are mainly determined by the number of ortho chlorine atoms, while the meta chlorine atoms have a small influence on the torsional angles and barriers. All 209 PCBs were sorted into 18 groups depending on the number of ortho and adjacent meta substituents. In each group the internal rotation behavior of PCB congeners is very similar. For PCBs with 2–4 ortho chlorine atoms, the calculated barrier heights are 10–80 kJ/mol higher than those determined earlier by semiempirical AM1 method.

Ideal gas thermodynamic properties of biphenyl

Ideal gas thermodynamic properties for biphenyl have been calculated by statistical thermodynamics method on the basis of available experimental data and the results of recent high-level quantum mechanical calculations. More precise information about the potential barriers to internal rotation and the lowest vibrational frequencies made it possible to achieve the best agreement with calorimetric results in comparison with statistical calculations published earlier. The thermodynamic functions have been also estimated using molecular structure, vibrational frequencies, and potential barrier heights of biphenyl calculated by B3LYP/cc-pVTZ density functional method.

Group additivity scheme for calculating the chemical thermodynamic properties of gaseous polycyclic aromatic hydrocarbons containing five-membered rings

Abstract An additive method is described for estimation of ideal gas thermodynamic properties and log K XXX F from 100 to 1500 K for polycyclic aromatic hydrocarbons containing five-membered rings.

Development of benson group additivity method for estimation of ideal gas thermodynamic properties of polycyclic aromatic hydrocarbons

Abstract The improved group additivity method has been applied to the prediction of ideal gas thermodynamic properties C p XXX , S XXX -( G XXX - H 0 XXX )/ T , H XXX - H 0 XXX , Δ f H XXX and log K f XXX between 100 and 1500 K for polycyclic aromatic hydrocarbons consisting of six-membered rings.

Standard thermodynamic properties of nitrobenzene in the ideal gas state

The standard enthalpy of formation of gaseous nitrobenzene was calculated by the G3X nonempirical quantum-mechanical method. The value obtained (56 kJ/mol) was noticeably lower than the experimental enthalpy, which casts doubt on the accuracy of measurements. The thermodynamic functions (C°p, S°, −[G° − H°(0)]/T, H° − H°(0), ΔfH°, and ΔfG°) of nitrobenzene in the ideal gas state were calculated by the statistical thermodynamics method over the temperature range 150–1500 K (the molecular constants, including the structural parameters, vibrational frequencies, and internal rotation potential used in the calculations were taken from the literature or estimated by the quantum-mechanical method).

The quantum-chemical determination of group contributions to the thermodynamic properties of organophosphorus compounds

The enthalpies of formation, entropies, and heat capacities of 95 organophosphorus derivatives calculated by nonempirical quantum-chemical methods were used to develop the additive method for estimating the thermodynamic properties of these compounds. 86 group contribution values were obtained for estimating the thermodynamic properties of diverse organic derivatives of phosphorus in the oxidation states 3 and 5 (three-and four-coordinate phosphorus atoms).