Phthalate acid esters （PAEs） possess endocrine disruptive effects and can produce reproductive and developmental toxicities. In this paper, both experimental and theoretical studies on FT-IR, Raman and 1H NMR spectra of diethyl phthalate （DEP） have been carried out. The geometrical structure of DEP was optimized at the HF/6-31G＊, HF/6-311G＊＊, B3LYP/6-31G＊, and B3LYP/6-31 IG＊＊ levels, respectively. The harmonic vibrational frequencies, IR intensity, Raman activity and 1H NMR chemical shifts have been computed at the B3LYP/6-31G＊ and B3LYP/6-311G＊＊ levels. Anharmonic corrections to frequencies were obtained by means of second-order perturbation theory （PT2） at the B3LYP/6-31G＊ level. Based on potential energy distribution （PED）, the vibrational assignments have also been performed. The theoretical calculation values were compared with the experimental observations and the results indicate they are in excellent agreement.
With the B3LYP calculation method of density functional theory（DFT）and the 6-31G＊ basis set,full optimization calculation was made for phenoxathiin10-oxide（PTO）and 135 polybromine phenoxathiin 10-oxides（PBPTOs）with the Gaussian 03 program and molar heat capacity in constant volume（CVθ）value of each molecule in the standard state was obtained.The relation between CVθ and the substitution position and number of bromine atom（NPBS）was studied,and the results indicated good correlation（R2 = 1.000）between CVθ and NPBS of PBPTO compounds.Based on the output file of Gaussian 03 program,molar heat capacity at constant pressure（Cp,m）of PBPTO compounds from 200 to 1,000 K was calculated with the statistical thermodynamics program,and the correlation equation between Cp,m and temperature（T,T-1 and T-2）was obtained with the least-squares method,and the correlation coefficient of the correlation equation（R2）was 1.000.In addition,based on the partition function of each molecule calculated by vibration analysis,the relative rate constant of formation of each molecule was calculated.
In this work, partial thermodynamic properties of polyhydroxylated dibenzo-p-dioxins （PHODDs） are calculated by density functional theory （DFT） with the Gaussian 03 program at the B3LYP/6-311G^＊＊ level. By comparing the total energy Eθ values, it is found that two types of hydrogen bonds exist in PHODDs, one between a hydroxyl and the parent compound （dibenzop-dioxin） with bond energy of approximate 15.7 kJ/mol and the other between two ortho hydroxyl groups with higher bond energy of about 18.3 kJ/mol. Hydrogen bonds have an effect on the conformation stability. On the basis of evaluating the strength of these two types of hydrogen bonds, 75 most stable congeners are ascertained. The relations of calculated thermodynamic parameters （total energy E^θ, zero-point vibrational energy ZPE, correction value of thermal energy Ethθ, heat capacity at constant volume CV^θ） with the number and position of hydroxyl substitution （NPHOS） are also discussed. The results show that the NPHOS models can be used to predict the thermodynamic properties for PHODD congeners. In addition, the values of molar heat capacities at constant pressure （Cp,m） from 200 to 1000 K for PHODD congeners are calculated, and the temperature dependence relation of Cp,m is obtained with the least-squares method.
Decabromodiphenyl ether （BDE-209）, the major congener in the high volume industrial flame retardant mixture ＂DecaBDE＂, has become a ubiquitous environmental contaminant. In the present work, combined experimental and theoretical studies have been undertaken on the structure and vibrational spectra of BDE-209. The FT-IR （400-4000 cm-1） and FT-Raman spectra （100-4000cm-1） of BDE-209 were recorded, while density functional B3LYP calculations were employed in conjunction with the 6-31G（d） basis set for investigating the corresponding geometric structure and vibrational spectroscopic properties. Besides, the detailed interpretations of fundamental vibrations were performed on the basis of experimental results and potential energy distribution （PED） of the vibrational modes. Optimized structures of the title compound were interpreted and compared with the earlier reported experimental values, which yield good agreement. Finally, the measured and calculated harmonic vibrational wavenumbers were compared with each other, and they were found to be in good accordance.
