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Same Reaction (same + reaction)
Terms modified by Same Reaction Selected AbstractsUnexpected Rearrangement Leading to Formation of a 1,3-Bis(triphenylphosphonio)prop-1-en-3-idyl CarboxylateEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2010R. Alan Aitken Abstract Whereas biphenyl-4,4,-dicarbonyl dichloride reacts with methylenetriphenylphosphorane to give the expected bis(acylylide) 1, the same reaction of biphenyl-2,2,-dicarbonyl dichloride results in a multistep rearrangement leading to the zwitterionic 2-[1,3-bis(triphenylphosphonio)prop-1-en-3-id-2-yl]biphenyl-2,-carboxylate 2. X-ray crystal structures of both 1 and 2 are reported. [source] An Expedient Synthesis of Perfluorinated Tetraazamacrocycles: New Ligands for Copper-Catalyzed Oxidation under Fluorous Biphasic ConditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2006Augustin de Castries Abstract Conjugate additions of cyclam to perfluorohexyl vinyl sulfone and sulfoxide, which act as efficient fluorous Michael acceptors, readily give access to new fluoro-ponytail tetraazamacrocycles in good yields. The solubility of the N -tetrasubstituted macrocycles depends dramatically on the nature of the polar function (SO or SO2): the sulfoxide cyclam derivative is soluble in perfluorodecaline (pfd) and perfluoromethylcyclohexane (pfmc) while the sulfonyl derivative is almost insoluble in organic or fluorous solvents. In agreement with the well known affinity of cyclam for copper(II) ions, stable copper complexes of the fluorous macrocyclic ligands have been isolated and characterized. In chloroform/methanol, complexes with four perfluorinated tails have been obtained from reaction of the tetra- N -perfluorohexylsulfinyl-substituted macrocycle with copper nitrate and copper perfluorocarboxylate. In trifluoroethanol, a selective retro-Michael reaction has been observed and the same reaction specifically gives copper complexes of the tri- N -substituted macrocycle. Complexes with three and four fluorous tails associated with perfluorocarboxylate counteranions are soluble in fluorous solvents (pfd and pfmc). These copper complexes were tested as catalysts for the oxidation of cyclohexene by molecular oxygen in the presence of tert -butyl hydroperoxide (tbhp). The oxidation reactions proceed under fluorous biphasic conditions and the catalyst can be recovered and reused. Quenching experiments indicate that cyclohexenyl hydroperoxide is the main oxidation product of the reaction performed with or without tbhp. Interestingly, these perfluorinated copper complexes are good, recyclable catalysts for the oxidation of cyclohexene by molecular oxygen without tbhp at room temperature and 65 °C.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Characterization of ,- d -glucosidase extracted from soil fractionsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2000M. D. Busto Summary One way to study the state in which stabilized extracellular enzymes persist and are active in the soil is by extraction from the soil, with subsequent fractionation of enzyme,organomineral complexes and characterization of such complexes. In order to investigate the location and characteristics of soil ,-glucosidase, three soil fractions were obtained both from real (undisturbed) soil aggregates and from structural (dispersed in water and physically disrupted) aggregates using two different granulometric procedures. The ,-glucosidase activity of the fraction was then assayed. When the aggregates were dispersed, more than 73% of activity was in the soil microaggregates with diameters of less than 50 ,m (SF50). These aggregates were associated with strongly humified organic matter. Solutions of diluted pyrophosphate at neutral pH liberated active ,-glucosidase from all fractions, although the efficacy of extraction varied according to the type of fraction. The SF50 fraction and aggregates of 2000,100 ,m obtained by sieving (SF2000) showed the greatest ,-glucosidase activity (34.5 and 36.0%, respectively). Micro- and ultrafiltration of SF50 extracts increased the total ,-glucosidase activity, whereas these procedures, applied to the RF2000 fraction, decreased it. Humus,,-glucosidase complexes in the SF50 fraction, between 0.45 ,m and 105 nominal molecular weight limit ( nmwl) (SF50II) and < 105nmwl (SF50III) showed an optimum pH at 5.4, and in the SF50I fraction (> 0.45 ,m) the optimum was 4.0. The stability of ,-glucosidase in the aggregates of the smallest size SF50II and SF50III decreased at acid pHs. The presence of two enzymes (or two forms of the same enzyme) catalysing the same reaction with different values of Michaelis constant and maximum velocity was observed in all but one of the ,-glucosidase complexes extracted and partially purified from the SF50 aggregates. [source] Role of glutathione in the formation of the active form of the oxygen sensor FNR ([4Fe-4S]·FNR) and in the control of FNR functionFEBS JOURNAL, Issue 15 2000Quang Hon Tran The oxygen sensor regulator FNR (fumarate nitrate reductase regulator) of Escherichia coli is known to be inactivated by O2 as the result of conversion of a [4Fe-4S] cluster of the protein into a [2Fe-2S] cluster. Further incubation with O2 causes loss of the [2Fe-2S] cluster and production of apoFNR. The reactions involved in cluster assembly and reductive activation of apoFNR isolated under anaerobic or aerobic conditions were studied in vivo and in vitro. In a gshA mutant of E. coli that was completely devoid of glutathione, the O2 tension for the regulatory switch for FNR-dependent gene regulation was decreased by a factor of 4,5 compared with the wild-type, suggesting a role for glutathione in FNR function. In isolated apoFNR, glutathione could be used as the reducing agent for HS, formation required for [4Fe-4S] assembly by cysteine desulfurase (NifS), and for the reduction of cysteine ligands of the FeS cluster in FNR. Air-inactivated FNR (apoFNR without FeS) could be reconstituted to [4Fe-4S]·FNR by the same reaction as used for apoFNR isolated under anaerobic conditions. The in vivo effects of glutathione on FNR function and the role of glutathione in the formation of active [4Fe-4S]·FNR in vitro suggest an important role for glutathione in the de novo assembly of FNR and in the reductive activation of air-oxidized FNR under anaerobic conditions. [source] The reaction between ethyl and molecular oxygen II: Further analysisINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 11 2001James A. Miller The present investigation is a rather substantial extension and elaboration of our previous work on the same reaction. In this article we accomplish four primary objectives: 1.We show quantitatively how sensitive the high-temperature rate coefficient k(T) is to E02, the threshold energy of the transition state for direct molecular elimination of HO2 from ethylperoxy radical (C2H5O2), thus deducing a value of E02=,3.0 kcal/mol (measured from reactants). 2.We derive the result that k0(T) , k,,(T) in the high-temperature regime, where k0(T) is the zero-pressure rate coefficient, and k,,(T) is the infinite-pressure rate coefficient for the bimolecular channel. 3.Most importantly, we discuss the three different regimes of the reaction (low-temperature, transition, and high-temperature) in terms of the eigenvectors and eigenvalues of G, the transition matrix of the master equation. The transition regime is shown to be a region of avoided crossing between the two chemically significant eigenvalue curves in which the thermal rate coefficient k (T ,p) jumps from one eigenvalue to the other. This jump is accompanied by a "mixing" of the corresponding eigenvectors, through which both eigenvectors deplete the reactant. The onset of the high-temperature regime is triggered by reaching the "stabilization limit" of the ethylperoxy adduct, a limit that is induced by a shift in equilibrium of the stabilization reaction. Our identification of the prompt and secondary HO2 formed by the reaction with these eigenvalue/eigenvector pairs leads to good agreement between theory and the experiments of Clifford et al. (J Phys Chem A 2000, 104, 11549,11560). 4.Lastly, we describe the master equation results in terms of a set of elementary reactions and phenomenological rate coefficients. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 732,740, 2001 [source] Novel gel-entrapped base catalysts for the Claisen,Schmidt reactionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2004Sachin S Chaphekar Abstract Novel gel-entrapped base catalysts (GEBCs) were prepared by entrapping aqueous solutions of bases in a gel matrix of agar agar. The bases used were NaOH, KOH, morpholine and piperidine. Ternary phase diagrams were constructed for the water,base,agar agar system to identify the various phases and especially the solid phase, useful as a solid base catalyst. The 10% NaOH solid gel was used to effect the Claisen,Schmidt reaction between benzaldehydes and acetophenones in ethanol under heterogeneous conditions to obtain 70,100% yield of the products. The solid GEBCs obtained using other bases were also used for the same reaction; however, the yields were lower. The catalyst needed no activation prior to use and could be recycled. Copyright © 2004 Society of Chemical Industry [source] Enhanced hydrogenation in a reverse flow chromatographic reactorAICHE JOURNAL, Issue 5 2006Guillermo A. Viecco Abstract An experimental study of the reverse flow chromatographic reactor is carried with the equilibrium limited hydrogenation of 1,3,5-trimethylbenzene (mesitylene, MES) to 1,3,5-trimethylcyclohexane. The reaction is pseudo first-order when carried out in excess hydrogen. A simple experimental setup is used to evaluate the effects of carrier flow, reactant feed concentration, and amount of catalyst on conversion. Conversions exceeding the thermodynamic equilibrium conversion are obtained for a wide variety of switching times, catalyst amounts, carrier flow rates, and reactant concentrations, showing the robustness of the system. While the qualitative features of the process can be predicted for a simple linear adsorption equilibrium model, the experimental results are best fitted by assuming a linear adsorption isotherm combined with an adjusted interfacial mass-transfer resistance. The experimental results are very similar to those reported in previous research of the same reaction in a simulated moving-bed chromatographic reactor. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Photoamination of 1-hydroxyanthraquinone in a water-acetonitrile mixed solventJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 4 2009Masahiro Tajima Abstract We investigated the photoamination kinetics of 1-hydroxyanthraquinones in a water-acetonitrile mixed solvent by stationary light irradiation. The progression of the reaction under an inert atmosphere demonstrated the existence of additional reaction pathways. The excited triplet state of the base form of the 1-hydroxyanthraquinones was found to be responsible for the additional pathways. On the other hand, the same reaction under air involved an attack of the amine-derived radical species (aminium and amino radicals) on the ground state of the 1-hydroxyanthraquinones. One of the pathways preferentially led to 2-amination, and the other led exclusively to 4-amination. Results also indicate the attainment of an equilibrium state between the aminium and amino radicals. Copyright © 2008 John Wiley & Sons, Ltd. [source] SN2 reaction of a sulfonate ester in the presence of alkyltriphenylphosphonium bromides and mixed cationic-cationic systemsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2006Michael M. Mohareb Abstract The effects of alkyltriphenylphosphonium bromides (CnTPB, n,=,10, 12, 14, 16) on the rates of SN2 reactions of methyl 4-nitrobenzenesulfonate and bromide ion have been studied. Observed first-order rate constants are significantly higher than those found for other cationic surfactants for the same reaction. The results have been analyzed by the pseudophase model of micellar kinetics and show true micellar catalysis in the sense that second-order micellar rate constants are higher than the second-order rate constants in water. An attempt has also been made to investigate mixed cationic,cationic surfactant systems with respect to observed rates and pseudophase regression parameters. In addition, modeling of some cationic head groups has illustrated possible differences in head group charges and counterion interactions that may prove kinetically relevant. Copyright © 2006 John Wiley & Sons, Ltd. [source] Reactive blending of poly (dimethylsiloxane) with nylon 6 and poly (styrene):Effect of reactivity on morphologyPOLYMER ENGINEERING & SCIENCE, Issue 4 2001M. Mari Reactive compatibilization was used to control and stabilize 20,30wt% poly(dimethylsioxane) (PDMS) dispersions in nylon 6 (PA) and poly(styrene) (PS), respectively. The effect of the type of reation (amine (NH2)/anhydride (An), NH2/ epoxy(E) and carboxylic acid (COOH)/E) on the morphology was studied with electron microscopy. PS and PDMS have mutual solvents thus it was possible to use gel permeation chromatography (GPC) to determine the concentration of block copolymer in PS/PDMS blends. Reactive blending of PA6 with difunctional PDMS-(AN)2 did not decrease the PDMS particle size compared to the non-reactive blend (,10,m). Particle size decreaeased significantly to about 0.5 ,m when PA6 was blended with a PDMS containing about 4 random An groups along the chain. For the PS/PDMS blends, GPC revealed that the NH2/An reaction formed about 3% block copolymer and produced stable PDMS particles , 0.4 ,m. No reaction was detected for the PS-NH2/PDMS-E blend and the morphology was coarse and unstable. Also, PS-NH2/PDMS-An reactivity was lower compared to other systems such as PS/ poly (isoprene) and PS/poly(methaacrylte) using the same reaction. This was attributed to the relatively thinner PS/PDMS interface dueto the high PS/PDMs immiscibility. [source] Pentacoordination versus tetracoordination in silicon derivatives of an O,N,O,-tridentate ligandACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010Uwe Böhme Bis[2-(2-hydroxy-3-methoxybenzylideneamino)phenolato-,O]dimethylsilicon, C30H30N2O6Si, (II), was isolated from the reaction of 2-(2-hydroxy-3-methoxybenzylideneamino)phenol, (I), with dichlorodimethylsilane at 339,K. It consists of two ligand molecules and the Me2Si unit forming a dialkoxydimethylsilane with a tetracoordinate Si atom. [2-(3-Methoxy-2-oxidobenzylideneamino)phenolato-,3O,N,O,]dimethylsilicon, C16H17NO3Si, (III), was isolated from the same reaction conducted at 263,K. In this complex, the dianion of (I) is coordinated via two O atoms and an azomethine N atom to the pentacoordinate Si atom. According to quantum chemical calculations, (II) is the thermodynamically stable product and (III) is the kinetically favoured product. [source] The copper(II) complexes di-,-bromo-bis{[2,6-bis(pyrazol-1-yl)pyridine]perchloratocopper(II)} and [2,6-bis(pyrazol-1-yl)pyridine]dibromocopper(II)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2004Surajit Chakrabarty The two title compounds, di-,-bromo-bis{[2,6-bis(pyrazol-1-yl-,N2)pyridine-,N](perchlorato-,O)copper(II)}, [Cu2Br2(ClO4)2(C11H9N5)2], (I), and [2,6-bis(pyrazol-1-yl)pyridine]dibromocopper(II), [CuBr2(C11H9N5)], (II), were synthesized by only slight modifications of the same reaction; compound (II) was formed by adding one molar equivalent of pyrazole (C3N2H4) to the reaction mixture of (I). Compound (I) is a bromo-bridged dinuclear copper(II) compound stabilized by weak interactions with the perchlorate anions (ClO4,), while (II) is a related mononuclear species, which has a distorted square-pyramidal geometry. [source] Synthesis and crystal structure of three nido 11-vertex platinaborane clustersAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2005Jianmin Dou Abstract The reaction of [PtCl2(PPh3)2] with closo -B10H102, in ethanol under reflux conditions gave two nido 11-vertex platinaundecaborane clusters: [(PPh3)2PtB10H10 -8,10-(OEt)2]·CH2Cl2(1) and [(PPh3)2PtB10H11 -11-OEt]·CH2Cl2(2). A novel B10H102, deboronated nido 11-vertex diplatinaundecaborane [(µ-PPh2)(PPh3)2Pt2B9H6 -3,9,11-(OEt)3]·CH2Cl2(3) was obtained when the same reaction was carried out under solvothermal conditions. All of these compounds were characterized by infrared spectroscopy, NMR spectroscopy, elemental analysis and single-crystal X-ray diffraction. Both clusters 1 and 2 have a nido 11-vertex {PtB10} polyhedral skeleton in which the Pt atom lies in the open PtB4 face. Each Pt atom connects with four B atoms and two P atoms of the PPh3 ligands. Cluster 3 has a nido 11-vertex {Pt2B9} polyhedral skeleton in which two Pt atoms sit in neighbouring positions of the open Pt2B3 face, bridged by a PPh2 group. Each Pt atom connects three B atoms and a P atom of the PPh3 ligand. Copyright © 2005 John Wiley & Sons, Ltd. [source] The RNA-Cleaving Bipartite DNAzyme Is a Distinctive MetalloenzymeCHEMBIOCHEM, Issue 1 2006Anat R. Feldman Dr. Abstract Much interest has focused on the mechanisms of the five naturally occurring self-cleaving ribozymes, which, in spite of catalyzing the same reaction, adopt divergent strategies. These ribozymes, with the exception of the recently described glmS ribozyme, do not absolutely require divalent metal ions for their catalytic chemistries in vitro. A mechanistic investigation of an in vitro-selected, RNA-cleaving DNA enzyme, the bipartite, which catalyzes the same chemistry as the five natural self-cleaving ribozymes, found a mechanism of significant complexity. The DNAzyme showed a bell-shaped pH profile. A dissection of metal usage indicated the involvement of two catalytically relevant magnesium ions for optimal activity. The DNAzyme was able to utilize manganese(II) as well as magnesium; however, with manganese it appeared to function complexed to either one or two of those cations. Titration with hexaamminecobalt(III) chloride inhibited the activity of the bipartite; this suggests that it is a metalloenzyme that utilizes metal hydroxide as a general base for activation of its nucleophile. Overall, the bipartite DNAzyme appeared to be kinetically distinct not only from the self-cleaving ribozymes but also from other in vitro-selected, RNA-cleaving deoxyribozymes, such as the 8,17, 10,23, and 614. [source] The Role of Solvent on the Mechanism of Proton Transfer to Hydride Complexes: The Case of the [W3PdS4H3(dmpe)3(CO)]+ Cubane ClusterCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2010Andrés Abstract The kinetics of reaction of the [W3PdS4H3(dmpe)3(CO)]+ hydride cluster (1+) with HCl has been measured in dichloromethane, and a second-order dependence with respect to the acid is found for the initial step. In the presence of added BF4, the second-order dependence is maintained, but there is a deceleration that becomes more evident as the acid concentration increases. DFT calculations indicate that these results can be rationalized on the basis of the mechanism previously proposed for the same reaction of the closely related [W3S4H3(dmpe)3]+ cluster, which involves parallel first- and second-order pathways in which the coordinated hydride interacts with one and two acid molecules, and ion pairing to BF4, hinders formation of dihydrogen bonded adducts able to evolve to the products of proton transfer. Additional DFT calculations are reported to understand the behavior of the cluster in neat acetonitrile and acetonitrile,water mixtures. The interaction of the HCl molecule with CH3CN is stronger than the WH,,,HCl dihydrogen bond and so the reaction pathways operating in dichloromethane become inefficient, in agreement with the lack of reaction between 1+ and HCl in neat acetonitrile. However, the attacking species in acetonitrile,water mixtures is the solvated proton, and DFT calculations indicate that the reaction can then go through pathways involving solvent attack to the W centers, while still maintaining the coordinated hydride, which is made possible by the capability of the cluster to undergo structural changes in its core. [source] Tuning the Reaction Site for Enzyme-Free Primer-Extension Reactions through Small Molecule SubstituentsCHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2006Jan A. Rojas Stütz Dr. Abstract The replication of genetic information relies on the template-directed extension of DNA primers catalyzed by polymerases. The active sites of polymerases accept four different substrates and ensure fidelity and processivity for each of them. Because of the pivotal role of catalyzed primer extension for life, it is important to better understand this reaction on a molecular level. Here we present results from primer-extension reactions performed with chemical systems that show high reactivity in the absence of polymerases. Small molecular caps linked to the 5,-terminus of templates are shown to enhance the rate and selectivity of primer extension driven by 2-methylimidazolides as activated monomers for any of the four different templating bases (A, C, G, and T). The most consistent effect is provided by a stilbene carboxamide residue, rather than larger aromatic or aliphatic substituents. Up to 20-fold rate enhancements were achieved for the reactions at the terminus of the template. The preference for a medium size cap can be explained by competing interactions with both the oligonucleotides and the incoming deoxynucleotide. The data also show that there is no particularly intractable problem in combining promiscuity with fidelity. Exploratory experiments involving a longer template and a downstream-binding strand with a 5,-cap show up to 38-fold rate acceleration over the same reaction templated by a single overhanging nucleotide. [source] Bifunctional-Thiourea-Catalyzed Diastereo- and Enantioselective Aza-Henry ReactionCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2006Xuenong Xu Dr. Abstract Bifunctional thiourea 1,a catalyzes aza-Henry reaction of nitroalkanes with N -Boc-imines to give syn -,-nitroamines with good to high diastereo- and enantioselectivity. Apart from the catalyst, the reaction requires no additional reagents such as a Lewis acid or a Lewis base. The N-protecting groups of the imines have a determining effect on the chirality of the products, that is, the reaction of N -Boc-imines gives R adducts as major products, whereas the same reaction of N -phosphonoylimines furnishes the corresponding S adducts. Various types of nitroalkanes bearing aryl, alcohol, ether, and ester groups can be used as nucleophiles, providing access to a wide range of useful chiral building blocks in good yield and high enantiomeric excess. Synthetic versatility of the addition products is demonstrated by the transformation to chiral piperidine derivatives such as CP-99,994. [source] Alkylations of N4 -(4-Pyridyl)-3,5-di(2-pyridyl)-1,2,4-triazole: First Observation of Room-Temperature Rearrangement of an N4 -Substituted Triazole to the N1 AnalogueCHEMISTRY - AN ASIAN JOURNAL, Issue 4 2010Jonathan Abstract Attempts to use alkylation to introduce a positive charge at the nitrogen atom of the 4-pyridyl ring in the bis(bidentate) triazole ligand N4 -(4-pyridyl)-3,5-di(2-pyridyl)-1,2,4-triazole (pydpt) were made to ascertain what effect a strongly electron-withdrawing group would have on the magnetic properties of any subsequent iron(II) complexes. Alkylation of pydpt under relatively mild conditions led in some cases to unexpected rearrangement products. Specifically, when benzyl bromide is used as the alkylating agent, and the reaction is carried out in refluxing acetonitrile, the N4 substituent moves to the N1,position. However, when the same reaction is performed in dichloromethane at room temperature, the rearrangement does not occur and the desired product containing an alkylated N4 substituent is obtained. Heating a pure sample of N4 -Bzpydpt,Br to reflux in MeCN resulted in clean conversion to N1 -Bzpydpt,Br. This is consistent with N4 -Bzpydpt,Br being the kinetic product whereas N1 -Bzpydpt,Br is the thermodynamic product. When methyl iodide is used as the alkylating agent, the N4 to N1 rearrangement occurs even at room temperature, and at reflux pydpt is doubly alkylated. The observation of the lowest reported temperatures for an N4 to N1 rearrangement is due to this particular rearrangement involving nucleophilic aromatic substitution: a possible mechanism for this transformation is suggested. [source] Kinetic and Equilibrium Studies of Reactions of N-Heterocycles with Dimeric and Monomeric Oxorhenium(V) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2003James H. Espenson Abstract Equilibrium constants have been evaluated for the reaction {MeReO(edt)}2 + 2 L , 2 MeReO(edt)L, where edt is 1,2-ethanedithiolate and L is any of 13 N-donor heterocyclic ligands. The values of K range from 1.37(27)×10,2 for pyrimidine to 1.95(6)×106 for imidazole at 25 °C in chloroform. A successful correlation of logK with log (Ka) of HL+ was realized except in the case of the 2-substituted ligands 2-picoline and quinoline, where steric effects make K smaller than expected from the proton basicity of L. The kinetics of the same reactions were studied; the rate law for the reaction in the forward direction is given by ,d[{MeReO(edt)}2]/dt = {ka + kb[L]}[L] × [{MeReO(edt)}2]. Except for 2-picoline and quinoline, the major pathway is provided by the term that shows the quadratic dependence on [L]. Values of log (kb) also correlate with log K, and therefore necessarily with log (Ka). [source] Development and testing of a comprehensive chemical mechanism for the oxidation of methaneINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 9 2001K. J. Hughes A comprehensive chemical mechanism to describe the oxidation of methane has been developed, consisting of 351 irreversible reactions of 37 species. The mechanism also accounts for the oxidation kinetics of hydrogen, carbon monoxide, ethane, and ethene in flames and homogeneous ignition systems in a wide concentration range. It has been tested against a variety of experimental measurements of laminar flame velocities, laminar flame species profiles, and ignition delay times. The highest sensitivity reactions of the mechanism are discussed in detail and compared with the same reactions in the GRI, Chevalier, and Konnov mechanisms. Similarities and differences of the four mechanisms are discussed. The mechanism is available on the Internet as a fully documented CHEMKIN data file at the address http://www.chem.leeds.ac.uk/Combustion/Combustion.html. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 513,538, 2001 [source] 2H -Pyran-2-one-3-carbothioamide derivatives: Synthesis and reaction with hydrazine hydrateJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2009Malika Makhloufi-Chebli N -Aryl-4-hydroxy-6-methyl-2H -pyran-2-one-3-carbothiamides and N -aryl-4-hydroxycoumarin-3-carbothiamides were synthesized by the reaction of arylisothiocyanates with 4-hydroxy-6-methylpyran-2-one and 4-hydroxycoumarin, respectively. Novel products 3-[bis(arylamino)methylene]-6-methyl-2H,4H -pyran-2,4-diones and N,N,-diaryl-4-hydroxycoumarin-3-carboximidamides have also been obtained in the same reactions. Novel 4-acetoacetyl-3-phenylamino-4,5-dihydro-5H -pyrazol-5-ones were synthesized from the reaction of N -aryl-4-hydroxy-6-methyl-2H -pyran-2-one-3-carbothiamides with an excess of hydrazine. The structure of all compounds was established by NMR and mass spectra. J. Heterocyclic Chem., (2009). [source] Kinetics and mechanism of the aminolysis of dimethyl and methyl phenyl phosphinic chlorides with anilinesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2009Nilay Kumar Dey Abstract The reactions of dimethyl phosphinic chloride (1) and methyl phenyl phosphinic chloride (2) with X-anilines have been studied kinetically in acetonitrile at 15.0 and 55.0,°C, respectively. The deuterium kinetic isotope effects (KIEs) involving deuterated aniline nucleophiles (XC6H4ND2) are also reported for the same reactions. The obtained KIEs for 1 are secondary inverse (kH/kD,=,0.703,0.899,<,1), while those for 2 are primary normal (kH/kD,=,1.62,2.10,>,1). A concerted mechanism involving predominantly backside nucleophilic attack is proposed for the anilinolysis of 1. A concerted mechanism involving predominantly frontside attack via a hydrogen-bonded four-center-type transition state is proposed for the anilinolysis of 2. The degree of steric hindrance is the major factor that determines both the reactivity of the phosphinates and the direction of the nucleophilic attack on the phosphinates. Copyright © 2008 John Wiley & Sons, Ltd. [source] Thermal transformation of monoterpenes within thionin-supported zeolite Na-Y.JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2003Acid-catalyzed or electron transfer-induced? Abstract Several monoterpenes (monocyclic, bicyclic or acyclic) isomerize and finally transform to p -cymene in the dark upon loading within thionin-supported zeolite Na-Y. The same reactions occur in Na-Y dried under the same conditions as thionin/Na-Y. It is postulated that the thermal treatment of Na-Y generates ,electron holes' (probably acidic sites). The transformation of monoterpenes occurs more likely via an electron transfer-induced reaction subordinated to the occurrence of the acidic sites. The radical cation of the more thermodynamically stable monoterpene, ,-terpinene, eventually dehydrogenates to p -cymene. For comparison, the same reactions were performed within methyl viologen-supported Na-Y. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||