Quantum Chemistry Study on Dissociation of Oxalyl Bromide

1 INTRODUCTION In experiment, it is difficult to reveal the pheno- menon that molecules decompose into several frag- ments by UV light mainly due to the insufficient en- ergy of illuminating source. But in oxalyl halides, their bond energies are relatively lower. As a typical system for the study of multi-channel dissociation, oxalyl chloride can be dissociated into four frag- ments: Cl˙, Cl˙, CO and CO, under proper UV light[1, 2], which is the chief way to obtain free radi- cals. …     

NMR study on solubility of benzyl alcohol and its transfer free energy from D_2O to cationic micelle

A new kind of surfactant, [CnH_(2n+1)OCH2CH(OH)CH2N(CH3)3]Cl (n=12, 14, 16) was synthesized. The solubility of benzyl alcohol in micellar solutions was determined by 1H NMR method. The results indicate that the length of alkyl chains of surfactant affects the solubility of ben-zyl alcohol in 2.5 × l0~(-2) mol/L micellar solutions. The solubility of benzyl alcohol per liter of micellar solution is 0.095 mole for n=12, 0.115 mole for n=14, 0.165 mole for n=16. The transfer free energy of benzyl alcohol from aqueous phase to micellar phase is -24.29 kJ/mol for n=12, -24.37 kJ/mol for n=14, -24.49 kJ/mol for n=16.     

Epoxidation of allyl chloride with H_2O_2 on Ti-ZSM-5 prepared by the isomorphous substitution

The epoxidation of allyl chloride with H2O2 on Ti-ZSM-5 prepared by isomorphous substitution of HZSM-5 with TiCl4 gas was studied. The results show that Ti-ZSM-5 has a high catalytic efficiency for the epoxidation of allyl chloride. The H2O2 utilization reaches 99.50% when the allyl chloride/H2O2 molar ratio is > 1. The effect of solvent species, catalyst concentration, H2O2 and allyl chloride concentration and reaction temperature on the epoxidation was investigated simultaneously. It is found that methanol is the best solvent for the reaction. The reaction rate equation with v = k[Cat. ] [H2O2]1/2-[C3H5Cl] and the apparent activation energy with Ea = 63.462 kJ/mol are obtained according to the kinetics study.     

含芯电子相关能修正的G2理论——G2(ful)

A general method in considering the core electronic correlation energies has been proposed and introduced into the standard Gaussian-2 (G2)[7] theory by small post-Hartree-Fock calculations. In this paper an additional MP2(FC)/6-31G(d) calculation over the G2 procedures is employed and examined in modification in modification to the flaw of Frozen-Core (FC) approximation of G2 vai eq.:
ΔE(full)= E[MP2(full)/6-31G(d)]-E[MP2(FC)/6-31G(d)]
where the MP2(full)/6-31G(d) energy has been obtained in the molecular geometry optimizations. This energy, ΔE(full), is directly added into the total G2 energy of a molecule in facilitating the effect of core electronic correlations for each molecule in chemical reactions. It has been shown that the over-all average absolute deviation for the 125 reaction energies of the G2 test set (test set 1) is slightly reduced from 5.09 to 5.01 kJ, mol(-1) while for the 55 D0 values, which have been used for the derivation of the A coefficient of the empirical High-Level...更多-Correction (HLC), it is also reduced from 4.99 [for both G2 and G2(COMPLETE)[8]]to 4.77 kJ• mol(-1). In addition, larger errors (greater than ±8.4 kJ•mol(-1) for the D0 energies are improved, especially for the largest error of the D0 of SO2 This error is reduced from 21.3 to 15.4 kJ. mol(-1), in which the experimental geometry would further reduce it by 7.1kJ.mol(-1)[8]. Another improvement is the absolute value of the A coefficient in HLC being reduced from 4.81 for G2 to 4.34 milli-hartrees which is believed to be useful in isolating the relationship between the HLC and the FC approximation. Modifications to the original G2 from this work is denoted as G2(fu 1) and thus the G2 (fu 1) total energy for a molecule is
E[G2(fu 1)]= E[G2]+Δ E(full)h
with a new ΔE[HLC] =-0.19α- 4.34nβ milli-hartree.     

Ab initio study on the mechanism of reaction HNCO+NH_2

Ab initio UMP2 and UQCISD(T) calculations, with 6-311G** basis sets, were performed for the titled reactions. The results show that the reactions have two product channels: NH2+ HNCO→NH3+NCO (1) and NH2+HNCO-N2H3+CO (2), where reaction (1) is a hydrogen abstraction reaction via an H-bonded complex (HBC), lowering the energy by 32.48 kJ/mol relative to reactants. The calculated QCISD(T)//MP2(full) energy barrier is 29.04 kJ/mol, which is in excellent accordance with the experimental value of 29.09 kJ/mol. In the range of reaction temperature 2300-2700 K, transition theory rate constant for reaction (1) is 1.68 × 1011- 3.29 × 1011 mL · mol-1· s-1, which is close to the experimental one of 5.0 ×1011 mL× mol-1· s-1 or less. However, reaction (2) is a stepwise reaction proceeding via two orientation modes, cis and trans, and the energy barriers for the rate-control step at our best calculations are 92.79 kJ/mol (for cis-mode) and 147.43 kJ/mol (for trans-mode), respectively, which is much higher than     

Study on the Deactivation Kinetics of Pd（PPh3）2Cl2 in the Monocarbonylation of Benzyl Chloride

The deactivation kinetics of Pd(PPh3)2Cl2 in the monocarbonylation of benzyl chloride to synthesize phenylacetic acid is studied in this paper. Solid 1-(2-pyridylazo)-2-naphthol (PAN) is used as the colouring agent, and the concentration of Pd(PPh3)2Cl2 in the system is measured through absorptiometry. The result shows that the optimum condition of the chromogenic reaction between Pd2+ and PAN is: 0.5 ml of 0.04% PAN added to 10 ml of Pd2+ solution (1.0×10-6-2.0×10-5 mol/L), and heated in a constant temperature water bath at 40℃ for about 30 min, with pH of the solution being about 3.0. The molar coefficient of absorption is 1.384×104 L/(mol·cm); the orders of the hydrolytic reaction to the concentration of Pd(PPh3)2Cl2, PPh3, phenylacetic acid and NaOH are 0.5, minus 0.8, 2 and 1.2, respectively. The activation energy (E) of the hydrolytic reaction is 75.59 kJ/mol, and the pre-exponential factor is 1.68×1012.     

D152树脂对铜(Ⅱ)的吸附性能

The sorption behavior and mechanism of D152 resin for Cu~(2+) is investigated.D152 resin has a good adsorptivity for Cu~(2+) in the HAc-NaAc medium at pH=4.73.The statically saturated sorption capacity is 309mg/g·(resin).Cu~(2+)adsorbed on D152 resin can be eluted quantitatively by using 0.1-2.0mol/L hydrochloric acid as an eluant.The apparent rate constant and activation energy are k_(298)=1.86×10~(-5) sec~(-1) and Ea=12.3kJ/mol.The sorption behavior of D152 resin for Cu~(2+) obeys the Freundlich isotherm.The sorption thermodynamic parameters of D152 resin for Cu~(2+)are enthalpy change ΔH=14.6 kJ/mol,free energy change ΔG=-0.72kJ/mol,entropy change ΔS=51.4J/(mol·K).respectively.     

Experimental Study of Hydrogen Isotope Kinetic Fractionation Between Ilvaite and Water——The Kinetics of D-H Exchange in Ilvaite-H_2O

Hydrogen isotope kinetic fractionation in the ilvaite and water system has been studied experimentally at 350-650℃. The result of study shows that the exchange mechanism of hydrogen isotope between ilvaite and water is dominated by hydrogen diffusion.The activation energy for hydrogen diffusion in ilvaite is 118.4 kJ/mol for cylinder model and 115.5 kJ/mol for plate model, respectively.The activation energy for hydrogen isotope exchange in ilvaite is 122.6 kJ/mol.The closure temperature for the cessation of hydrogen isotope exchange between ilvaite and water is much lower than its formation temperature.So, after ilvaite crystallizes, the hydrogen isotope exchange between ilvaite and late hydrothermal solution will continue to take place.     

On the Reaction Mechanism of Br2 with OCS

The reaction mechanism of photochemical reaction between Br2 (^1∑) and OCS (^1∑) is predicted by means of theoretical methods. The calculated results indicate that the direct addition of Br2 to the CS bond of OCS molecule is more favorable in energy than the direct addition of Br2 to the CO bond. Furthermore, the intermediate isomer syn-BrC(O)SBr is more stablethe rmodynamically and kinetically than anti-BrC(O)SBr. The original resultant anti-BrC(O)SBr formed in the most favorable reaction channel can easily isomerize into the final product syn-BrC(O)SBr with only 31.72 kJ/mol reaction barrier height. The suggested mechanism is in good agreement with previous experimental study.     

Kinetics and Mechanism of the Polymerization of Methyl Methacrylate in a Y(acac)3/n-BuMgCl System

Based on the kinetics equation proposed by T. Kagiya, the kinetic study on the polymerization of methyl methacrylate(MMA) by Y(acac)3/n-BuMgCl was carried out with a dilatometer. It was found that the rate of propagation is the first order with respect to the concentration of both active center and monomer. Thus, the equation of propagation rate can be described as Rp=Kp[c*][M]. In addition, the instantaneous chain initiation and single molecular termination were concluded for the present system. The activation energy is close to 32 kJ/mol. In the polymerization, n-BuMgCl acts not only as the cocatalyst, but also as chain transfer agent with cI=3.6×10-4.     

Ab initio Mechanism Study on the Reaction of Chlorine Atom with Formic Acid

The potential energy surface(PES) for the reaction of Cl atom with HCOOH is predicted using ab initio molecular orbital calculation methods at UQCIDS(T,full)6-311 G(3df,2p)//UMP2(full)/6-311 G(d,P) level of theory with zero-point vibrational energy (ZPVE) correction.The calculated results show that the reaction mechanism of Cl atom with formic acid is a C-site hydrogen abstraction reaction from cis-HOC(H)O molecule by Cl atom with a 3.73kJ/mol reaction barrier height,leading to the formation of cis-HOCO radical which will reacts with Cl atom or other molecules in such a reaction system.Because the reaction barrier height of O-site hydrogen abstraction reaction from cis-HOC(H)O molecule by Cl atom which leads to the formation of HCO2 radical is 67.95kJ/mol,it is a secondary reaction channel in experiment,This is in good agreement with the prediction based on the previous experiments.     

Simulation and energy performance assessment of CO2 removal from crude synthetic natural gas via physical absorption process

The paper presents an energy performance assessment of CO2 removal for crude synthetic natural gas (SNG) upgrade by Selexol absorption process. A simplified process simulation of the Selexol process concerning power requirement and separation performance was developed. The assessment indicates that less pressure difference between crude SNG and absorption pressure favors the energy performance of CO2 removal process. When both crude SNG and absorption pressures are 20 bar, CO2 removal process has the best energy performance. The optimal specific power consumption of the CO2 removal process is 566 kJ/kg CO2 . The sensitivity analysis shows that the CO2 removal efficiency would significantly influence the total power consumption of the removal process, as well as higher heating value (HHV) and CO2 content in SNG. However, the specific power consumption excluding crude SNG and SNG compressions changes little with the variance of CO2 removal efficiency. If by-product CO2 is compressed for CO2 capture, the process would turn into a CO2 -sink for the atmosphere. Correspondingly, an increase of 281 kJ/kg CO2 in specific power consumption is required for compressing the separated CO2 .     

Mineralization of 4-Chlorophenol under Visible Light Irradiation in the Presence of Aluminum and Zinc Phthalocyaninesulfonates

Photosensitized oxidation of 4-chlorophenol (4CP) by the title complexes (AIPcS and ZnPcS) in aerated aqueous solution uponvisible light irradiation(λ=450nm) has been investigated using methanol as a disassociating reagent.It is confirmed that the monomeric species of the sesitizer is more active than the corresponding dimer in singlet oxygen generation for 4CP oxidation.However,the monomer is also the main component found in the sensitlzer‘s photobleaching, In this reload, AIPcS is much more stable than ZnPcS, and the Dhotoble~hlno is observed to proceed via singlet and triplet oxygen, respectlvely.The final products of 4CP oxidation in alkaline solution are carbon dioxide and chloride ions.while at pH=7 and pH=3 the p-benzoquinone is the product.The temperature is found to have influence on both the photosensitized degradation of methyl orange and ZnPcS photobleaching,with an activation energy of 15.8 and 24.2kJ/mol,respectively.     

THE KINETICS OF THE DECOMPOSITION OF CYCLOHEXYL HYDROPEROXIDE IN THE PRESENCE OF VANADYL DIBENZOYLMETHANE

The kinetics of the decomposition of cyclohexyl hydroperoxide(CHHP) in benzene catalyzed by vanadyl dibenzoylmethane[V0(DBM).,] has been studied.It was found that the products of decomposition of CHHP were cyclohexanol and cyclohexanone,which are produced in about equimolar amount,and the product cyclohexanol obviously inhibited the decomposition of CHHP.The kinetics data can be satisfactorily described by the following equation (with [CHHP]0>>[VO(DBM)2]0)R0=kK[CHHP]0[VO(DBM)2]0/(1+k[CHHP]0)This is the kinetic evidence for the formation of a catalyst-hydro-peroxide intermediate.In the equation K is the stability constant of the catalyst-hydroperoxide intermediate complex;k is the rate constant for the decomposition of the complex.The rate constant K at 500℃ may be expressed as follows:k=1.9×108exp(-53.7×103/RT)S-1 with the activation energy Ea=53.7kJ mol-1     

Ab initio potential energy surface and excited vibrational states for the electronic ground state of Li_2H

A 285-pomt multi-reference configuration-interaction involving single and double excitations ( MRS DCI) potential energy surface for the electronic ground state of L12H is determined by using 6-311G (2df,2pd)basis set.A Simons-Parr-Finlan polynomial expansion is used to fit the discrete surface with a x2 of 4.64×106 The equn librium geometry occurs at Rc=0.172 nm and,LiHL1=94.10°.The dissociation energy for reaction I2H(2A)→L12(1∑g)+H(2S) is 243.910 kJ/mol,and that for reaction L12H(2A')→HL1(1∑) + L1(2S) is 106.445 kl/mol The inversion barrier height is 50.388 kj/mol.The vibrational energy levels are calculated using the discrete variable representation (DVR) method.     

Ab initio Study of the Potential Energy Surface and Product Branching Ratios for Reaction of O（^1D） with C2H5CI

The potential energy surface of O（^1D）＋C2H5Cl reaction was studied using QCISD（T）/6- 311＋＋G（d,p）//MP2/6-31G（d,p） method. The calculations reveal an insertion-elimination mechanism. The insertion reaction of O（^1D） and C2H5Cl produces two energy-rich intermediates, IM1 and IM2, which subsequently decompose into various products. The calculations of the branching ratios of various products formed through the two intermediates were carried out using RRKM （Rice-Ramsperger-Kassel-Marcus） theory at the collision energies of 0, 20.9, 41.8, 62.7, 83.6, 104.5, and 125.4 kJ/mol. HCl is the main decomposition product for IM1; CH2OH is the main decomposition product for IM2. Since IM1 is more stable than IM2, HCl is probably the main product of the O（^1D）＋C2H5Cl reaction.     

Theoretical Studies on the Mechanism of Photocycloaddition Reaction Between 6 Azauracil and Acetone

The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as follows:(1) A T1 state exciplex is on the T1 state energy surface; (2) T exciplex as a reactant will proceed along the energy surface of T1 state to form a diradical intermediate. The energy barrier of this reaction step is 63. 6 kJ/mol; (3) The T1 state diradical intermediate happens to be close in energy to the ground state intermediate with a similar geometry. Such a situation turns out to be very favorable for an intersystem crossing (jump from the T, state to the ground state) ; (4) The final product will be formed from the ground S0 state intermediate via an energy barrier 88. 2 kJ/mol.     

A Density Functional Study for the Reaction Mechanism of CO Oxidation on the Copper Cluster

We have studied the reaction mechanism of CO oxidation on the Cu_(13) cluster via density functional theory. There are two main reaction pathways to be considered: Eley-Rideal(ER) and Langmuir-Hinshelwood(LH) mechanisms, respectively. According to these two main reaction mechanisms, we have obtained five reaction pathways for the first CO oxidation(denoted as R_(ER1),R_(ER2), R_(LH1), R_(LH_2) and R_(LH3), respectively): R_(ER1) is CO_(gas) + O_(2(ads)) → O(ads) + CO_(2(gas)); R_(ER2) is CO_(gas) + O_(2(ads)) → CO_(3(ads)) → O(ads) + CO_(2(gas)); R_(LH1) refers to CO(ads) + O_(2(ads)) → O(ads) + CO_(2(gas)); R_(LH_2) refers to CO(ads) + O_(2(ads)) → OOCO(ads) → O(ads) + CO_(2(gas)) and R_(LH3) refers to O_(2(ads)) + CO(ads)→ O(ads) + O(ads) + CO(ads) → O(ads) + CO_(2(gas)). These pathways have low energy barriers and are strongly exothermic, suggesting the Cu_(13) cluster is very favorable catalyst for the first CO oxidation. However, there are higher energy barriers of 99. 8 and 45.4 kJ/mol in the process of producing and decomposing intermediates along the R_(LH_2) and R_(ER2), indicating that R_(ER1), R_(LH1) and R_(LH3) are superior pathways with lower energy barriers, especially the R_(ER1) channel. Thereafter, the second CO is more prone to react with the remaining oxygen atom on Cu_(13) along the ER channel in comparison with the LH pathway, in which the moderate barrier is 70.0 kJ/mol and it is exothermic by 59.6 kJ/mol. Furthermore, the interaction between the absorbate and cluster is analyzed by electronic analysis to gain insights into high activity of the copper cluster.     

Oxygenolysis reaction mechanism of copper-dependent quercetin 2,3-dioxygenase: A density functional theory study

The mechanism of the action of copper-dependent quercetin 2,3-dioxygenase(2,3QD) has been investigated by means of hybrid density functional theory.The 2,3QD enzyme cleaves the O-heterocycle of a quercetin by incorporation of both oxygen atoms into the substrate and releases carbon monoxide.The calculations show that dioxygen attack on the copper complex is energetically favorable.The adduct has a possible near-degeneracy of states between [Cu 2+-(substrate-H +)] and [Cu +-(substrate-H).],and in addition the pyramidalized C 2 atom is ideally suited for forming a dioxygen-bridged structure.In the next step,the C 3-C 4 bond is cleaved and intermediate Int 5 is formed via transition state TS 4.Finally,the O a-O b and C 2-C 3 bonds are cleaved,and CO is released in one concerted transition state(TS 5) with the barrier of 63.25 and 61.91 kJ/mol in the gas phase and protein environments,respectively.On the basis of our proposed reaction mechanism,this is the rate-limiting step of the whole catalytic cycle and is strongly driven by a relatively large exothermicity of 100.86 kJ/mol.Our work provides some valuable fundamental insights into the behavior of this enzyme.     

Theoretical study on the reaction mechanism of CN radical with ketene

The bimolecular single collision reaction potential energy surface of CN radical with ketene (CH2CO) was investigated by means of B3LYP and QCISD(T) methods. The calculated results indicate that there are three possible channels in the reaction. The first is an attack reaction by the carbon atom of CN at the carbon atom of the methylene of CH2CO to form the intermediate NCCH2CO followed by a rupture reaction of the C-C bond combined with -CO group to the products CH2CN CO. The second is a direct addition reaction between CN and CH2CO to form the intermediate CH2C(O)CN followed by its isomerization into NCCH2CO via a CN-shift reaction, and subsequently, NCCH2CO dissociates into CH2CN CO through a CO-loss reaction. The last is a direct hydrogen abstraction reaction of CH2CO by CN radical. Because of the existence of a 15.44 kJ/mol reaction barrier and higher energy of reaction products, the path can be ruled out as an important channel in the reaction kinetics. The present theoretical computation results, which give an available suggestion on the reaction mechanism, are in good agreement with previous experimental studies.