Studies on the Hydrosilation of Aromatic Aldehydes

The dependence of reactivity on molecular structure in hydro-silation of aromatic aldehydes catalyzed by (PPh3)3 RhCl was studied by “IN SITU” FT-IR technique and a plausible mechanism was proposed.The results show that: (1) Model reaction Ⅰ, Ⅱ and Ⅲ are all characterized by an induction period; (2) The reaction constant of model reaction Ⅰ is +1.57, so the rare of reaction Ⅰ is increased by the electron-withdrawing groups; (3) The rate of model reaction Ⅲ decreases when the size of R1 becomes larger; (4) The reaction constant of model reaction Ⅲ is -0. 50, so the rate of it is increased by electron-donating groups.     

Mechanochemical Reactions of Fullerenes under High-Speed Vibration Milling

Since a novel technique called "high-speed vibration milling" (HSVM) was first applied to the Reformatskytype reaction of C60 in 1996, [1] this technique has been applied to various kinds of fullerene functionalizations including the preparation of C120. [2] Most recent reactions of fullerenes under HSVM conditions will be discussed: (1)reaction of C60/C70 with N-alkylglycines and aldehydes (Scheme 1); (2) reaction of C60 with active methylene compounds in the presence of bases (Scheme 2); (3) reaction of C6o with diazo compounds (Scheme 3); (4) reaction of C6o with anthracene derivatives (Scheme 4).     

DFT study on the selective oxidation of vinyl chloride on different metal surfaces

Selective epoxidation of vinyl chloride on Ag(111), Pt(111) and Rh(111) with pre-adsorbed atomic oxygen has been studied by density functional theory (DFT) calculation with the periodic slab model. The reaction energies and activation energies of the epoxidation reaction are determined. Because of the asymmetry of vinyl chloride, three competitive reaction pathways are investigated. The results indicate that the most possible reaction pathway is pathway III. Compared the activation energies of the epoxidation reaction on Ag(111), Pt(111) and Rh(111), it is obvious that the reaction via OMMC(3) on Ag(111) is the most possible process. However, the selectivity to the target product over Ag(111) is the lowest among the three metals. The results also indicate that the formation of chloroacetaldehyde is more favorable than that of chloroepoxide.     

Topological studies on IRC paths of the isomerization reaction of silicon methyl-nitrene

On the basis of kinetic study of isomerization reaction of H_3Si-N, ab initio (RHF, UHF/6-31G) calculations on some points of the singlet and triplet reaction paths were carried out. The breakage and formation of chemical bond in the reaction are discussed. The calculated results show that there is a transitional structure of three-membered ring on each of reaction paths. A 'structural transition region' and a 'structural transition state' in both of studied reaction are found. Our previous conclusion that the structure transition state (STS) always appears before the energy transition state (ETS) in endothermic reaction and after ETS in exothermic reaction is further confirmed. The relationship between the change of spin density distribution and the structural transition state are investigated.     

Theoretical Study of the AlCl Disproportionation Reaction Mechanism on the Al(100) Surface

The surface disproportionation reaction mechanism of aluminum subchloride on the aluminum (100) surfaces has been investigated by the plane-wave density functional theory (DFT).Three kinds of possible reaction mechanism of AlCl disproportionation reaction on the aluminum (100) surfaces have been taken into account.The structures of reactants and products have been optimized,transition states have been confirmed and activation energies have been calculated.The adsorption energy of reactants and desorption energy of products have been determined.All of these have been employed to confirm the reaction mechanism and the rate determining step of AlCl disproportionation reaction on the aluminum (100) surfaces.     

Thermokinetics on the reaction of formation of Dy[(C_5H_8NS_2)_3(C_(12)H_8N_2)]

The enthalpy change of formation of the reaction of hydrous dysprosium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen·H2O) in absolute ethanol at 298.15 K has been determined as (-16.12±0.05) kJ·mol-1 by a microcalor-meter. Thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), rate constant and kinetics parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of the reaction have also been calculated. The enthalpy change of the solid-phase reaction at 298.15 K has been obtained as (53.59±0.29) kJ·mol-1 by a thermochemistry cycle. The values of the enthalpy change of formation both in liquid-phase and solid-phase reaction indicated that the complex could only be synthesized in liquid-phase reaction.     

MCSCF STUDIES ON THE IRC AND REACTION RATE CONSTANTS FOR THE DEHYDROGENATION REACTION OF VINYL RADICAL

The transition state(TS) and Intrinsic Reaction Coordinate (IRC) for the titled reaction were traced by means of MCSCF/6-31G (210 configurations). The reaction activation energy of this reaction is 140.2KJ/mol. The reaction rate constants of five temperetures were calculated by CVT involving the tunneling effects.     

PREPARATION OF STARCH SUCCINATE WITH INTERMEDIATE DS BY AQUEOUS SLURRY REACTION

The succinylation of cornstarch by slurry reaction has been studied using sodium hydroxide as catalyst.Several reaction parameters affecting the succinylation were investigated including the concentration of starch in water,the ratio of succinic anhydride to starch,the reaction time and the reaction temperature,The favorable conditions for an intermediate degree of substitution(DS) and reasonably high reaction efficiency(RE) are pH 8.5-9.0,50% starch by weight to water.succinic anhydride to starch 1/1(w/w),reaction time 4h,reaction temperature 30℃ .Under these conditions,the DS of 0.45 and RE of 28% were achieved.The addition of an adequate amount of crosslinking agent imparted starch succinate water absorbency.     

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.     

Catalytic Systems Containing p-Toluenesulfonic Acid for the Coupling Reaction of Formaldehyde and Methyl Formate

The coupling reaction of formaldehyde(FA)and methyl formate(MF)to form methyl glycolate(MG)and methyl methoxy acetate(MMAc),catalyzed by p-toluenesulfonic acid(p-TsOH)as well as assisted by different kinds of solvents or Ni-containing compounds,had been investigated.The results showed that when the reaction was carried out at 140℃,with a molar ratio of FA to MF of 0.65:1, molar fraction of p-TsOH to total feedstock of 11.0%,and reaction time of 3 h,the yield of MG and MMAc was 31.1% and 17.1%,respectively,p-TsOH catalyzed the coupling reaction by means of the synergistic catalysis of protonic acidity and soft basicity.Adding extra solvents to the reaction system was unfavorable for the reaction.The composite catalytic system consisting of p-TsOH and NiX_2(X=Cl,Br,I)exhibited a high catalytic performance for the coupling reaction,and NiX_2 acted as a promoter in the reaction,whose promotion for the catalysis increased in the following order:NiCl_2相似文献   

ClONO2与Cl(2P3/2)的反应机理

在密度泛函理论B3LYP/6-31G^*水平上,研究了ClONO₂+Cl(²P_3/2)Cl₂+NO₃和ClONO₂+Cl(²P_3/2)ClO+ClONO(cis)及ClONO₂+Cl(²P_3/2)ClOCl+NO₂的反应机理.计算得到各可能反应途径的过渡态,并经过内禀反应坐标(IRC)分析加以证实.反应ClONO₂+Cl(²P_3/2)Cl₂+NO₃反应活化能垒最低,为4.5kJ/mol,是反应主通道.     

A systematic computational study of the reactions of HO2 with RO2: the HO2 + CH2ClO2, CHCl2O2, and CCl3O2 reactions

Potential energy surfaces for the reactions of HO(2) with CH(2)ClO(2), CHCl(2)O(2), and CCl(3)O(2) have been calculated using coupled cluster theory and density functional theory (B3LYP). It is revealed that all the reactions take place on both singlet and triplet surfaces. Potential wells exist in the entrance channels for both surfaces. The reaction mechanism on the triplet surface is simple, including hydrogen abstraction and S(N)2-type displacement. The reaction mechanism on the singlet surface is more complicated. Interestingly, the corresponding transition states prefer to be 4-, 5-, or 7-member-ring structures. For the HO(2) + CH(2)ClO(2) reaction, there are two major product channels, viz., the formation of CH(2)ClOOH + O(2) via hydrogen abstraction on the triplet surface and the formation of CHClO + OH + HO(2) via a 5-member-ring transition state. Meanwhile, two O(3)-forming channels, namely, CH(2)O + HCl + O(3) and CH(2)ClOH + O(3) might be competitive at elevated temperatures. The HO(2) + CHCl(2)O(2) reaction has a mechanism similar to that of the HO(2) + CH(2)ClO(2) reaction. For the HO(2) + CCl(3)O(2) reaction, the formation of CCl(3)O(2)H + O(2) is the dominant channel. The Cl-substitution effect on the geometries, barriers, and heats of reaction is discussed. In addition, the unimolecular decomposition of the excited ROOH (e.g., CH(2)ClOOH, CHCl(2)OOH, and CCl(3)OOH) molecules has been investigated. The implication of the present mechanisms in atmospheric chemistry is discussed in comparison with the experimental measurements.     

Synthesis of 3-substituted-2-benzothiazolinone, 2-benzoxazolinone and benzothiazoline-2-thione

The reaction of 2-benzothiazolinone, 2-benzoxazolinone or benzothiazoline-2-thione under basic conditions with various electrophiles afforded the titled compounds 1-13, 29-31 and 40-48. The 3-(substituted-aminomethyl)-2-benzothiazolinone and related compounds 14-25 were prepared by the reaction of 3-(hydroxymethyl)-2-benzothiazolinone or the appropriate 2-benzothiazolinone and formaldehyde with the appropriate amine or substituted aniline. The reaction of 9, 13 or 25 with methyl iodide afforded the quaternary ammonium iodides 26-28. The reaction of the appropriate potassium salts of various phenol with 3-(chloromethyl)-2-benzothiazolinone afforded the 3-(substituted-phenoxymethyl)-2-benzothiazolinone and related compounds 32-39. The ethyl or isopropylxanthates 49-54 were synthesized by the reaction of 3-(chloromethyl)-2-benzo-thiazolinone and appropriate compounds with potassium ethyl or isopropyl xanthate. The reaction of 3-(chloromethyl)-2-benzothiazolinone with sodium sulfide afforded the sulfide 55.     

Theoretical Study on the Mechanism of CF2 Reaction with CH2O

The insertion reaction mechanism of CF2 with CH2O was investigated at the B3LYP/6-311G（d）//MP2/6-311G（d） level. The geometric conformations at each stationary point in reaction potential surface were fully optimized and the transition states were verified by intrinsic reaction coordinate （IRC） and frequency analysis. The energies of all reactants were calculated with CCSD（T）/6-311G（d）//G2MP2 methods. Results indicated that the P1 reaction route with difuoroaldehyde as product is the dominant reaction pathway, which exhibits nucleophilic character. According to NBO analysis, the starting point of insertion reaction is the interaction between carbene LP（C3） and formaldehyde π（Cl-O2）. Besides, the thermodynamic and dynamic properties of dominated reaction （1） at different temperature were studied with statistic thermodynamic method and Eyring transition state theory adjusted by Wigner means, from which the proper temperature （500- 1200 K） of reaction （1） could be estimated. Finally, the thermo- dynamic and dynamic properties of insertion reaction mechanisms （CF2, CX2 （X = Cl, Br） with CH2O） were compared and discussed.     

Atrazine toxicity reduction following H2O2/TiO2- photocatalyzed reaction and comparison with H2O2- photolytic reaction

An atrazine photodegradation study carried out by a Q-Panel suntest apparatus is reported in this work. H2O2/TiO2 photocatalyzed reaction yield and parameters (time, irradiance, temperature, H2O2 (40%) volume, TiO2 amount) were exactly determined relating to the used atrazine concentration. An experimental kinetic study was performed to establish the reaction order in fixed conditions. Using a biosensor method, 10(-4) M Atrazine solution toxicity and final photocatalytic reaction solution toxicity were quantitatively determined. A consistent toxicity decrease was observed on passing from the analyte to the products of the photocatalytic reaction. An analogous photolytic reaction carried out in absence of TiO2, but in the same experimental conditions of time, irradiance, temperature and H2O2 volume, brings to a toxicity increase.     

Formal [(2+2)+2] and [(2+2)+(2+2)] nonconjugated dienediyne cascade cycloadditions

[reaction: see text] Fluoranthene 2 and heptacycle 3 are easily accessible from the reaction of diyne 1 and norbornadiene (NBD) in the presence of the rhodium catalyst. The unusual [(2+2)+(2+2)] adduct 3 was confirmed by the X-ray crystal structure analysis.     

Studies on the Reaction Mechanism of Br2 ＋ I2 = 2IBr

1 INTRODUCTION Interhalogen compounds have played an impor- tant role in environment and chemical engineering production. During the course of ozone exhaustion induced by sunlight in polar region, Br2, BrCl and HOBr are all precursors of Br atom[1]. Lately, scien- tists have detected that the content of BrCl in polar region sunlight was 35 ppt, larger than that of Br2 (25 ppt). Previous studies suggested that the con- centration of BrCl and O3 exhibits obvious negative correlation: w…     

A systematic computational study on the reactions of HO2 with RO2: The HO2 + CH3O2(CD3O2) and HO2 + CH2FO2 reactions

A systematic theoretical study of the reactions of HO2 with RO2 has been carried out. The major concern of the present work is to gain insight into the reaction mechanism and then to explain experimental observations and to predict new product channels for this class of reactions of importance in the atmosphere. In this paper, the reaction mechanisms for two reactions, namely, HO2 + CH3O2 and HO2 + CH2FO2, are reported. Both singlet and triplet potential energy surfaces are investigated. The complexity of the present system makes it impossible to use a single ab initio method to map out all the reaction paths. Various ab initio methods including MP2, CISD, QCISD(T), CCSD(T), CASSCF, and density function theory (B3LYP) have been employed with the basis sets ranging from 6-31G(d) to an extrapolated complete basis set (CBS) limit. It has been established that the CCSD(T)/cc-pVDZ//B3LYP/6-311G(d,p) scheme represents the most feasible method for our systematic study. For the HO2 + CH3O2 reaction, the production of CH3OOH is determined to be the dominant channel. For the HO2 + CH2FO2 reaction, both CH2FOOH and CHFO are major products, whereas the formation of CHFO is dominant in the overall reaction. The computational findings give a fair explanation for the experimental observation of the products.     

Structural evolution in a hydrothermal reaction between Nb2O5 and NaOH solution: from Nb2O5 grains to microporous Na2Nb2O6.2/3H2O fibers and NaNbO3 cubes

Niobium pentoxide reacts actively with concentrate NaOH solution under hydrothermal conditions at as low as 120 degrees C. The reaction ruptures the corner-sharing of NbO(7) decahedra and NbO(6) octahedra in the reactant Nb(2)O(5), yielding various niobates, and the structure and composition of the niobates depend on the reaction temperature and time. The morphological evolution of the solid products in the reaction at 180 degrees C is monitored via SEM: the fine Nb(2)O(5) powder aggregates first to irregular bars, and then niobate fibers with an aspect ratio of hundreds form. The fibers are microporous molecular sieve with a monoclinic lattice, Na(2)Nb(2)O(6).(2)/(3)H(2)O. The fibers are a metastable intermediate of this reaction, and they completely convert to the final product NaNbO(3) cubes in the prolonged reaction of 1 h. This study demonstrates that by carefully optimizing the reaction condition, we can selectively fabricate niobate structures of high purity, including the delicate microporous fibers, through a direct reaction between concentrated NaOH solution and Nb(2)O(5). This synthesis route is simple and suitable for the large-scale production of the fibers. The reaction first yields poorly crystallized niobates consisting of edge-sharing NbO(6) octahedra, and then the microporous fibers crystallize and grow by assembling NbO(6) octahedra or clusters of NbO(6) octahedra and NaO(6) units. Thus, the selection of the fibril or cubic product is achieved by control of reaction kinetics. Finally, niobates with different structures exhibit remarkable differences in light absorption and photoluminescence properties. Therefore, this study is of importance for developing new functional materials by the wet-chemistry process.     

2-Amino-2-thiazoline. V. phenylthioureido and phenylureido derivatives of 2-thiazoline

The reaction of 2-amino-2-thiazoline (I) with phenylisothiocyanate has been reported to give 2-imino-3-phenylthiocarbamoylthiazolidine (II) at low temperatures and l-phenyl-3-(2-thiazolin-2-yl)-2-thiourea (III) at ca. 100°. When performed by us, however, this reaction gave only a single mono-adduct regardless of the temperature. Nmr and chemical evidence indicates that structure III is the correct one. Treatment of I with phenylisocyanate also gave a mono-adduct which was established to be l-phenyl-3-(2-thiazolin-2-yl)urea (V). Compound I does not form a simple di-adduct with excess phenylisothiocyanate but does so with phenylisocyanate to give 2-phenylcarbamoylimino-3-phenylcarbamoylthiazolidine (VI). The reaction of III with phenylisocyanate gives 2-phenylthiocarbamoylimino-3-phenylcarbamoylthiazolidine (VII), however, the corresponding reaction of V with phenylisothiocyanate does not give the anticipated product but a mixture of compounds which includes VI and VII.