Quantum chemical study on insertion and abstraction reaction of dichlorocarbene with methyl alcohol and methyl mercaptan

The insertion and abstraction reaction mechanisms of singlet and triplet CCl₂ with CH₃MH (M=O, S) have been studied by using the DFT, NBO and AIM methods. The geometries of reactions, the transition state and products were completely optimized by B3LYP/6–311G(d, p). All the energy of the species was obtained at the CCSD(T)/6–311G(d, p) level. The calculated results indicated that the major pathways of the reaction were obtained on the singlet potential energy surface. The singlet CCl₂ can not only trigger the insertion reaction with C-H and M-H in four pathways, by which the products P1 [CH₃OCHCl₂, reaction I(1)], P3[Cl₂HCCH₂OH, reaction I(2)], P5[CH₃SCHCl₂, reaction II(1)] and P7[Cl₂HCCH₂SH, reaction II(2)] are produced respectively, but also abstract M-H, resulting P4 [CH₂O+CH₂Cl₂, reaction I(3)] and P8[CH₂S+CH₂Cl₂, reaction II(3)]. In addition, the important geometries in domain pathways have been studied by AIM and NBO theories. Supported by the National Natural Science Foundation of China (Grant No. 20335030) and Foundation of Education Committee of Gansu Province (Grant No. 0708-11)     

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.     

The reaction of the hydroxyl radical with acetylene

The reaction of OH with acetylene was studied in a discharge flow system at room temperature. OH was generated by the reaction of atomic hydrogen with NO₂ and was monitored throughout the reaction using ESR spectroscopy. Mass-spectrometric analysis of the reaction products yielded the following results: (1) less than 3 molecules of OH were consumed, and less than 2 molecules of H₂O were formed for every molecule of acetylene that reacted; (2) CO was identified as the major carbon-containing product; (3) NO, formed in the generation of OH, reacted with a reaction intermediate to give among other products N₂O. These observations placed severe limitations on the choice of a reaction mechanism. A mechanism containing the reaction OH + C₂H₂ → HC₂O + H₂ better accounted for the experimental results than one involving the abstraction reaction OH + C₂H₂ → C₂H + H₂O. The rate constant for the initial reaction was measured as 1.9 ± 0.6 × 10^?13 cm³ molecule^?1 sec^?1.     

Free radical SH2′ reaction mechanism study by comparing free radical SH2′ reaction with free radical addition reaction

It is not clear whether the mechanism of the S_H2′ reaction of allyl chloride is concerted or stepwise. The relative rates of the competitive free radical addition to two different double bonds in (2-chloroallyl)-(2-choromethylallyl) ether have been determined. There are two competitive free radical addition reactions, one is free radical S_H2′ reaction and the other is free radical addition reaction. The mechanism of the S_H2′ reaction is discussed by comparing free radical S_H2′ reaction with free radical addition reaction.     

Über die Umsetzung von Adipinsäurediamid mit Phosphorpentachlorid

Reaction of Adipic Acid Diamide with Phosphorus Pentachloride The reaction of adipamide (I) with phosphorus pentachloride in a solvent leads to (Cl₃P?NCCl₂CCl₂CH₂)₂ (II). The stages of the reaction are: 1. chlorination of the keto and methylen groups 2. formation of the ? N?PCl₃ group. This result is a supplement of the existing conception about the course of the reaction of carboxylic acid amides with phosphorus pentachloride. The reaction of (I) with PCl₅ without any solvent has been reproduced and the course of reaction has also been investigated. This reaction gives mainly NC(CH₂)₄CN. The resulting product of a careful hydrolysis of (II) is (Cl₂OPN?CClCl₂CH₂)₂. A total hydrolysis gives back (I).     

Theoretical Study of the Reaction Mechanism and Kinetics of HO2 with XCHO (X = F,Cl)

The reactions of HO₂ with FCHO and ClCHO have been theoretically investigated by combining beyond‐CCSD(T) electronic structure benchmarks, validated density functional theory, and canonical variational transition state theory with small‐curvature tunneling, coupled‐torsions anharmonicity, and high‐frequency anharmonicity. This investigation explores three different reaction mechanisms: radical addition plus a hydrogen transfer, radical addition, and hydrogen abstraction. The calculated results show that the dominant reaction pathway is the terminal oxygen atom of HO₂ added to the carbon atom of XCHO (X = F, Cl) and simultaneously the hydrogen atom of HO₂ transferred to the oxygen atom of the C=O group in XCHO. The reaction barriers of the other reaction pathways are so high that these processes are negligible in the atmosphere. Although the barrier height of the dominant reaction pathway in the HO₂ + FCHO reaction is 0.61 kcal/mol higher than that of the corresponding HO₂ + ClCHO reaction, the HO₂ + FCHO reaction is faster than the HO₂ + ClCHO reaction because the variational effects of HO₂ + ClCHO is more obvious than that of the HO₂ + FCHO. The present results show that the HO₂ + FCHO reaction may be important in the atmosphere. The present results should be useful in evaluating the atmospheric fate of XCHO (X = F, Cl).     

纳米Cu2O催化二苯甲烷二氨基甲酸苯酯无溶剂热分解制备二苯甲烷二异氰酸酯

研究了无溶剂条件下纳米Cu₂O催化二苯甲烷二氨基甲酸苯酯(MDPC)热分解制备二苯甲烷二异氰酸酯(MDI),考察了纳米Cu₂O的制备条件与反应条件对MDPC热分解反应性能的影响.结果表明,水解法制备的纳米Cu₂O在Ar中于300℃焙烧2h,其催化性能最佳;最佳的反应条件为Cu₂O用量为原料总重的0.06%,反应温度220℃,反应压力0.6kPa,反应时间12min,此时MDPC转化率达到99.8%,MDI选择性86.2%.     

Ligand effects in the hydroformylation of acrylonitrile by cobalt carbonyl

The hydroformylation of acrylonitrile (VCN) using Co₂(CO)₈/L (L  HN(CH₂CN)₂, H₂C(CH₂)₃NMe, Me₂N(CH₂)₂NMeH, PPh₃, and PCy₃) has been examined in methanol solvent. Four reaction pathways are observed which are dependent on L. With no L or with L  HN(CH₂CN)₂, the reaction produces the desired acetal (MeO)₂CHCH₂CH₂CN. For the more basic amines the reaction produces ～ 50% yields of hydrodimerization products NCCHMe(CH₂)₂CN/NC(CH₂)₄CN in a 10/1 ratio and an ～ 30% yield of the hydrogenation product CH₃CH₂CN. These reactions are shown to be metal catalyzed. The main reaction for Co₂(CO)₈/PR₃ catalyzed systems appears to be a classical Michael addition reaction of the solvent, methanol, with acrylonitrile to give MeOCH₂CH₂CN. Evidence is given to show that this reaction is catalyzed by phosphine which has dissociated under reaction conditions and not by a ligated cobalt complex.     

Synthesis of 4-halophosphaisocoumarins via halocyclization of 2-(1-alkynyl)phenylphosphonates

A series of 4-halophosphaisocoumarins were prepared with high regioselectivity in good to excellent yields under mild conditions by the reaction of 2-(1-alkynyl)phenylphosphonic acid diesters with I₂ in CHCl₃ or ICl in CH₂Cl₂, or by the reaction of 2-(1-alkynyl)phenylphosphonic acid monoesters with NBS or NCS in DMF. Whether the alkynylphosphonates could cyclize or not was affected by the substituents, reaction solvents and electrophiles. A rationale for this reaction is discussed.     

A new reforming process based on CH4 decomposition using a hydrogen-permeating membrane reactor

A new reforming process was studied using Ni/SiO₂ with a hydrogen-permeating membrane reactor. Nickel catalyst supported on SiO₂ is highly active for CH₄-H₂O-O₂ reaction in membrane reactor and the reaction close to CH₄ + 0.35O₂ + 1.3H₂O → CO₂ + 3.3H₂ proceeds at 873 K. Since the selectivity to carbon and CO₂ increased and decreased with decreasing contact time respectively, it is considered that the reaction was started by decomposition of CH₄ followed by oxidation of C and water shift reaction. Therefore, the reaction mechanism was different from so-called autothermal reforming (ATR) reaction.     

Diverse Reactivity of an Electrophilic Phosphasilene towards Anionic Nucleophiles: Substitution or Metal–Amino Exchange

The reaction of MesLi (Mes=2,4,6‐trimethylphenyl) with the electrophilic phosphasilene R₂(NMe₂)Si‐RSi=PNMe₂ ( 2 , R=Tip=2,4,6‐triisopropylphenyl) cleanly affords R₂(NMe₂)Si‐RSi=PMes and thus provides the first example of a substitution reaction at an unperturbed Si=P bond. In toluene, the reaction of 2 with lithium disilenide, R₂Si=Si(R)Li ( 1 ), apparently proceeds via an initial nucleophilic substitution step as well (as suggested by DFT calculations), but affords a saturated bicyclo[1.1.0]butane analogue as the final product, which was further characterized as its Fe(CO)₄ complex. In contrast, in 1,2‐dimethoxyethane the reaction of 1 with 2 results in an unprecedented metal–amino exchange reaction.     

Operando Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy of the NO Reduction Reaction over Rhodium-Based Catalysts

Operando shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) with on-line mass spectrometry (MS) has been used to investigate the surface species, such as NO, NOH, NO₂, N₂O, and reaction products of the NO reduction reaction with CO and H₂ over supported Rh-based catalysts in the form of catalyst extrudates. By correlating surface intermediates and reaction products, new insights in the reaction mechanism could be obtained. Upon applying different reaction conditions (i. e., H₂ or CO), the selectivity of the catalytic reaction could be tuned towards the formation of N₂. Furthermore, in the absence of Rh, no reaction products were detected. The importance of the operando SHINERS as a surface-sensitive characterization technique in the field of heterogeneous catalysis provides routes towards a better understanding of catalytic performance.     

Regenerative Electroless Etching of Silicon

Regenerative electroless etching (ReEtching), described herein for the first time, is a method of producing nanostructured semiconductors in which an oxidant (Ox₁) is used as a catalytic agent to facilitate the reaction between a semiconductor and a second oxidant (Ox₂) that would be unreactive in the primary reaction. Ox₂ is used to regenerate Ox₁, which is capable of initiating etching by injecting holes into the semiconductor valence band. Therefore, the extent of reaction is controlled by the amount of Ox₂ added, and the rate of reaction is controlled by the injection rate of Ox₂. This general strategy is demonstrated specifically for the production of highly luminescent, nanocrystalline porous Si from the reaction of V₂O₅ in HF(aq) as Ox₁ and H₂O₂(aq) as Ox₂ with Si powder and wafers.     

A new reforming process based on CH4 decomposition using a hydrogen-permeating membrane reactor

A new reforming process was studied using Ni/SiO₂ with a hydrogen-permeating membrane reactor. Nickel catalyst supported on SiO₂ is highly active for CH₄?H₂O?O₂ reaction in membrane reactor and the reaction close to CH₄+0.35O₂+1.3H₂O→CO₂+3.3H₂ proceeds at 873 K. Since the selectivity to carbon and CO₂ increased and decreased with decreasing contact time respectively, it is considered that the reaction was started by decomposition of CH₄ followed by oxidation of C and water shift reaction. Therefore, the reaction mechanism was different from so-called autothermal reforming (ATR) reaction.     

（TEAH）nH3-nPW12O40催化苯甲醇选择氧化及其反应机理

以Keggin结构的磷钨酸和三乙胺（TEA）为原料,通过简单的酸碱反应合成了磷钨酸的TEA盐.并以它们为催化剂,考察了以H₂O₂为氧化剂、以水为溶剂的体系中苯甲醇选择氧化制备苯甲醛的反应性能.结果表明,（TEAH）_nH_3-nPW₁₂O₄₀（n=1,2,3）系列催化剂对苯甲醇的选择氧化反应有很高的活性和选择性,且可被分离和循环使用.在适宜的反应条件下,最佳催化剂（TEAH）H₂PW₁₂O₄₀上,苯甲醇的转化率可达99.6%,苯甲醛的选择性为100%.还采用IR,³¹PNMR谱和元素分析技术,对催化剂和反应过程中催化剂物种的转化和分布进行了考察,进而导出了反应机理.在这个水--油两相反应中,（PW₁₂O₄₀）^3-首先在H₂O₂的作用下,氧化降解为溶于水的小分子过氧物种（PO₄（WO（O₂）₂）₄）^3-和自由W物种.（PO₄（WO（O₂）₂）₄）^3-是真正的活性物种,可将部份溶于水层的苯甲醇氧化为苯甲醛,自身转变为失去活性氧的反应后物种（SAR）.而SAR又可与自由W物种一起聚合为前驱体状态的（PW₁₂O₄₀）^3-,完成催化循环.     

Nonlinear chemical reaction between Na2S2O3 and Peroxide compound

Kinetics of reaction between Na₂S₂0₃ and peroxide compound (H₂0₂ or Na₂S₂O₃) in a batch reactor and in a continuous stirring tank reactor (CSTR) were studied. Steady oscillations in uncatalyzed reactions in a CSTR were first discovered. In Na₂S₂0₃-H₂O₂-H₂S0₄ reaction system, Pt potential and pH of higher and lower flow rates beyond oscillation flow rates were in around the same extreme values. The reaction catalyzed by Cu²⁺ consists of the catalyzed oscillation process and the uncatalyzed osciliation one. On the basis of experiment, a reaction mechanism consisting of three stages was put forward. The three stages are H⁺ positive-feedback reactions, proton negative-feedback (uncatalyzed negative-feedback and catalyzed negative-feedback) reactions and transitional reactions. The mechanism is able to explain reasonably the nonlinear chemical phenomena appearing in the thiosulfate oxidation reaction by peroxide compounds. Project supported by the National Natural Science Foundation of China.     

Anion Modulation of Pt-Group Metals and Electrocatalysis Applications

Pt-group metal (PGM) electrocatalysts with unique electronic structures and irreplaceable comprehensive properties play crucial roles in electrocatalysis. Anion engineering can create a series of PGM compounds (such as RuP₂, IrP₂, PtP₂, RuB₂, Ru₂B₃, RuS₂, etc.) that provide a promising prospect for improving the electrocatalytic performance and use of Pt-group noble metals. This review seeks the electrochemical activity origin of anion-modulated PGM compounds, and systematically analyzes and summarizes their synthetic strategies and energy-relevant applications in electrocatalysis. Orientation towards the sustainable development of nonfossil resources has stimulated a blossoming interest in the design of advanced electrocatalysts for clean energy conversion. The anion-modulated strategy for Pt-group metals (PGMs) by means of anion engineering possesses high flexibility to regulate the electronic structure, providing a promising prospect for constructing electrocatalysts with superior activity and stability to satisfy a future green electrochemical energy conversion system. Based on the previous work of our group and others, this review summarizes the up-to-date progress on anion-modulated PGM compounds (such as RuP₂, IrP₂, PtP₂, RuB₂, Ru₂B₃, RuS₂, etc.) in energy-related electrocatalysis from the origin of their activity and synthetic strategies to electrochemical applications including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), N₂ reduction reaction (NRR), and CO₂ reduction reaction (CO₂RR). At the end, the key problems, countermeasures and future development orientations of anion-modulated PGM compounds toward electrocatalytic applications are proposed.     

HO2自由基与NO2反应通道的理论研究

应用密度泛函理论DFT/B3LYP对HO₂＋NO₂反应进行了研究, 在B3LYP/6-311G^**和CCSD(T)/6-311G^**水平上计算了HO₂自由基与NO₂分子反应的单重态和三重态反应势能面, 计算结果表明, 单重态反应势能面中的直接氢抽提反应机理是此反应的主要反应通道, 即HO₂自由基的氢原子转移到NO₂分子的氮原子上形成产物P₁ (HNO₂＋³O₂), 另一个可能的反应通道是单重态反应势能面上HO₂中的端位氧原子进攻NO₂分子中的氮原子形成中间体1 (HOONO₂), 接着中间体1 (HOONO₂)经过氢转移形成产物P₂ (trans-HONO＋³O₂), 以上两个反应通道都是放热反应通道, 分别放热90.14和132.52 kJ•mol^－1.     

Dissection of the Multichannel Reaction O(3P) + C2H2: Differential Cross-Sections and Product Energy Distributions

The O(³P) + C₂H₂ reaction plays an important role in hydrocarbon combustion. It has two primary competing channels: H + HCCO (ketenyl) and CO + CH₂ (triplet methylene). To further understand the microscopic dynamic mechanism of this reaction, we report here a detailed quasi-classical trajectory study of the O(³P) + C₂H₂ reaction on the recently developed full-dimensional potential energy surface (PES). The entrance barrier TS1 is the rate-limiting barrier in the reaction. The translation of reactants can greatly promote reactivity, due to strong coupling with the reaction coordinate at TS1. The O(³P) + C₂H₂ reaction progress through a complex-forming mechanism, in which the intermediate HCCHO lives at least through the duration of a rotational period. The energy redistribution takes place during the creation of the long-lived high vibrationally (and rotationally) excited HCCHO in the reaction. The product energy partitioning of the two channels and CO vibrational distributions agree with experimental data, and the vibrational state distributions of all modes of products present a Boltzmann-like distribution.     

Reaction Mechanisms of Strontium Ferrites Synthesis

The reactions between strontium and iron nitrates have been studied in an open atmosphere system using three different molar ratios, 1:1 (I), 1:2 (II) and 2:1 (III) at different temperatures as pointed out from the DTA data. The reaction mechanism was discussed based on the chemical composition characterized by means of thermal analysis, X‐ray diffraction patterns, infrared spectra and magnetic susceptibility. It was found that the reaction products depend on both temperature of reaction and the ratio between reactants. The reaction products were found to be composed of a variety of iron compounds that possess different valences: SrFeO_2.86, SrFeO_2.97, SrFe₂O₄, SrFe₁₂O₁₉, Sr₂Fe₂O₅ and Sr₇Fe₁₀O₂₂ in addition to some accessory reaction products namely α‐Fe₂O₃ and FeO(OH).