Yixin Qu

Molecular structural, IR and NMR spectroscopic studies on the four isomers of thiotriazinone by DFT and HF calculations

One of the isomers of thiotriazinone, 6-hydroxy-2-methyl-3-thioxo-2H-1,2,4-triazin-5-one, was characterized by single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2(1)/c with a=9.5837(19)Å, b=5.7006(11)Å, c=15.065(4)Å, α=90°, β=128.540(19)° and γ=90°. The molecular geometries and vibrational frequencies of the four isomers of thiotriazinone in the ground state have been calculated using the density functional theory (DFT) and Hartree-Fock (HF) methods with 6-311++G(d,p) basis set, and compared with the experimental data. Gauge-including atomic orbital (GIAO) (13)C and (1)H NMR chemical shift values were calculated by DFT/6-311++G(2d,2p) and HF/6-311++G(2d,2p) methods, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters. The theoretical IR spectra and (13)C and (1)H NMR chemical shift values also show good agreement with experimental data. In addition, frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) analysis of the four isomers were investigated using theoretical calculations.

Molecular structure and vibrational spectra of o-chlorotoluene, m-chlorotoluene, and p-chlorotoluene by ab initio HF and DFT calculations.

In this work, experimental and theoretical study on the molecular structure and the vibrational spectra of o-chlorotoluene (OCT), m-chlorotoluene (MCT) and p-chlorotoluene (PCT) are presented. The vibrational frequencies of these compounds were obtained theoretically by ab initio HF and DFT/B3LYP calculations employing the standard 6-311++G(d,p) basis set for optimized geometries and were compared with Fourier transform infrared (FTIR) in the region of 400-4000 cm(-1) and with Raman spectra in the region of 100-4000 cm(-1). Complete vibrational assignment, analysis and correlation of the fundamental modes for these compounds have been carried out. The vibrational harmonic frequencies were scaled using scale factors, yielding a good agreement between the experimentally recorded and the theoretically calculated values.

Comprehensive comparison and evaluation of the mixing rules of WS, MHV2, and Twu et al.

A comprehensive comparison and evaluation of three mixing rules, the Wong-Sandler (WS), MHV2 and Twu et al., have been conducted. Their capabilities for correlating and predicting vapor-liquid equilibria of diversified systems have been tested. Sensitivity analysis has been carried out to clarify the effect on the prediction accuracy of variations in model parameters.

The Initial Reactions of H3PO4 and NaH2PO4 Supported on Silica: A Joint Experimental and Theoretical Study

A combination of X-ray powder diffraction, thermogravimetric analysis, diffuse reflection infrared Fourier transform, and 31P magic-angle spinning nuclear magnetic resonance techniques with density function computation was used to elucidate the products and mechanism of the reactions among silica, H3PO4, and NaH2PO4 during the preparation of silica supported H3PO4 and NaH2PO4 catalysts. The spectral test results indicate that besides polyphosphoric acid, silicon phosphates on silica supported H3PO4 are also formed. On silica supported NaH2PO4 only sodium polyphosphates are present. Density functional theory (DFT) simulations indicate that in the initial stage, reaction of H3PO4 with silanol groups on the silica support is more favorable than that between H3PO4 itself. In contrast, dimerization and trimerization of NaH2PO4 are predicted to be the predominant initial reactions for the silica supported NaH2PO4 catalyst.

The influence of transition metal ions on the catalytic performance of Ru particles during the liquid phase hydrogenation of benzene to cyclohexene

The influence of some transition metal ions including Fe2+, Ni2+, Cr3+, Mn2+, Zn2+, Cd2+ on the catalytic performance of Ru particles during the liquid phase partial hydrogenation of benzene to cyclohexene was investigated in a titanium autoclave and a stainless steel autoclave. The Ru particles were prepared by the precipitation method. The catalysts were characterized using XRD, BET surface area measurement and XPS. The structure configurations and formation enthalpies of the hydrated metal ions, the complexes of the metal ions with benzene and cyclohexene as well as the complexes of hydrated metal ions with benzene and cyclohexene were optimized and evaluated using quantum chemical calculation methods. It was found that the poisoning effect of the transition metal ions on the catalytic activity of Ru particles only partially obeys the “Maxted rule”. The enhancing effect of the transition metal ions on the cyclohexene selectivity is associated with both the interaction of the metal ions with the active sites on Ru surface and with the tendency of metal ions to form hydrated complexes. In the stainless steel autoclave, the Fe2+, Ni2+ and Cr3+ resulted from the corrosion of the stainless steel have a synergetic effect with Zn2+, leading to a higher selectivity to cyclohexene.

Investigations on the reaction kinetics and the catalytic effect of Cu(II) and V(V) in the oxidation of cyclohexanol by nitric acid

In this paper, the reaction kinetics of the oxidation of cyclohexanol by nitric acid to adipic acid (AA) with and without using Cu(II) and V(V) as catalysts was studied in a continuous flow stirred tank reactor at conditions close to the industrial process. Rate equations of power law type and lumping of the reaction intermediates were applied to describe the reaction kinetics. The effect of the catalyst on the selectivity of products including the dicarboxylic acid and the unrecoverable N2 and N2O was investigated. Cu(II) or V(V) alone and the combination of them enhance the selectivity of AA by suppressing the formation of the by-product glutaric acid and succinic acid with Cu(II) being more effective than V(V), and the combination of Cu(II) and V(V) being more effective than Cu(II). In the presence of the catalysts, the consumption of HNO3 and the production of the unrecoverable nitrogen containing compounds per mole of AA are reduced. Based on the experimental results, the way for the catalysts to influence the reaction mechanism was proposed.

Solubilities of (α,Z)-2-Amino-α-(methoxyimino)-4-thiazole-ethanethioic Acid S-2-Benzothiazolyl Ester in Pure Solvents and a Mixture of Acetonitrile and Dichloromethane

Using a laser monitoring technique, the solubility of (α,Z)-2-amino-α-(methoxyimino)-4-thiazole-ethanethioic acid S-2-benzothiazolyl ester in ethanol, 1-propanol, 1-butanol, 1-pentanol, 2-propanol, 2-methyl-1-propanol, 3-methyl-1-butanol, and a mixture of acetonitrile and dichloromethane was determined from (278.15 to 308.15) K. The solubility data were correlated with a semiempirical equation. The calculated results of which are proven to show fine representation of the experimental data.