Ein neuer Beitrag zur Phosphazoreaktion

A New Contribution to the Phosphazo Reaction The reaction of acrylonitrile with phosphorus pentachloride gives ClCH₂CCl₂CCl₂NPCl₃ (I) and a hexachlorophosphate with the composition C₃H₂Cl₁₄NP₃ (II). For the first time the structure of (II) has been exactly determined by using ¹H- and ³¹P-NMR-spectra. The course of reaction was studied in detail. 3-chloropropionitrile has been found as the product of a secondary reaction. The reaction of butyramide with PCl₅ has also been investigated, and was found to be analogous.     

Study of the reaction of MoOS2(S2CNR2)2 with PPh3 in 1,2-dichloroethane: Part II. Detection of reaction intermediate pentavalent molybdenum using ESR method at low temperature

Intermediate product of the reaction of MoOS₂(S₂CNR₂)₂ and PPh₃ in dichloroethane has been detected by ESR spectroscopy. Two ESR signals have been observed at low temperature in the reaction system which was stopped by quenching it in liquid nitrogen. The g values are 2.020 ± 0.001 and 1.972 ± 0.001 respectively. The signal at g = 2.020 is attributed to a reaction intermediate with pentavalent molybdenum. A reaction mechanism has been proposed which is consistent with the observation of pentavalent molybdenum as the intermediate in the process of reaction.     

Formation pathways of CH3SOH from CH3S(OH)CH3 in the presence of O2: a theoretical study

Methane sulfenic acid (CH₃SOH, MSEA) has been suggested in the literature as a possible stable product within the addition channel of the OH-initiated oxidation of dimethyl sulfide. In particular, it has been proposed as one of the thermodynamically feasible products of the reaction of CH₃S(OH)CH₃ adduct with O₂. However, MSEA has never been experimentally observed and a detailed theoretical analysis of all the reaction pathways leading to MSEA formation has never been reported. In this study, the first density functional and ab initio electronic structure calculations are carried out to characterize those reaction channels yielding MSEA. The adduct formed by the reaction of DMS-OH with O₂ (CH₃S(O₂)(OH)CH₃) has been taken as the starting point. On the other hand, a new reaction pathway, which competes with the MSEA formation yielding DMSO instead, is also presented. The kinetic relevance of those different reaction pathways is discussed to assert their contribution to the experimental measurements of the end-products of DMS-OH-initiated oxidation.     

Experimental determination of the equilibrium constant of the reaction CH3 + O2 ⇄ CH3O2 during the gas-phase oxidation of methane

For the experimental determination of the equilibrium constant of the reaction CH₃ + O₂ ? CH₃O₂ (1), the process of methane oxidation has been studied over the temperature range of 706–786 K. The concentration of CH₃O₂ has been measured by the radical freezing method, and that of CH₃ from the rate of accumulation of ethane, assuming that C₂H₆ is produced by the reaction CH₃ + CH₃ → C₂H₆ (2). The equilibrium constant of reaction (1) has been obtained at four temperatures. For the heat of the reaction the value Δ?H₂₉₈ = -32.2 ± 1.5 kcal/mol is recommended.     

Determination of heats of aluminothermic redox reaction of V2O5 and MnO2

Differential thermal analysis has been used for quantitative determination of heats of aluminothermic redox reaction of MnO₂ and V₂O₅ over a wide range of temperatures. Heat of reaction V₂O₅?Al and MnO₂?Al systems have been determined using the calibration plot established. The experimentally determined values compare well with those predicted from thermodynamic data available in the literature. It has been found that V₂O₅?Al system involves a higher heat of reaction in comparison to the MnO₂?Al system.     

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).     

Addition of dipropylamine to multiacrylate and its model compound catalyzed by lithium dipropylamide

The nucleophilic addition reaction of dipropylamine to vinyl groups of multiacrylate - poly(2-acryloyloxyethyl methacrylate) and to 2-butyrylethyl acrylate as model compound has been investigated. Based on the results obtained, it has been shown that the addition reaction rate of dipropylamine to multiacrylate and 2-butyrylethyl acrylate is proportional to [CH₂=CH-] and to [(C₃H₇)₂NLi] with the ratio [(C₃H₇)₂NH]_o/[(C₃H₇)₂NLi]_o = 20. Second-order addition reaction rate constants and activation energies for the systems under investigation have been determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

气相中CrO2+活化甲烷C—H键的理论研究

用密度泛函UB3LYP/6-311＋＋G**方法计算研究了气相中CrO₂⁺ (²A₁/⁴A")活化甲烷C—H键的微观机理, 找到了四条反应通道. 对其中涉及的两态反应(TSR)进行了分析, 并对影响反应机理和反应速率的势能面交叉现象(potential energy surfaces crossing)进行了详细讨论, 进而运用Hammond假设和Yoshizawa等的内禀坐标单点垂直激发计算的方法找出了一系列势能面交叉点[crossing points (CPs)], 并作了相应的讨论. 进一步用碎片分子轨道理论[fragment molecular orbital (FMO)]对TS1中的轨道相互作用进行了分析, 解释了CrO₂⁺活化甲烷C—H键的机理.     

Identification of the [(bpy)2Ru(Im)(H2O)]2+ complex as an reaction intermediate by reversed-phase high-performance liquid chromatography

Summary The synthesis of the complex [(bpy)₂Ru(Im)₂]²⁺ (bpy=2,2-bipyridine; Im=imidazole) has been monitored by reversed-phase HPLC. The analytical results obtained during the reaction have shown that it is feasible to identify and isolate the [(bpy)₂RuIm(H₂O)]²⁺ complex as a reaction intermediate. The optimization of the synthetic procedures for these two species has been established and the compounds have been obtained in high purity. The use of HPLC has enabled complete analytical control of the synthesis of the [(bpy)₂RuL₂]²⁺ class of compounds, enabling the identification of reaction intermediates.     

A pyridine-containing ruthenium–indenylidene complex: Synthesis and activity in ring-closing metathesis

The reaction of Cl₂Ru(PCy₃)₂(3-phenylindenylidene) with excess pyridine leads to the new pyridine-containing ruthenium-based complex: Cl₂Ru(PCy₃)(Py)₂(3-phenylindenylidene) in good yield. This catalyst has been fully characterized and tested in ring-closing metathesis. Its moderate activity has been examined by kinetic studies using several substrates and different reaction conditions.     

Studies on the interactions of copper(II) chelate complexes with SO2

The reaction of bis (acetylacetonato) copper(II) with SO₂ yields CuSo₄ as a final product. Using e.p.r. technique mixed-ligand complexes of the type Cu(acac) (acacSO₂) have been detected at 100 K. The e.p.r. spectrum of the latter complex disappeared under passing argon through the sample. Lewis bases accelerated the reaction. No interaction of SO₂ with other complexes containing CuO₂N₂, CuN₂S₂, CuS₄ chromophores has been detected. In a common solution of Cu(acac)₂ and Cu(dtc)₂ the reaction proceeded only with Cu(acac)₂ though a mixed-ligand complex Cu(acac) (dtc) was formed. The addition of bases accelerated the reaction, all spectra disappeared and only Cu^I(dtc) has been found as a final product.     

U原子和CO反应机理的第一性原理的理论研究

在有关实验结果的基础上提出了U原子和CO分子的各种可能反应通道, 然后采用第一性原理对反应通道上的各物种的几何构型、谐振频率以及总能量进行了计算和研究, 计算结果表明, 初级和次级反应的稳定产物分别为CUO和(η²-C₂)UO₂. 提出了最可能反应通道为U原子以C端或侧位进攻CO分子引起反应, 并用分子轨道理论解释了该反应机理.     

Synthesis of α,ω-dimethoxyfluoropolyethers: reaction mechanism and kinetics

A new class of hydrofluoropolyethers, the α,ω-dimethoxyfluoropolyethers (DM-FPEs), characterized by the copolymeric structure CH₃O(CF₂CF₂O)_n(CF₂O)_mCH₃ has been recently developed. The synthesis of DM-FPEs here described, has been carried out via a new synthetic route which consists of the reaction of a perfluoropolyether diacyl fluoride with methyl fluoroformate in the presence of a metal fluoride. The reaction products are DM-FPEs and carbon dioxide.Several reaction conditions has been tested varying type of solvent, temperature, type and amount of metal fluoride. The best results were obtained using tetraglyme as solvent and CsF as metal fluoride.     

An ab initio study of the potential surface for the reaction H2COH → HCO + H2

The potential surface for the reaction H₂CO⁺H → HCO⁺ + H₂ has been studied by ab initio SCF calculations, using gaussian-type basis functions. A saddle point on the surface has been found, and a reaction path is proposed to explain the observed release of kinetic energy. The energy of activation and ΔE for the reaction have been estimated.     

Theoretical investigation on the reaction of N2O and CO catalyzed by Fe(C6H6)

The reaction of N₂O with CO, catalyzed by Fe⁺(C₆H₆) and producing N₂ and CO₂, has been investigated at the UB3LYP/6-311+G(d) level. The computation results revealed that the reaction of Fe⁺(C₆H₆), N₂O and CO, is an O-atom abstraction mechanism. For the reaction channels, the geometries and the vibrational frequencies of all species have been calculated and the frequency modes analysis also have been given to elucidate the reaction mechanism. On the basis for geometry optimizations, the thermodynamic data of these reactions channels have been calculated using the statistical theory at 295.15 K and pressure of 0.35 Torr. Using Eyring transition state theory with Wigner correction, the activation thermodynamic data, rate constant and frequency factors for the these reaction channels also have been given. The results showed that CO and N₂O do not react without catalyst and Fe⁺(C₆H₆) can excellently mediate the reaction of N₂O and CO.     

Study on the kinetics of isomerization of some unsymmetrical bis(μ-alkylthio) hexacarbonyldiiron by NMR method

The kinetics of the isomerization of (μ-PhCH₂S) (μ-RS)Fe₂(CO)₆ (R?Me, Et) and (μ-PhCH₂S) (μ-t-BuS)Fe₂(CO)₆ has been studied by conventional and dynamic NMR methods respectively. A possible mechanism for the reaction has been proposed and the factors which influence the reaction rate have been discussed.     

Catalytic Pyrolysis of Methane

Methane decomposition over metal oxides/SiO₂ surface was investigated. At 1400 K obtained product distribution of this decomposition varied with metal oxide used. The effectiveness of these catalysts has been discussed in terms of activity and C₂ selectivity. ThO₂/SiO₂ was found to be the most effective catalyst for the catalytic decomposition of methane. Positive catalytic effect of ThO₂/SiO₂ on the pyrolysis has also been confirmed at 1073 K. At low reaction conversions, ethane and ethylene are found as major products. Yields of ethylene and other unsaturated products are sensitively inhibited by NO impurities in the methane. A reaction mechanism has been proposed to account observed experimental results.     

Modeling the thermal DENOx process in flow reactors. Surface effects and Nitrous Oxide formation

We have investigated the impact of surface reactions such as NH₃ decomposition and radical adsorption on quartz flow reactor data for Thermal DeNO_x using a model that accounts for surface chemistry as well as molecular transport. Our calculations support experimental observations that surface effects are not important for experiments carried out in low surface to volume quartz reactors. The reaction mechanism for Thermal DeNO_x has been revised in order to reflect recent experimental results. Among the important changes are a smaller chain branching ratio for the NH₂ + NO reaction and a shorter NNH lifetime than previously used in modeling. The revised mechanism has been tested against a range of experimental flow reactor data for Thermal DeNO_x with reasonable results. The formation of N₂O in Thermal DeNO_x has been modelled and calculations show good agreement with experimental data. The important reactions in formation and destruction of N₂O have been identified. Our calculations indicate that N₂O is formed primarily from the reaction between NH and NO, even though the NH₂ + NO₂ reaction possibly contributes at lower temperatures. At higher temperatures N₂O concentrations are limited by thermal dissociation of N₂O and by reaction with radicals, primarily OH. © 1994 John Wiley & Sons, Inc.     

A kinetics study of the reaction of SO2 with CH3O2

The reaction ot CH₃O₂ with SO₂ has been studied using the flash photolysis/ultraviolet absorption technique. In contrast to previous measurements, no reaction could be detected over the temperature range 298–423 K. An upper limit of 5 × 10^?17 cm³ molecule^?1 s^?1 has been determined for the reaction rate constant.     

Reaction of carbonyl fluoride with fluorine in the presence of various fluorides as catalysts

The fluorides KF, RbF and CsF have been known to serve as catalysts for the reaction CF₂O + F₂→ CF₃OF. The list of catalysts for this process has now been enlarged to include NaF, MgF₂, CaF₂, SrF₂, BaF₂ and LaF₃. Lithium fluoride and thorium fluoride also give CF₃OF but are less active. Perhaps the substances CsF·HF, KAgF₄ and NiF₂ should be included in this list. Silver fluoride, usually as a mixture of AgF₂ with AgF, has been known to catalyze the reaction of CF₂O with F₂ to give both CF₃OF and CF₃OOCF₃. The proportion of the latter in the mixture of products increases with decreasing temperature. At 25°, the reaction is slow and the yield of CF₃OOCF₃ is very high. It has now been shown that TIF₃ behaves like silver fluoride. It has also been shown that many other fluorides of metals give higher yields of CF₃OOCF₃ than of CF₃OF but require higher temperatures than AgF₂ (100-ca. 150°) to be effective. Various possible mechanisms for these catalytic processes are discussed.