Density functional theory calculation on the C―H bond insertion reaction of dibromocarbene with acetaldehyde

The insertion reaction mechanism of CBr_2 with CH_3CH_O has been studied by using the B3LYP/6-31G(d) method. The geometries of reactions, transition state and products were completely optimized. All the energy of the species was obtained at the CCSD(T)/6-31G(d) level. All the transition state is verified by the vibrational analysis and the internal reaction coordinate (IRC) calculations. The results show that the propionaldehyde (~HP1) is the main product of CH_2 insertion with CH_3CH_O. The calculated results indicated that all the major pathways of the reaction were obtained on the singlet potential energy surface. The singlet CBr_2 not only can insert the C_α-H [reaction I(1)]) but also can react with C_β-H [reaction II(1)]. The statistical thermodynamics and Eyring transition state theory with Wigner correc- tion are used to study the thermodynamic and kinetic characters of I(1) and II(1) in temperature range from 100 to 2200 K. The results show that the appropriate reaction temperature rang is 250 to 1750 K and 250 to 1600 K at 1.0 atm for I(1) and II(1) respectively. The rate constant and equilibrium constant are distinct in the range from 250 to 1000 K so that I(1) more easily occurs, while the reactions are not selected in the temperature range of 1000-1600 K     

Dissolution behavior and dissolution mechanism of palygorskite in HCl solution

The 1 mol/L, 3 mol/L and 5 mol/L HCl solutions were employed to leach two palygorskites with different trioctahedral contents in their crystal structure for different period of time. The results of the dissolution experiments show that the dissolution process could be divided into three steps, and that this dissolution behavior can be attributed to its higher Mg2+ content, and is restricted by the extraction behavior of Si4+. The preferential extraction for Mg2+ promotes the extraction behavior of Si4+ from Si-O framework. Because the Si4+ in the form of amorphous SiO2 is adsorbed onto the surface of palygorskite fibre, the reaction between palygorskite and acid is obstructed. With the elapsing of time, or the increasing of the acid concentration, the amorphous SiO2 flocculates, and then the channels of chemical reaction are reopened. The ratio value of Mg2+/(Fe3++Al3+) in leaching solution tends to a fixed value, showing that the acid attacks not only the surface but also the structural channels. There are no obvious three steps observed during the acid attack on the palygorskite with a lower trioctahedral content. The differential behavior for two palygorskites is discussed.     

Density functional theory study on the insertion reaction mechanism of dibromocarbene with formaldehyde

The insertion reaction mechanism of CBr2 with CH3CH2O has been studied by using the B3LYP/6-311G(d) and CCSD(T)/6-311G(d) at single point. The geometries of reactions,transition state and products were completely optimized. All the transition state is verified by the vibrational analysis and the internal re-action coordinate (IRC) calculations. The results show that reaction (1) is the dominant reaction path,which proceeds via two steps: i) two reactants form an intermediate (IM1),which is an exothermal re-action of 8.62 kJ·mol?1 without energy barrier; ii) P1 is obtained via the TS1 and the H-shift,in which the energy barrier is 44.53 kJ·mol?1. The statistical thermodynamics and Eyring transition state theory with Wigner correction are used to study the thermodynamic and kinetic characters of this reaction in temperature range from 100 to 2200 K. The results show that the appropriate reaction temperature ranges from 200 to 1900 K at 1.0 atm,in which the reaction has a bigger spontaneity capability,equi-librium constant (K) and higher rate constant (k).     

Reduction mechanism of high-chromium vanadium–titanium magnetite pellets by H_2–CO–CO_2 gas mixtures

The reduction of high-chromium vanadium–titanium magnetite as a typical titanomagnetite containing 0.95wt% V2O5 and 0.61wt% Cr2O3 by H2–CO–CO2 gas mixtures was investigated from 1223 to 1373 K. Both the reduction degree and reduction rate increase with increasing temperature and increasing hydrogen content. At a temperature of 1373 K, an H2/CO ratio of 5/2 by volume, and a reduction time of 40 min, the degree of reduction reaches 95%. The phase transformation during reduction is hypothesized to proceed as follows: Fe2O3 → Fe3O4 → FeO → Fe; Fe9 TiO 15 + Fe2Ti3O9 → Fe2.75Ti0.25O4 → FeT iO 3 → TiO 2;(Cr0.15V0.85)2O3 → Fe2VO4; and Cr1.3Fe0.7O3 → FeC r2O4. The reduction is controlled by the mixed internal diffusion and interfacial reaction at the initial stage; however, the interfacial reaction is dominant. As the reduction proceeds, the internal diffusion becomes the controlling step.     

Reactivity and structural characterization of divalent samarium aryloxide with diethylaluminum chloride

Reaction of (ArO)2Sm(THF)4 (ArO=2,6-ditert-butyl-4-methylphenolate) with Et2AICI in THF gives SmCI2 (1) and (ArO)AIEt2(THF) (2) via ligand exchange.Complex 1 reacts with cyclooctatetraene (C8H8) to give [(C8H8)SmCI(THF)2]2 (3). Crystal structural determinations show that complex 2 has a monomeric structure, the aluminum atom is coordinated by two carbon atoms and two oxygen atoms, to form a distorted tetrahedron. Complex 3 has a dimeric structure, the samarium atom is coordinated by a cyclooctatetraenyl ring, two chorine atoms and two oxygen atoms, the coordination number of the central metal is 9.     

Syntheses,Crystal Structures and Photoluminescence Properties of Two Cadmium(Ⅱ) Coordination Polymers

The solvothermal reaction of CdCl_2·2.5 H_2O with terephthalic acid yields two new three-dimensional(3 D) cadmium(II) coordination polymers(CPs), namely {[Cd(C_8H_4O_4)Cl]·C_2H_8N}_n and [Cd(C_8H_4O_4)]_n, we use the abbreviations CP1 and CP2 to refer to them, respectively. The compounds are characterized in detail by single-crystal X-ray diffraction, powder X-ray diffraction, IR spectroscopy, elemental analysis and thermogravimetric analysis(TGA). The results indicate that compounds CP1 and CP2 are 3 D frameworks, and both the compounds feature a uninodal 4-connected framework with a dia net. The empty spaces of such 3 D framework are filed by the other two identical frameworks, leading to a 3-fold interpenetrated network. In addition, the photochemical properties of the frameworks are also investigated. The two frameworks show strong solid-state fluorescence emission at 463 and 503 nm, respectively, which are obvious red-shift compared to the emission of ligand.     

Investigation on the key factors in the hydrothermal synthesis of BN： The way of introducing sodium azide

The way of introducing sodium azide (NaN_3) into the reaction solution played an important role in the preparation of cBN by hydrothermal synthesis method. The results showed that both cBN content and crystalline perfection of the samples improved with increasing R_N value, and pure cBN could be obtained at 300℃ and 10 MPa when R_N increased to 3:1. Here R_N is defined as R_N =NaN_3(I)/NaN_3(II), wherNaN_3(I) denotes the amount of NaN_3 (in molar) that is added into the autoclave at the beginning of threaction process, and NaN_3(II) is the amount of NaN_3 (also in molar) introduced into the autoclave ahigh temperature and high pressure (i.e. 300℃ and 10 MPa). In order to explain the experimental results, a preliminary model was proposed in this paper.     

A comparison of transition state of phenol in H-atom abstraction by methyl and methylperoxyl radicals

DFT method was employed to locate transition state for H-atom transfer from phenol by methyl radical and methylperoxyl radical. The reaction pathway energy profiles and the structure of transition state show that a common feature is the out-of-plane structure of the transition state: in contrast to the en- ergetic minima of a hydrogen-bonded intermediate, the hydrogen bond in transition structures is con- siderably twisted out of the aromatic ring. From the values of enthalpy (△H) and activation energy (Ea) obtained, it is found that the rate of the reaction of peroxyl radical with phenolic antioxidant is higher than that of alkyl radical with antioxidant. Spin density distributions show that the electron transmis- sion is between methyl (methylperoxyl) radical and phenol.     

Synthesis,Characteristics and Applications of Fibrous Composites with Immobilized Nanomolecular Layers of Ferrocyanides and Phosphates of Some d-Elements

1 Results The general principle of the synthesis of fibrous inorganic ion-exchanging composites, containing the combination of polymer analogous conversion reactions of the fibres and cycles of ion-molecular layering is advanced. Synthesis of thin nanomolecular layers of the acid Ti(Ⅳ) and Zr(Ⅳ) phosphates on surface of the cotton fibres and Cu(Ⅱ) and Fe(Ⅲ) ferrocyanides-on polyacrylonitrile fibres was performed on the basis of this principle. By the method of X-ray analysis it was stated that the formed pellicular inorganic layers have a crystalline structure. The synthesis of thin layers of Cu(Ⅱ) and Fe(Ⅲ) hexacyanoferrates (Ⅱ) was performed by the method of the chemosorption layering on a matrix which represented the derivatives of polyacrylonitrile fibres containing HO-N=C·-NH2 groups with the degree of substitution of CN-groups about 50%. According to the data from the X-ray studying of the synthesized pellicular hexacyanoferrates, their composition is described by the formulas KxCu(2-x)[Fe(CN)6]·4H2O and KxFe(4-x)[Fe(CN)6]3 (compounds Ⅰand Ⅱ respectively). By the methods of IR-spectroscopy, formation of heteroatomic cycles by polyacrylonitrile derivatives (with participation of strong H-bonds) was shown. They were capable to disintegrate under the effect ofthe ions of d-metals. It is suggested that strong adhesion of the layers withthe matrix is caused by formation of linkage between [Fe(CN)6]4-ions and the ions in chelates' composition through CN-bridges. The equilibrium ion-exchange capacity on the Rubidium, Cesium and Thallium ions linearly depends on the layer's thickness, which is determined by the number of layering cycles (n) and is equal to 1.0 mmol·g-1 when n=8. Theion-exchange property testing of the synthesized compositions on the basis of the acid Ti(Ⅳ) and Zr(Ⅳ) phosphates was carried out by sorption from water solutions of the strontium and caesium-137 ions, on the basis of the Cu(Ⅱ) and Fe(Ⅲ) ferrocyanides-stable and radioactive caesium isotopes. There is a linear dependency of ion-exchange capacity on the amount of the cycles layering in case the acid Ti(Ⅳ)and Zr(Ⅳ) phosphates is observed. Moreover, the equality of the ionite ion-exchange capacity both on ion strontium, and on ion caesium is observed under fourfold cycle layering. S-figurative nature of such dependence was stated for ferrocyanides. It is shown that the process of the ion exchange proceeding in two stages. The full ion-exchange capacity of ionites on the basis of the acid Ti(Ⅳ) and Zr(Ⅳ) phosphates reaches 2.0 mmol-equ/g, but on the basis Cu(Ⅱ) and Fe(Ⅲ) ferrocyanides-1.0 mmol-equ/g. Ion-exchange equilibrium on synthesized ionites is reachedapproximately 30 times faster, than on corresponding powdery crystalline phosphates and ferrocyanides. Conclusion about prospect of the synthesized material usage in ion-exchange technology, including for extraction of radionuclides is made.     

Research of Inclusion Complexation of 4,4'-Thiodiphenol Effected by β-Cyclodextrin in Aqueous Solutions and the Effect on Photodegradation

The inclusion behavior of 4,4′ -Thiodiphenol (TDP),a typical bisphenol and endocrine disruptor,reacts with β-cyclodextrin (β-CD) in aqueous solutions has been investigated by means of UV absorption spectrum and quantum-chemical calculation with Gaussian 98 software. The results show that the inclusion behavior of TDP is quite different in acidic solutions (pH 5.9) from that in alkaline solutions (pH 10.0). This behavior difference is attributed to the different formula structures in aqueous solutions at acidic and alkaline pH values that are demonstrated by quantumchemical modeling and calculation. TDP forms a 1∶1 β-CD inclusion complex in aqueous solutions. The equilibrium constant K was calculated to be 553.49 L/mol at pH 5.9 and 1 318.20 L/mol at pH 10.0 respectively for the inclusion complex reaction by using the modified Benesi-Heldbrand equation. After inclusion TDP's structure is changed especially at the inclusion part with the bond order becoming larger,which results in inhibitive photodegradation during direct photooxidation and H2O2 assisted photooxidation.     

Effects of Influencing Factors on Fenton Oxidation of Antibiotic Pharmaceutical Wastewater by a Statistical Design Approach

A series of batch-scale experiments were completed to investigate the effects of operational parameters on chemical oxygen demand (COD) removal by Fenton reagent for antibiotic pharmaceutical wastewater (APW). The significance of five operational factors including the mass ratio of H2O2/COD (g/g), the mole ratio of H2O2/Fe2+ (mol/mol), initial pH, oxidation temperature T, and reaction time t were evaluated statistically by Box-Behnken design (BBD). It was found that the five parameters were all significant to the COD removal efficiency by t-test, as well as the interactions between mass ratio/reaction time and oxidation temperature/reaction. The optimal COD removal efficiency (89.50%) was achieved when the mass ratio of H2O2/COD and the mole ratio of H2O2/Fe2+ were 3.00 and 5.00 respectively, with pH value of 3.68 at 298K for 72min reaction. A quadratic regression model with 0.9907 regression coefficient (R2) was developed which had good agreement to the experimental data.     

Mechanism of Cathode Process of B(Ⅲ) in LiF-NaF-KBF4 Melt by Electrochemical Titration Technique

The mechanism of cathode process of B(Ⅲ) at molybdenum and platinum electrodes in LiF-NaF-KBF₄ melt was studied and the transferred electron number of the reaction was calculated by means of cyclic voltammetry.The effect of adsorption of electroactive component on the electrochemical response (e.g., the voltammetric i─E curves) was analyzed and discussed. The "electrochemical spectra" for linear sweep voltammetry was used to elucidate the electrode reaction accompanied by a following transform process. The results show that the reduction of B(Ⅲ) to B(0) proceeds in reversible one step three-electron reaction and the cathode process of B(Ⅲ) is affected by product adsorbed strongly at the electrode surface. It is assumed that the reduction and deposition of B(Ⅲ) at molybdenum and platinum electrodes proceed in two kinds of mechanism: (1) B(Ⅲ)+ 3e = B_ads→ B (surface diffusion deposition mechanism) and (2) B(Ⅲ) + 3e = B (direct deposition mechanism).     

Hydrogen production by draTGB hupL double mutant of Rhodospirillum rubrum under different light conditions

To increase H2 yield of Rhodospirillum rubrum in two-stage hydrogen production process, two deletion mutants were constructed. One is single mutant designated R. rubrum UR801 that deleted hupL gene encoding the large subunit of uptake hy- drogenase, and the other is a double mutant desig- nated R. rubrum UR805 lacked both draTGB encod- ing regulators for the activity of nitrogenase and hupL. Comparing H2 yields of two mutants with R. rubrum UR2 (wild type) and UR472 (ΔdraTGB) under differ- ent light conditions, the results showed that the H2 yield of R. rubrum UR801 under continuous light is the highest (5700 mL of H2 per liter culture), and it is 1.56, 2.24 and 2.32-fold that of R. rubrum UR2, UR472 and UR805, respectively. However, the total H2 yield of R. rubrum UR805 in two-stage hydrogen production process is the highest (4303 mL/L), and it is 1.35, 1.21 and 1.04-fold that of R. rubrum UR2, UR801 and UR472, respectively. Thus, R. rubrum UR805 might be a valuable strain to produce a large amount of hydrogen in two-stage hydrogen produc- tion process.     

Simulation experiments on the reaction system of CH_4-MgSO_4-H_2O

H2S-rich gas in carbonate reservoirs is usually attributed to thermochemical sulfate reduction (TSR). In this paper, thermal simulation experiments on the reaction system of CH4-MgSO4-H2O were carried out using autoclave at 425℃―525℃. The threshold temperature for initiating TSR is much lower than our previous studies (550 ℃ ). Properties of the reaction products were analyzed by microcoulometry, gas-chromatography (GC), Fourier transform-infrared spectrometry (FT-IR) and X-ray diffraction (XRD) methods. Thermodynamics and reaction kinetics of TSR processes were investigated on the basis of the experimental data. The results show that thermochemical reduction of magnesium sulfate with methane can proceed spontaneously to produce magnesium oxide, hydrogen sulfur, and carbon diox-ide as the main products, and high temperature is thermodynamically favorable to the reaction. Ac-cording to the reaction model, the calculated activation energy of TSR is 101.894 kJ/mol, which is lower than that by most previous studies. Mg2 may have played a role of catalytic action in the process of TSR. The elementary steps of TSR and reaction mechanism were discussed tentatively. The study can provide important information on the explanation of geochemical depth limit for natural gas and on the generation of high H2S gas in deep carbonates reservoirs.     

不同硅饱和系数水榴石的碳酸化分解动力学

Carbonated decomposition of hydrogarnet is one of the vital reactions of the calcification–carbonation method, which is designed to dispose of low-grade bauxite and Bayer red mud and is a novel eco-friendly method. In this study, the effect of the silica saturation coefficient (x) on the carbonation of hydrogarnet was investigated from the kinetic perspective. The results indicated that the carbonation of hydrogarnets with different x values (x = 0.27, 0.36, 0.70, and 0.73) underwent two stages with significantly different rates, and the kinetic mechanisms of the two stages can be described by the kinetic functions R3 and D3. The apparent activation energies at Stages 1 and 2 were 41.96–81.64 and 14.80–34.84 kJ/mol, respectively. Moreover, the corresponding limiting steps of the two stages were interfacial chemical reaction and diffusion.     

Quantum chemical studies on tuning the second-order nonlinear optical molecular switching of triarylborane derivatives

In this work, density functional theory (DFT) combined with the finite field (FF) method has been adopted to analyze the second-order nonlinear optical (NLO) properties of the triarylborane (TAB) derivatives obtained by introducing different inductive electron groups into the phenylene ring of the TAB (RTAB, where R=2-C6H5-C2B10H10(1),R=F(2), R=Me(3),R=NO2(4),R=NH2(5)). The static first hyperpolarizabilities (βtot) of the RTAB molecules can be switched by binding one F- to the boron center (RTAB′) or one-electron reduction (RTAB"). The DFT-FF calculations show that the βtot values of 2′, 3′ and 5′ decrease while those of 1′ and 4′ increase compared with the values of their neutral molecules, which was attributed to the fact that the charge transfers of 2, 3 and 5 become smaller and those of 1 and 4 become larger by binding one F- ion to the boron center, according to time-domain DFT (TD-DFT) analysis. However, the incorporation of one electron enhances the second-order NLO properties of the RTAB molecules remarkably, especially for system 1. It is notable that the βtot value of reduced form 1″ is 508.69×10-30 esu, i.e. about 578 times larger than that of system 1. Frontier molecular orbital (FMO) and natural bond orbital (NBO) analyses suggest that the reversal of the charge distribution between the neutral molecules and their reduced forms leads to low HOMO-LUMO energy gaps (E0) and thus large βtot values for the reduced forms.     

Kinetics of carbonated decomposition of hydrogarnet with different silica saturation coefficients

Carbonated decomposition of hydrogarnet is one of the vital reactions of the calcification–carbonation method, which is designed to dispose of low-grade bauxite and Bayer red mud and is a novel eco-friendly method. In this study, the effect of the silica saturation coefficient(x) on the carbonation of hydrogarnet was investigated from the kinetic perspective. The results indicated that the carbonation of hydrogarnets with different x values(x = 0.27, 0.36, 0.70, and 0.73) underwent two stages with significantly different rates, and the kinetic mechanisms of the two stages can be described by the kinetic functions R3 and D3. The apparent activation energies at Stages 1 and 2 were 41.96–81.64 and14.80–34.84 k J/mol, respectively. Moreover, the corresponding limiting steps of the two stages were interfacial chemical reaction and diffusion.     

Synthesis, crystal structure and properties of binuclear manganese complex [(bipy)2Mn2(μ-O)(μ-Ac)2(H2O)2](ClO4)2

Binuclear manganese complex [(bipy)2Mn2(μ-O)(μ-Ac)2(H2O)2](ClO4)2 was synthesized by the reaction of MnAc3·2H2O with 2,2′- -bipyridine in the HAc-NaAc buffer (pH = 4.0). X-ray diffraction result for the single crystal shows that the crystal is monoclinic, space group C2/C, with a = 3.408 2(7), b = 0.864 4(2), c = 2.174 9(4) nm, β=105.2°,V =6.186(2) nm3, Z = 8. There are two very strong peaks of UV-Vis spectrum in the range of 400-600 nm, which are similar to those of Mn catalase and Mn ribonuleotide reductase extracted from organisms. Cyclic voltammogram shows that the complex in CH3CN undergoes quasi-reversible one-electron reduction and oxidation at E1/2=1.15 V.     

Research of Inclusion Complexation of 4,4＇-Thiodiphenol Effected by β-Cyclodextrin in Aqueous Solutions and the Effect on Photodegradation

The inclusion behavior of 4, 4＇ -Thiodiphenol （TDP）, a typical bisphenol and endocrine disruptor, reacts with β-cyclodextrin （β-CD） in aqueous solutions has been investigated by means of UV absorption spectrum and quantum-chemical calculation with Gaussian 98 software. The results show that the inclusion behavior of TDP is quite different in acidic solutions （pH 5.9） from that in alkaline solutions （pH 10.0）. This behavior difference is attributed to the different formula structures in aqueous solutions at acidic and alkaline pH values that are demonstrated by quantum- chemical modeling and calculation. TDP forms a 1 ： 1 fl-CD inclusion complex in aqueous solutions. The equiiibrium constant K was calculated to be 553.49 L/mol at pH 5.9 and 1 318.20 L/mol at pH 10.0 respectively for the inclusion complex reaction by using the modified Benesi-Heldbrand equation. After inclusion TDP＇s structure is changed especially at the inclusion part with the bond order becoming larger, which results in inhibitive photodegradation during direct photooxidation and H2O2 assisted photooxidation.