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Decomposition Reactions (decomposition + reaction)
Terms modified by Decomposition Reactions Selected AbstractsThermal Decomposition Reactions as a Tool for the Synthesis of New Thermodynamic Metastable Modifications: Synthesis, Structures, and Properties of (Formato)nickel(II) Coordination Polymers Based on 4,4,-BipyridineEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2010Jan Boeckmann Abstract The reaction of nickel formate with 4,4,-bipyridine (bipy) in aqueous solution at room temperature leads to the formation of the hydrated compound [Ni(HCO2)2(H2O)(bipy)·4H2O]n (1) reported recently. On heating, compound 1 decomposes into the new anhydrous compound of composition [Ni(HCO2)2(bipy)]n (2II), which decomposes on further heating. Interestingly, if the anhydrous compound is prepared from solution, a new modification 2I is obtained. Investigations on the stability of both forms show that modification 2I presents the thermodynamically most stable form between room and decomposition temperature, whereas modification 2II, which can only be prepared by thermal decomposition, is metastable. In the crystal structure of 2I, the Ni2+ cations are coordinated by four ,2 - anti,anti bridging formato anions and two bridging ,2 -bipy ligands in a slightly distorted octahedralgeometry. The formato anions bridge the metal cations in zigzag chains, which are further connected by ,2 - anti,anti formato anions and bipy ligands to give a three-dimensional coordination network. IR spectroscopic investigations on the metastable form 2II also indicate that all formato anions act as bridging ligands. Magnetic measurements of the hydrated and anhydrous compounds reveal different behavior with a ferromagnetic ordering for compound 2I and an antiferromagnetic ordering for compound 1. For form 2II, only Curie,Weiss paramagnetism was found. [source] Reaction Mechanism and Dynamic Investigations of Poly-channel Decomposition Reactions of o -Pyridyl RadicalCHINESE JOURNAL OF CHEMISTRY, Issue 8 2005Cheng Xue-Li Abstract Utilizing Gaussian94 program package, all species involved in decomposition reactions of o -pyridyl radical were optimized fully at B3LYP/6-311++G** level. Intrinsic reaction coordinate calculations were employed to confirm the connections of the transition states and products, and transition states were ascertained by the number of imaginary frequency (0 or 1). The reaction mechanism was elucidated by the vibrational mode analysis and electronic population analysis, and the reaction rate constants were calculated with transition state theory. [source] Rate constant estimation for C1 to C4 alkyl and alkoxyl radical decompositionINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2006H. J. Curran Rate coefficients for alkyl and alkoxy radical decomposition are important in combustion, biological, and atmospheric processes. In this paper, rate constant expressions for C1C4 alkyl and alkoxy radicals decomposition via ,-scission are recommended based on the reverse, exothermic reaction, the addition of a hydrogen atom or an alkyl radical to an olefin or carbonyl species with the decomposition reaction calculated using microscopic reversibility. The rate expressions have been estimated based on a wide-range study of available experimental data. Rate coefficients for hydrogen atom and alkyl radical addition to an olefin show a strong temperature curvature. In addition, it is found that there is a correlation between the activation energy for addition and (i) the type of atom undergoing addition and (ii) whether this radical adds to the internal or terminal carbon atom of the olefin. Rate coefficients for alkoxy radical decomposition show a strong correlation to the ionization potential of the alkyl radical leaving group and on the enthalpy of reaction. It is shown that the activation energy for alkyl radical addition to a carbonyl species can be estimated as a function of the alkyl radical ionization potential and enthalpy of reaction. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 250,275, 2006 [source] Experimental study on sulfur trioxide decomposition in a volumetric solar receiver,reactorINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2009Adam Noglik Abstract Process conditions for the direct solar decomposition of sulfur trioxide have been investigated and optimized by using a receiver,reactor in a solar furnace. This decomposition reaction is a key step to couple concentrated solar radiation or solar high-temperature heat into promising sulfur-based thermochemical cycles for solar production of hydrogen from water. After proof-of-principle a modified design of the reactor was applied. A separated chamber for the evaporation of the sulfuric acid, which is the precursor of sulfur trioxide in the mentioned thermochemical cycles, a higher mass flow of reactants, an independent control and optimization of the decomposition reactor were possible. Higher mass flows of the reactants improve the reactor efficiency because energy losses are almost independent of the mass flow due to the predominant contribution of re-radiation losses. The influence of absorber temperature, mass flow, reactant initial concentration, acid concentration, and residence time on sulfur trioxide conversion and reactor efficiency has been investigated systematically. The experimental investigation was accompanied by energy balancing of the reactor for typical operational points. The absorber temperature turned out to be the most important parameter with respect to both conversion and efficiency. When the reactor was applied for solar sulfur trioxide decomposition only, reactor efficiencies of up to 40% were achieved at average absorber temperature well below 1000°C. High conversions almost up to the maximum achievable conversion determined by thermodynamic equilibrium were achieved. As the re-radiation of the absorber is the main contribution to energy losses of the reactor, a cavity design is predicted to be the preferable way to further raise the efficiency. Copyright © 2009 John Wiley & Sons, Ltd. [source] A new method of potassium chromate production from chromite and KOH-KNO3 -H2O binary submolten salt systemAICHE JOURNAL, Issue 10 2009Zhi Sun Abstract A new method of chromate production by applying a new reaction system of KOH-KNO3 -H2O (binary submolten salt system) is proposed and proved feasible. Under conditions of temperature 350°C, KOH-to-chromite ore ratio 2:1, stirring speed 700 rpm, KNO3 -to-chromite ore ratio 0.8:1, oxygen partial pressure 50%, and gas flow 1 L/min, chromium conversion ratio obtained is >98% with reaction time around 300 min. The decomposition of chromite ore in the system is a typical process of solid, liquid,gas reaction, which is coordinately controlled by mass diffusion in product layer and interface reaction. Apparent activation energy of decomposition in the temperature range from 280 to 370°C is 55.63 kJ/mol. During reaction, oxygen dissolves into KOH-KNO3 -H2O melt system first and some cluster, e.g. O, is formed and the mass diffusion coefficient of the cluster was calculated. The system can be considered as both a media of oxygen transportation and reactant donator. Potassium nitrate plays a role of catalyst in the oxidation decomposition reaction of chromite ore and potassium hydroxide. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Fabrication of Nitrogen-Containing Cordierite CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2010Noritaka Saito We have investigated the crystallization behavior of cordierite-based oxynitride glass prepared by melting a powder mixture of cordierite and silicon nitride. The results indicated that two polymorphs exist: a stable ,-form, which has a low coefficient of thermal expansion, and a metastable ,-form. The time,temperature,transformation diagram of the crystallization of the ,-form shows a typical C-shaped curve that has a nose around 1420 K. Above 1373 K, the ,-form can be directly obtained by the isothermal crystallization of the oxynitride glass and the ,-form inverts to the ,-form at temperatures below 1273 K. We also have fabricated an ,-cordierite ceramic that has a nitrogen content of 1.55 mass%, which is much lower than the content of the batch composition (5 mass%); this is mainly owing to the decomposition reaction of nitrogen in the oxynitride melts and glasses during heat treatment. However, the fabricated nitrogen-containing ,-cordierite ceramics showed the coefficient of thermal expansion of 10,7 K,1, which is comparable with that of the oxide ,-cordierite ceramics. Moreover, Young's modulus of the ,-cordierite ceramics improved with the incorporation of nitrogen. [source] Kinetics of Urea Decomposition in the Presence of Transition Metal Ions: Ni2+JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2006Bora Mavis The literature on kinetics of the urea decomposition reaction was reviewed for the 333,373 K range of temperature. Possible reactions in the pH range of 5,9 were identified. Kinetic simulations indicated significant accumulation of the cyanate intermediate in the pH-time,temperature range that was studied. The effects of Ni2+ hydrolysis and complexation with the urea decomposition products were incorporated into the simulations. The kinetic simulation of the rate of Ni2+ removal from the solutions was compared against the experimental data. The experimental results indicated an agglomerative growth mechanism for the precipitation process. Chemical analyses showed that the composition of the precipitate varies with digestion time, in agreement with the predictions of the kinetic simulation. [source] Thermal Behavior and Non-isothermal Decomposition Reaction Kinetics of NEPE Propellant with Ammonium DinitramideCHINESE JOURNAL OF CHEMISTRY, Issue 5 2010Weiqiang Pang Abstract Thermal decomposition behavior and non-isothermal decomposition reaction kinetics of nitrate ester plasticized polyether NEPE propellant containing ammonium dinitramide (ADN), which is one of the most important high energetic materials, were investigated by DSC, TG and DTG at 0.1 MPa. The results show that there are four exothermic peaks on DTG curves and four mass loss stages on TG curves at a heating rate of 2.5 K·min,1 under 0.1 MPa, and nitric ester evaporates and decomposes in the first stage, ADN decomposes in the second stage, nitrocellulose and cyclotrimethylenetrinitramine (RDX) decompose in the third stage, and ammonium perchlorate decomposes in the fourth stage. It was also found that the thermal decomposition processes of the NEPE propellant with ADN mainly have two mass loss stages with an increase in the heating rate, that is the result of the decomposition heats of the first two processes overlap each other and the mass content of ammonium perchlorate is very little which is not displayed in the fourth stage at the heating rate of 5, 10, and 20 K·min,1 probably. It was to be found that the exothermal peak temperatures increased with an increase in the heating rate. The reaction mechanism was random nucleation and then growth, and the process can be classified as chemical reaction. The kinetic equations of the main exothermal decomposition reaction can be expressed as: d,/dt=1012.77(3/2)(1,,)[,ln(1,,)]1/3 e,1.723×104/T. The critical temperatures of the thermal explosion (Tbe and Tbp) obtained from the onset temperature (Te) and the peak temperature (Tp) on the condition of ,,0 are 461.41 and 458.02 K, respectively. Activation entropy (,S,), activation enthalpy (,H,), and Gibbs free energy (,G,) of the decomposition reaction are ,7.02 J·mol,1·K,1, 126.19 kJ·mol,1, and 129.31 kJ·mol,1, respectively. [source] Reduction of Nitric Oxide over Rutile-supported Cu Surfaces: A Quantum Chemical StudyCHINESE JOURNAL OF CHEMISTRY, Issue 11 2005Kai Tan Abstract The adsorption and decomposition of NO on the stoichiometric rutile-supported Cu surfaces have been studied by means of density functional calculations with an embedded cluster model. The calculation results indicate that NO is favorably adsorbed as O-down and could easily attach another NO molecule to form N2O intermediate or directly be dissociated into N2 and O2. On the basis of the calculated energetics, possible mechanism of NO decomposition reaction has been proposed. [source] Kinetics and mechanism of the thermal decomposition reaction of 3,3-Bis(azidomethyl)oxetane/tetrahydrofuran copolymerCHINESE JOURNAL OF CHEMISTRY, Issue 11 2004Yang Luo Abstract The thermal behavior, mechanism and kinetic parameters of the exothermic decomposition reaction of 3,3-bis(azidomethyl)oxetane/tetrahydrofuran (BAMO/THF) copolymer in a temperature-programmed mode have been investigated by means of DSC, TG-DTG, fast and lower thermolysis/FTIR and TG-MS. The reaction mechanism was proposed. The apparent activation energy and pre-exponential constant of exothermic decomposition reaction of the compound at 0.1 MPa are 167.04 kJ*mol,1 and 1014.41 s,1, respectively. The corresponding critical temperatures of thermal explosion obtained from the onset temperature Tc, and the peak temperature Tp are 223.20 and 245.78°C, respectively. The kinetic equation of the exothermic decomposition process of BAMO/THF at 0.1 MPa could be expressed as: . [source] Interactions of Cationic Palladium(II)- and Platinum(II)-,3 -Allyl Complexes with Fluoride: Is Asymmetric Allylic Fluorination a Viable Reaction?EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2006Lukas Hintermann Abstract The complex cations [M(,3 -R2All)(PPFPz{3- tBu})]+ (M = PdII, R2All = 1,3-diphenylallyl, 1,3-dicyclohexylallyl, indenyl; M = PtII, R2All = 1,3-diphenylallyl; PPFPz-{3- tBu} = 3- tert -butyl-1-{1-[2-diphenylphosphanyl-ferrocenyl]ethyl}-1H -pyrazole)have been prepared as salts with PF6, or SbF6,. They have been characterized by NMR spectroscopy in solution and by X-ray crystallography in the solid state. Their reactions with sources of nucleophilic and "naked" fluoride have been investigated by multinuclear NMR spectroscopy. The PdII complexes did not undergo any nucleophilic substitution with concomitant release of allyl fluorides. The dicyclohexylallyl fragment was released as a 1,3-diene by elimination, but with other allyl complexes nonspecific decomposition reactions predominated. The complex [Pt(,3 -1,3-Ph2C3H3)(PPFPz{3- tBu})]PF6 underwent an anion exchange with Me4NF to give [Pt(1,3-Ph2C3H3)(PPFPz{3- tBu})]F which existed as a mixture of interconverting allyl isomers in solution at ambient temperature. For the bromide salt, [Pt(,3 -1,3-Ph2C3H3)(PPFPz{3- tBu})]Br, allyl isomerization was slow at ambient temperature. Precursors of Pt0 reacted with bromo-1,3-diphenylprop-2-ene to give [Pt2(,-Br)2(,3 -1,3-Ph2All)2] and precursors of Pd0 underwent oxidative additions with bromo- and fluoro-1,3-diphenyl-2-propene to give 1,3-diphenylallyl complexes of PdII. Therefore, the nucleophilic attack of fluoride on the allyl fragment of PdII complexes is endergonic, and the high energy barrier of this step is difficult to overcome in a catalytic allylic fluorination reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Dynamic Collapse Mechanisms in Metal Foam ExpansionADVANCED ENGINEERING MATERIALS, Issue 6 2010Dirk Lehmhus Abstract The study provides insight into decomposition of titanium hydride as foaming agent for powder metallurgically produced aluminum foams. Decomposition is characterized using thermal and kinetic analysis, allowing prediction of decomposition reactions. Such predictions are made for various time,temperature cycles, which are experimentally evaluated in parallel foaming experiments. A new explanation of foam collapse is derived from the results, which interprets hints at a maximum gas release rate, limiting maximum expansion, in terms of the existence of a maximum cell wall stretching rate and expanding foam can sustain. Thus a dynamic collapse criterion is added to existing static ones. [source] The nonisothermal decomposition kinetics of copper(II) complexes with phthalanilic acids and amino acidsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2003Li-Ping Ren Fifteen new kinds of mixed ligand complexes Cu(x-P)A [P = 2-(COO)C6H4CONH-C6H4; x = H, 2-Cl, 2-CH3, 2-OCH3, 4-OCH2CH3; A = dehydronium Met, Leu, Phen] were synthesized. The thermal decomposition behavior of each complex is studied by TG. Coats--Redfern, MacCallum--Tammer, and Zsako methods are adopted to estimate the values of the apparent activation energy Ea, the activation entropy ,S,, the reaction order n, and the frequency factor A. The results showed that the reaction order is 2/3 for each of the complex. Studies on the mechanism of the thermal decomposition reactions suggested that these reactions all fit the kinetic equation 1 , (1 , ,)1/3 = © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 623,628, 2003 [source] Efficient Heterogeneous Dual Catalyst Systems for Alkane MetathesisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Zheng Huang Abstract A fully heterogeneous and highly efficient dual catalyst system for alkane metathesis (AM) has been developed. The system is comprised of an alumina-supported iridium pincer catalyst for alkane dehydrogenation/olefin hydrogenation and a second heterogeneous olefin metathesis catalyst. The iridium catalysts bear basic functional groups on the aromatic backbone of the pincer ligand and are strongly adsorbed on Lewis acid sites on alumina. The heterogeneous systems exhibit higher lifetimes and productivities relative to the corresponding homogeneous systems as catalyst/catalyst interactions and bimolecular decomposition reactions are inhibited. Additionally, using a "two-pot" device, the supported Ir catalysts and metathesis catalysts can be physically separated and run at different temperatures. This system with isolated catalysts shows very high turnover numbers and is selective for the formation of high molecular weight alkanes. [source] Gas phase behavior of radical cations of perfluoroalkyl-1,2,4-triazines: an experimental and theoretical studyJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2009Gianluca Giorgi Abstract Electron ionization mass spectrometry and low-energy collision-induced decomposition reactions occurring in a tridimensional ion trap, together with density functional theory (DFT) calculations on neutrals, even- and odd-electron cations, have been used to study the gas-phase ion chemistry of a series of perfluoroalkyl-1,2,4-triazines. Loss of oxygen, due to thermal degradation occurring before ionization, likely involving the hydroxylamino group, has been observed. Compounds having a carbonyl group at position 6 of the triazine ring fragment in the source by elimination of NO followed by HF or CO. The decomposition pathways occurring due to CID experiments have shown interesting features depending on the nature and structure of precursor ions. Most of them involve elimination of endocyclic atoms, thereby producing contraction of the original six-membered ring or formation of acyclic structures. DFT (B3LYP/6-31G(d,p)) calculations have been used for evaluating structure, stability and properties of neutral and ionic species involved in gas-phase processes. In particular, it has been calculated that in the molecular ion the unpaired electron is mainly located on the exocyclic nitrogen, while the positive charge is on the C(6) carbon atom. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis, characterization, and antimicrobial activity of some novel poly(ether ketone)sJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2003Samir A. Patel Abstract Low molecular weight poly(ether ketone)s were synthesized from phenol, 1,4-phenylenedioxy diacetylchloride, chloroacetylchloride, and dichloroalkanes [1,2-dichloroethane and dichloromethane] by a Friedel,Crafts reaction with anhydrous aluminum chloride as a catalyst and carbon disulfide as a solvent. The conditions for the preparation of the poly(ether ketone)s and the chlorine contents obtained with the Carius method were examined, and a reaction scheme for each resin was established. The molecular weights and polydispersities of the resins were obtained by gel permeation chromatography. The polyketones were characterized by IR spectroscopy. The characteristic frequencies due to different functional groups were assigned. The thermal properties of the resins were studied with thermogravimetry and differential scanning calorimetry. The characteristic temperatures of thermal degradation for the poly(ether ketone)s were evaluated with thermogravimetric analysis. The kinetic parameters for the decomposition reactions of the resins were obtained with Broido and Doyle's method, and the heats of fusion were obtained from differential scanning calorimetry thermograms. The polyketones were thermally stable up to 200 °C. All the polyketones were tested for their microbial properties against bacteria, fungi, and yeast. The effect of poly(ether ketone)s on the growth of these microorganisms was investigated, and the polyketones were found to inhibit the growth of the microorganisms to a considerable extent. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2335,2344, 2003 [source] Development and application of a two-tier multiple choice diagnostic instrument to assess high school students' understanding of inorganic chemistry qualitative analysis,JOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 4 2002Kim Chwee Daniel Tan This article describes the development and application of a two-tier multiple choice diagnostic instrument to assess high school students' understanding of inorganic chemistry qualitative analysis. The development of the diagnostic instrument was guided by the framework outlined by Treagust. The instrument was administered to 915 Grade 10 students (15 to 17 years old) from 11 schools after they had learned the theory involved in qualitative analysis and after a series of qualitative analysis practical sessions. The Cronbach alpha reliability of the instrument was .68, the facility indices ranged from .17 to .48, and the discrimination indices ranged from .20 to .53. The study showed that the Grade 10 students had difficulty understanding the reactions involved in the identification of cations and anions, for example, double decomposition reactions, the formation and reaction of complex salts, and thermal decomposition. The findings of the study and literature on practical work were used to develop a qualitative analysis teaching package. © 2002 Wiley Periodicals Inc. J Res Sci Teach 39: 283,301, 2002 [source] Use of Genetic Algorithm to Determine the Kinetic Model of Solid-State ReactionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007S. Maitra Solid-state reactions take place by different rate-controlling heterogeneous processes. To find the appropriate kinetic model for a particular solid-state reaction, a genetic algorithm-based simulation technique was carried out using DTA data with a fitness function, and a computer program was developed for the same. The process was applied to the decomposition reactions of limestone and magnesite samples. It was observed that both the decomposition reactions mostly followed the Avrami,Erofeev kinetics model. [source] Investigation of polarity dependent InN{0001} decomposition in N2 and H2 ambientPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009R. Togashi Abstract The polarity dependence of decomposition of the (0001) In- and (000) N-polarity InN layers grown by hydride vapor phase epitaxy (HVPE) on freestanding GaN substrates was investigated. In flowing N2, In- and N-polarity InN layers start to decompose over 550 and 610 °C, respectively. Therefore, the N-polarity InN layer is more stable than the In-polarity InN layer. On the other hand, in flowing H2, InN layers of both polarities start to react with H2 at a low temperature of 350 °C leaving In droplets on the surfaces. Further more, the decomposition rate of the N-polarity InN layer is larger than that of the In-polarity InN layer below approximately 450 °C, while the decomposition rate of the In-polarity InN layer is larger than that of the N-polarity InN above 450 °C. An Arrhenius plot of the decomposition rates revealed that the activation energies, EA, for the decomposition reactions of In- and N- polarity InN layers are 168 and 107 kJ/mol, respectively, which are much smaller than that for GaN and AlN decomposition. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Quantitative determination of perfluorooctanoic acid ammonium salt in human serum by high-performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2002Cristina Sottani A sensitive, specific, accurate and reproducible analytical method was developed and validated to quantify perfluorooctanoic acid (PFOA) in human serum. After initial extraction with an ion-paring reagent, the procedure for quantifying PFOA is based on high-performance liquid chromatography (HPLC) interfaced to negative ion tandem mass spectrometry, operating in selected ion monitoring mode. The retention times of PFOA and its internal standard (D,L-malic acid) were 5.85 and 1.70,min, respectively. The assay was linear over the range 0,500,ng/mL, with a lower limit of quantification (LOQ) of 25,ng/mL, and with a coefficient of variation (CV) of 7.3%. The lower limit of detection (LOD) was assessed as 10,ng/mL. The overall precision and accuracy were assessed on three different days. The within- and between-day precision was ,9.7 and 6.8%, respectively, and the accuracy was in the range 96,114%. The mean extracted recovery assessed at three different concentrations (100, 250, and 500,ng/mL) was always more than 85%. With this method no derivatization procedure was needed, thus avoiding possible thermal and chemical decomposition reactions of PFOA. The assay was applied to quantify perfluorooctanoic acid in serum from employees exposed to fluorochemicals commonly used in industrial applications for polymer production. The quantitative results for PFOA blood levels were found to vary between 100 and 982,ng/mL. Copyright © 2002 John Wiley & Sons, Ltd. [source] Pyrolysis Kinetics of Wood and Wood ComponentsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2005T. Willner Abstract The kinetics of pyrolysis decomposition reactions of wood and its components are described employing mathematical modeling tools for first and nth order reactions, autocatalytic reactions, and parallel first order and autocatalytic reactions. Secondary reactions may accelerate the reaction rate and a new autocatalytic reaction model was developed to describe this specific behavior. [source] Structure Formation Principles and Reactivity of Organolithium CompoundsCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2009Viktoria Abstract Organolithium chemistry! An overview of the structure formation principles and the strong structure,reactivity relationship of lithium organics is given. By means of the commonly used lithium bases the deaggregation of the oligomeric parent structures to small adducts is presented (see examples) and compared to the related chemistry of lithiosilanes. The structure,reactivity relationship is an important feature of organolithium compounds. The knowledge of the structure of reactive species is crucial for the elucidation of reaction mechanisms and the understanding of observed selectivities. This concept article gives an overview over the structural principles of lithium organics and their Lewis base coordinated complexes in the solid state. The transition from the oligomeric parent structures to smaller adducts, such as dimers and monomers, as well as special degrees of aggregation is presented. Besides the commonly used alkyllithium compounds, a short overview over the structural principles of the higher homologous silyllithium compounds is given. Moreover, the structure,reactivity relationship is depicted by means of the reactivity of the Lewis bases towards intramolecular decomposition reactions with the organolithium compound. Selected examples confirm the importance of structure elucidation for the understanding of mechanistic pathways and selectivities. [source] Reaction Mechanism and Dynamic Investigations of Poly-channel Decomposition Reactions of o -Pyridyl RadicalCHINESE JOURNAL OF CHEMISTRY, Issue 8 2005Cheng Xue-Li Abstract Utilizing Gaussian94 program package, all species involved in decomposition reactions of o -pyridyl radical were optimized fully at B3LYP/6-311++G** level. Intrinsic reaction coordinate calculations were employed to confirm the connections of the transition states and products, and transition states were ascertained by the number of imaginary frequency (0 or 1). The reaction mechanism was elucidated by the vibrational mode analysis and electronic population analysis, and the reaction rate constants were calculated with transition state theory. [source] | ||||||||||||||||||||||||||||