Thermokinetics of the Formation Reaction of Zinc Histidine Complex

The enthalph change of reaction of zinc chloride with L-α-histidine in the temperature range of 25-50℃ has been determined by a microcalorimeter.On the basis of experimental and calculated results,three thermodynamics parameters (the activation enthalpy,the activation entropy,the activation free energy),the rate constant and three kinetic parameters (the activation energy,the pre-exponential constant and the reaction order) of the reaction,and the standard enthalpy of formation of Zn(His)^2 (aq.) are obtained.The results showed that the title reaction easily took place at the studied temperature.     

A Study on the Kinetics of the Catalytic Reforming Reaction of CH4 with CO2： Determination of the Reaction Order

The kinetics of the catalytic reforming reaction of methane with carbon dioxide to produce synthesis gas on a Ni/(α-A1203 and a HSD-2 type commercial catalyst has been studied. The results indicate that the reaction orders are one and zero for methane and carbon dioxide, respectively, when the carbon dioxide partial pressure was about 12.5-30.0 kPa and the temperature was at 1123-1173 K. However, when the carbon dioxide partial pressure was changed to 30.0-45.0 kPa under the same temperature range of 1123-1173 K, the reaction orders of methane and carbon dioxide are one. Furthermore, average rate constants at different temperatures were determined.     

Density Functional Theory and MP2 Calculations of the Transition States and Reaction Paths on Coupling Reaction of Methane through Plasma

The two possible reaction paths of producing ethane on coupling reaction of methane through plasma were theoretically investigated by B3LYP and MP2 methods with 6-311G^* respectively and further compared with the previous results calculated from B3LYP/6-31G^*. The new investigated results consistently confirmed the previous conclusion. And the influences of the calculation methods and basis sets on the calculated results were also discussed.     

Reaction Mechanism of the Multi-channel Decomposition Reactions of C_(10)H_(14)~+·

n-Butylbenzene cations C10H14^＋ serve as a model compound to investigate the reaction mechanisms of alkylbenzene cations. The reactions of C10H14^＋. decomposition reaction system have been studied extensively at the B3LYP/6-311＋＋G^＊＊ level with Gaussion98 package. The chain reaction of C10H14^＋ dissociation was initiated by C-H bond rupture. All reaction channels initiated by C-H rupture were fully investigated with the vibrational mode analvsis to confirm the transition states and to reveal the reaction mechanism. A theoretical investigation on the reactions of this positive ion free radical can help us fully understand the decomposition processes.     

Theoretical Studies on Reaction Mechanism of CH3SO with NO

The potential energy surface （PES） of CH3SO radical with NO reaction has been studied at MP2/6-311G（2df, p） and QCISD/6-311G（2df, p） levels. Geometries of the reactants, transition states （TS） and products were optimized at B3LYP/6-311G （d,p） level. The geometries of the transition states were found for the first time. The calculated results show that the reaction can proceed via singlet-state or triplet-state PES. Because of the high energy barrier of triplet surface, the singlet surface reactions are dominant. The topological analysis of electron density shows that there are two kinds of structaral transition states （the bifurcation-type ring structure transition state and the T-shaped conflict structure transition state） in the titled reaction. The total electronic density of the reactants, TS and products and the spin electronic density on the triplet surface were also discussed in this paper.     

Theoretical Study of the Isomerization Reaction of 1-3 H Transfer on Formamidine Substituted by Halogen

The ab initio method has been used to study the 1-3 H transfer reaction on formamidine substituted by halogen. The calculation results show that the substituted halogen has two effects on the 1-3 H transfer reaction: decreasing the activation energy and stabilizing the C=N double bond owing to the conjugative effect of p-π-p of products and transition states.     

Kinetics of the First Order Autocatalytic Decomposition Reaction of Nitrocellulose （13.86% N）

The kinetics of the first order autocatalytic decomposition reaction of nitrocellulose (NC, 13.86% N) was studied by using DSC. The results show that the DSC curve for the initial 50% of conversion degree of NC can be de scribed by the first order autocatalytic equation dy/dt =-10^16.3 exp (-181860/RT)y-10^16.7ex(-173050/RT)y(1-y) and that for the latter 50% conversion degree of NC described by the reaction equations dy/dt=-10^16.4exp(-154820/RT)y (n=1) and dy/dt=-10^16.9 exp(-155270/RT) y^2.80(n≠1).     

Mechanism and Kinetics for the Reaction of NCS and OH Radicals

The mechanism and dynamical properties for the reaction of NCS and OH radicals have been investigated theoretically. The minimum energy paths (MEP) of the reaction were calculated using the density functional theory(DFT) at the B3LYP/6-311 G^** level, and the energies along the MEP were further refined at the QCISD(T)/6-311 G^** level. As a result, the reaction mechanism of the title reaction involves three channels, producing HCS NO and HNC SO products, respectively. Path Ⅰ and path Ⅱ are competitive, with some advantages for path Ⅰ in kinetics. As for path Ⅲ, it looks difficult to react for its high energy barrier. Moreover, the rate constant have been calculated over the temperature range of 8190-2500K using canonical variational transition-state theory (CVT). It was found that the rate constants for both path Ⅰ and path Ⅱ are negatively dependent on temperature, which is similarwith the experimental results for reactions of NCS with NO and NO2, and the variational effect for the rate constant calculation olavs an important role in whole temperature range.     

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.     

Enzymatic Promiscuity： Escherichia coli BioH Esterase-catalysed Aldol Reaction and Knoevenagel Reaction

Esterase BioH,which is obligatory for biotin synthesis in Escherichia coli,was found to exhibit a promiscuous ability to catalyse Aldol and Knoevenagel reactions with moderate to good yields.The reaction conditions including organic solvent,molar ratio of ketone to aldehyde,enzyme amount,and reaction time were investigated to evaluate the effect of different reaction conditions on yield.Target compounds were afforded in the best yield of 91.2％ for Aldol reaction and 54.7％ for Knoevenagel reaction.In addition,because the enzyme could be prepared with a low cost,this protocol could provide an economic route to conduct Aldol and Knoevenagel reactions,which expand the field of enzymatic promiscuity.     

The Application of Suzuki Coupling Reaction on the Preparation of Carbosilane Dendrimers with 4-（Naphthalen-l-yl）phenyl Core

Carbosilane dendrimers with p-bromophenyl core were synthesized by alternating Grignard and hydrosilylation reaction. And the α-naphthalenyl was connected to the core by the Suzuki coupling reaction. A new carbosilane dendrimer with big π-conjugated structure [4-（naphthalen-l-yl）phenyl core] was given. It shows Suzuki coupling reaction is an effective and powerful core-functionalization method and the satisfactory result can be obtained through prolonging the reaction time with the increase of the generation of dendrimer.     

The Reaction of Molybdenum with 2,3-Dihydroxynaphthalene

[H2N（CH2）3NH312[MoO2（C10H6O2）2] （1） was synthesized by the 2,3-dihydroxynaphthalene in the mixed solvent of CH3OH, CH3CN reaction of （n-Bu4N）4[Mo8O26] with and 1,3-propanediarnine. （C5HllN2）2- [HeN（CH2）3NH2][MoO2（CloH6O2）2] （2） was obtained by the reaction of Na2MoO4.2H20 with 2,3-dihydroxynaphthalene in the same solvent above. Both of the complexes possess complex anion [Mo（VI）O2（OC10H6O）2]^2- which shows pseudo-octahedrally coordinated fashion, while the counterions are two protonated 1,3-propanediamine in complex 1 and （CsH11N2）^＋ in complex 2. （C5H11N2）＋ is the byproduct of reaction 2, which results from combination of acetonitrile with 1,3-propanediamine. Packing diagrams of the two complexes are also different. There is anti-parallel-aligned-double-meso-bilayer unit in complex 1. However there are four chiral anions arranged in anticlockwise orientation in complex 2.     

DFT Study on Intermolecular Cleavage Reaction of N-（2-Hydroxyphenyl）-phthalamic Acid

The reaction mechanisms of intermolecular cleavage reaction of N-（2-hydroxyphenyl）-phthalamic acid were studied via the density functional theory（DFT）. All geometries of the reactant, transition states, and products were optimized at the B3LYP/6-31G（d, p） level. Vibration analysis was carried out to confirm its identity as transitions＇ structure, and the intrinsic reaction coordinate method（IRC） was used to search the minimum energy path. Two possible reaction channels are reported in this article. The calculated results indicate that O-cyclization reaction channel has the lower activation barrier, and therefore, it occurs more easier than the other.     

Cluster—cracking Reaction,a New Method to Synthesize Unsymmetrical Dithiolate Complexes for the Study of Third—Order Nonlinear Optical Properties

A new coluster-cracking method to synthesize dithiolate metal complexes was reported and four unsymmetric complexes with formula(Me4N)2[M(Ln)(SPh)2](M=Cd and Zn,L1=dmit=1,3-dithiole-2-thione4-5,dithiolate,L2=dmid=1,3-dithiole-2-one-4,5-dithiolate,SPh=thiophenolate)(1-4)were characterized by elemental analysis,IR,UV NMR spectra and so on.The advantages of this method are summarized in two aspects:(1) the preparation is very convenient;(2) the reaction usually completed giving the product with high pruity.The crystal structure of 1 showed that the bond distances of Cd(Ⅱ）to the sulfur of the thiophenolate group are shorter than those of Cd(Ⅱ）to the sulfur of dmit,so that the thiophenolate group does not be replaced in the reaction and thmixed ligand complexes are the dominant produxts.The dmit complexes showed well third-order NLO properties,but not of the dmid complexes,although dmid is an analogue to dmit.     

On QSAR Study of Stereoselectivity for Wittig Reaction

1INTRODUCTION Witting reaction is an important and well-known organic reaction.In this reaction system,phospho-nium ylides react with aldehydes or ketones to gene-rate olefins and phosphonium oxides.Obviously,the position of double bond in olefins is exactly the po-sition of carbonyl group in the reactants,so there are no other position isomers in products.Due to this advantage,Witting reaction has been widely used in organic synthesis[1].Witting reaction could introduce double bond to c…     

Kinetics of the Exothermic Decomposition Reaction of N-Methyl-N-nitro-2,2,2- trinitroethanamine

The thermal behavior and kinetic parameters of the exothermic decomposition reaction of N-methyl-N-nitro-2,2,2-trinitroethanamine in a temperature-programmed mode have been investigated by means of differential scanning calorimetry (DSC).The kinetic equation of the exothermic decomposition process of the compound is proposed. The values of the apparent activation energy (Ea), pre-exponential factor (A), entropy of activation (ΔS^≠ ), enthalpy of activation (ΔH^≠ ), and free energy of activation (ΔG^≠ ) of this reaction and the critical temperature of thermal explosion of the compound are reported. Information is obtained on the mechanism of the initial stage of the thermal decomposition of the compound.     

Theoretical Studies on the Reaction Mechanism of AsCl_3 with H_2 in the Vapor Phase Epitaxy of GaAs

The reaction mechanism of AsCl3 with H2 has been studied by using the method of BHandHLYP in Density Functional Theory (DFT) at the 6-311G** basis set. The transition state of each reaction is verified via the analysis of vibration mode and Intrinsic Reaction Coordinate (IRC). Meanwhile,single-point energy has been calculated at the QCISD(T)/6-311G** level,and the zero-point energy correction has been made to the total energy and reaction energy barrier. It shows that AsCl3 reacts with H2 to first result in AsHCl2 which may incline to self-decompose and finally afford the product As2,or continue to react with H2 to provide the product AsH3. The computing result demonstrates that the former is the main reaction channel.     

Reaction Chemistry of W—Mn／SiO2 Catalyst for the Oxidative Coupling of Methane

Reaction chemistry of the OCM reaction on W-Mn/SiO2 catalyst has been reviewed in this account.Initial activity and selectivity,stability in a long-term reaction,reaction at elevated pressures and a modelling test in a stainless-steel fluidized-bed reactor show that W-Mn/SiO2 has promising performance for the development of an OCM process that directly produces ethylene from natural gas.A study on surface catalytic reaction kinetics and used cataly st structure characterization revealed a possible reason why C2 and COx selectivity changed during the long-term reaction.Further improvement of the catalyst composition and preparation metbod should be a future direction of study on OCM reaction over W-Mn/SiO2 catalyst.     

Photoinitiated Reaction of β-Bromonaphthalene with Pinacolone Ion in DMSO

The radical nucleophilic substitution reaction (SRN1) has been studied widely. The reaction has constituted an important synthetic possibility to achieve substitution of different substrates with different nucleophiles1-3. The main steps of the reaction process are presented in Scheme 1.Scheme 1. Pinacolone enolate ions are widely used as nucleophiles within SRN1reaction 4-6 because it can introduce six carbon atoms into substitution products. In the paper, the photoinitiated reaction of …     

Synthesis of Novel Bisoxazoline Ligands for the Enantioselective Diels-Alder Reaction

The Diels-Alder reaction is the most useful method for six-membered ring formation1. As a consequence, a number of effective enantioselective processes have been developed over the years 2-4. Of particular interest, metal bisoxazoline complexes formed fro…