Sample records for ammonia synthesis reaction

  1. Ammonia Synthesis

    Microsoft Academic Search

    Noorhana Yahya; Poppy Puspitasari; Krzysztof Koziol; Pavia Guiseppe

    \\u000a Ammonia production is a very energy- and capital-intensive industry as it requires high temperature (400–500°C) and also high\\u000a pressure (150–300 bar) for its daily operations. Two moles of ammonia are obtained by reacting one mole of nitrogen and three\\u000a moles of hydrogen gases in the presence of conventional catalyst which is magnetite. The process to produce ammonia is known\\u000a as

  2. Ammonia-mediated, large-scale synthesis of ammonia borane.

    PubMed

    Ramachandran, P Veeraraghavan; Mistry, Hitesh; Kulkarni, Ameya S; Gagare, Pravin D

    2014-11-28

    A simple, large-scale synthesis of ammonia borane from NaBH4 and (NH4)2SO4 at 0 °C-rt in THF containing 5% NH3 is described. The presence of ammonia is critical for the reaction to proceed and allows the reaction at high concentrations and ambient temperature without the need for anhydrous solvent or inert atmosphere. PMID:25274135

  3. Catalytic Organometallic Reactions of Ammonia

    PubMed Central

    Klinkenberg, Jessica L.

    2012-01-01

    Until recently, ammonia had rarely succumbed to catalytic transformations with homogeneous catalysts, and the development of such reactions that are selective for the formation of single products under mild conditions has encountered numerous challenges. However, recently developed catalysts have allowed several classes of reactions to create products with nitrogen-containing functional groups from ammonia. These reactions include hydroaminomethylation, reductive amination, alkylation, allylic substitution, hydroamination, and cross-coupling. This Minireview describes examples of these processes and the factors that control catalyst activity and selectivity. PMID:20857466

  4. Development of ammonia synthesis

    Microsoft Academic Search

    Poppy Puspitasari; Noorhana Yahya

    2011-01-01

    Ammonia production is a high energy and capital-intensive industry as it obliges high temperature (400–500°C) and also high pressure (150–300 bar) for its daily processes. Two moles of ammonia are obtained by reacting one mole of nitrogen and three moles of hydrogen gases in the existence of conventional catalyst which are magnetite (Fe3O4). The process to produce ammonia is known

  5. Nitride synthesis using ammonia and hydrazine—a thermodynamic panorama

    Microsoft Academic Search

    K. T. Jacob; R. Verma; R. M. Mallya

    2002-01-01

    Because of the wide variety of projected applications of ultrapure nitrides in advanced technologies, there is interest in developing new cost-effective methods of synthesis. Explored in this study is the use of ammonia and hydrazine for the synthesis of nitrides from oxides, sulfides and chlorides. Even when the standard Gibbs energy change for the nitridation reactions involved are moderately positive,

  6. Automatic control system for the process of synthesis of ammonia from coke oven gas

    SciTech Connect

    Minakov, A.S.; Kopytov, V.F.; Medvedev, R.B.; Fedorov, A.V.

    1982-01-01

    A discussion of an automatic control system of an ammonia synthesis unit at a Soviet coking plant is presented. The control scheme required optimization of two factors - maximizing ammonia production and minimizing energy usage. The adjustment of the synthesis column, control of the temperature in the synthesis column reaction zones, and control of the composition of the nitrogen-hydrogen feed mixture were among the operating parameters controlled. The control scheme produced significant savings in operation. (JMT)

  7. Ammonia, oxidation leaching of chalcopyrite —reaction kinetics

    Microsoft Academic Search

    L. W. Beckstead; J. D. Miller

    1977-01-01

    The reaction for the ammonia, oxidation leaching of chalcopyrite, CuFeS2 + 4NH3 + 17\\/4 O2 + 2 OH- ? Cu(NH3)+2\\u000a 42 + l\\/2Fe2O3 + 2 SO4 + H2O was studied using monosize particles in an intensely stirred reactor under moderate pressures to determine the important\\u000a chemical factors which govern the kinetic response of the system. The reaction kinetics were studied

  8. The Sugar Model: Autocatalytic Activity of the Triose-Ammonia Reaction

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    2006-01-01

    Reaction of triose sugars with ammonia under anaerobic conditions yielded autocatalytic products. The autocatalytic behavior of the products was examined by measuring the effect of the crude triose-ammonia reaction product on the kinetics of a second identical triose-ammonia reaction. The reaction product showed autocatalytic activity by increasing both the rate of disappearance of triose and the rate formation of pyruvaldehyde, the product of triose dehydration. This synthetic process is considered a reasonable model of origin-of-life chemistry because it uses plausible prebiotic substrates, and resembles modern biosynthesis by employing the energized carbon groups of sugars to drive the synthesis of autocatalytic molecules.

  9. Prebiotic Amino Acid Thioester Synthesis: Thiol-Dependent Amino Acid Synthesis from Formose Substrates (Formaldehyde and Glycolaldehyde) and Ammonia

    Microsoft Academic Search

    Arthur L. Weber

    1998-01-01

    Formaldehyde and glycolaldehyde (substrates of the formose autocatalytic cycle) were shown to react with ammonia yielding alanine and homoserine under mild aqueous conditions in the presence of thiol catalysts. Since similar reactions carried out without ammonia yielded alpha-hydroxy acid thioesters (Weber, 1984a, b), the thiol-dependent synthesis of alanine and homoserine is presumed to occur via amino acid thioesters - intermediates

  10. Prebiotic Amino Acid Thioester Synthesis: Thiol-Dependent Amino Acid Synthesis from Formose Substrates (Formaldehyde and Glycolaldehyde) and Ammonia

    Microsoft Academic Search

    Arthur L. Weber

    1998-01-01

    Formaldehyde and glycolaldehyde (substrates of the formose autocatalytic cycle) were shown to react with ammonia yielding alanine and homoserine under mild aqueous conditions in the presence of thiol catalysts. Since similar reactions carried out without ammonia yielded a-hydroxy acid thioesters (Weber, 1984a, b), the thiol-dependent synthesis of alanine and homoserine is presumed to occur via amino acid thioesters – intermediates

  11. Prebiotic Amino Acid Thioester Synthesis: Thiol-Dependent Amino Acid Synthesis from Formose substrates (Formaldehyde and Glycolaldehyde) and Ammonia

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1998-01-01

    Formaldehyde and glycolaldehyde (substrates of the formose autocatalytic cycle) were shown to react with ammonia yielding alanine and homoserine under mild aqueous conditions in the presence of thiol catalysts. Since similar reactions carried out without ammonia yielded alpha-hydroxy acid thioesters, the thiol-dependent synthesis of alanine and homoserine is presumed to occur via amino acid thioesters-intermediates capable of forming peptides. A pH 5.2 solution of 20 mM formaldehyde, 20 mM glycolaldehyde, 20 mM ammonium chloride, 23 mM 3-mercaptopropionic acid, and 23 mM acetic acid that reacted for 35 days at 40 C yielded (based on initial formaldehyde) 1.8% alanine and 0.08% homoserine. In the absence of thiol catalyst, the synthesis of alanine and homoserine was negligible. Alanine synthesis required both formaldehyde and glycolaldehyde, but homoserine synthesis required only glycolaldehyde. At 25 days the efficiency of alanine synthesis calculated from the ratio of alanine synthesized to formaldehyde reacted was 2.1%, and the yield (based on initial formaldehyde) of triose and tetrose intermediates involved in alanine and homoserine synthesis was 0.3 and 2.1%, respectively. Alanine synthesis was also seen in similar reactions containing only 10 mM each of aldehyde substrates, ammonia, and thiol. The prebiotic significance of these reactions that use the formose reaction to generate sugar intermediates that are converted to reactive amino acid thioesters is discussed.

  12. Prebiotic Amino Acid Thioester Synthesis: Thiol-Dependent Amino Acid Synthesis from Formose Substrates (Formaldehyde and Glycolaldehyde) and Ammonia

    NASA Astrophysics Data System (ADS)

    Weber, Arthur L.

    1998-06-01

    Formaldehyde and glycolaldehyde (substrates of the formose autocatalytic cycle) were shown to react with ammonia yielding alanine and homoserine under mild aqueous conditions in the presence of thiol catalysts. Since similar reactions carried out without ammonia yielded ?-hydroxy acid thioesters (Weber, 1984a, b), the thiol-dependent synthesis of alanine and homoserine is presumed to occur via amino acid thioesters - intermediates capable of forming peptides (Weber and Orgel 1979). A pH 5.2 solution of 20 mM formaldehyde, 20 mM glycolaldehyde, 20 mM ammonium chloride, 23 mM 3-mercaptopropionic acid, and 23 mM acetic acid that reacted for 35 days at 40°C yielded (based on initial formaldehyde) 1.8% alanine and 0.08% homoserine. In the absence of thiol catalyst, the synthesis of alanine and homoserine was negligible. Alanine synthesis required both formaldehyde and glycolaldehyde, but homoserine synthesis required only glycolaldehyde. At 25 days the efficiency of alanine synthesis calculated from the ratio of alanine synthesized to formaldehyde reacted was 2.1%, and the yield (based on initial formaldehyde) of triose and tetrose intermediates involved in alanine and homoserine synthesis was 0.3 and 2.1%, respectively. Alanine synthesis was also seen in similar reactions containing only 10 mM each of aldehyde substrates, ammonia, and thiol. The prebiotic significance of these reactions that use the formose reaction to generate sugar intermediates that are converted to reactive amino acid thioesters is discussed.

  13. Electrolytic synthesis of ammonia in molten salts under atmospheric pressure.

    PubMed

    Murakami, Tsuyoshi; Nishikiori, Tokujiro; Nohira, Toshiyuki; Ito, Yasuhiko

    2003-01-15

    Ammonia was successfully synthesized by using a new electrochemical reaction with high current efficiency at atmospheric pressure and at lower temperatures than the Haber-Bosch process. In this method, nitride ion (N3-), which is produced by the reduction from nitrogen gas at the cathode, is anodically oxidized and reacts with hydrogen to produce ammonia at the anode. PMID:12517136

  14. Electride support boosts nitrogen dissociation over ruthenium catalyst and shifts the bottleneck in ammonia synthesis

    PubMed Central

    Kitano, Masaaki; Kanbara, Shinji; Inoue, Yasunori; Kuganathan, Navaratnarajah; Sushko, Peter V.; Yokoyama, Toshiharu; Hara, Michikazu; Hosono, Hideo

    2015-01-01

    Novel approaches to efficient ammonia synthesis at an ambient pressure are actively sought out so as to reduce the cost of ammonia production and to allow for compact production facilities. It is accepted that the key is the development of a high-performance catalyst that significantly enhances dissociation of the nitrogen–nitrogen triple bond, which is generally considered a rate-determining step. Here we examine kinetics of nitrogen and hydrogen isotope exchange and hydrogen adsorption/desorption reactions for a recently discovered efficient catalyst for ammonia synthesis—ruthenium-loaded 12CaO·7Al2O3 electride (Ru/C12A7:e?)—and find that the rate controlling step of ammonia synthesis over Ru/C12A7:e? is not dissociation of the nitrogen–nitrogen triple bond but the subsequent formation of N–Hn species. A mechanism of ammonia synthesis involving reversible storage and release of hydrogen atoms on the Ru/C12A7:e? surface is proposed on the basis of observed hydrogen absorption/desorption kinetics. PMID:25816758

  15. Solid-state electrochemical synthesis of ammonia: a review

    Microsoft Academic Search

    Ibrahim A. Amar; Rong Lan; Christophe T. G. Petit; Shanwen Tao

    Ammonia is one of the most produced chemicals worldwide, and it is not only a major end product but also an important energy\\u000a storage intermediate. The solid-state electrochemical synthesis of ammonia has the promise to overcome the limitations of\\u000a the conventional catalytic reactors such as the limited conversion, severe environmental pollution and high energy consumption.\\u000a Solid-state electrolytes either protonic or

  16. Prebiotic amino acid thioester synthesis: thiol-dependent amino acid synthesis from formose substrates (formaldehyde and glycolaldehyde) and ammonia.

    PubMed

    Weber, A L

    1998-06-01

    Formaldehyde and glycolaldehyde (substrates of the formose autocatalytic cycle) were shown to react with ammonia yielding alanine and homoserine under mild aqueous conditions in the presence of thiol catalysts. Since similar reactions carried out without ammonia yielded alpha-hydroxy acid thioesters (Weber, 1984a, b), the thiol-dependent synthesis of alanine and homoserine is presumed to occur via amino acid thioesters--intermediates capable of forming peptides (Weber and Orgel 1979). A pH 5.2 solution of 20 mM formaldehyde, 20 mM glycolaldehyde, 20 mM ammonium chloride, 23 mM 3-mercaptopropionic acid, and 23 mM acetic acid that reacted for 35 days at 40 degrees C yielded (based on initial formaldehyde) 1.8% alanine and 0.08% homoserine. In the absence of thiol catalyst, the synthesis of alanine and homoserine was negligible. Alanine synthesis required both formaldehyde and glycolaldehyde, but homoserine synthesis required only glycolaldehyde. At 25 days the efficiency of alanine synthesis calculated from the ratio of alanine synthesized to formaldehyde reacted was 2.1%, and the yield (based on initial formaldehyde) of triose and tetrose intermediates involved in alanine and homoserine synthesis was 0.3 and 2.1%, respectively. Alanine synthesis was also seen in similar reactions containing only 10 mM each of aldehyde substrates, ammonia, and thiol. The prebiotic significance of these reactions that use the formose reaction to generate sugar intermediates that are converted to reactive amino acid thioesters is discussed. PMID:9611766

  17. Process for synthesis of ammonia borane for bulk hydrogen storage

    SciTech Connect

    Autrey, S Thomas [West Richland, WA; Heldebrant, David J [Richland, WA; Linehan, John C [Richland, WA; Karkamkar, Abhijeet J [Richland, WA; Zheng, Feng [Richland, WA

    2011-03-01

    The present invention discloses new methods for synthesizing ammonia borane (NH.sub.3BH.sub.3, or AB). Ammonium borohydride (NH.sub.4BH.sub.4) is formed from the reaction of borohydride salts and ammonium salts in liquid ammonia. Ammonium borohydride is decomposed in an ether-based solvent that yields AB at a near quantitative yield. The AB product shows promise as a chemical hydrogen storage material for fuel cell powered applications.

  18. Sources and sinks for ammonia and nitrite on the early Earth and the reaction of nitrite with ammonia

    NASA Technical Reports Server (NTRS)

    Summers, D. P.

    1999-01-01

    An analysis of sources and sinks for ammonia and nitrite on the early Earth was conducted. Rates of formation and destruction, and steady state concentrations of both species were determined by steady state kinetics. The importance of the reaction of nitrite with ammonia on the feasibility of ammonia formation from nitrite was evaluated. The analysis considered conditions such as temperature, ferrous iron concentration, and pH. For sinks we considered the reduction of nitrite to ammonia, reaction between nitrite and ammonia, photochemical destruction of both species, and destruction at hydrothermal vents. Under most environmental conditions, the primary sink for nitrite is reduction to ammonia. The reaction between ammonia and nitrite is not an important sink for either nitrite or ammonia. Destruction at hydrothermal vents is important at acidic pH's and at low ferrous iron concentrations. Photochemical destruction, even in a worst case scenario, is unimportant under many conditions except possibly under acidic, low iron concentration, or low temperature conditions. The primary sink for ammonia is photochemical destruction in the atmosphere. Under acidic conditions, more of the ammonia is tied up as ammonium (reducing its vapor pressure and keeping it in solution) and hydrothermal destruction becomes more important.

  19. Vibrational and collisional energy effects in the reaction of ammonia ions with methylamine

    E-print Network

    Zare, Richard N.

    Vibrational and collisional energy effects in the reaction of ammonia ions with methylamine investigated the reactions of vibrationally state-selected ammonia ions with d3-methylamine over the center-of-mass collisional energy range of 0.5 to 10.0 eV and for ammonia ion vibrational states ranging from 2 1­9. Under

  20. Theoretical analysis and experimental results of a 1 kW chem ammonia synthesis reactor for a solar thermochemical energy storage system

    Microsoft Academic Search

    H. Kreetz; K. Lovegrove

    1999-01-01

    A closed-loop solar thermochemical energy storage and transport system using the dissociation and synthesis reactions of ammonia has been investigated at the Australian National University (ANU). Work relating to the optimisation of the heat recovery part of the system is reported. Experimental investigation has shown a 1-kWchem laboratory-scale ammonia synthesis reactor to operate in a stable and repeatable manner. A

  1. The Sugar Model: Autocatalytic Activity of the Triose–Ammonia Reaction

    Microsoft Academic Search

    Arthur L. Weber

    2007-01-01

    Reaction of triose sugars with ammonia under anaerobic conditions yielded autocatalytic products. The autocatalytic behavior\\u000a of the products was examined by measuring the effect of the crude triose–ammonia reaction product on the kinetics of a second\\u000a identical triose–ammonia reaction. The reaction product showed autocatalytic activity by increasing both the rate of disappearance\\u000a of triose and the rate of formation of

  2. Synthesis of nanoscale particles of Ta and Nb3Al by homogeneous reduction in liquid ammonia

    E-print Network

    Sadoway, Donald Robert

    Synthesis of nanoscale particles of Ta and Nb3Al by homogeneous reduction in liquid ammonia Hongmin and electronic). This prediction was confirmed by reacting TaCl5 with sodium, each dissolved in liquid ammoniaCl5 and AlCl3 both dissolved in liquid ammonia. I. INTRODUCTION Reduction in particle size from

  3. CONVERSION OF CATTLE FEEDLOT MANURE TO ETHYLENE AND AMMONIA SYNTHESIS GAS

    EPA Science Inventory

    An investigation was undertaken to scale-up a partial oxidation reactor to evaluate the potential for producing an ammonia synthesis gas from cattle feedlot residue. The synthesis gas from the reactor can be further processed to produce ammonia using existing, commercial technolo...

  4. Ammonia synthesis using a stable electride as an electron donor and reversible hydrogen store.

    PubMed

    Kitano, Masaaki; Inoue, Yasunori; Yamazaki, Youhei; Hayashi, Fumitaka; Kanbara, Shinji; Matsuishi, Satoru; Yokoyama, Toshiharu; Kim, Sung-Wng; Hara, Michikazu; Hosono, Hideo

    2012-11-01

    Industrially, the artificial fixation of atmospheric nitrogen to ammonia is carried out using the Haber-Bosch process, but this process requires high temperatures and pressures, and consumes more than 1% of the world's power production. Therefore the search is on for a more environmentally benign process that occurs under milder conditions. Here, we report that a Ru-loaded electride [Ca(24)Al(28)O(64)](4+)(e(-))(4) (Ru/C12A7:e(-)), which has high electron-donating power and chemical stability, works as an efficient catalyst for ammonia synthesis. Highly efficient ammonia synthesis is achieved with a catalytic activity that is an order of magnitude greater than those of other previously reported Ru-loaded catalysts and with almost half the reaction activation energy. Kinetic analysis with infrared spectroscopy reveals that C12A7:e(-) markedly enhances N(2) dissociation on Ru by the back donation of electrons and that the poisoning of ruthenium surfaces by hydrogen adatoms can be suppressed effectively because of the ability of C12A7:e(-) to store hydrogen reversibly. PMID:23089869

  5. Ammonia synthesis using a stable electride as an electron donor and reversible hydrogen store

    NASA Astrophysics Data System (ADS)

    Kitano, Masaaki; Inoue, Yasunori; Yamazaki, Youhei; Hayashi, Fumitaka; Kanbara, Shinji; Matsuishi, Satoru; Yokoyama, Toshiharu; Kim, Sung-Wng; Hara, Michikazu; Hosono, Hideo

    2012-11-01

    Industrially, the artificial fixation of atmospheric nitrogen to ammonia is carried out using the Haber-Bosch process, but this process requires high temperatures and pressures, and consumes more than 1% of the world's power production. Therefore the search is on for a more environmentally benign process that occurs under milder conditions. Here, we report that a Ru-loaded electride [Ca24Al28O64]4+(e-)4 (Ru/C12A7:e-), which has high electron-donating power and chemical stability, works as an efficient catalyst for ammonia synthesis. Highly efficient ammonia synthesis is achieved with a catalytic activity that is an order of magnitude greater than those of other previously reported Ru-loaded catalysts and with almost half the reaction activation energy. Kinetic analysis with infrared spectroscopy reveals that C12A7:e- markedly enhances N2 dissociation on Ru by the back donation of electrons and that the poisoning of ruthenium surfaces by hydrogen adatoms can be suppressed effectively because of the ability of C12A7:e- to store hydrogen reversibly.

  6. AMMONIA

    EPA Science Inventory

    This document summarizes the available information on ammonia as it relates to its effects on man and his environment. Ammonia is a ubiquitous substance and is known widely as a household cleaning agent and as a fertilizer. It plays an important role in the nitrogen cycle--in the...

  7. Vibrational Mode Effects as a Probe of Inter-channel Coupling in the Reactions of Formaldehyde Cation with Ammonia and Water

    E-print Network

    Anderson, Scott L.

    interactions. Quantum chemistry and Rice- Ramsperger-Kassel-Marcus (RRKM) theory calculations were carried out* Department of Chemistry, 315 S 1400 E, Room 2020, UniVersity of Utah, Salt Lake City, Utah 84112 Recei. Introduction Reactions of H2CO+ with ammonia and water are important in molecular synthesis in interstellar gas

  8. Modeling and simulation of ammonia removal from purge gases of ammonia plants using a catalytic Pd–Ag membrane reactor

    Microsoft Academic Search

    M. R. Rahimpour; A. Asgari

    2008-01-01

    In this work, the removal of ammonia from synthesis purge gas of an ammonia plant has been investigated. Since the ammonia decomposition is thermodynamically limited, a membrane reactor is used for complete decomposition. A double pipe catalytic membrane reactor is used to remove ammonia from purge gas. The purge gas is flowing in the reaction side and is converted to

  9. ECUT energy data reference series: ammonia synthesis energy-use and capital stock information

    SciTech Connect

    Young, J.K.; Johnson, D.R.

    1984-07-01

    Energy requirements for ammonia synthesis totaled 0.55 quadrillion Btu of natural gas in 1980 and 28,500 MMBtu (8.3 x 10/sup 6/ kWh) of electricity. Efficiencies ranged from 0.72 to 0.8 for natural gas and 0.65 for electricity. Ammonia production in 1980 is estimated at 21 million tones. In the year 2000, U.S. ammonia production is estimated to be between 27 to 34 million tones with 19 to 31 million tons being produced using natural gas. A most likely value of 25 million tons of ammonia from natural gas feedstock is projected. As much as 20% of the energy from natural gas fuel could be saved if a more active catalyst could be developed that would reduce the operating pressure of ammonia synthesis to 1 atm.

  10. Liquid composition having ammonia borane and decomposing to form hydrogen and liquid reaction product

    DOEpatents

    Davis, Benjamin L; Rekken, Brian D

    2014-04-01

    Liquid compositions of ammonia borane and a suitably chosen amine borane material were prepared and subjected to conditions suitable for their thermal decomposition in a closed system that resulted in hydrogen and a liquid reaction product.

  11. Exploration of Ionic Liquids as Soluble Supports for Organic Synthesis. Demonstration with a Suzuki Coupling Reaction

    Microsoft Academic Search

    Weishi Miao; Tak Hang Chan

    2003-01-01

    The efficiency of ionic liquid supported synthesis was demonstrated by the Suzuki reaction of ionic liquid supported iodobenzoate compounds with arylboronic acids in aqueous media to give, after cleavage with ammonia\\/methanol, biaryl products in good yields and high purities, without the need for chromatographic purification.

  12. Gas phase proton transfer reaction of nitric acid-ammonia and the role of water

    Microsoft Academic Search

    Fu-Ming Tao

    1998-01-01

    The gas-phase proton transfer reaction of nitric acid-ammonia and the effect of the first three water molecules are investigated by high level ab initio calculations on the molecular clusters HNO3-NH3-(H2O)n, n=0,1,2,3. The equilibrium structures, binding energies, and harmonic frequencies of the clusters as well as the potential energy surfaces along the proton transfer pathway of nitric acid-ammonia are calculated at

  13. Regeneration of ammonia borane spent fuel by direct reaction with hydrazine and liquid ammonia.

    PubMed

    Sutton, Andrew D; Burrell, Anthony K; Dixon, David A; Garner, Edward B; Gordon, John C; Nakagawa, Tessui; Ott, Kevin C; Robinson, J Pierce; Vasiliu, Monica

    2011-03-18

    Ammonia borane (H(3)N-BH(3), AB) is a lightweight material containing a high density of hydrogen (H(2)) that can be readily liberated for use in fuel cell-powered applications. However, in the absence of a straightforward, efficient method for regenerating AB from dehydrogenated polymeric spent fuel, its full potential as a viable H(2) storage material will not be realized. We demonstrate that the spent fuel type derived from the removal of greater than two equivalents of H(2) per molecule of AB (i.e., polyborazylene, PB) can be converted back to AB nearly quantitatively by 24-hour treatment with hydrazine (N(2)H(4)) in liquid ammonia (NH(3)) at 40°C in a sealed pressure vessel. PMID:21415349

  14. Reaction synthesis of heat-resistant materials

    SciTech Connect

    Deevi, S.C.; Sikka, V.K.

    1995-12-31

    Exothermicity associated with the synthesis of aluminides can be utilized to obtain aluminides of transition metals. Combustion synthesis, extrusion, and hot pressing were utilized to obtain dense intermetallics and their composites. Composites were analyzed by X- ray diffraction and microscopy techniques, and tensile properties were measured on button-head and sheet specimens of intermetallics and their composites. Mechanical properties of intermetallics obtained by reaction synthesis and densification compare well with conventionally processed materials. Reaction-synthesis principles were also extended to weld overlays. Possible approaches to obtaining dense products by reaction synthesis and densification are summarized in a schematic illustration. 19 refs., 14 figs., 3 tabs.

  15. Unusual reactions of C 60 with aldehydes in the presence of aqueous ammonia

    Microsoft Academic Search

    Akifumi Komori; Masayuki Kubota; Takayuki Ishida; Haruki Niwa; Takashi Nogami

    1996-01-01

    Fullerene C60 reacts with alkylaldehydes in the presence of aqueous ammonia to give 2,5-dialkyl-substituted pyrrolidine derivatives. The reaction of phenylacetaldehyde under similar conditions afforded C60(H)(CH2Ph) via possible decarbonylation. On the basis of the product analysis, reaction mechanisms are proposed in which C60 plays the role of a dipolarophile or radical scavenger.

  16. Ammonia synthesis. Ammonia synthesis by N? and steam electrolysis in molten hydroxide suspensions of nanoscale Fe?O?.

    PubMed

    Licht, Stuart; Cui, Baochen; Wang, Baohui; Li, Fang-Fang; Lau, Jason; Liu, Shuzhi

    2014-08-01

    The Haber-Bosch process to produce ammonia for fertilizer currently relies on carbon-intensive steam reforming of methane as a hydrogen source. We present an electrochemical pathway in which ammonia is produced by electrolysis of air and steam in a molten hydroxide suspension of nano-Fe2O3. At 200°C in an electrolyte with a molar ratio of 0.5 NaOH/0.5 KOH, ammonia is produced at 1.2 volts (V) under 2 milliamperes per centimeter squared (mA cm(-2)) of applied current at coulombic efficiency of 35% (35% of the applied current results in the six-electron conversion of N2 and water to ammonia, and excess H2 is cogenerated with the ammonia). At 250°C and 25 bar of steam pressure, the electrolysis voltage necessary for 2 mA cm(-2) current density decreased to 1.0 V. PMID:25104378

  17. Photochemical reactions for commercial synthesis

    SciTech Connect

    Guillet, J. E.

    1985-06-25

    Photochemical reactions are conducted using floating polymer beads on the surface of a moving body of water. The polymer bead is impregnated with a reactant, floated on the water in direct sunlight so as to expose the reactant to solar radiation, collected at a downstream location, treated to remove product from the polymer, and then the bead can be recycled. The process can be used to collect and store solar energy in chemical form, or for conducting photochemical synthesis to produce useful chemical products.

  18. [Development of efficient methods for synthesis of nitrogen-containing compounds using carbamates, acylhydrazines, and ammonia].

    PubMed

    Sugiura, Masaharu

    2006-12-01

    For the efficient synthesis of divergent nitrogen-containing compounds of pharmaceutical and agricultural importance, the development of efficient, complementary, and new synthetic methodologies is essential. One of the key subjects is how to introduce nitrogen atoms in to organic molecules. This review summaries our recent efforts on this issue, focusing on the use of carbamates, acylhydrazines, and ammonia as nitrogen sources. PMID:17139157

  19. Synergism of iron and ruthenium in ammonia synthesis catalyst at low temperature

    Microsoft Academic Search

    H. Mahapatra; E. S. Kalyuzhnaya; S. M. Yunusov; V. B. Shur

    1998-01-01

    Synthesis of ammonia from dinitrogen and dihydrogen by the Haber-Bosch process at high temperature and high pressure is energy intensive and capital intensive. Low temperature and low pressure operation calls for a suitable catalyst that can work well at low temperature. Iron is the established catalyst for high temperature where as ruthenium is identified as a potential catalyst for low

  20. SEM-EDAX investigations of use-related microstructural changes in an ammonia synthesis catalyst

    Microsoft Academic Search

    T. Egyházi; J. Scholtz; V. S. Beskov

    1984-01-01

    Changes in the topography and distribution of the chemical constituents in the microspaces of oxide type catalysts and prereduced catalysts have been investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDAX) before and after six years of use in industrial ammonia synthesis reactors.

  1. The Inversion Potential of Ammonia: An Intrinsic Reaction Coordinate Calculation for Student Investigation

    ERIC Educational Resources Information Center

    Halpern, Arthur M.; Ramachandran, B. R.; Glendening, Eric D.

    2007-01-01

    A report is presented to describe how students can be empowered to construct the full, double minimum inversion potential for ammonia by performing intrinsic reaction coordinate calculations. This work can be associated with the third year physical chemistry lecture laboratory or an upper level course in computational chemistry.

  2. Photochemical synthesis of organic compounds on Jupiter initiated by the photolysis of ammonia

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Nakagawa, C.; Chen, C. T.

    1977-01-01

    The photolysis of ammonia in the presence of certain concentrations of hydrogen, helium, and methane was studied at ambient temperatures and at 115 K. The ratio of reacting methane to photolyzed ammonia varies with concentrations and temperature. Reaction products include almost equal amounts of HCN, ethane, and propane accompanied by lesser amounts of hydrazine, n-butane, n-butane isomers, and pentane isomers. Free radical pathways participating in the reactions are discussed. The components of the starting mixture were chosen because they are believed to be present in the upper atmosphere of Jupiter, and the results are examined with reference to the Jovian atmosphere.

  3. AMINO ACID SYNTHESIS IN PHOTO-SYNTHESIZING SPINACH CELLS. EFFECTS OF AMMONIA ON POOL SIZES AND RATES OF LABELING FROM {sup 14}CO{sub 2}

    SciTech Connect

    Larsen, Peder Olesen; Cornwell, Karen L.; Gee, Sherry L.; Bassham, James A.

    1980-10-01

    Isolated cells from leaves of Spinacea oleracea have been maintained in a state capable of high rates of photosynthetic CO{sub 2} fixation for more than 60 h. The incorporation of {sup 14}CO{sub 2} under saturating CO{sub 2} conditions into carbohydrates, carboxylic acids, and amino acids, and the effect of ammonia on this incorporation have been studied. Total incorporation, specific radioactivity and pool size have been determined as a function of time for most of the protein amino acids and for {gamma}-aminobutyric acid. the measurements of specific activities and of the approaches to {sup 14}C "saturation" of some amino acids indicate the presence and relative sizes of metabolically active and passive pools of these amino acids. Added ammonia decreased carbon fixation into carbohydrates and increased fixation into carboxylic acids and amino acids. Different amino acids were, however, affected in different and highly specific ways. Ammonia caused large stimulatory effects in incorporation of {sup 14}C into glutamine (a factor of 16), No effect or slight decreases were seen in glycine, serine, phenylalanine, and tyrosine labeling, In.the case of glutamate, {sup 14}C-labeling decreased, but specific activity increased. The production of labeled {gamma}-aminobutyric acid was virtually stopped by ammonia. The results indicate that added ammonia stimulates the reactions mediated by pyruvate kinase and phosphoenolpyruvate carboxylase, as seen with other plant systems. The data on the effects of added ammonia on total labeling, pool sizes, and specific activities of several amino acids provides a number of indications about the intracellular sites of principal synthesis from carbon skeletons of these amino acids and the selective nature of effects of increased intracellular ammonia concentration on such synthesis.

  4. Effect of Ammonia Reaction Time on the Calytic Poperties of Sputtered Iron-Based Electrocatalyst

    NASA Astrophysics Data System (ADS)

    Lee, Ki-Seong; Lee, Minku; Hong, Tae-Whan; Ju, HyunChul; Kim, Whangi; Kim, Dongmin

    2013-10-01

    Fe-based electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs) were produced using a sputter deposition process involving a carbon paper (CP) and a NH3 heat treatment environment. The Fe-N-CP sample reacted with ammonia for 10 min at 950 °C displayed a greater current density than the samples reacted with ammonia for other reaction times. The impedance of the samples treated for 10 min with ammonia shows the highest value, which means much higher ligand formation and lower electric conductivity, which are consistent with the results of cyclic voltammetry (CV). This is directly due to the formation of ligands between the Fe and CP used when exposed to a nitrogen environment. While the current density of the Fe-based electrocatalysts under review did not exceed that of standard Pt/C electrocatalysts, the results herein suggest that nonprecious metal electrodes may be a viable alternative in PEMFCs.

  5. Gas phase proton transfer reaction of nitric acid-ammonia and the role of water

    NASA Astrophysics Data System (ADS)

    Tao, Fu-Ming

    1998-01-01

    The gas-phase proton transfer reaction of nitric acid-ammonia and the effect of the first three water molecules are investigated by high level ab initio calculations on the molecular clusters HNO3-NH3-(H2O)n, n=0,1,2,3. The equilibrium structures, binding energies, and harmonic frequencies of the clusters as well as the potential energy surfaces along the proton transfer pathway of nitric acid-ammonia are calculated at the second-order Møller-Plesset perturbation (MP2) level with two extended basis sets 6-31+G(d) and 6-311++G(d,p). It is found that, either without water or with one water molecule, the nitric acid-ammonia system exists as hydrogen bonded, with nitric acid acting as the hydrogen bond donor and ammonia as the acceptor. With two or three water molecules, the system becomes an ion pair resulting from the complete transfer of a proton from the nitric acid to ammonia. The potential energy surfaces along the proton transfer pathway are analyzed to understand the effect of the water molecules. The water molecules stepwise added into the system are found to increase the stability of the ion pair over the hydrogen bonded form. The first water molecule is not enough to stabilize the ion pair, but it results in a flatter potential energy pathway for the proton transfer. The second water molecule produces additional stabilization energy which helps fully stabilize the ion pair. The third water molecule contributes to further stabilize the ion pair. The harmonic frequencies and infrared intensities of the clusters are analyzed, which provide further evidence in agreement with the transition from the hydrogen bond to the ion pair structure as the water molecules are stepwise introduced. On the basis of these results, we conclude that ammonium nitrate might be formed by the gas phase reaction of nitric acid with ammonia in the presence of adequate water vapor.

  6. GaN CVD Reactions: Hydrogen and Ammonia Decomposition and the Desorption of Gallium

    SciTech Connect

    Bartram, Michael E.; Creighton, J. Randall

    1999-05-26

    Isotopic labeling experiments have revealed correlations between hydrogen reactions, Ga desorption, and ammonia decomposition in GaN CVD. Low energy electron diffraction (LEED) and temperature programmed desorption (TPD) were used to demonstrate that hydrogen atoms are available on the surface for reaction after exposing GaN(0001) to deuterium at elevated temperatures. Hydrogen reactions also lowered the temperature for Ga desorption significantly. Ammonia did not decompose on the surface before hydrogen exposure. However, after hydrogen reactions altered the surface, N15H3 did undergo both reversible and irreversible decomposition. This also resulted in the desorption of N2 of mixed isotopes below the onset of GaN sublimation, This suggests that the driving force of the high nitrogen-nitrogen bond strength (226 kcal/mol) can lead to the removal of nitrogen from the substrate when the surface is nitrogen rich. Overall, these findings indicate that hydrogen can influence G-aN CVD significantly, being a common factor in the reactivity of the surface, the desorption of Ga, and the decomposition of ammonia.

  7. Engineering methylaspartate ammonia lyase for the asymmetric synthesis of unnatural amino acids

    NASA Astrophysics Data System (ADS)

    Raj, Hans; Szyma?ski, Wiktor; de Villiers, Jandré; Rozeboom, Henriëtte J.; Veetil, Vinod Puthan; Reis, Carlos R.; de Villiers, Marianne; Dekker, Frank J.; de Wildeman, Stefaan; Quax, Wim J.; Thunnissen, Andy-Mark W. H.; Feringa, Ben L.; Janssen, Dick B.; Poelarends, Gerrit J.

    2012-06-01

    The redesign of enzymes to produce catalysts for a predefined transformation remains a major challenge in protein engineering. Here, we describe the structure-based engineering of methylaspartate ammonia lyase (which in nature catalyses the conversion of 3-methylaspartate to ammonia and 2-methylfumarate) to accept a variety of substituted amines and fumarates and catalyse the asymmetric synthesis of aspartic acid derivatives. We obtained two single-active-site mutants, one exhibiting a wide nucleophile scope including structurally diverse linear and cyclic alkylamines and one with broad electrophile scope including fumarate derivatives with alkyl, aryl, alkoxy, aryloxy, alkylthio and arylthio substituents at the C2 position. Both mutants have an enlarged active site that accommodates the new substrates while retaining the high stereo- and regioselectivity of the wild-type enzyme. As an example, we demonstrate a highly enantio- and diastereoselective synthesis of threo-3-benzyloxyaspartate (an important inhibitor of neuronal excitatory glutamate transporters in the brain).

  8. Multicomponent Reactions in Total Synthesis Kevin Allan

    E-print Network

    Stoltz, Brian M.

    · Ugi Reaction · Cycloadditions · Povarov Reaction · Knoevenagel / Hetero-Diels-Alder Cycloaddition · 1-VCH; Weinheim, 2005. Orru, R. V. A.; de Greef, M. Synthesis 2003, 10, 1471-1499. Ugi, I. Pure Appl. Chem. 2001, 73, 187-191. Bienaymé, H.; Hulme, C.; Oddon, G.; Schmitt, P. Chem. Eur. J. 2000, 6, 3321-3329. Ugi, I

  9. Reaction of state-selected ammonia ions with methane Michael A. Everest, John C. Poutsma, Jonathan E. Flad, and Richard N. Zarea)

    E-print Network

    Zare, Richard N.

    Reaction of state-selected ammonia ions with methane Michael A. Everest, John C. Poutsma, Jonathan 94305 Received 19 April 1999; accepted 18 May 1999 We have investigated the reaction of ammonia ions with methane molecules (CD4) over the collision energy range of 0.5­10.0 eV and for ammonia ion vibrational

  10. Reaction dynamics of synthesis of superheavy elements

    Microsoft Academic Search

    Y. Abe

    2002-01-01

    :   Based on the theory of the compound nucleus reaction, a brief review is given on the special aspects of the reaction dynamics\\u000a in the synthesis of the superheavy elements (SHE), where the fusion probability is the most unknown factor. A new viewpoint\\u000a of the fusion reaction is proposed that it consists of two processes; the first process up to

  11. Electrochemical ammonia synthesis from steam and nitrogen using proton conducting yttrium doped barium zirconate electrolyte with silver, platinum, and lanthanum strontium cobalt ferrite electrocatalyst

    NASA Astrophysics Data System (ADS)

    Yun, Dae Sik; Joo, Jong Hoon; Yu, Ji Haeng; Yoon, Hyung Chul; Kim, Jong-Nam; Yoo, Chung-Yul

    2015-06-01

    Electrochemical ammonia synthesis from steam and nitrogen has been systematically investigated using a proton-conducting electrolyte supported cell based on 20 mol% yttrium doped barium zirconate (BaZr0.8Y0.2O3-?) in a temperature range of 475-600 °C at atmospheric pressure. Silver (Ag), platinum (Pt), and lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3-?) are used for both anode and cathode electrocatalysts. Maximum ammonia formation rates of 4.9 × 10-11 mol cm-2 s-1 and 8.5 × 10-11 mol cm-2 s-1 are observed for Ag and La0.6Sr0.4Co0.2Fe0.8O3-? electrocatalysts, respectively, when a voltage of 0.8 V is applied. However, Pt electrocatalyst shows a negligible ammonia formation rate lower than 1 × 10-12 mol cm-2 s-1. This is ascribed to the high activity of Pt for the hydrogen evolution reaction rather than the ammonia formation reaction. The conversion efficiency of all electrocatalysts is below 1%, primarily due to the limited nitrogen disassociation activity of the electrocatalysts.

  12. Process for the liquefaction of solid carbonaceous materials wherein nitrogen is separated from hydrogen via ammonia synthesis

    DOEpatents

    Stetka, Steven S. (Fleetwood, PA); Nazario, Francisco N. (Parsippany, NJ)

    1982-01-01

    In a process for the liquefaction of solid carbonaceous materials wherein bottoms residues are upgraded with a process wherein air is employed, the improvement wherein nitrogen buildup in the system is avoided by ammonia synthesis. In a preferred embodiment hydrogen from other portions of the liquefaction process will be combined with hydrogen produced as a result of the bottoms upgrading to increase the H.sub.2 :N.sub.2 ratio in the ammonia reactor.

  13. Pericyclic reactions in organic synthesis

    E-print Network

    Robinson-Surry, Julia M. (Julia Mae)

    2011-01-01

    Part I of this thesis describes a formal, metal-free, [2 + 2 + 2] cycloaddition strategy based on a cascade of two pericyclic processes. An intramolecular propargylic ene reaction of a 1,6-diyne is used to generate a ...

  14. Polyurethane synthesis reactions in asphalts

    SciTech Connect

    Bukowski, A.; Gretkiewicz, J.

    1982-04-01

    A series of asphalt-polyurethane composites was prepared by means of polyurethane synthesis in asphalt and carried out in melt. The applied materials were asphalts of differentiated group components content, polyester polyols of chain structure from linear to strongly branched, 2,4-tolylene diisocyanate, 4,4-methylenebis(phenyl isocyanate), and tinorganic catalyst. The asphalt components react with isocyanates to a minimal degree. The influence of the applied substrates, temperature, and polyurethane content in the system on the basic kinetic relations characterizing the process is presented. Polyurethane synthesis in asphalts does not differ in a fundamental way from the obtaining of polyurethanes, especially when their content in the composition is significant, 20 wt% and more.

  15. Ammonia from Iron(II) Reduction of Nitrite and the Strecker Synthesis: Do Iron(II) and Cyanide Interfere with Each Other?

    NASA Technical Reports Server (NTRS)

    Summers, David P.; Lerner, Narcinda; Chang, Sherwood (Technical Monitor)

    1996-01-01

    The question of whether the production of ammonia, from the reduction of nitrite by iron(II), is compatible with its use in the Strecker synthesis of amino acids, or whether the iron and the cyanide needed for the Strecker synthesis interfere with each other, is addressed. Results show that the presence of iron(II) appears to have little, or no, affect on the Strecker synthesis. The presence of cyanide does interfere with reduction of nitrite, but the reduction proceeds at cyanide/iron ratios of less than 4:1. At ratios of about 2:1 and less there is only a small effect. The two reactions can be combined to proceed in each other's presence, forming glycine from nitrite, Fe(+2), formaldehyde, and cyanide.

  16. Vibrational and Translational Energy Effects in the Reaction of Ammonia Ions with Water Michael A. Everest, John C. Poutsma, and Richard N. Zare*

    E-print Network

    Zare, Richard N.

    Vibrational and Translational Energy Effects in the Reaction of Ammonia Ions with Water Molecules of vibrationally state-selected ammonia ions with deuterated water is investigated with a quadrupole energies from 0.5 to 10.0 eV (center of mass) and ammonia ion vibrational states 1020-10 and 1122

  17. Vibrationally state-selected reactions of ammonia ions. II. NHt(v)+CH4 William E. Conaway, Takayuki Ebata,8) and Richard N. Zare

    E-print Network

    Zare, Richard N.

    Vibrationally state-selected reactions of ammonia ions. II. NHt(v)+CH4 William E. Conaway, Takayuki (Received 31 March 1987; accepted 18 May 1987) The effects of vibrational excitation of the ammonia v2 level of the ion. Added vibration in the ammonia ion umbrella-bending mode facilitates the transition

  18. Photochemical reactions for commercial synthesis

    Microsoft Academic Search

    Guillet

    1985-01-01

    Photochemical reactions are conducted using floating polymer beads on the surface of a moving body of water. The polymer bead is impregnated with a reactant, floated on the water in direct sunlight so as to expose the reactant to solar radiation, collected at a downstream location, treated to remove product from the polymer, and then the bead can be recycled.

  19. Removal of boron from wastewater by the hydroxyapatite formation reaction using acceleration effect of ammonia.

    PubMed

    Yoshikawa, Eishi; Sasaki, Atsushi; Endo, Masatoshi

    2012-10-30

    The mechanism was discussed for the removal of boron by the hydroxyapatite (HAp) formation reaction using Ca(OH)(2) and (NH(4))(2)HPO(4) in room temperature. Time required to remove boron was 20 min by adding Ca(OH)(2) and (NH(4))(2)HPO(4) for the remaining boron to below 1mg/L. The removal rate of boron was controlled by the HAp precipitate formation and the presence of ammonia. From the XRD patterns and SEM images, HAp could be confirmed in the precipitate product. The reaction between borate ions and calcium hydroxide was accelerated by dehydration with ammonia; the borate-calcium hydroxide compound coprecipitated with resulting HAp. Although the removal of boron decreased in the presence of sulfate, phosphate, and aluminum, these effects could be prevented by adding excess Ca(OH)(2). Interference of fluoride ions was eliminated by adding Al(3+). Sodium alpha-olefin sulfonate was the most effective coagulant for HAp precipitation. The proposed boron removal method has several advantages about treating time and ability of boron removal. The method was successfully applied to the real hot spring wastewater. PMID:22981286

  20. A theoretical study of the dynamics of the reaction of P+ with ammonia

    NASA Astrophysics Data System (ADS)

    Flores, J. R.; Redondo, P.

    The dynamics of the reaction of P+ with ammonia has been studied by means of an approximate classical trajectory method and statistical theory using ab initio potential surfaces computed at relatively high levels of theory, including Gaussian 2 and QCISD(T) in combination with relatively large basis sets such as D95+ + (3df,2p), cc-pVDZ and cc-VTZ. The trajectory computations for the capture step include the Landau-Zener model for dealing with the electron transfer process, allow for the coupling of the orbital angular momenta of the collision with the rotation of the reactants, and use what is thought to be a suitable representation of both long and short range potentials. The observed rate coefficient is reproduced by the most complete capture model employed as well as the branching ratio between the two channels giving respectively PNH+ + H and P+ NH+ . We also predict that this branching ratio should be essentially constant with varying temperature, making the reaction of P+ with ammonia a likely first step for the production of small molecules containing P-N bonds in interstellar clouds. 2 3

  1. Synthesis of nanosilver on polyamide fabric using silver/ammonia complex.

    PubMed

    Montazer, Majid; Shamei, Ali; Alimohammadi, Farbod

    2014-05-01

    In this paper, a novel synthesis method for nanosilver has been introduced on or within the polymeric chains of polyamide 6 fabric by using silver/ammonia complex [Ag(NH3)2](+). The silver complex was reduced directly by functional groups of polyamide chains without using any additional chemical reducing agents. The polyamide fabric was also stabilized with formation of new linkages between the polymeric chains of the nylon fabric through silver nanoparticle synthesis. The presence of nanosilver on the fabric was confirmed by UV-vis spectra, EDX patterns and XRD patterns. In addition, X-ray photoelectron spectroscopy (XPS) was utilized to identify the chemical state of silver in a range of silver oxide and silver metal. The SEM images confirmed the presence of nanosilver on the polyamide within the size of 20 and 150 nm. Excellent antibacterial properties were achieved with the treated fabrics against Staphylococcus aureus and Escherichia coli. Further, the antibacterial properties of the polyamide fabric treated with 35 mg/L silver/ammonia were durable against washing as they only decreased to 98.6% after 20 washes. In addition, some other properties of the treated fabrics including color changes, dimensional stability, water droplet adsorption, and reflectance spectrum are reported and thoroughly discussed. PMID:24656365

  2. Novel Haloperoxidase Reaction: Synthesis of Dihalogenated Products

    PubMed Central

    Geigert, John; Neidleman, Saul L.; Dalietos, Demetrios J.; DeWitt, Susanne K.

    1983-01-01

    The enzymatic synthesis of vicinal, dihalogenated products from alkenes and alkynes is described. The enzymatic reaction required an alkene or alkyne, dilute hydrogen peroxide, a haloperoxidase, and molar amounts of halide ions. Vicinal dichloro, dibromo, and diiodo products could be formed. A hydroxyl group on the carbon adjacent to the carbon-carbon double or triple bond lowered the halide ion concentration needed to produce the dihalo product. This reaction offers one explanation for the origin of natural, vicinal, dihalogenated products, such as those found frequently in marine microogranisms. PMID:16346293

  3. Sol synthesis from zirconyl chloride octahydrate in NTA-ammonia solution

    NASA Astrophysics Data System (ADS)

    Wang, Maw-Ling; Liu, Biing-Lang; Shih, Zong-Whie

    1998-01-01

    This work first synthesized sol of the precursor of zirconium oxide by reacting zirconyl chloride octahydrate (ZrOCl 2 · 8H 2O) with nitrilotriacetic acid (NTA) in ammonia solution. NTA (R(COO -) n), acts as the complex compound, reacts with ammonium hydroxide to produce an ionized complex agent R(COO -) n. Reaction of ZrOCl 2 · 8H 2O and R(COO -) n was achieved through sequential hydrolysis and condensation, i.e., tetramer product ([Zr 4(OH) 8(OH 2) 16] 8+) was produced via hydrolysis and a large complex molecule ([Zr 4(OH) 8 - n(OH 2) 16(-OOC) nR] 8+ or [Zr 4(OH) 8(OH 2) 16 - n(OOC-) nR] 8+) was generated via condensation. In addition, the effects of the reaction conditions including the temperature, the molar concentration of ZrOCl 2 · 8H 2O, the amount of ammonia and the agitation speed on the average size of sol particle and the viscosity of the sol were investigated. Rational reaction mechanism, accounting for the formation, growth of the particles, and the viscosity of the sol, was also proposed to satisfactorily account for the experimental results.

  4. Structure and reactivity of Ru nanoparticles supported on modified graphite surfaces: a study of the model catalysts for ammonia synthesis.

    PubMed

    Song, Zhen; Cai, Tanhong; Hanson, Jonathan C; Rodriguez, Jose A; Hrbek, Jan

    2004-07-14

    Supported ruthenium metal catalysts have higher activity than traditional iron-based catalysts used industrially for ammonia synthesis. A study of a model Ru/C catalyst was carried out to advance the understanding of structure and reactivity correlations in this structure-sensitive reaction where dinitrogen dissociation is the rate-limiting step. Ru particles were grown by chemical vapor deposition (CVD) via a Ru(3)(CO)(12) precursor on a highly oriented pyrolytic graphite (HOPG) surface modified with one-atomic-layer-deep holes mimicking activated carbon support. Scanning tunneling microscopy (STM) has been used to investigate the growth, structure, and morphology of the Ru particles. Thermal desorption of dissociatively adsorbed nitrogen has been used to evaluate the reactivity of the Ru/HOPG model catalysts. Two different Ru particle structures with different reactivities to N(2) dissociation have been identified. The initial sticking coefficient for N(2) dissociative adsorption on the Ru/HOPG model catalysts is approximately 10(-6), 4 orders larger compared to that of Ru single-crystal surfaces. PMID:15238017

  5. Fundamental study of ammonia-sulfur dioxide reactions to form solid particles. Final report

    SciTech Connect

    Biswas, P.; Bai, H. [Cincinnati Univ., OH (United States). Dept. of Civil and Environmental Engineering

    1994-01-18

    The effects of reaction residence time, presence of inert particles and moisture content on the SO{sub 2} removal and the product particle size distributions have been determined. Results indicated that both gas phase and particle phase reach equilibria in a very short time. The presence of inert particles increases the SO{sub 2} removal efficiency slightly, with a greater increase in removal efficiency at higher surface areas. Moisture content is the most important parameter affecting SO{sub 2} removal. Increasing the moisture content from 1.6% to 6.4% by volume results in a 30% increase of the SO{sub 2} removal at a reaction temperature of 51{degree}C. The products at near anhydrous conditions were concluded to be NH{sub 3}SO{sub 2}, (NH{sub 3}){sub 2}SO{sub 2} and (NH{sub 4}){sub 2}S{sub 2}O{sub 5}. While the products at humid conditions could be either the 1:1 sulfites, NH{sub 4}HSO{sub 3} and (NH{sub 4}){sub 2}S{sub 2}O{sub 5}, or the 2:1 sulfites, (NH{sub 4}){sub 2}SO{sub 3} and (NH{sub 4}){sub 2}SO{sub 3} {minus}H{sub 2}O, or a mixture of the 1:1 and 2:1 sulfite. Those sulfite particles could subsequently oxidize to form the more stable sulfate particles. A gas-to-particle formation model has been developed to simulate the NH{sub 3}-SO{sub 2} system in the presence and absence of seed aerosols at trace water conditions. This model accounts for simultaneous nucleation, coagulation, condensation and chemical reaction. The applicability of utilizing ammonia injection to a flue gas system has been discussed in terms of two possible removal schemes. One utilizes ammonia injection alone and the other is in conjunction with the injection of Ca(OH){sub 2} slurry in a spray dryer system. Both schemes have the potential of achieving over 90% SO{sub 2} removal from power plants burning high-sulfur coals.

  6. Novel System for the Synthesis of Nitriles from Aldehydes Using Aqueous Ammonia and [Bis(Trifluoroacetoxy)iodo]benzene

    Microsoft Academic Search

    Vikas N. Telvekar; Rajesh A. Rane; Tejal V. Namjoshi

    2010-01-01

    A simple and mild method for the conversion of varieties of aldehydes to the corresponding nitriles using aqueous ammonia and trivalent hypervalent iodine reagent, [bis(trifluoroacetoxy)iodo]benzene, at room temperature is discussed. Advantages of this system are short reaction time, easy workup, and moderate to good yields.

  7. Injected mRNA does not increase protein synthesis in unfertilized, fertilized, or ammonia-activated sea urchin eggs.

    PubMed

    Colin, A M; Hille, M B

    1986-05-01

    We have investigated whether the rate of protein synthesis in unfertilized and fertilization-activated sea urchin eggs is limited by the availability of mRNA by injecting eggs, zygotes, and ammonia-activated eggs with globin mRNA. Message-injected and buffer-injected cells were labeled with radioactive amino acids and the proteins separated on a polyacrylamide gel. The relative amounts of newly synthesized globin and endogenous proteins were obtained by scanning the gel fluorograph. Globin mRNA is translated poorly in Strongylocentrotus droebachiensis eggs and does not significantly increase or decrease endogenous protein synthesis. In zygotes and ammonia-activated eggs, however, globin mRNA is translated well and appears to compete with endogenous mRNAs for the limiting component of the translational machinery as it is released. Our results are consistent with the hypothesis that either ribosomes or recruitment factors are gradually activated after fertilization or ammonia treatment, that such components are the rate-limiting factor, and that they impart the typical sigmoidal increase in protein synthesis rate observed in fertilized eggs before the first cleavage. PMID:3699245

  8. Superheavy Elements -- Synthesis, Structure and Reaction Mechanism

    SciTech Connect

    Ackermann, Dieter [Gesellschaft fuer Schwerionenforschung GSI, D-64846 Darmstadt (Germany)

    2006-08-14

    The exciting results search for superheavy elements which have been achieved in the recent years have triggered a broad range of activities. Apart from experiments to attempt the synthesis of new elements, nuclear structure investigations in the transactinide region has become possibly for Z up to 108 or 110. Heavy element chemistry has successfully placed Hs in the periodic table and is no attacking element 112. The development of accelerators and experimental methods promises advances to enable the extension of these investigations in regions closer to the ''island of stability''. Mass measurements using ion traps and neutron rich unstable beam species for the systematic investigation of nuclear structure and reaction mechanisms for heavy neutron rich system are believed to complete the variety of tools in future.

  9. Vibrationally state-selected reactions of ammonia ions. I. NH3+ (v) + O2 Richard J. S. Morrison,a) William E. Conaway, Takayuki Ebata, and Richard N. Zare

    E-print Network

    Zare, Richard N.

    Vibrationally state-selected reactions of ammonia ions. I. NH3+ (v) + O2 Richard J. S. Morrison multiphoton ionization has been applied to the production ofvibrationally state-selected ion beams. Ammonia, vibrationally state- selected ions for reaction dynamics studies. Ammonia is an ideal candidate for state

  10. Synthesis and application of graphene–silver nanowires composite for ammonia gas sensing

    NASA Astrophysics Data System (ADS)

    Tran, Quang Trung; Hoa Huynh, Tran My; Tong, Duc Tai; Tam Tran, Van; Dinh Nguyen, Nang

    2013-12-01

    Graphene, consisting of a single carbon layer in a two-dimensional (2D) lattice, has been a promising material for application to nanoelectrical devices in recent years. In this study we report the development of a useful ammonia (NH3) gas sensor based on graphene–silver nanowires ‘composite’ with planar electrode structure. The basic strategy involves three steps: (i) preparation of graphene oxide (GO) by modified Hummers method; (ii) synthesis of silver nanowires by polyol method; and (iii) preparation of graphene and silver nanowires on two electrodes using spin and spray-coating of precursor solutions, respectively. Exposure of this sensor to NH3 induces a reversible resistance change at room temperature that is as large as ?R/R0 ˜ 28% and this sensitivity is eight times larger than the sensitivity of the ‘intrinsic’ graphene based NH3 gas sensor (?R/R0 ˜ 3,5%). Their responses and the recovery times go down to ˜200 and ˜60 s, respectively. Because graphene synthesized by chemical methods has many defects and small sheets, it cannot be perfectly used for gas sensor or for nanoelectrical devices. The silver nanowires are applied to play the role of small bridges connecting many graphene islands together to improve electrical properties of graphene/silver nanowires composite and result in higher NH3 gas sensitivity.

  11. Regiocontrol in an intramolecular Schmidt reaction: total synthesis of (+)-aspidospermidine.

    PubMed

    Iyengar, R; Schildknegt, K; Aubé, J

    2000-06-01

    [reaction--see text] A total synthesis of (+)-aspidospermidine (1) is described, featuring an intramolecular Schmidt reaction as the key step. The effects of stereochemistry and protecting group status on the regio- and chemoselectivity of this reaction were examined. PMID:10841495

  12. The Art of Total Synthesis Through Cascade Reactions

    PubMed Central

    Chen, Jason S.

    2009-01-01

    The growing importance of cascade reactions reflects and imparts advances in the state of the art of organic synthesis and underscores the desire of synthetic chemists to achieve higher levels of elegance and efficiency. Besides their aesthetic appeal, cascade processes offer economical and environmentally friendly means for generating molecular complexity. Because of their many advantages, these reactions have found numerous applications in the synthesis of complex molecules, both natural and designed. In this Tutorial Review, we highlight the design and execution of cascade reactions within the context of total synthesis as demonstrated with selected examples from these laboratories. PMID:19847336

  13. The Role of Glutamine Synthetase and Glutamate Dehydrogenase in Cerebral Ammonia Homeostasis

    PubMed Central

    Cooper, Arthur J. L.

    2012-01-01

    In the brain, glutamine synthetase (GS), which is located predominantly in astrocytes, is largely responsible for the removal of both blood-derived and metabolically generated ammonia. Thus, studies with [13N]ammonia have shown that about 25% of blood-derived ammonia is removed in a single pass through the rat brain and that this ammonia is incorporated primarily into glutamine (amide) in astrocytes. Major pathways for cerebral ammonia generation include the glutaminase reaction and the glutamate dehydrogenase (GDH) reaction. The equilibrium position of the GDH-catalyzed reaction in vitro favors reductive amination of ?-ketoglutarate at pH 7.4. Nevertheless, only a small amount of label derived from [13N]ammonia in rat brain is incorporated into glutamate and the ?-amine of glutamine in vivo. Most likely the cerebral GDH reaction is drawn normally in the direction of glutamate oxidation (ammonia production) by rapid removal of ammonia as glutamine. Linkage of glutamate/?-ketoglutarate-utilizing aminotransferases with the GDH reaction channels excess amino acid nitrogen toward ammonia for glutamine synthesis. At high ammonia levels and/or when GS is inhibited the GDH reaction coupled with glutamate/?-ketoglutarate-linked aminotransferases may, however, promote the flow of ammonia nitrogen toward synthesis of amino acids. Preliminary evidence suggests an important role for the purine nucleotide cycle (PNC) as an additional source of ammonia in neurons (Net reaction: L-Aspartate + GTP + H2O ? Fumarate + GDP + Pi + NH3) and in the beat cycle of ependyma cilia. The link of the PNC to aminotransferases and GDH/GS and its role in cerebral nitrogen metabolism under both normal and pathological (e.g. hyperammonemic encephalopathy) conditions should be a productive area for future research. PMID:22618691

  14. GREEN CHEMICAL SYNTHESIS THROUGH CATALYSIS AND ALTERNATE REACTION CONDITIONS

    EPA Science Inventory

    Green chemical synthesis through catalysis and alternate reaction conditions Encompassing green chemistry techniques and methodologies, we have initiated several projects at the National Risk Management Research laboratory that focus on the design and development of chemic...

  15. Action-Reaction Learning: Analysis and Synthesis of Human

    E-print Network

    Jebara, Tony

    Action-Reaction Learning: Analysis and Synthesis of Human Behaviour by Tony Jebara B Massachusetts Institute of Technology, 1998 All Rights Reserved Signature of Author Program in Media Arts: Analysis and Synthesis of Human Behaviour by Tony Jebara Submitted to the Program in Media Arts

  16. Extended sugar synthesis from a gas phase formose reaction

    Microsoft Academic Search

    Abraham F. Jalbout; Leif Abrell; Ludwik Adamowicz; Robin Polt; L. M. Ziurys

    2007-01-01

    The prebiotic possibilities for the synthesis of interstellar ribose through a protic variant of the formose reaction under gas phase conditions were studied with the use of a proton source as a known catalyst. Mass spectrometry was sought as a method to probe the synthesis of higher order sugars. Ab initio calculations were used to evaluate protic formose mechanism possibilities

  17. Reactions of synthesis of heavy nuclei: Brief summary and outlook

    SciTech Connect

    Oganessian, Yu. Ts. [Joint Institute for Nuclear Research (Russian Federation)], E-mail: luda.rom@jinr.ru

    2006-06-15

    The possible reactions of synthesis of extremely heavy nuclei with almost closed proton and neutron shells are analyzed on the basis of current experimental and theoretical data on the properties of the isotopes of superheavy elements. It has been shown that advances in obtaining extremely heavy nuclei for which microscopic models predict an increase in stability require further investigations of the mechanism of synthesis reactions. Direct and model experiments aimed at solving this problem are discussed.

  18. Increased urea synthesis and\\/or suppressed ammonia production in the African lungfish, Protopterus annectens , during aestivation in air or mud

    Microsoft Academic Search

    Ai M. Loong; Cheryl Y. M. Pang; Kum C. Hiong; Wai P. Wong; Shit F. Chew; Yuen K. Ip

    2008-01-01

    The objective of this study was to elucidate how the African lungfish, Protopterus annectens, ameliorated ammonia toxicity during 12 or 46 days of aestivation in air or in mud. Twelve days of aestivation in air led\\u000a to significant increases in contents of urea, but not ammonia, in tissues of P. annectens. The estimated rate of urea synthesis increased 2.7-fold despite the

  19. Experimental investigation of aminoacetonitrile formation through the Strecker synthesis in astrophysical-like conditions: reactivity of methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN)

    NASA Astrophysics Data System (ADS)

    Danger, G.; Borget, F.; Chomat, M.; Duvernay, F.; Theulé, P.; Guillemin, J.-C.; Le Sergeant D'Hendecourt, L.; Chiavassa, T.

    2011-11-01

    Context. Studing chemical reactivity in astrophysical environments is an important means for improving our understanding of the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. Laboratory simulations of the reactivity of ice analogs provide important insight into the reactivity in these environments. Here, we use these experimental simulations to investigate the Strecker synthesis leading to the formation of aminoacetonitrile in astrophysical-like conditions. The aminoacetonitrile is an interesting compound because it was detected in SgrB2, hence could be a precursor of the smallest amino acid molecule, glycine, in astrophysical environments. Aims: We present the first experimental investigation of the formation of aminoacetonitrile NH2CH2CN from the thermal processing of ices including methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN) in interstellar-like conditions without VUV photons or particules. Methods: We use Fourier Transform InfraRed (FTIR) spectroscopy to monitor the ice evolution during its warming. Infrared spectroscopy and mass spectroscopy are then used to identify the aminoacetonitrile formation. Results: We demonstrate that methanimine can react with -CN during the warming of ice analogs containing at 20 K methanimine, ammonia, and [NH4+ -CN] salt. During the ice warming, this reaction leads to the formation of poly(methylene-imine) polymers. The polymer length depend on the initial ratio of mass contained in methanimine to that in the [NH4+ -CN] salt. In a methanimine excess, long polymers are formed. As the methanimine is progressively diluted in the [NH4+ -CN] salt, the polymer length decreases until the aminoacetonitrile formation at 135 K. Therefore, these results demonstrate that aminoacetonitrile can be formed through the second step of the Strecker synthesis in astrophysical-like conditions.

  20. ActionReaction Learning: Analysis and Synthesis of Human

    E-print Network

    Jebara, Tony

    an action and its reaction by observing time sequences. I apply this method to analyze human interactionAction­Reaction Learning: Analysis and Synthesis of Human Behaviour by Tony Jebara BMassachusetts Institute of Technology, 1998 All Rights Reserved Signature of Author Program in Media Arts and Sciences 15

  1. Sugar Synthesis from a Gas-Phase Formose Reaction

    Microsoft Academic Search

    Abraham F. Jalbout; Leif Abrell; Ludwik Adamowicz; Robin Polt; A. J. Apponi; L. M. Ziurys

    2007-01-01

    Prebiotic possibilities for the synthesis of interstellar ribose through a protic variant of the formose reaction under gas-phase conditions were studied in the absence of any known catalyst. The ion-molecule reaction products, diose and triose, were sought by mass spectrometry, and relevant masses were observed. Ab initio calculations were used to evaluate protic formose mechanism possibilities. A bilateral theoretical and

  2. Shock-induced reaction synthesis (SRS) of nickel aluminides

    Microsoft Academic Search

    N. N. Thadhani; S. Work; R. A. Graham; W. F. Hammetter

    1992-01-01

    Shock-induced chemical reactions between nickel and aluminum powders (mixed in NiâAl stoichiometry) are used for the synthesis of nickel aluminides. It is shown that the extent of shock-induced chemical reactions and the nature of the shock-synthesized products are influenced by the morphology of the starting powders. Irregular (flaky type) and fine morphologies of the powders undergo complete reactions in contrast

  3. Multicomponent reactions of isocyanides in the synthesis of heterocycles

    NASA Astrophysics Data System (ADS)

    Ivachtchenko, Aleksandr V.; Ivanenkov, Ya A.; Kysil, Vladimir M.; Krasavin, Mikhail Yu; Ilyin, Aleksei P.

    2010-11-01

    The latest achievements in the field of isocyanide-based multicomponent reactions for the synthesis of heterocycles are generalized. The attention is focused on the intramolecular Ugi reactions of oxocarboxylic acids and the reactions of diaza nucleophiles developed in recent years. The data on the biological activities of the products are presented and the advantages of this method as a convenient and effective tool of medicinal chemistry are demonstrated.

  4. Model Catalysis of Ammonia Synthesis ad Iron-Water Interfaces - ASum Frequency Generation Vibrational Spectroscopic Study of Solid-GasInterfaces and Anion Photoelectron Spectroscopic Study of Selected Anionclusters

    SciTech Connect

    Ferguson, Michael James

    2005-12-15

    The ammonia synthesis reaction has been studied using single crystal model catalysis combined with sum frequency generation (SFG) vibrational spectroscopy. The adsorption of gases N{sub 2}, H{sub 2}, O{sub 2} and NH{sub 3} that play a role in ammonia synthesis have been studied on the Fe(111) crystal surface by sum frequency generation vibrational spectroscopy using an integrated Ultra-High Vacuum (UHV)/high-pressure system. SFG spectra are presented for the dissociation intermediates, NH{sub 2} ({approx}3325 cm{sup -1}) and NH ({approx}3235 cm{sup -1}) under high pressure of ammonia or equilibrium concentrations of reactants and products on Fe(111) surfaces. Special attention was paid to understand how potassium promotion of the iron catalyst affects the intermediates of ammonia synthesis. An Fe(111) surface promoted with 0.2 monolayers of potassium red shifts the vibrational frequencies of the reactive surface intermediates, NH and NH{sub 2}, providing evidence for weakened the nitrogen-hydrogen bonds relative to clean Fe(111). Spectral features of these surface intermediates persisted to higher temperatures for promoted iron surfaces than for clean Fe(111) surfaces implying that nitrogen-iron bonds are stronger for the promoted surface. The ratio of the NH to NH{sub 2} signal changed for promoted surfaces in the presence of equilibrium concentrations of reactants and products. The order of adding oxygen and potassium to promoted surfaces does not alter the spectra indicating that ammonia induces surface reconstruction of the catalyst to produce the same surface morphology. When oxygen is co-adsorbed with nitrogen, hydrogen, ammonia or potassium on Fe(111), a relative phase shift of the spectra occurs as compared to the presence of adsorbates on clean iron surfaces. Water adsorption on iron was also probed using SFG vibrational spectroscopy. For both H{sub 2}O and D{sub 2}O, the only spectral feature was in the range of the free OH or free OD. From the absence of SFG spectra of ice-like structure we conclude that surface hydroxides are formed and no liquid water is present on the surface. Other than model catalysis, gas phase anion photoelectron spectroscopy of the Cl + H{sub 2} van der Waals well, silicon clusters, germanium clusters, aluminum oxide clusters and indium phosphide clusters were studied. The spectra help to map out the neutral potential energy surfaces of the clusters. For aluminum oxide, the structures of the anions and neutrals were explored and for silicon, germanium and indium phosphide the electronic structure of larger clusters was mapped out.

  5. Microwave initiated reactions: Pechmann coumarin synthesis, Biginelli reaction, and acylation

    Microsoft Academic Search

    Maghar S. Manhas; Subhendu N. Ganguly; Somdatta Mukherjee; Amit K. Jain; Ajay K. Bose

    2006-01-01

    An energy-efficient protocol has been developed for solvent-free reactions that are mildly exothermic but not spontaneous. The exothermic reaction mixture—on several g-scale—is exposed for about 30s to low power (about 200W) microwaves and then the microwave oven is switched off. After this short burst of energy, the exothermic reaction gets initiated and proceeds on its own to completion. A number

  6. Theoretical studies of possible processes for the interstellar production of phosphorus compounds. Reaction of P sup + with ammonia

    SciTech Connect

    Largo, A.; Barrientos, C. (Universidad de Oviedo (Spain)); Fores, J.R. (Universidad de Valladolid (Spain)); Ugalde, J.M. (Euskal Herriko Unibertsitatea (Spain))

    1991-01-01

    A theoretical study of the reaction of P{sup +} with ammonia, as a possible source of interstellar phosphorus-nitrogen compounds, has been carried out. The geometries of the possible products of this reaction, (HNP){sup +} and (H{sub 2}NP){sup +}, as well as of the relevant species on the triplet (H{sub 3}NP){sup +} potential energy surface have been optimized at the Hartree-Fock level. Relative energies were obtained through correlated calculations at the fourth-order Moller-Plesset theory. Calculations demonstrate that PNH{sup +} is the lowest lying (HNP){sup +} triplet state, with HPN{sup +} lying 50 kcal/mol higher at the correlated level. In the case of the (H{sub 2}NP){sup +} system, PNH{sub 2}{sup +} is found to be the ground state with trans-HPNH{sup +} and H{sub 2}PN{sup +} lying 44 and 93 kcal/mol, respectively, higher in energy at the correlated level. The PNH{sub 3}{sup +} ion-molecule complex is the lowest lying triplet (H{sub 3}NP){sup +} structure by a relatively high value, i.e. 40 kcal/mol. The stability order of this system is PNH{sub 3}{sup +} > HPNH{sub 2}{sup +} > H{sub 2}PNH{sup +} > H{sub 3}PN{sup +}. The reaction of P{sup +} with ammonia has been found to be endothermic in all cases except for the production of PNH{sub 2}{sup +}. In addition, two different mechanisms for producing PNH{sub 2}{sup +} that are barrier free have been found. Therefore, the reaction of P{sup +} with NH{sub 3}, leading to PNH{sub 2}{sup +}, seems to be a plausible interstellar process, since it is exothermic and also proceeds with no activation barrier.

  7. Detection of nerve agents using proton transfer reaction mass spectrometry with ammonia as reagent gas.

    PubMed

    Ringer, Joachim M

    2013-01-01

    The chemical warfare agents (CWA) Sarin, Soman, Cyclosarin and Tabun were characterised by proton transfer mass spectrometry (PTRMS). It was found that PTRMS is a suitable technique to detect nerve agents highly sensitively, highly selectively and in near real-time. Methods were found to suppress molecule fragmentation which is significant under PTRMS hollow cathode ionisation conditions. In this context, the drift voltage (as one of the most important system parameters) was varied and ammonia was introduced as an additional chemical reagent gas. Auxiliary chemicals such as ammonia affect ionisation processes and are quite common in context with detectors for CWAs based on ion mobility spectrometry (IMS). With both, variation of drift voltage and ammonia as the reagent gas, fragmentation can be suppressed effectively. Suppression of fragmentation is crucial particularly concerning the implementation of an algorithm for automated agent identification in field applications. On the other hand, appearance of particular fragments might deliver additional information. Degradation and rearrangement products of nerve agents are not distinctive for the particular agent but for the chemical class they belong to. It was found that switching between ammonia doped and ordinary water ionisation chemistry can easily be performed within a few seconds. Making use of this effect it is possible to switch between fragment and molecular ion peak spectra. Thus, targeted fragmentation can be used to confirm identification based only on single peak detection. PTRMS turned out to be a promising technique for future CWA detectors. In terms of sensitivity, response time and selectivity (or confidence of identification, respectively) PTRMS performs as a bridging technique between IMS and GC-MS. PMID:24308198

  8. Prebiotic Synthesis of Simple Sugars by an Interstellar Formose Reaction

    Microsoft Academic Search

    Abraham F. Jalbout

    2008-01-01

    The prebiotic possibilities for the synthesis of interstellar carbohydrates through a protic variant of the formose reaction\\u000a under gas phase conditions were studied. Ab initio calculations were used to evaluate potential mechanisms. Based on considerations\\u000a of barrier heights and temperature variations in the Interstellar Medium the plausibility of extended sugar synthesis will\\u000a be discussed.

  9. Synthesis of dendritic iridium nanostructures based on the oriented attachment mechanism and their enhanced CO and ammonia catalytic activities.

    PubMed

    Wang, Chao; Xiao, Guanjun; Sui, Yongming; Yang, Xinyi; Liu, Gang; Jia, Mingjun; Han, Wei; Liu, Bingbing; Zou, Bo

    2014-12-21

    Branched iridium nanodendrites (Ir NDs) have been synthesized by a simple method based on the oriented attachment mechanism. Transmission electron microscopy images reveal the temporal growth process from small particles to NDs. Precursor concentrations and reaction temperatures have a limited effect on the morphology of Ir NDs. Metal oxide and hydroxide-supported Ir NDs exhibit enhanced activity for catalytic CO oxidation. Particularly, the Fe(OH)x-supported Ir NDs catalyst with a 4 wt% Ir loading show superior CO oxidation catalytic activity with a full conversion of CO at 120 °C. Furthermore, compared with Ir NPs and commercial Ir black, Ir NDs exhibit higher activity and stability for ammonia oxidation. The specific activity and mass activity of Ir NDs for ammonia oxidation are 1.7 and 7 times higher than that of Ir NPs. The improved catalytic activities of Ir NDs are attributed not only to their large specific surface area, but also to their considerably high index facets and rich edge and corner atoms. Hence, the obtained Ir NDs provide a promising alternative for direct ammonia fuel cells and proton-exchange membrane fuel cells. PMID:25366566

  10. A photochemical study of the kinetics of the reactions of NH2 with phosphine, ethylene, and acetylene using flash photolysis-laser induced fluorescence. Ph.D. Thesis Catholic Univ. of America; [ammonia in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Bosco, S. R.

    1982-01-01

    The photochemistry of the reactions of NH2 was investigated in an attempt to explain the existence of an abundance of ammonia in the Jovian atmosphere. The production of ammonia reservoirs from the coupling of ammonia with other atmospheric constituents was considered. The rate constants for the reactions of NH2 radicals with phosphine, acetylene, and ethylene were measured. Flash photolysis was used for the production of NH2 radicals and laser induced fluorescence was employed for radical detection. It was determined that the rates of the reactions were too slow to be significant as a source of ammonia reservoirs in the Jovian atmosphere.

  11. Reactions of Synthesis of Heavy Nuclei Results and Perspectives

    SciTech Connect

    Oganessian, Yu. [Flerov Laboratory of Nuclear reactions, Joint Institute for Nuclear Research, 141980 Dubna, Moscow region (Russian Federation)

    2006-08-14

    The experimental and theoretical results on the properties of the isotopes of superheavy elements, obtained up to now, have made it possible to consider different reactions for the synthesis of heavier nuclei located in the vicinity of the closed proton and neutron shells. It is shown that the advance to the heaviest possible nuclei, for which the microscopic models predict further rise of stability, is inseparably linked to the future investigation of the mechanism of synthesis reactions. Direct and model experiments, aimed at solving this problem, are also discussed.

  12. The Chemistry of Liquid Ammonia.

    ERIC Educational Resources Information Center

    Lagowski, J. J.

    1978-01-01

    The solvent and chemical properties of liquid ammonia are presented. In a certain sense, ammonia is a more versatile solvent than is water because of its ability to solubilize, without reaction, highly negative or reducing species. (Author/BB)

  13. Shock-induced reaction synthesis (SRS) of nickel aluminides

    SciTech Connect

    Thadhani, N.N.; Work, S. (Center for Explosives Technology Research (CETR), New Mexico Tech, Socorro, New Mexico 87801 (United States)); Graham, R.A.; Hammetter, W.F. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

    1992-05-01

    Shock-induced chemical reactions between nickel and aluminum powders (mixed in Ni{sub 3}Al stoichiometry) are used for the synthesis of nickel aluminides. It is shown that the extent of shock-induced chemical reactions and the nature of the shock-synthesized products are influenced by the morphology of the starting powders. Irregular (flaky type) and fine morphologies of the powders undergo complete reactions in contrast to partial reactions occurring in coarse and uniform morphology powders under identical shock loading conditions. Furthermore, irregular morphology powders result in the formation of the equiatomic (B2 phase) NiAl compound while the Ni{sub 3}Al (L1{sub 2} phase) compound is the reaction product with coarse and regular morphology powders. Shock-induced reaction synthesis can be characterized as a bulk reaction process involving an intense mechanochemical'' mechanism. It is a process in which shock compression induces fluid-like plastic flow and mixing, and enhances the reactivity due to the introduction of defects and cleansing of particle surfaces, which strongly influence the synthesis process.

  14. Modeling and simulation of ammonia removal from purge gases of ammonia plants using a catalytic Pd-Ag membrane reactor.

    PubMed

    Rahimpour, M R; Asgari, A

    2008-05-01

    In this work, the removal of ammonia from synthesis purge gas of an ammonia plant has been investigated. Since the ammonia decomposition is thermodynamically limited, a membrane reactor is used for complete decomposition. A double pipe catalytic membrane reactor is used to remove ammonia from purge gas. The purge gas is flowing in the reaction side and is converted to hydrogen and nitrogen over nickel-alumina catalyst. The hydrogen is transferred through the Pd-Ag membrane of tube side to the shell side. A mathematical model including conservation of mass in the tube and shell side of reactor is proposed. The proposed model was solved numerically and the effects of different parameters on the rector performance were investigated. The effects of pressure, temperature, flow rate (sweep ratio), membrane thickness and reactor diameter have been investigated in the present study. Increasing ammonia conversion was observed by raising the temperature, sweep ratio and reducing membrane thickness. When the pressure increases, the decomposition is gone toward completion but, at low pressure the ammonia conversion in the outset of reactor is higher than other pressures, but complete destruction of the ammonia cannot be achieved. The proposed model can be used for design of an industrial catalytic membrane reactor for removal of ammonia from ammonia plant and reducing NO(x) emissions. PMID:17936505

  15. Green synthesis of biopolymer-silver nanoparticle nanocomposite: an optical sensor for ammonia detection.

    PubMed

    Pandey, Sadanand; Goswami, Gopal K; Nanda, Karuna K

    2012-11-01

    Biopolymer used for the production of nanoparticles (NPs) has attracted increasing attention. In the presence article we use aqueous solution of polysaccharide Cyamopsis tetragonaloba commonly known as guar gum (GG), from plants. GG acts as reductive preparation of silver nanoparticles which are found to be <10 nm in size. The uniformity of the NPs size was measured by the SEM and TEM, while a face centered cubic structure of crystalline silver nanoparticles was characterized using powder X-ray diffraction technique. Aqueous ammonia sensing study of polymer/silver nanoparticles nanocomposite (GG/AgNPs NC) was performed by optical method based on surface plasmon resonance (SPR). The performances of optical sensor were investigated which provide the excellent result. The response time of 2-3 s and the detection limit of ammonia solution, 1 ppm were found at room temperature. Thus, in future this room temperature optical ammonia sensor can be used for clinical and medical diagnosis for detecting low ammonia level in biological fluids, such as plasma, sweat, saliva, cerebrospinal liquid or biological samples in general for various biomedical applications in human. PMID:22750580

  16. High yield shock synthesis of ammonia from iron, water and nitrogen available on the early Earth

    NASA Astrophysics Data System (ADS)

    Nakazawa, Hiromoto; Sekine, Toshimori; Kakegawa, Takeshi; Nakazawa, Satoru

    2005-06-01

    Ammonia is a necessary precursor of amino acids in terms of the origin of life on the early Earth. However, the formation of ammonia is problematic in the non-reducing atmosphere that presently believed on the early Earth. The abiotic reduction of nitrogen is, therefore, debated currently in the oceanic and hydrothermal conditions [[J.A. Brandes, N.Z. Boctor, G.D. Cody, B.A. Cooper, R.M. Hazen, H.S. Yoder Jr., Abiotic nitrogen reduction on the early Earth, Nature 395 (1998), 365-367; D.P. Summers, S. Chang, Prebiotic ammonia from reduction of nitrite by iron (II) on the early Earth, Nature 365 (1993), 630-633; M. Dörr, J. Kaessbohrer, R. Grunert, G. Kreisel, W.A. Brand, R.A. Werner, H. Geilmann, C. Apfel, C. Robl, W. Weigand, A possible prebiotic formation of ammonia from dinitrogen on iron sulfide surfaces, Angew. Chem. Int. Ed. 42 ( 2003), 1540-1543 [1-3

  17. Shock-induced chemical reactions and synthesis of nickel aluminides

    Microsoft Academic Search

    I. Song; N. N. Thadhani

    1992-01-01

    Chemical reactions in Ni and Al powder mixtures, initiated by the passage of shock waves, are used for the synthesis of nickel\\u000a aluminides. Mechanistic investigations reveal that the extent of these shock-induced chemical reactions and the type (stoichiometry)\\u000a of shock-synthesized compound formed depend on shock-loading conditions and the initial powder particle morphology. More intense\\u000a shock conditions and irregular powder morphology

  18. Synthesis of porous gold nanoshells by controlled transmetallation reaction

    NASA Astrophysics Data System (ADS)

    Pattabi, Manjunatha; M, Krishnaprabha

    2015-06-01

    Aqueous synthesis of porous gold nanoshells in one step is carried out through controlled transmetallation (TM) reaction using a naturally available egg shell membrane (ESM) as a barrier between the sacrificial silver particles (AgNPs) and the gold precursor solution (HAuCl4). The formation of porous gold nanoshells via TM reaction is inferred from UV-Vis spectroscopy and the scanning electron microscopic (SEM) studies.

  19. Combustion synthesis of advanced materials: Part I. Reaction parameters

    Microsoft Academic Search

    John J. Moore; H. J. Feng

    1995-01-01

    An explanation of combustion (self propagating high temperature) synthesis (SHS) is given together with a historical perspective of the examination of such exothermic reactions. The application of thermochemical functions has been used to predict theoretically the maximum adiabatic temperature, Tad. This, combined with a knowledge of the ignition temperature, Tig, and the actual combustion temperature, Tc, has been used to

  20. Microwave synthesis Microwave assisted reactions with gas reagents

    Microsoft Academic Search

    ELENA PETRICCI; MAURIZIO TADDEI

    Controlled microwave heating has found many important applications in organic synthesis. Almost all kinds of reactions have been tested using microwaves. Major successes in carrying out rapid organic transformations have been achieved when high temperatures are required and substrates or reagents do not survive to prolonged heating. On the other hand, very few reports deal with the use of gas

  1. Phytochrome-mediated de Novo Synthesis of Phenylalanine Ammonia-Lyase in Cell Suspension Cultures of Parsley 1

    PubMed Central

    Wellmann, Eckard; Schopfer, Peter

    1975-01-01

    After a preirradiation with ultraviolet light, phenylalanine ammonia-lyase activity in cell suspension cultures of parsley (Petroselinum hortense Hoff.) is controlled by phytochrome (red/far red photoreversibility). Isopycnic CsCl density gradient centrifugation, after labeling with 15N (90 atom%) under inductive and noninductive conditions, was used to investigate the mode of action of phytochrome in this response. After a 5hour labeling period, a buoyant density shift of 0.009 kg·l?1 (0.7%) without band-broadening (indicating close to maximal labeling of the enzyme), was observed in irradiated cells. In dark-grown controls, the density shift was 0.004 kg·l?1 (0.3%), accompanied by significant band-broadening, indicating turnover of about half of the enzyme pool during 5 hours. These results are taken as evidence that phytochrome controls de novo synthesis of this enzyme over a background of basal turnover. PMID:16659175

  2. EXAFS-XANES evidence of in situ cesium reduction in Cs-Ru/C catalysts for ammonia synthesis.

    PubMed

    Rossetti, Ilenia; Sordelli, Laura; Ghigna, Paolo; Pin, Sonia; Scavini, Marco; Forni, Lucio

    2011-04-18

    We present here a X-ray absorption spectroscopy (XAS) investigation on the local chemical order and electronic structure of Cs and Ba, promoters of the Ru/C catalysts for ammonia synthesis that attracted interest because of highly increased productivity. The role of the promoters is still largely unclear, although indirect evidence for Cs partial reduction has been obtained by this and other groups. Our XAS analysis with in situ H(2) reduction directly supports the partial Cs reduction in the promoted Ru/C catalysts, depending on the presence of Ru and on the graphitization degree of the support. Higher coordination of Ba was observed with respect to Cs in the reduced samples, without evidence of heavy atoms (Ru, Cs, and Ba) in the surroundings. Because of the strong electropositive nature of Cs, direct experimental evidence of its partial reduction is of outstanding significance also for other applications. PMID:21434615

  3. Facile and controllable synthesis of hydroxyapatite/graphene hybrid materials with enhanced sensing performance towards ammonia.

    PubMed

    Zhang, Qing; Liu, Yong; Zhang, Ying; Li, Huixia; Tan, Yanni; Luo, Lanlan; Duan, Junhao; Li, Kaiyang; Banks, Craig E

    2015-07-13

    In this work, needle-like and micro-spherical agglomerates of nanocrystalline hydroxyapatite (HA) were successfully assembled on the surface of graphene sheets with the aid of dopamine having two roles, as a template and a reductant for graphite oxide during the process of self-polymerization. The crystalline structure and micromorphology of HA can be conveniently regulated by controlling the mineralization route either with a precipitation (cHA/GR) or biomimetic methodology (bHA/GR). Both the composites exhibit improvements of ?150% and ?250% in sensitivity towards the sensing of ammonia at room temperature, compared with that of bare graphene. The combination of the multi-adsorption capability of HA and the electric conductivity of graphene is proposed to be the major reason for the observed enhancements. Gas sensing tests demonstrated that the HA/GR composites exhibit excellent selectivity, high sensitivity and repeatable stability towards the analytical sensing of ammonia. PMID:26066071

  4. Aqueous solution synthesis of Pt-M (M = Fe, Co, Ni) bimetallic nanoparticles and their catalysis for the hydrolytic dehydrogenation of ammonia borane.

    PubMed

    Wang, Shuai; Zhang, Duo; Ma, Yanyun; Zhang, Hui; Gao, Jing; Nie, Yuting; Sun, Xuhui

    2014-08-13

    Platinum-based bimetallic nanocatalysts have attracted much attention due to their high-efficiency catalytic performance in energy-related applications such as fuel cell and hydrogen storage, for example, the hydrolytic dehydrogenation of ammonia borane (AB). In this work, a simple and green method has been demonstrated to successfully prepare Pt-M (M = Fe, Co, Ni) NPs with tunable composition (nominal Pt/M atomic ratios of 4:1, 1:1, and 1:4) in aqueous solution under mild conditions. All Pt-M NPs with a small size of 3-5 nm show a Pt fcc structure, suggesting the bimetallic formation (alloy and/or partial core-shell), examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS) analysis. The catalytic activities of Pt-M NPs in the hydrolytic dehydrogenation of AB reveal that Pt-Ni NPs with a ratio of 4:1 show the best catalytic activity and even better than that of pure Pt NPs when normalized to Pt molar amount. The Ni oxidation state in Pt-Ni NPs has been suggested to be responsible for the corresponding catalytic activity for hydrolytic dehydrogenation of AB by XAFS study. This strategy for the synthesis of Pt-M NPs is simple and environmentally benign in aqueous solution with the potential for scale-up preparation and the in situ catalytic reaction. PMID:25058566

  5. Heat transfer in the plate heat exchanger of an ammonia-synthesis column

    Microsoft Academic Search

    Y. G. Obolentsev; M. S. Chus; O. A. Norobchanskii; Y. S. Teplitshi; L. L. Tovazhnyanskii

    1983-01-01

    The planning and construction of high-capacity synthetic ammonia plants requires the development and fabrication of unique, high unit-power equipment with high technical and economic characteristics. In foreign and domestic practice, tubular heat exchangers with relatively low heat-transfer coefficients are used. Plate heat exchangers are a promising alternative. They are compact and have a high heat energy efficiency and a relatively

  6. Novel domino reactions for diterpene synthesis.

    PubMed

    Bhar, Shanta S; Ramana, M M V

    2004-12-10

    New types of concerted domino acylation-cycloalkylation/alkylation-cycloacylation reactions have been described. These processes promoted by methanesulfonic acid-phosphorus pentoxide and concentrated H(2)SO(4), respectively, provide efficient, elegant, and expeditious routes for biologically active naturally occurring diterpenoids, namely (+/-)-ferruginol (1), (+/-)-nimbidiol (2), (+/-)-nimbiol (3), (+/-)-totarol (4), and ar-abietatriene (5). PMID:15575777

  7. Trifluoromethylation reactions for the synthesis of ?-trifluoromethylamines.

    PubMed

    Egami, Hiromichi; Kawamura, Shintaro; Miyazaki, Ayako; Sodeoka, Mikiko

    2013-07-22

    A multitalented system: N-migratory oxytrifluoromethylation and one-pot three-component reactions of allylamines as well as the aminotrifluoromethylation of alkenyl amines all proceeded efficiently in the presence of the Togni reagent (1) and CuI to afford a variety of ?-trifluoromethylamine derivatives (see scheme). PMID:23765709

  8. A molybdenum complex bearing PNP-type pincer ligands leads to the catalytic reduction of dinitrogen into ammonia

    NASA Astrophysics Data System (ADS)

    Arashiba, Kazuya; Miyake, Yoshihiro; Nishibayashi, Yoshiaki

    2011-02-01

    The synthesis of transition metal-dinitrogen complexes and the stoichiometric transformation of their coordinated dinitrogen into ammonia and hydrazine have been the subject of considerable research, with a view to achieving nitrogen fixation under ambient conditions. Since a single example in 2003, no examples have been reported of the catalytic conversion of dinitrogen into ammonia under ambient conditions. The dimolybdenum-dinitrogen complex bearing PNP pincer ligands was found to work as an effective catalyst for the formation of ammonia from dinitrogen, with 23 equiv. of ammonia being produced with the catalyst (12 equiv. of ammonia are produced based on the molybdenum atom of the catalyst). This is another successful example of the catalytic and direct conversion of dinitrogen into ammonia under ambient reaction conditions. We believe that the results described in this Article provide valuable information with which to develop a more effective nitrogen-fixation system under mild reaction conditions.

  9. Synthesis of bimetallic systems using replacement reactions

    Microsoft Academic Search

    Songrui Wang; Jian’an He; Jinglin Xie; Yuexiang Zhu; Youchang Xie; Jingguang G. Chen

    2008-01-01

    Series of bimetallic systems were prepared by replacement reactions and characterized by XRD and XPS. The results suggest that the ad-metals are monolayer dispersed on the surface of sub-metal in Pd(Pt, Cu)\\/Co(Ni) systems, while in Pd(Pt, Au)\\/Cu systems surface solid solution is formed. In Ag(Au)\\/Co(Ni) and Ag\\/Cu systems no interaction between the metals is observed just as in the simple

  10. Sugar synthesis from a gas-phase formose reaction.

    PubMed

    Jalbout, Abraham F; Abrell, Leif; Adamowicz, Ludwik; Polt, Robin; Apponi, A J; Ziurys, L M

    2007-06-01

    Prebiotic possibilities for the synthesis of interstellar ribose through a protic variant of the formose reaction under gas-phase conditions were studied in the absence of any known catalyst. The ion-molecule reaction products, diose and triose, were sought by mass spectrometry, and relevant masses were observed. Ab initio calculations were used to evaluate protic formose mechanism possibilities. A bilateral theoretical and experimental effort yielded a physical model for glycoaldehyde generation whereby a hydronium cation can mediate formaldehyde dimerization followed by covalent bond formation leading to diose and water. These results advance the possibility that ion-molecule reactions between formaldehyde (CH(2)O) and H(3)O(+) lead to formose reaction products and inform us about potential sugar formation processes in interstellar space. PMID:17630839

  11. Facile single-step ammonia heat-treatment and quenching process for the synthesis of improved Pt/N-graphene catalysts

    NASA Astrophysics Data System (ADS)

    Xiong, Bin; Zhou, Yingke; O'Hayre, Ryan; Shao, Zongping

    2013-02-01

    In this work, we present a facile route to prepare electrocatalysts for methanol oxidation. The catalyst synthesis route involves the simultaneous reduction and nitrogen doping of graphene oxide (GO) along with the reduction of H2PtCl6 to Pt by a facile ammonia gas heat-treatment and quenching process. The resulting catalysts are characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy while their electrocatalytic activity toward the oxidation of methanol is evaluated by cyclic voltammetry. The obtained Pt/graphene composites consist of crystalline Pt nanoparticles in the range of 1-4 nm which are well-dispersed on the N-doped graphene sheets. The best Pt/N-graphene catalyst composite is obtained after a 5 min ammonia treatment at 800 °C followed by rapid ammonia gas quenching at room temperature. This catalyst demonstrates superior catalytic activity for methanol electro-oxidation, with a peak current density of 0.218 A mgPt-1, which is about five times higher than an undoped (hydrogen treated and quenched) Pt/graphene control catalyst. The excellent electrocatalytic performance of the ammonia quenched catalyst is attributed to the nitrogenous functional groups and dopants in the graphene sheets that are formed during the facile quenching process in ammonia.

  12. Rational design of metal nitride redox materials for solar-driven ammonia synthesis.

    PubMed

    Michalsky, Ronald; Pfromm, Peter H; Steinfeld, Aldo

    2015-06-01

    Fixed nitrogen is an essential chemical building block for plant and animal protein, which makes ammonia (NH3) a central component of synthetic fertilizer for the global production of food and biofuels. A global project on artificial photosynthesis may foster the development of production technologies for renewable NH3 fertilizer, hydrogen carrier and combustion fuel. This article presents an alternative path for the production of NH3 from nitrogen, water and solar energy. The process is based on a thermochemical redox cycle driven by concentrated solar process heat at 700-1200°C that yields NH3 via the oxidation of a metal nitride with water. The metal nitride is recycled via solar-driven reduction of the oxidized redox material with nitrogen at atmospheric pressure. We employ electronic structure theory for the rational high-throughput design of novel metal nitride redox materials and to show how transition-metal doping controls the formation and consumption of nitrogen vacancies in metal nitrides. We confirm experimentally that iron doping of manganese nitride increases the concentration of nitrogen vacancies compared with no doping. The experiments are rationalized through the average energy of the dopant d-states, a descriptor for the theory-based design of advanced metal nitride redox materials to produce sustainable solar thermochemical ammonia. PMID:26052421

  13. Applied reaction dynamics: Efficient synthesis gas production via single collision partial oxidation of methane to CO on Rh,,111...

    E-print Network

    Sibener, Steven

    Applied reaction dynamics: Efficient synthesis gas production via single collision partial dissociation. These results demonstrate the efficient conversion of methane to synthesis gas, CO+2H2 fuel production Fischer-Tropsch or methanol synthesis . Moreover, under the reaction conditions

  14. Synthesis of heterocycles by the aza-Wittig reaction

    NASA Astrophysics Data System (ADS)

    Gusar, N. I.

    1991-02-01

    This review is devoted to the synthesis of N-heterocycles by the interaction of phosphazo groups (either preformed or prepared in situ) with carbonyl or thiocarbonyl groups. Examples are presented systematically for syntheses by an intramolecular aza-Wittig reaction or where the latter is incorporated in a multi-step route. The feasibility of preparing various types of heterocycle by this method has been examined. The bibliography contains 73 references.

  15. The hot extrusion reaction synthesis of nickel aluminide alloys

    Microsoft Academic Search

    E. J. Minay; H. B. McShane; R. D. Rawlings

    2004-01-01

    Elemental powder compacts of Ni–13.3 wt.% Al, the composition that corresponds to stoichiometric Ni3Al, have been processed by hot extrusion reaction synthesis (HERS) to form a dense rod. A narrow processing window has been determined for the experimental scale rig used. The success of the processing route has been shown to be highly dependent on the initial billet temperature, the

  16. Ammonia-Treated Ordered Mesoporous Carbons as Catalytic Materials for Oxygen Reduction Reaction

    Microsoft Academic Search

    Xiqing Wang; Jeseung Lee; Qing Zhu; Jun Liu; Yong Wang; Sheng Dai

    2010-01-01

    Polymer electrolyte membrane fuel cells (PEMFCs) have been considered as promising alternative power sources for many mobile and stationary applications. Compared to the fast hydrogen oxidation at the anode, the sluggish oxygen reduction reaction (ORR) at the cathode requires high-performance catalysts. Currently, platium (Pt) nanoparticles supported on high surface area carbons remain the best catalysts for ORR. However, both instability

  17. A Theoretical Investigation of the Plausibility of Reactions Between Ammonia and Carbonyl Species (Formaldehyde, Acetaldehyde, and Acetone) in Interstellar Ice Analogs at Ultracold Temperatures

    NASA Technical Reports Server (NTRS)

    Chen, Lina; Woon, David E.

    2011-01-01

    We have reexamined the reaction between formaldehyde and ammonia, which was previously studied by us and other workers in modestly sized cluster calculations. Larger model systems with up to 12H2O were employed, and reactions of two more carbonyl species, acetaldehyde and acetone, were also carried out. Calculations were performed at the B3LYP/6-31+G** level with bulk solvent effects treated with a polarizable continuum model; limited MP2/6-31+G** calculations were also performed. We found that while the barrier for the concerted proton relay mechanism described in previous work remains modest, it is still prohibitively high for the reaction to occur under the ultracold conditions that prevail in dense interstellar clouds. However, a new pathway emerged in more realistic clusters that involves at least one barrierless step for two of the carbonyl species considered here: ammonia reacts with formaldehyde and acetaldehyde to form a partial charge transfer species in small clusters (4H2O) and a protonated hydroxyamino intermediate species in large clusters (9H2O, 12H2O); modest barriers that decrease sharply with cluster size are found for the analogous processes for the acetone-NH3 reaction. Furthermore, if a second ammonia replaces one of the water molecules in calculations in the 9H2O clusters, deprotonation can occur to yield the same neutral hydroxyamino species that is formed via the original concerted proton relay mechanism. In at least one position, deprotonation is barrierless when zero-point energy is included. In addition to describing the structures and energetics of the reactions between formaldehyde, acetaldehyde, and acetone with ammonia, we report spectroscopic predictions of the observable vibrational features that are expected to be present in ice mixtures of different composition.

  18. Synthesis of superheavy nuclei: A search for new production reactions

    SciTech Connect

    Zagrebaev, Valery [Flerov Laboratory of Nuclear Reactions, JINR, Dubna, Moscow Region (Russian Federation); Greiner, Walter [Frankfurt Institute for Advanced Studies, J. W. Goethe-Universitaet, Frankfurt (Germany)

    2008-09-15

    Nuclear reactions leading to the formation of new superheavy (SH) elements and isotopes are discussed in the paper. 'Cold' and 'hot' synthesis, fusion of fission fragments, transfer reactions, and reactions with radioactive ion beams are analyzed along with their abilities and limitations. If the possibility of increasing the beam intensity and the detection efficiency (by a total of one order of magnitude) is found, then several isotopes of new elements with Z=120-124 could be synthesized in fusion reactions of titanium, chromium, and iron beams with actinide targets. The use of light- and medium-mass neutron-rich radioactive beams may help us fill the gap between the SH nuclei produced in the hot fusion reactions and the mainland. In these reactions, we may really approach the 'island of stability.' Such a possibility is also provided by the multinucleon transfer processes in low-energy damped collisions of heavy actinide nuclei. The production of SH elements in fusion reactions with accelerated fission fragments looks less encouraging.

  19. Optimal reaction for synthesis of superheavy element 117

    SciTech Connect

    Liu, Z. H. [China Institute of Atomic Energy, P. O. Box 275, Beijing 102413 (China); Bao Jingdong [Department of Physics, Beijing Normal University, Beijing 100875 (China); Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China); Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 730000 (China)

    2009-09-15

    Fusion reactions leading to the formation of superheavy element 117 are systematically analyzed. Among the reactions considered, the {sup 250}Bk({sup 48}Ca,4n){sup 294}117 reaction has the largest evaporation residue (ER) cross section of about 2 pb. However, this reaction is hard to realize experimentally because it is difficult to accumulate sufficient amount of target material due to the short lifetime of {sup 250}Bk nucleus. For the reaction {sup 48}Ca+{sup 249}Bk, our estimation shows that the ER cross sections in 3n and 4n channels may be expected to be greater than 1 pb. Therefore, {sup 48}Ca and {sup 249}Bk should be the optimal projectile-target combination for synthesis of superheavy element 117 in practice. In addition, as a main result of systematic analysis, we find that the ER cross section exponentially depends on the mass difference (in unit of temperature) of fission and neutron emission saddle points. Therefore, it is of essential importance for the successful synthesis of superheavy nuclei to select the isotopic composition of projectile and/or target so as the mass difference of fission and neutron emission saddle points as large as possible. Entrance channel effects are examined by means of a comparison of the reactions {sup 48}Ca+{sup 245}Bk, {sup 50}Ti+{sup 243}Am, and {sup 55}Mn+{sup 238}U leading to the same compound nucleus {sup 293}117. The ER cross sections of the reactions {sup 50}Ti+{sup 243}Am and {sup 55}Mn+{sup 238}U are much smaller than that of {sup 48}Ca+{sup 245}Bk.

  20. Ammonia causes decreased brain monoamines in fathead minnows (Pimephales promelas)

    USGS Publications Warehouse

    Ronan, P.J.; Gaikowski, M.P.; Hamilton, S.J.; Buhl, K.J.; Summers, C.H.

    2007-01-01

    Hyperammonemia, arising from variety of disorders, leads to severe neurological dysfunction. The mechanisms of ammonia toxicity in brain are not completely understood. This study investigated the effects of ammonia on monoaminergic systems in brains of fathead minnows (Pimephales promelas). Fish serve as a good model system to investigate hyperammonemic effects on brain function since no liver manipulations are necessary to increase endogenous ammonia concentrations. Using high performance liquid chromatography with electrochemical detection, monoamines and some associated metabolites were measured from whole brain homogenate. Adult males were exposed for 48??h to six different concentrations of ammonia (0.01-2.36??mg/l unionized) which bracketed the 96-h LC50 for this species. Ammonia concentration-dependent decreases were found for the catecholamines (norepinephrine and dopamine) and the indoleamine serotonin (5-HT). After an initial increase in the 5-HT precursor 5-hydroxytryptophan it too decreased with increasing ammonia concentrations. There were also significant increases in the 5-HIAA/5-HT and DOPAC/DA ratios, often used as measures of turnover. There were no changes in epinephrine (Epi) or monoamine catabolites (DOPAC, 5-HIAA) at any ammonia concentrations tested. Results suggest that ammonia causes decreased synthesis while also causing increased release and degradation. Increased release may underlie behavioral reactions to ammonia exposure in fish. This study adds weight to a growing body of evidence demonstrating that ammonia leads to dysfunctional monoaminergic systems in brain which may underlie neurological symptoms associated with human disorders such as hepatic encephalopathy. ?? 2007 Elsevier B.V. All rights reserved.

  1. Ammonia-treated Ordered Mesoporous Carbons as Catalytic Materials for Oxygen Reduction Reaction

    SciTech Connect

    Wang, Xiqing; Lee, Je Seung; Zhu, Qing; Liu, Jun; Wang, Yong; Dai, Sheng

    2010-04-13

    Polymer electrolyte membrane fuel cells (PEMFCs) have been considered as promising alternative power sources for many mobile and stationary applications. Compared to the fast hydrogen oxidation at the anode, the sluggish oxygen reduction reaction (ORR) at the cathode requires high-performance catalysts. Currently, platium (Pt) nanoparticles supported on high surface area carbons remain the best catalysts for ORR. However, both instability and high cost of Pt-based catalysts represent two main obstacles limiting the commercial applications of PEMFCs. The instability of supported Pt catalysts is mainly due to the corrosion of carbon support under operation conditions and the agglomation and detachment of Pt particles, leading to a decrease in catalytic surface areas. Development of corrosion resistant supports and enhancement of the interactions between Pt and supports are two strategies to improve the cathode long-term activity.

  2. Revisiting a classic approach to the Aspidosperma alkaloids: an intramolecular Schmidt reaction mediated synthesis of (+)-aspidospermidine.

    PubMed

    Iyengar, Rajesh; Schildknegt, Klaas; Morton, Martha; Aubé, Jeffrey

    2005-12-23

    [reaction: see text] A total synthesis of (+)-aspidospermidine (1) is described. The key reactions used in the synthesis of this pentacyclic Aspidosperma alkaloid were a deracemizing imine alkylation/Robinson annulation sequence, a selective "redox ketalization", and an intramolecular Schmidt reaction. A Fischer indolization step carried out on a tricyclic ketone mirrored the sequence reported by Stork and Dolfini in their classic aspidospermine synthesis. PMID:16355981

  3. Pressure-reaction synthesis of titanium composite materials

    DOEpatents

    Oden, Laurance L. (Albany, OR); Ochs, Thomas L. (Albany, OR); Turner, Paul C. (Albany, OR)

    1993-01-01

    A pressure-reaction synthesis process for producing increased stiffness and improved strength-to-weight ratio titanium metal matrix composite materials comprising exothermically reacting a titanium powder or titanium powder alloys with non-metal powders or gas selected from the group consisting of C, B, N, BN, B.sub.4 C, SiC and Si.sub.3 N.sub.4 at temperatures from about 900.degree. to about 1300.degree. C., for about 5 to about 30 minutes in a forming die under pressures of from about 1000 to 5000 psi.

  4. Synthesis of DiamidoPyrrolyl Molybdenum Complexes Relevant to Reduction of Dinitrogen to Ammonia

    PubMed Central

    Chin, J. M.; Müller, P.

    2010-01-01

    A potentially useful trianionic ligand for the reduction of dinitrogen catalytically by molybdenum complexes is one in which one of the arms in a [(RNCH2CH2)3N]3? ligand is replaced by a 2-mesitylpyrrolyl-?-methyl arm, i.e., [(RNCH2CH2)2NCH2(2-MesitylPyrrolyl)]3? (R = C6F5, 3,5-Me2C6H3, or 3,5-t-Bu2C6H3). Compounds have been prepared that contain the ligand in which R = C6F5 ([C6F5N)2Pyr]3?); they include [(C6F5N)2Pyr]Mo(NMe2), [(C6F5N)2Pyr]MoCl, [(C6F5N)2Pyr]MoOTf, and [(C6F5N)2Pyr]MoN. Compounds that contain the ligand in which R = 3,5-t-Bu2C6H3 ([Art-BuN)2Pyr]3?) include {[(Art-BuN)2Pyr]Mo(N2)}Na(15-crown-5), {[(Art-Bu N)2Pyr]Mo(N2)}[NBu4], [(Art-Bu N)2Pyr]Mo(N2) (?NN = 2012 cm?1 in C6D6), {[(Art-Bu N)2Pyr]Mo(NH3)}BPh4, and [(Art-Bu N)2Pyr]Mo(CO). X-ray studies are reported for [(C6F5N)2Pyr]Mo(NMe2), [(C6F5N)2Pyr]MoCl, and [(Art-BuN)2Pyr]MoN. The [(Art-BuN)2Pyr]Mo(N2)0/? reversible couple is found at ?1.96 V (in PhF versus Cp2Fe+/0), but the [(Art-BuN)2Pyr]Mo(N2)+/0 couple is irreversible. Reduction of {[(Art-BuN)2Pyr]Mo(NH3)}BPh4 under Ar at approximately ?1.68 V at a scan rate of 900 mV/sec is not reversible. Ammonia in [(Art-BuN)2Pyr]Mo(NH3) can be substituted for dinitrogen in about 2 hours if 10 equivalents of BPh3 are present to trap the ammonia that is released. [(Art-BuN)2Pyr]Mo-N=NH is a key intermediate in the proposed catalytic reduction of dinitrogen that could not be prepared. Dinitrogen exchange studies in [(Art-BuN)2Pyr]Mo(N2) suggest that steric hindrance by the ligand may be insufficient to protect decomposition of [(Art-BuN)2Pyr]Mo-N=NH through a variety of pathways. Three attempts to reduce dinitrogen catalytically with [(Art-BuN)2Pyr]Mo(N) as a “catalyst” yielded an average of 1.02 ± 0.12 equivalents of NH3. PMID:20799738

  5. Fischer-Tropsch synthesis in supercritical reaction media

    SciTech Connect

    Subramaniam, B.; Bochniak, D.; Snavely, K.

    1993-04-01

    The reactor configuration has been modified to handle tows both in the upflow and downflow directions. For comparison to bubble column operation, an upflow mode of operation will be used. For comparison to trickle-bed operation, a downflow mode will be employed. Thus, this modification allows the most flexibility for studying the effects of liquid and supercritical reaction media on the Fischer-Tropsch synthesis reaction and permits comparisons of our experimental results with previous work. A stainless steel reactor tube was ordered. This unit along with three other pieces of tubing (greater than 1/4in. i. d.) are to be sent to Alon Processing Co. for alonizing (passivating) the internal surface. This process had been employed by Huff and Satterfield (1983) to ensure that the stainless steel surfaces are catalytically inert at high temperatures (> 200[degree]C).

  6. Ammonia from iron(II) reduction of nitrite and the Strecker synthesis: do iron(II) and cyanide interfere with each other?

    NASA Technical Reports Server (NTRS)

    Summers, D. P.; Lerner, N.

    1998-01-01

    The question of whether the production of ammonia, from the reduction of nitrite by iron(II), is compatible with its use in the Strecker synthesis of amino acids, or whether the iron and the cyanide needed for the Strecker synthesis interfere with each other, is addressed. Results show that the presence of iron(II) appears to have little, or no, effect on the Strecker synthesis. The presence of cyanide does interfere with reduction of nitrite, but the reduction proceeds at cyanide/iron ratios of less than 4:1. At ratios of about 2:1 and less there is only a small effect. The reduction of nitrite and the Strecker can be combined to proceed in each other's presence, to yield glycine from a mixture of nitrite, Fe+2, formaldehyde, and cyanide.

  7. Tris(Cyclopentadienyl)Uranium-t-Butyl: Synthesis, reactions, and mechanisms

    SciTech Connect

    Weydert, M.

    1993-04-01

    Compounds (RC{sub 5}H{sub 4}){sub 3}U(t-Bu) were prepared for R = H, Me, Et. Their decomposition products in aromatic solvents are consistent with a radical decomposition pathway induced by solvent-assisted U-C bond homolysis. NMR was used to study the reactions of (RC{sub 5}H{sub 4}){sub 3}UCl with t-BuLi (R = t-Bu, Me{sub 3}Si). Reactions of (MeC{sub 5}H{sub 4}){sub 3}U(t-Bu) with Lewis bases and fluorocarbons were studied. Analogous reaction chemistry between (RC{sub 5}H{sub 4}){sub 3}ThX systems and t-BuLi was also studied, and reactivity differences between U and Th are discussed. Synthesis of sterically crowded (RC{sub 5}H{sub 4}){sub 4}U compounds is next considered. Reaction of the trivalent (RC{sub 5}H{sub 4}){sub 3}U with (RC{sub 5}H{sub 4}){sub 2}Hg results in formation of (RC{sub 5}H{sub 4}){sub 4}U. Steric congestion, cyclopentadienyl ligand exchange, and electron transfer are discussed. (DLC)

  8. Tris(Cyclopentadienyl)Uranium-t-Butyl: Synthesis, reactions, and mechanisms

    SciTech Connect

    Weydert, M.

    1993-04-01

    Compounds (RC[sub 5]H[sub 4])[sub 3]U(t-Bu) were prepared for R = H, Me, Et. Their decomposition products in aromatic solvents are consistent with a radical decomposition pathway induced by solvent-assisted U-C bond homolysis. NMR was used to study the reactions of (RC[sub 5]H[sub 4])[sub 3]UCl with t-BuLi (R = t-Bu, Me[sub 3]Si). Reactions of (MeC[sub 5]H[sub 4])[sub 3]U(t-Bu) with Lewis bases and fluorocarbons were studied. Analogous reaction chemistry between (RC[sub 5]H[sub 4])[sub 3]ThX systems and t-BuLi was also studied, and reactivity differences between U and Th are discussed. Synthesis of sterically crowded (RC[sub 5]H[sub 4])[sub 4]U compounds is next considered. Reaction of the trivalent (RC[sub 5]H[sub 4])[sub 3]U with (RC[sub 5]H[sub 4])[sub 2]Hg results in formation of (RC[sub 5]H[sub 4])[sub 4]U. Steric congestion, cyclopentadienyl ligand exchange, and electron transfer are discussed. (DLC)

  9. Combustion Synthesis Reactions in Cold-Rolled Ni\\/Al and Ti\\/Al Multilayers

    Microsoft Academic Search

    Xiaotun Qiu; Ranran Liu; Shengmin Guo; Jesse Harris Graeter; Laszlo Kecskes; Jiaping Wang

    2009-01-01

    In this article, a cold rolling method was developed to fabricate Ni\\/Al and Ti\\/Al multilayer foils, and the combustion synthesis\\u000a reactions in the cold-rolled foils were investigated. Combustion synthesis reactions were initiated by heating one end of\\u000a the cold-rolled foil in a flame for several seconds. The Ni\\/Al foils went through three reaction stages. The first reaction\\u000a stage was a

  10. Effects of ammonia on carbon metabolism in photosynthesizing isolated mesophyll cells from Papaver somniferum L

    Microsoft Academic Search

    John S. Paul; Karen L. Cornwell; James A. Bassham

    1978-01-01

    Addition of ammonia to a suspension of photosynthesizing isolated mesophyll cells from P. somniferum quantitatively alters the pattern of carbon metabolism by increasing rates of certain key ratelimiting steps leading to amino-acid synthesis and by decreasing rates of rate-limiting steps in alternative biosynthetic pathways. Of particular importance is the stimulation of reactions mediated by pyruvate kinase and phosphoenolpyruvate carboxylase. The

  11. Retrofits: A Means for Reducing Energy Consumption in Ammonia Manufacture

    E-print Network

    LeBlanc, J. R.; Moore, D. O.; Schneider, R. V., III

    1982-01-01

    on catalytic reforming of hydrocarbons with steam to produce raw synthesis gas. This gas is further processed in carbon monoxide shift converters and purified to form ammonia synthesis gas, which is converted to ammonia. The plant described herein is based... on an ammonia production rate of 1000 STPD using natural gas feed. The process is divided into the following three sections with utilities included as an additional section: Reforming and shift C02 removal and methanation Compression and ammonia synthesis...

  12. Templated Synthesis of Peptide Nucleic Acids via Sequence-Selective Base-Filling Reactions

    E-print Network

    Liu, David R.

    Templated Synthesis of Peptide Nucleic Acids via Sequence-Selective Base-Filling Reactions Jennifer describe the templated synthesis of both native and modified peptide nucleic acids (PNAs) through base, 2009; E-mail: drliu@fas.harvard.edu Template-directed nucleic acid synthesis is an essential compo

  13. The Metal-Ammonia Reduction of 1-Naphthoic Acid

    Microsoft Academic Search

    Peter W. Rabideau; Earl G. Burkholder; Michael J. Yates

    1980-01-01

    The reduction of aromatic compounds with alkali metals in liquid anhydrous ammonia (Birch Reduction and its modifications) has developed as an effective method for the synthesis of 1,4-cyclohexadiene derivatives, and has been the subject of several reviews. In many cases, particularly with polynuclear compounds, the reaction is complicated by subsequent isomerizations, and\\/or the reduction of initial products which are often

  14. Intermixing criteria for reaction synthesis of Ni/Al multilayered microfoils

    E-print Network

    Hong, Soon Hyung

    synthesis technique for intermetallics involves both a self-propagating high-temperature synthe- sis (SHS from the reactant had a much smaller effect on reaction propagation than did the conductive heat lossesIntermixing criteria for reaction synthesis of Ni/Al multilayered microfoils Hee Y. Kim a , Dong S

  15. Electrocatalytic study of ammonia synthesis and methane dimerization in high temperature solid electrolyte cells

    SciTech Connect

    Stoukides, M.

    1990-01-25

    The present report covers the first year of the three year project. The work is funded 50-50{percent} by the National Science Foundation and the Department of Energy. The NSF support started on February 15, 1989 while the DOE support started on September 15, 1989. This created some minor difficulties in the budget distribution but hopefully within the second year everything will be smoothed out. The personnel involved in the project includes the principal investigator (M. Stoukides) who devotes 25-30{percent} of his time during the year. Douglas Eng who recently received his Ph.D. degree is going to work as a research scientists in the project on a full-time basis. Dr. Eng worked under the P.I. in the area of methane oxidation and he is probable the most qualified person for this position. Mr. Po-Hung Chiang has started working as a Ph.D. candidate in the H{sup +} solid electrolyte aided study of methane dimerization. Mr. Hyatham Algahtang, a new graduate student, is the most favorite candidate for the study of NH{sub 3} synthesis. He is already examining preliminary aspects of the project. Most of the equipment required for this research was in operating condition in the laboratory. Additional equipment purchased included a Lindberg furnace that could reach as high as 1500{degree}C (for fabrication of the solid electrolyte) and a Rosemount Analytical hydrogen analyzer (for continuous measurement of the concentration of hydrogen on either the cathodic or the anodic side). 12 refs., 2 figs.

  16. Penicillin acylase-catalyzed synthesis of pivampicillin: Effect of reaction variables and organic cosolvents

    Microsoft Academic Search

    Min Gon Kim; Sun Bok Lee

    1996-01-01

    Enzymatic synthesis of pivampicillin (PVM) from D-?-phenylglycine methyl ester (PGM) and pivaloyloxymethyl 6-aminopenicillanic acid (POM-6-APA) was investigated using an immobilized Escherichia coli penicillin acylase. The effects of reaction variables such as enzyme concentration, pH, temperature, and molar ratio of the substrates on PVM synthesis were investigated. The time-course profiles of the PVM synthesis reaction followed a typical pattern of the

  17. Targeting spatiotemporal dynamics of planktonic SAGMGC-1 and segregation of ammonia-oxidizing thaumarchaeota ecotypes by newly designed primers and quantitative polymerase chain reaction.

    PubMed

    Restrepo-Ortiz, Claudia X; Auguet, Jean-Christophe; Casamayor, Emilio O

    2014-03-01

    The annual dynamics of three different ammonia-oxidizing archaea (AOA) ecotypes (amoA gene) and of the SAGMGC-1 (Nitrosotalea-like aquatic Thaumarchaeota) group (16S rRNA gene) were studied by newly designed specific primers and quantitative polymerase chain reaction analysis in a deep oligotrophic high mountain lake (Lake Redon, Limnological Observatory of the Pyrenees, Spain). We observed segregated distributions of the main AOA populations, peaking separately in time and space, and under different ammonia concentrations and irradiance conditions. Strong positive correlation in gene abundances was found along the annual survey between 16S rRNA SAGMAGC-1 and one of the amoA ecotypes suggesting the potential for ammonia oxidation in the freshwater SAGMAGC-1 clade. We also observed dominance of Nitrosotalea-like ecotypes over Nitrosopumilus-like (Marine Group 1.1a) and not the same annual dynamics for the two thaumarchaeotal clades. The fine scale segregation in space and time of the different AOA ecotypes indicated the presence of phylogenetically close but ecologically segregated AOA species specifically adapted to specific environmental conditions. It remains to be elucidated what would be such environmental drivers. PMID:23848190

  18. Glow Discharge Enhanced Chemical Reaction: Application in Ammonia Synthesis and Hydrocarbon Gas Cleanup 

    E-print Network

    Ming, Pingjia

    2014-06-05

    of 74% and 54% available output energy was achieved. At the same time, the concentration of ethane, ethylene, propane, propylene, and acetylene were cleaned-up to value of 1.01%, 1.67%, 0.08%, 0.00%, and 0.50%, respectively, less than 20...

  19. Glow Discharge Enhanced Chemical Reaction: Application in Ammonia Synthesis and Hydrocarbon Gas Cleanup

    E-print Network

    Ming, Pingjia

    2014-06-05

    ....................................................................... 35 Figure 15. Mass spectrometer and vacuum pump ........................................................ 36 Figure 16. SRI 8600C multiple gas analyzer GC .......................................................... 37 Figure 17. Valve is in the LOAD... to development of alternate energy generation techniques like fuel cells. Since the products are mainly water and less undesirable noxious, which have lower 5 impact on environment. Moreover, high temperature fuel cell system is better tolerance...

  20. Wittig reactions in water. Synthesis of new water-soluble phosphonium salts and their reactions with substituted benzaldehydes

    Microsoft Academic Search

    Matthew G Russell; Stuart Warren

    1998-01-01

    We report the synthesis of new phosphonium salts which are soluble and stable in basic aqueous solution. The Wittig reactions of these phosphonium salts with substituted benzaldehydes in aqueous sodium hydroxide are discussed. These reactions exclude the use of any organic solvents and the products are isolated by a simple filtration.

  1. Solid-state reaction synthesis of boron carbonitride nanotubes

    NASA Astrophysics Data System (ADS)

    Mo, Libin; Chen, Yongjun; Luo, Lijie

    2010-07-01

    In this study, a simple route for synthesis of ternary boron carbonitride (B-C-N) nanotubes was demonstrated, by heating ball-milled mixture powders of amorphous boron and activated charcoal with a small amount of iron oxide (Fe2O3) at 1000-1200°C under a mixture gas flow of nitrogen (N2) and hydrogen (H2). The reduction of Fe2O3 by H2 at 650°C produced Fe nanoparticles, playing the role of a catalyst during the nanotube growth. The nanotubes synthesized at 1100°C exhibit two morphologies. One is a bamboo-like structure with thick compartments. The other is a quasi-cylindrical structure with thin or disappearing compartments. The average diameter of the nanotubes is about 80 nm. It is found that the reaction temperature has a great influence on the morphology, diameter and yield of the B-C-N nanotubes. Higher temperature (1200°C) is favorable for the formation of quasi-cylindrical nanotubes with larger diameters, while lower temperature (1000°C) enhances the formation of bamboo-like nanotubes with smaller diameters; the yield of nanotubes decreases with the rise of reaction temperature. The nanotubes grow via a combination mechanism of solid-liquid-solid (SLS) and vapor-liquid-solid (VLS) models.

  2. Method for polymer synthesis in a reaction well

    DOEpatents

    Brennan, Thomas M. (San Francisco, CA)

    1998-01-01

    A method of synthesis for building a polymer chain, oligonucleotides in particular, by sequentially adding monomer units to at least one solid support for growing and immobilizing a polymer chain thereon in a liquid reagent solution. The method includes the step of: A) depositing a liquid reagent in a reaction well (26) in contact with at least one solid support and at least one monomer unit of the polymer chain affixed to the solid support. The well (26) includes at least one orifice (74) extending into the well (26), and is of a size and dimension to form a capillary liquid seal to retain the reagent solution in the well (26) to enable polymer chain growth on the solid support. The method further includes the step of B) expelling the reagent solution from the well (26), while retaining the polymer chain therein. This is accomplished by applying a first gas pressure to the reaction well such that a pressure differential between the first gas pressure and a second gas pressure exerted on an exit (80) of the orifice (74) exceeds a predetermined amount sufficient to overcome the capillary liquid seal and expel the reagent solution from the well (26) through the orifice exit (80).

  3. Ammonia Monitor

    NASA Technical Reports Server (NTRS)

    Sauer, Richard L. (Inventor); Akse, James R. (Inventor); Thompson, John O. (Inventor); Atwater, James E. (Inventor)

    1999-01-01

    Ammonia monitor and method of use are disclosed. A continuous, real-time determination of the concentration of ammonia in an aqueous process stream is possible over a wide dynamic range of concentrations. No reagents are required because pH is controlled by an in-line solid-phase base. Ammonia is selectively transported across a membrane from the process stream to an analytical stream to an analytical stream under pH control. The specific electrical conductance of the analytical stream is measured and used to determine the concentration of ammonia.

  4. Coproduct Promoted Povarov Reaction: Synthesis of Substituted Quinolines from Methyl Ketones, Arylamines, and ?-Ketoesters.

    PubMed

    Gao, Qinghe; Liu, Shan; Wu, Xia; Zhang, Jingjing; Wu, Anxin

    2015-06-01

    A highly efficient I2-catalyzed Povarov-type reaction of methyl ketones, arylamines, and ?-ketoesters is developed. This reaction utilizes a catalytic amount of HI coproduct as a promoter for the synthesis of substituted quinolones. This simple procedure represents an interesting new form of reactivity for the Povarov reaction with good functional group compatibility. PMID:25973528

  5. A Concise Approach to the Synthesis of opp-Dibenzoporphyrins through the Heck Reaction

    SciTech Connect

    Deshpande, Rohit [Miami University, Oxford, OH; Jiang, Lin [Miami University, Oxford, OH; Schmidt, Gregory [Miami University, Oxford, OH; Rakovan, John [Miami University, Oxford, OH; Wang, Xiaoping [ORNL; Wheeler, Kraig [Eastern Illinois University; Wang, Hong [Miami University, Oxford, OH

    2009-01-01

    A concise approach to the synthesis of functionalized opp-dibenzoporphyrins is described. In this method, introduction of alkenyl groups to the porphyrin periphery through the vicinal 2-fold Heck reaction, 6- electrocyclization, and subsequent aromatization occur in one pot.

  6. Sulfated zirconia as an efficient catalyst for organic synthesis and transformation reactions

    Microsoft Academic Search

    Benjaram M. Reddy; Pavani M. Sreekanth; Pandian Lakshmanan

    2005-01-01

    The efficacy of sulfated zirconia catalyst was investigated towards various acid-catalyzed organic syntheses and transformation reactions in the liquid phase. The SO42?\\/ZrO2 efficiently catalyzes synthesis of 1,5-benzodiazepine derivatives, electrophilic substitution of indoles with aldehydes to afford the corresponding bis(indolyl)methanes, synthesis of 3,4-dihydropyrimidinones, synthesis of diaryl sulfoxides, and tetrahydropyranylation of alcohols and phenols. Various advantages associated with these protocols include, simple

  7. Surfactant-free synthesis of plasmonic tungsten oxide nanowires with visible-light-enhanced hydrogen generation from ammonia borane.

    PubMed

    Lou, Zaizhu; Gu, Quan; Xu, Lin; Liao, Yusen; Xue, Can

    2015-06-01

    WO3-x nanowires were successfully synthesized through a simple surfactant-free solvothermal method. These nanowires exhibit strong plasmonic absorption in the visible and near-infrared region owing to the abundant oxygen vacancies. The plasmon excitation of these WO3-x nanowires provide five times enhancement on the hydrogen generation from ammonia borane. PMID:25873477

  8. Synthesis of non-racemic ?-hydroxyphosphonates via asymmetric phospho-aldol reaction.

    PubMed

    Spilling, Christopher D; Malla, Raj K

    2015-01-01

    It has been more than 50 years since the first phospho-aldol reactions of dialkyl phosphites were reported. These efficient P-C bond-forming reactions have become the cornerstone of methods for the synthesis of ?-hydroxyphosphonates and, by numerous available substitution reactions, the synthesis of other ?- and ?-substituted phosphonates and phosphonic acids. Much of the interest in ?- and ?-substituted phosphonates and phosphonic acids has been stimulated by reports of their biological activity, which is often dependent upon their absolute and relative stereochemistry. In this chapter, we review diastereoselective and enantioselective additions of dialkyl phosphites to aldehydes and ketones, otherwise called the phospho-aldol, Pudovik or Abramov reactions. PMID:25467537

  9. A diastereoselective synthesis of pyrano fused coumarins via organocatalytic three-component reaction.

    PubMed

    Ahadi, Somayeh; Zolghadr, Mahdi; Khavasi, Hamid Reza; Bazgir, Ayoob

    2013-01-14

    A new method for the synthesis of pyran fused coumarins by 3-bromo-4-hydroxycoumarins as cyclic ?-halo ketones based on an organocatalyst assisted three-component tandem reaction is investigated. To the best of our knowledge, cyclic ?-halo ketones have not yet been used for the synthesis of pyran fused coumarins. PMID:23174817

  10. Synthesis of 1,4,5 trisubstituted ?-lactams via a 3-component cascade reaction.

    PubMed

    Petersen, Michael Xman; Mortensen, Michael A; Cohrt, A Emil; Petersen, Rico; Wu, Peng; Fleury-Brégeot, Nicolas; Morgentin, Rémy; Lardy, Claude; Nielsen, Thomas E; Clausen, Mads H

    2015-06-01

    A three component one-pot cascade reaction was developed for the synthesis of 1,4,5-trisubstituted ?-lactams. The resulting scaffold can be modified independently at three positions, two of which are conveniently accessed by changing the components of the one-pot reaction. The phases of building block generation, scaffold synthesis and subsequent appendage modification were adapted to library production, which resulted in a screening library of 500 compounds. PMID:25684425

  11. Thermal and combined thermal and radiolytic reactions involving nitrous oxide, hydrogen, nitrogen, and ammonia in contact with tank 241-SY-101 simulated waste

    SciTech Connect

    Bryan, S.A.; Pederson, L.R.

    1996-02-01

    Work described in this report was conducted at Pacific Northwest National Laboratory (PNNL) for the Flammable Gas Safety Project, the purpose of which is to develop information needed to support Westinghouse Hanford Company (WHC) in their efforts to ensure the safe interim storage of wastes at the Hanford Site. Described in this report are the results of tests to evaluate the rates of thermal and combined thermal and radiolytic reactions involving flammable gases in the presence of Tank 241-SY-101 simulated waste. Flammable gases generated by the radiolysis of water and by the thermal and radiolytic decomposition of organic waste constituents may themselves participate in further reactions. Examples include the decomposition of nitrous oxide to yield nitrogen and oxygen, the reaction of nitrous oxide and hydrogen to produce nitrogen and water, and the reaction of nitrogen and hydrogen to produce ammonia. The composition of the gases trapped in bubbles in the wastes might therefore change continuously as a function of the time that the gas bubbles are retained.

  12. Revisiting a Classic Approach to the Aspidosperma Alkaloids: An Intramolecular Schmidt Reaction-Mediated Synthesis of (+)-Aspidospermidine

    PubMed Central

    Iyengar, Rajesh; Schildknegt, Klaas; Morton, Martha; Aubé, Jeffrey

    2008-01-01

    A total synthesis of (+)-aspidospermidine (1) is described. The key reactions used in the synthesis of this pentacyclic Aspidosperma alkaloid were a deracemizing imine alkylation/Robinson annulation sequence, a selective “redox ketalization” and an intramolecular Schmidt reaction. A Fischer indolization step carried out on a tricyclic ketone mirrored the sequence reported by Stork and Dolfini in their classic aspidospermine synthesis. PMID:16355981

  13. A detailed investigation of proposed gas-phase syntheses of ammonia in dense interstellar clouds

    NASA Technical Reports Server (NTRS)

    Herbst, Eric; Defrees, D. J.; Mclean, A. D.

    1987-01-01

    The initial reactions of the Herbst and Klemperer (1973) and the Dalgarno (1974) schemes (I and II, respectively) for the gas-phase synthesis of ammonia in dense interstellar clouds were investigated. The rate of the slightly endothermic reaction between N(+) and H2 to yield NH(+) and H (scheme I) under interstellar conditions was reinvestigated under thermal and nonthermal conditions based on laboratory data. It was found that the relative importance of this reaction in synthesizing ammonia is determined by how the laboratory data at low temperature are interpreted. On the other hand, the exothermic reaction between N and H3(+) to form NH2(+) + H (scheme II) was calculated to possess significant activation energy and, therefore, to have a negligible rate coefficient under interstellar conditions. Consequently, this reaction cannot take place appreciably in interstellar clouds.

  14. Ammonia Test

    MedlinePLUS

    ... diagnose the cause of a coma of unknown origin or to help support the diagnosis of Reye's ... clearing them. Normal concentrations of ammonia do not rule out hepatic encephalopathy . Other wastes can contribute to ...

  15. Ammonia - blood

    MedlinePLUS

    ... is most commonly used to diagnose and monitor hepatic encephalopathy , a severe liver disease. Ammonia (NH3) is ... Elsevier; 2011:chap 149. Nevah MI, Fallon MB. Hepatic encephalopathy, hepatorenal syndrome, hepatopulmonary syndrome, and systemic complications ...

  16. Synthesis and structural characterization of a C? cumulene including 4-pyridylidene units, and its reactivity towards ammonia-borane.

    PubMed

    Wu, Di; Li, Yongxin; Ganguly, Rakesh; Kinjo, Rei

    2014-10-21

    A novel type of C4 cumulene derivative featuring 4-pyridylidene units has been synthesized. X-ray diffraction analysis revealed the presence of consecutive C=C double bonds in the C4 backbone as well as the quinoidal pyridylidene structure. This C4 cumulene derivative readily reacted with ammonia-borane, which resulted in transfer hydrogenation of the central C=C double bond. PMID:25185673

  17. Ammonia formation by metal-ligand cooperative hydrogenolysis of a nitrido ligand.

    PubMed

    Askevold, Bjorn; Nieto, Jorge Torres; Tussupbayev, Samat; Diefenbach, Martin; Herdtweck, Eberhardt; Holthausen, Max C; Schneider, Sven

    2011-07-01

    Bioinspired hydrogenation of N(2) to ammonia at ambient conditions by stepwise nitrogen protonation/reduction with metal complexes in solution has experienced remarkable progress. In contrast, the highly desirable direct hydrogenation with H(2) remains difficult. In analogy to the heterogeneously catalysed Haber-Bosch process, such a reaction is conceivable via metal-centred N(2) splitting and unprecedented hydrogenolysis of the nitrido ligands to ammonia. We report the synthesis of a ruthenium(IV) nitrido complex. The high nucleophilicity of the nitrido ligand is demonstrated by unusual N-C coupling with ?-acidic CO. Furthermore, the terminal nitrido ligand undergoes facile hydrogenolysis with H(2) at ambient conditions to produce ammonia in high yield. Kinetic and quantum chemical examinations of this reaction suggest cooperative behaviour of a phosphorus-nitrogen-phosphorus pincer ligand in rate-determining heterolytic hydrogen splitting. PMID:21697873

  18. Ammonia formation by metal-ligand cooperative hydrogenolysis of a nitrido ligand

    NASA Astrophysics Data System (ADS)

    Askevold, Bjorn; Nieto, Jorge Torres; Tussupbayev, Samat; Diefenbach, Martin; Herdtweck, Eberhardt; Holthausen, Max C.; Schneider, Sven

    2011-07-01

    Bioinspired hydrogenation of N2 to ammonia at ambient conditions by stepwise nitrogen protonation/reduction with metal complexes in solution has experienced remarkable progress. In contrast, the highly desirable direct hydrogenation with H2 remains difficult. In analogy to the heterogeneously catalysed Haber-Bosch process, such a reaction is conceivable via metal-centred N2 splitting and unprecedented hydrogenolysis of the nitrido ligands to ammonia. We report the synthesis of a ruthenium(IV) nitrido complex. The high nucleophilicity of the nitrido ligand is demonstrated by unusual N-C coupling with ?-acidic CO. Furthermore, the terminal nitrido ligand undergoes facile hydrogenolysis with H2 at ambient conditions to produce ammonia in high yield. Kinetic and quantum chemical examinations of this reaction suggest cooperative behaviour of a phosphorus-nitrogen-phosphorus pincer ligand in rate-determining heterolytic hydrogen splitting.

  19. Evaluation of candidate catalysts for an ammonia-based solar thermochemical receiver

    SciTech Connect

    Nandy, S.; Lenz, T.G.; Harris, J.A.; Wright, J.H.

    1981-01-01

    An experimental program is under way to determine the feasibility of using a reversible ammonia dissociation-synthesis reaction to collect and transport high temperature solar energy. Different heat and mass transfer rate limiting steps for this reaction are being analyzed. Current experimental work centers on evaluation of activities of nickel and iron catalysts (on ..cap alpha..- and ..gamma..-Al/sub 2/O/sub 3/ substrates). This paper describes experimental evaluation of the activities of these ammonia dissociation catalysts. For example, we found 6.9 weight % Ni on ..cap alpha..-Al/sub 2/O/sub 3/ substrate to have an activation energy of about 50 kcal/gm mole in high pressure ammonia dissociation.

  20. Action Reaction Learning: Automatic Visual Analysis and Synthesis of Interactive Behaviour

    E-print Network

    Jebara, Tony

    ] utilizes neural learning techniques to predict walking behaviours and discusses interactive behaviourAction Reaction Learning: Automatic Visual Analysis and Synthesis of Interactive Behaviour Tony/arl Abstract We propose Action-Reaction Learning as an approach for analyzing and synthesizing human be

  1. Action Reaction Learning: Automatic Visual Analysis and Synthesis of Interactive Behaviour

    E-print Network

    behaviour. Johnson [17] utilizes neural learning techniques to predict walking behaviours and discussesAction Reaction Learning: Automatic Visual Analysis and Synthesis of Interactive Behaviour Tony://www.media.mit.edu/¸jebara/arl Abstract We propose Action­Reaction Learning as an approach for analyzing and synthesizing human be

  2. Synthesis and Decomposition of Zinc Iodide: Model Reactions for Investigating Chemical Change in the Introductory Laboratory

    Microsoft Academic Search

    Stephen Demeo

    1995-01-01

    The purpose of this article is to discuss two colorful reactions not widely used by chemical educators in high schools or college chemistry laboratories: The synthesis of zinc iodide from its elements, zinc and iodine, and the subsequent decomposition of zinc iodide back into its elements. These reactions are important for chemistry teachers to know about because they can be

  3. Research Paper Sugar Synthesis from a Gas-Phase Formose Reaction

    Microsoft Academic Search

    ABRAHAM F. JALBOUT; LEIF ABRELL; LUDWIK ADAMOWICZ; ROBIN POLT; A. J. APPONI; L. M. ZIURYS

    Prebiotic possibilities for the synthesis of interstellar ribose through a protic variant of the formose reaction under gas-phase conditions were studied in the absence of any known cat- alyst. The ion-molecule reaction products, diose and triose, were sought by mass spectrome- try, and relevant masses were observed. Ab initio calculations were used to evaluate protic formose mechanism possibilities. A bilateral

  4. Carbon-Carbon Bond Cleavage Reaction: Synthesis of Multisubstituted Pyrazolo[1,5-a]pyrimidines.

    PubMed

    Saikia, Pallabi; Gogoi, Sanjib; Boruah, Romesh C

    2015-07-01

    A new carbon-carbon bond cleavage reaction was developed for the efficient synthesis of multisubstituted pyrazolo[1,5-a]pyrimidines. This base induced reaction of 1,3,5-trisubstituted pentane-1,5-diones and substituted pyrazoles afforded good yields of the pyrazolo[1,5-a]pyrimidines. PMID:26083788

  5. First principle analysis of the catalytic reaction pathways in the synthesis of vinyl acetate

    Microsoft Academic Search

    Rutger A van Santen; WD Provine; DA Dixon; GW Coulston; JJ Lerou; Santen van RA

    1996-01-01

    Acetoxylation of ethylene over supported palladium and palladium\\/gold is a well established commercial route for the formation of vinyl acetate. While the overall reaction chemistry for the synthesis of vinyl acetate was uncovered some thirty years ago (Eur. Chem. News 1967; World Pet. Cong. Proc. 1968, U.S. Patent 1967 & 1977), the active catalytic surface ensembles, key reaction intermediates, and

  6. Combustion Synthesis Reactions in Cold-Rolled Ni/Al and Ti/Al Multilayers

    NASA Astrophysics Data System (ADS)

    Qiu, Xiaotun; Liu, Ranran; Guo, Shengmin; Graeter, Jesse Harris; Kecskes, Laszlo; Wang, Jiaping

    2009-07-01

    In this article, a cold rolling method was developed to fabricate Ni/Al and Ti/Al multilayer foils, and the combustion synthesis reactions in the cold-rolled foils were investigated. Combustion synthesis reactions were initiated by heating one end of the cold-rolled foil in a flame for several seconds. The Ni/Al foils went through three reaction stages. The first reaction stage was a displacement of reaction zone with Al3Ni as the reaction product. During the second stage, the part of the foil in the flame underwent thermal explosion. In the last stage, the heat released by thermal explosion triggered a self-propagating high-temperature synthesis (SHS) reaction across the foil that resulted in the formation of AlNi. In contrast, the Ti/Al foils experienced only two reaction stages. First, a displacement of the reaction zone propagated across the foil with formation of Al3Ti at the Ti/Al interface. Then a thermal explosion reaction occurred in the part of foil that was heated in the flame, resulting in many different phases in the reacted foil.

  7. Chem 115Stereoselective Olefination Reactions: The Wittig ReactionMyers Olefin synthesis employing phosphonium ylides was introduced in 1953 by Wittig and Geissler

    E-print Network

    Chem 115Stereoselective Olefination Reactions: The Wittig ReactionMyers Olefin synthesis employing phosphonium ylides was introduced in 1953 by Wittig and Geissler: Wittig Olefination, Background: Wittig, G Reactions: The Wittig ReactionMyers Fan Liu Stabilized ylides are proposed to have a later and more product

  8. Isotope effects in the transient phases of the reaction catalyzed by ethanolamine ammonia-lyase: determination of the number of exchangeable hydrogens in the enzyme-cofactor complex.

    PubMed

    Bandarian, V; Reed, G H

    2000-10-01

    Transient phases of the reaction catalyzed by ethanolamine ammonia-lyase (EAL) from Salmonella typhimurium have been investigated by stopped-flow visible spectrophotometry and deuterium kinetic isotope effects. The cleavage of adenosylcobalamin (coenzyme B(12)) to form cob(II)alamin (B(12r)) with ethanolamine as the substrate occurred within the dead time of the instrument whenever coenzyme B(12) was preincubated with enzyme prior to mixing with substrate. The rate was, however, slowed sufficiently to be measured with perdeutero ethanolamine as the substrate. Optical spectra indicate that, during the steady states of the reactions with ethanolamine and with S-2-aminopropanol as substrates, approximately 90% of the active sites contain B(12r). Reformation of the carbon-cobalt bond of the cofactor occurs following depletion of substrate in the reaction mixtures, and the rate constant for this process reflects k(cat) of the respective substrates. This late phase of the reaction also exhibits (2)H isotope effects similar to those measured for the overall reaction with (2)H-labeled substrates. With unlabeled substrates, the rate of cofactor reassembly is independent of the number of substrate molecules turned over in the steady-state phase. However, with (2)H-labeled substrates, kinetic isotope effects appear in the reassembly phase, and these isotope effects are maximal after only approximately 2 equiv of substrate/active site are processed. With 5'-deuterated coenzyme B(12) and deuterated substrate, the isotope effect on reassembly is independent of the number of substrate molecules that are turned over. These results indicate that the pool of exchangeable hydrogens in the enzyme-cofactor complex is two-a finding consistent with the hydrogens in the C5' methylene of coenzyme B(12). PMID:11009622

  9. Synthesis of tetrasubstituted 1-silyloxy-3-aminobutadienes and chemistry beyond Diels-Alder reactions.

    PubMed

    Li, Xijian; Peng, Siyu; Li, Li; Huang, Yong

    2015-01-01

    Electron-rich dienes have revolutionized the synthesis of complex compounds since the discovery of the legendary Diels-Alder cycloaddition reaction. This highly efficient bond-forming process has served as a fundamental strategy to assemble many structurally formidable molecules. Amino silyloxy butadienes are arguably the most reactive diene species that are isolable and bottleable. Since the pioneering discovery by Rawal, 1-amino-3-silyloxybutadienes have been found to undergo cycloaddition reactions with unparalleled mildness, leading to significant advances in both asymmetric catalysis and total synthesis of biologically active natural products. In sharp contrast, this class of highly electron-rich conjugated olefins has not been studied in non-cycloaddition reactions. Here we report a simple synthesis of tetrasubstituted 1-silyloxy-3-aminobutadienes, a complementarily substituted Rawal's diene. This family of molecules is found to undergo a series of intriguing chemical transformations orthogonal to cycloaddition reactions. Structurally diverse polysubstituted ring architectures are established in one step from these dienes. PMID:25898310

  10. Synthesis of tetrasubstituted 1-silyloxy-3-aminobutadienes and chemistry beyond Diels–Alder reactions

    PubMed Central

    Li, Xijian; Peng, Siyu; Li, Li; Huang, Yong

    2015-01-01

    Electron-rich dienes have revolutionized the synthesis of complex compounds since the discovery of the legendary Diels–Alder cycloaddition reaction. This highly efficient bond-forming process has served as a fundamental strategy to assemble many structurally formidable molecules. Amino silyloxy butadienes are arguably the most reactive diene species that are isolable and bottleable. Since the pioneering discovery by Rawal, 1-amino-3-silyloxybutadienes have been found to undergo cycloaddition reactions with unparalleled mildness, leading to significant advances in both asymmetric catalysis and total synthesis of biologically active natural products. In sharp contrast, this class of highly electron-rich conjugated olefins has not been studied in non-cycloaddition reactions. Here we report a simple synthesis of tetrasubstituted 1-silyloxy-3-aminobutadienes, a complementarily substituted Rawal's diene. This family of molecules is found to undergo a series of intriguing chemical transformations orthogonal to cycloaddition reactions. Structurally diverse polysubstituted ring architectures are established in one step from these dienes. PMID:25898310

  11. Ultrasound-assisted synthesis of unsymmetrical biaryls by Stille cross-coupling reactions.

    PubMed

    Domini, Claudia E; Silbestri, Gustavo F; Fernández Band, Beatriz; Chopa, Alicia B

    2012-05-01

    We describe herein an efficient method for the synthesis of unsymmetrically-substituted biphenyls using a sonochemical variation of the Stille coupling, whose results have also been compared with the conventional silent reaction. Ultrasound significantly enhances this useful organometallic transformation affording products in higher yields and in shorter reaction times than non-irradiated reactions. The scope has been explored with a selection of arylstannanes as precursors and, remarkably, no by-products resulting from homo-coupling could be detected. PMID:22019789

  12. Synthesis of transactinide nuclei in cold fusion reactions using radioative beams

    E-print Network

    Smolanczuk, Robert

    2009-01-01

    Chances of synthesis of transactinide nuclei in cold fusion reactions (one-neutron-out) reactions using radioactive beams are evaluated. Because intensities of radioactive beams are in most of the cases significantly lower than the ones of the stable beams, reactions with the highest radioactive beam intensities for the particular elements are considered. The results are compared with the recent ones obtained by Loveland who investigated the same nuclei.

  13. Synthesis of transactinide nuclei in cold fusion reactions using radioative beams

    E-print Network

    Robert Smolanczuk

    2009-12-04

    Chances of synthesis of transactinide nuclei in cold fusion reactions (one-neutron-out) reactions using radioactive beams are evaluated. Because intensities of radioactive beams are in most of the cases significantly lower than the ones of the stable beams, reactions with the highest radioactive beam intensities for the particular elements are considered. The results are compared with the recent ones obtained by Loveland who investigated the same nuclei.

  14. Synthesis of transactinide nuclei in cold fusion reactions using radioactive beams

    SciTech Connect

    Smolanczuk, Robert [Theoretical Physics Department, Soltan Institute for Nuclear Studies, Hoza 69, PL-00-681 Warszawa (Poland)

    2010-06-15

    Chances of synthesis of transactinide nuclei in cold fusion reactions (one-neutron-out reactions) using radioactive beams are evaluated. Because in most of the cases intensities of radioactive beams are significantly less than those of the stable beams, reactions with the greatest radioactive-beam intensities for the particular elements are considered. The results are compared with the recent ones obtained by Loveland [Phys. Rev. C 76, 014612 (2007)], who investigated the same nuclei.

  15. Combustion synthesis of fine AlN powder and its reaction control

    Microsoft Academic Search

    T. Sakurai; O. Yamada; Y. Miyamoto

    2006-01-01

    Aluminum nitride powder produced by the combustion synthesis (SHS) usually contains coarse particles because of its high reaction temperature. These particles make it difficult to achieve sintering. To improve sinterability, the reaction temperature was controlled by adding hydrogen gas up to 20vol.% to the reactant gas (nitrogen), and NH4F up to 1.5mass% to the reactant mixture. The reaction temperature was

  16. Screening of electrocatalysts for direct ammonia fuel cell: Ammonia oxidation on PtMe (Me: Ir, Rh, Pd, Ru) and preferentially oriented Pt(1 0 0) nanoparticles

    Microsoft Academic Search

    F. J. Vidal-Iglesias; J. Solla-Gullón; V. Montiel; J. M. Feliu; A. Aldaz

    2007-01-01

    Ammonia has attracted attention as a possible fuel for direct fuel cells since it is easy to handle and to transport as liquid or as concentrated aqueous solution. However, on noble metal electrodes ammonia oxidation is a sluggish reaction and the electrocatalyst needs to be improved for developing efficient ammonia fuel cells. In this work, ammonia electrooxidation reaction on 3–4-nm

  17. Samarium Diiodide-Mediated Reactions in Total Synthesis

    PubMed Central

    Nicolaou, K. C.; Ellery, Shelby P.; Chen, Jason S.

    2009-01-01

    Introduced by Henri Kagan more than three decades ago, samarium diiodide (SmI2) has found increasing applications in chemical synthesis. This single-electron reducing agent has been particularly useful in C–C bond formations, including those found in total synthesis endeavors. This Review highlights selected applications of SmI2 in total synthesis, with special emphasis on novel transformations and mechanistic considerations. The examples discussed are both illustrative of the power of this reagent in complex molecule construction and inspirational for the design of synthetic strategies toward such targets, both natural and designed. PMID:19714695

  18. The synthesis and benzannulation reactions of (trialkylsilyl)vinylketenes

    E-print Network

    Austin, Wesley F

    2008-01-01

    (Trialkylsilyl)vinylketenes ("TAS-vinylketenes") are versatile four-carbon building blocks in a variety of methods for the synthesis of carbocyclic and heterocyclic compounds. This thesis discusses the development of a new ...

  19. Developing novel organocatalyzed aldol reactions for the enantioselective synthesis of biologically active molecules

    PubMed Central

    Bhanushali, Mayur; Zhao, Cong-Gui

    2011-01-01

    Aldol reaction is one of the most important methods for the formation of carbon-carbon bonds. Because of its significance and usefulness, asymmetric versions of this reaction have been realized with different approaches in the past. Over the last decade, the area of organocatalysis has made significant progresses. As one of most studied reactions in organocatalyses, organocatalyzed aldol reaction has emerged as a powerful tool for the synthesis of a large number of useful products in optically enriched forms. In this review, we summarize our efforts on the development of novel organocatalyzed aldol reactions for the enantioselective synthesis of biological active molecules. Literatures closely related to our studies are also covered. PMID:21918584

  20. Self-sustained high-temperature reactions: initiation, propagation and synthesis

    Microsoft Academic Search

    M. Martinez Pacheco

    2007-01-01

    Self-Propagating High-Temperature Synthesis (SHS), also called combustion synthesis is an exothermic and self-sustained reaction between the constituents, which has assumed significance for the production of ceramics and ceramic-metallic materials (cermets), because it is a very rapid processing technique without the need of complex furnaces. However, one of the drawbacks of this route is the high porosity of the final product

  1. Expedient synthesis of a highly substituted tropolone via a 3-oxidopyrylium [5+2] cycloaddition reaction

    Microsoft Academic Search

    Jack E. Baldwin; Alexander V. W. Mayweg; Gareth J. Pritchard; Robert M. Adlington

    2003-01-01

    An expedient ten-step synthesis of a substituted tropolone is described. The synthesis involves a 3-oxidopyrylium [5+2] cycloaddition reaction with acrylonitrile as the key step, affording a highly functionalized [3.2.1]-bicycle 10 as a single regioisomer. The nitrile substituent of the reduced cycloadduct 12 permits efficient ether-bridge cleavage and tropolone 15 is obtained after a final bis-oxidation procedure. The pyranulose acetate cycloaddition

  2. Formation of ammonia from dinitrogen under primordial conditions

    NASA Astrophysics Data System (ADS)

    Weigand, W.; Dörr, M.; Robl, C.; Kreisel, G.; Grunert, R.; Käßbohrer, J.; Brand, W.; Werner, R.; Popp, J.; Tarcea, N.

    2002-11-01

    Ammonia is one of the most largely industrially produced basic compounds, leading to a variety of important secondary products. In the chemical industry, ammonia is produced in large amounts via the HABER-BOSCH-process. In contrast to the industrial process, the nitrogenase enzyme operates in organisms under very mild conditions at atmospheric pressure and ambient temperature. In this article, we describe a method for the synthesis of ammonia from molecular nitrogen using H2S and freshly precipitated iron sulfide as a mediator thus serving as a primordial inorganic substitute for the enzyme nitrogenase. The reductand, as well as the reaction conditions (atmospheric nitrogen pressure and temperatures on the order of 70 - 80°C) are rather mild and therefore comparable to the biological processes. The driving force of the overall reaction is believed to be the oxidation of iron sulfide to iron disulfide, and the formation of hydrogen from H2S. The reactions reported in this article may support the theory of an archaic nitrogen-fixing Fe-S cluster.

  3. Divergent synthesis of chiral heterocycles via sequencing of enantioselective three-component reactions and one-pot subsequent cyclization reactions.

    PubMed

    Tang, Min; Xing, Dong; Huang, Haoxi; Hu, Wenhao

    2015-07-01

    A highly efficient sequencing of catalytic asymmetric three-component reactions of alcohols, diazo compounds and aldimines/aldehydes with one-pot subsequent cyclization reactions was reported. The development of a robust and versatile Rh(ii)/Zr(iv)-BINOL co-catalytic system not only gives high diastereo- and enantioselective controls of the three-component reaction, but also shows excellent functionality tolerances that allow a wide range of functionalities to be pre-installed in each component and readily undergo one-pot subsequent cyclization reactions, thus providing rapid and diversity-oriented synthesis (DOS) of different types of chiral nitrogen- and/or oxygen-containing polyfunctional heterocycles. PMID:25864421

  4. Diffusion of ammonia gas in PDMS characterized by ATR spectroscopy

    NASA Astrophysics Data System (ADS)

    Levinský, Petr; Kalvoda, Ladislav; Aubrecht, Jan; Fojtíková, Jaroslava

    2015-01-01

    The kinetic parameters of a chemo-optical transducer layer sensitive to gaseous ammonia are characterized by means of attenuation total reflection method. The tested layer consists of cross-linked polydimethylsiloxane matrix sensitized by quinoline-based organometallic dye showing the selective chemical reaction with ammonia. Upper and lower limits of the ammonia diffusion coefficient and the ammonia-dye reaction constant are derived from the obtained experimental data and compared with other data available in literature and obtained from computer simulations.

  5. Oxidative and nitrosative stress in ammonia neurotoxicity.

    PubMed

    Skowro?ska, Marta; Albrecht, Jan

    2013-04-01

    Increased ammonia accumulation in the brain due to liver dysfunction is a major contributor to the pathogenesis of hepatic encephalopathy (HE). Fatal outcome of rapidly progressing (acute) HE is mainly related to cytotoxic brain edema associated with astrocytic swelling. An increase of brain ammonia in experimental animals or treatment of cultured astrocytes with ammonia generates reactive oxygen and nitrogen species in the target tissues, leading to oxidative/nitrosative stress (ONS). In cultured astrocytes, ammonia-induced ONS is invariably associated with the increase of the astrocytic cell volume. Interrelated mechanisms underlying this response include increased nitric oxide (NO) synthesis which is partly coupled to the activation of NMDA receptors and increased generation of reactive oxygen species by NADPH oxidase. ONS and astrocytic swelling are further augmented by excessive synthesis of glutamine (Gln) which impairs mitochondrial function following its accumulation in there and degradation back to ammonia ("the Trojan horse" hypothesis). Ammonia also induces ONS in other cell types of the CNS: neurons, microglia and the brain capillary endothelial cells (BCEC). ONS in microglia contributes to the central inflammatory response, while its metabolic and pathophysiological consequences in the BCEC evolve to the vasogenic brain edema associated with HE. Ammonia-induced ONS results in the oxidation of mRNA and nitration/nitrosylation of proteins which impact intracellular metabolism and potentiate the neurotoxic effects. Simultaneously, ammonia facilitates the antioxidant response of the brain, by activating astrocytic transport and export of glutathione, in this way increasing the availability of precursors of neuronal glutathione synthesis. PMID:23142151

  6. Enhanced chemical synthesis at soft interfaces: a universal reaction-adsorption mechanism in microcompartments.

    PubMed

    Fallah-Araghi, Ali; Meguellati, Kamel; Baret, Jean-Christophe; El Harrak, Abdeslam; Mangeat, Thomas; Karplus, Martin; Ladame, Sylvain; Marques, Carlos M; Griffiths, Andrew D

    2014-01-17

    A bimolecular synthetic reaction (imine synthesis) was performed compartmentalized in micrometer-diameter emulsion droplets. The apparent equilibrium constant (Keq) and apparent forward rate constant (k1) were both inversely proportional to the droplet radius. The results are explained by a noncatalytic reaction-adsorption model in which reactants adsorb to the droplet interface with relatively low binding energies of a few kBT, react and diffuse back to the bulk. Reaction thermodynamics is therefore modified by compartmentalization at the mesoscale--without confinement on the molecular scale--leading to a universal mechanism for improving unfavorable reactions. PMID:24484045

  7. Synthesis of branched iminosugars through a hypervalent iodine(III)-mediated radical-polar crossover reaction.

    PubMed

    Santana, Andrés G; Paz, Nieves R; Francisco, Cosme G; Suárez, Ernesto; González, Concepción C

    2013-08-01

    The synthesis of a novel type of branched iminosugars is described. This synthetic strategy is based on two key reactions: first, an aldol reaction with formaldehyde in order to introduce selectively the hydroxymethyl branch, and second, a tandem ?-fragmentation-intramolecular cyclization reaction. The combination of both reactions afforded a battery of compounds exhibiting a great structural complexity, with the concomitant formation of a quaternary center, starting from readily available aldoses. With this approach we have demonstrated the usefulness of the fragmentation of anomeric alkoxyl radicals (ARF) promoted by the PhIO/I2 system for the preparation of new compounds with potential interest for both medicinal and synthetic chemists. PMID:23834195

  8. Synthesis and Minisci Reactions of Organotrifluoroborato Building Blocks

    PubMed Central

    Presset, Marc; Fleury-Brégeot, Nicolas; Oehlrich, Daniel

    2013-01-01

    Copper-catalyzed borylation of a variety of organic halides with bis(pinacolato)diboron allows the preparation of diverse potassium organotrifluoroborates. The reactions are mild and general, providing access to a variety of interesting, boron-containing building blocks, including those containing piperidine, pyrrole, azetidine, tetrahydropyran and oxetane substructures. Representative Minisci reactions are reported for select examples. PMID:23594305

  9. Fischer-Tropsch synthesis in supercritical reaction media

    Microsoft Academic Search

    Subramaniam

    1995-01-01

    The goal of the proposed research is to develop novel reactor operating strategies for the catalytic conversion of syngas to transportation grade fuels and oxygenates using near-critical (nc) fluids as reaction media. This will be achieved through systematic investigations aimed at a better fundamental understanding of the physical and chemical rate processes underlying catalytic syngas conversion in nc reaction media.

  10. Synthesis of Single-Crystalline Niobate Nanorods via Ion-Exchange Based on Molten-Salt Reaction

    E-print Network

    Wang, Zhong L.

    Synthesis of Single-Crystalline Niobate Nanorods via Ion-Exchange Based on Molten-Salt Reaction by employing hydrothermal reaction2 or templates,3 molten-salt syn- thesis,4 and composite- exchange approach for the synthesis of single-crystal sodium and calcium niobates nanorods based on molten-salt

  11. Organocatalytic asymmetric cascade reactions of 7-vinylindoles: diastereo- and enantioselective synthesis of C7-functionalized indoles.

    PubMed

    Shi, Feng; Zhang, Hong-Hao; Sun, Xiao-Xue; Liang, Jing; Fan, Tao; Tu, Shu-Jiang

    2015-02-16

    The first catalytic asymmetric cascade reaction of 7-vinylindoles has been established by the rational design of such substrates. Cascade reactions with isatin-derived 3-indolylmethanols in the presence of a chiral phosphoric acid derivative allow the diastereo- and enantioselective synthesis of C7-functionalized indoles as well as the construction of cyclopenta[b]indole and spirooxindole frameworks (all >95:5 d.r., 94->99?% ee). This approach not only addresses the great challenge of the catalytic asymmetric synthesis of C7-functionalized indoles, but also provides an efficient method for constructing biologically important cyclopenta[b]indole and spirooxindole scaffolds with excellent optical purity. Investigation of the reaction pathway and activation mode has suggested that this cascade reaction proceeds through a vinylogous Michael addition/Friedel-Crafts process, in which dual H-bonding activation of the two reactants plays a crucial role. PMID:25521722

  12. Fischer-Tropsch synthesis in supercritical reaction media

    SciTech Connect

    Subramaniam, B.; Bochniak, D.; Snavely, K.

    1993-01-01

    Our goals for this quarter were to complete construction of the reactor and analytical units for carrying out Fischer-Tropsch (F-T) synthesis in liquid (n-hexadecane) and in supercritical n-hexane phases. Progress during this quarter was slower than expected.

  13. Solid phase synthesis of allylic alcohols via the Baylis-Hillman reaction.

    PubMed

    Richter, H; Jung, G

    An efficient method for the solid phase synthesis of allylic alcohols via the Baylis-Hillman reaction has been developed. In the presence of DABCO or 3-quinuclidinol the coupling of resin bound acrylic acid with different aldehydes yields allylic alcohols. Aldehydes with different reactivity were used and gave modest to excellent yields upon simply varying the base or the reaction time. The allylic alcohols were reacted with primary amines to form 1,3-aminoalcohols. PMID:9680650

  14. Synthesis of alumina–silicon carbide composites by chemically activated self-propagating reactions

    Microsoft Academic Search

    Larisa S. Abovyan; Hayk H. Nersisyan; Suren L. Kharatyan; Roberto Orrù; Rita Saiu; Giacomo Cao; Davide Zedda

    2001-01-01

    The synthesis of alumina\\/silicon carbide composites by self-propagating reactions activated by Teflon is investigated. It is shown that small amounts of this material (i.e. 0.20–0.25 wt.%) guarantee the occurrence of self-propagation reactions leading to the formation of a composite. In particular, under argon atmosphere, it consists of well-formed crystals of alumina, fine grained silicon carbide and whiskers-shaped crystallites of SiC.

  15. Reaction synthesis of TiB 2–TiC composites with enhanced toughness

    Microsoft Academic Search

    G. Wen; S. B. Li; B. S. Zhang; Z. X. Guo

    2001-01-01

    In situ toughened TiB2–TiCx composites were fabricated using reaction synthesis of B4C and Ti powders at high temperatures. The resulting materials possessed very high relative densities and well developed TiB2 plate-like grains, leading to a rather high fracture toughness, up to 12.2 MPa?m1\\/2. The microstructure was examined by means of XRD, SEM, TEM and EDAX. The reaction products mainly consisted

  16. Facile Synthesis of Functionalized Bis(arylethynyl)benzene Derivatives via Sila–Sonogashira Reaction

    Microsoft Academic Search

    Zhang-Lin Zhou; Lihua Zhao; Sean Zhang; Kent Vincent; Sity Lam; Dick Henze

    2012-01-01

    This article describes a facile synthesis of a new series of symmetrical bis(arylethynyl)benzene derivatives via a one-pot coupling reaction between trialkylsilyl protected arylalkynyes and aryldihalides bearing both electron-withdrawing (EW) and electron-donating groups (ED) in the presence of PdCl2(PPh3)2(5%) \\/ CuI\\/tetrabutylammonium fluoride \\/ triethylamine \\/ tetrahydrofuran (sila–Sonogashira reaction) at room temperature.

  17. Integrated optic ammonia sensor

    NASA Astrophysics Data System (ADS)

    Klein, Rainer; Voges, Edgar I.

    1993-05-01

    Most of the disadvantages that exist with electrochemical devices (e.g., short lifetimes, difficult to miniaturize, need of reference electrodes) can be avoided by using optical sensors. Smock et al. describe a device incorporating a ninhydrin coated fused silica rod that could detect ammonia vapor at concentrations below 100 ppb, however, the reaction is irreversible. Guiliani et al. describe a reversible sensor using a dye coated capillary tube. The dye utilized is oxazine perchlorate, a laser dye. They report that the presence of water vapor is an important factor in the detection of ammonia, and the concentration of water vapor must be controlled. Optical sensors built-up in integrated-optic technique with planar waveguide configurations allow the construction of optical sensor systems for a parallel detection of several chemical species, provide the generation of reference signals, and facilitate the problem of cross-sensitivities. Here, we report on integrated-optic sensors for ammonia detection with a sensitivity in the ppb-range. The reaction is reversible, and the response is independent of the water vapor concentration in the test gas.

  18. Asymmetric synthesis of 4-deoxyverrucarol via two types of ring expansion reactions

    PubMed

    Miyata; Nemoto; Ihara

    2000-01-28

    Asymmetric synthesis of a trichothecane analogue, 4-deoxyverrucarol (2), was carried out through two types of ring expansion reactions. First, synthesis of the racemate of 2 was investigated. Thus, 1-[1-(tert-butyldimethylsiloxy)-ethyl]-1-methoxycarbonyl-2-hexen-4-on e (10), prepared by Diels-Alder reaction, was converted into the cyclopropylidene 15. The cyclobutanone (+/-)-18 was obtained from 15 via dihydroxylation, followed by successive treatments with SO(2)Cl(2) in the presence of imidazole and Florisil. After transformation of (+/-)-18 into the vinylcyclobutanol (+/-)-19, the second ring expansion reaction was performed with Pd(OAc)(2) to provide the cyclopentanone (+/-)-20. The product was converted into the racemate of 4-deoxyverrucarol (2) through the cyclohexenone (+/-)-22, but the diastereoselectivity during the introduction of the double bond was unsatisfactory. The selectivity was improved in the case of the asymmetric synthesis. The optically active cyclobutanone (+)-18 was prepared via AD reaction of 15 with 73% ee. After the transformation of (+)-18 into the cyclohexanone (-)-30 through the palladium-mediated ring expansion reaction, (-)-30 was subjected to the diastereoselective deprotonation reaction using the chiral amide. The key synthetic intermediate (-)-25 of 4-deoxyverrucarol (2) was synthesized in an optically pure form by taking advantage of a kind of kinetic resolution that occurred during the deprotonation step. PMID:10813964

  19. Reaction intermediates of methanol synthesis and the water-gas-shift reaction on the ZnO(0001) surface

    NASA Astrophysics Data System (ADS)

    Chuasiripattana, Katawut; Warschkow, Oliver; Delley, Bernard; Stampfl, Cathy

    2010-09-01

    The polar Zn-ZnO(0001) surface is involved in the catalysis of methanol synthesis and the water-gas-shift reaction. We use density functional theory calculations to explore the favorable binding geometries and energies of adsorption of several molecular species relevant to these reactions, namely carbon monoxide (CO), carbon dioxide (CO 2), water (H 2O) and methanol (CH 3OH). We also consider several proposed reaction intermediates, including hydroxymethyl (CH 2OH), methoxyl (CH 3), formaldehyde (CH 2O), methyl (CH 3), methylene (CH 2), formic acid (HCOOH), formate (HCOO), formyl (HCO), hydroxyl (OH), oxygen (O) and hydrogen (H). For each, we identify the preferred binding geometry at a coverage of 1/4 monolayers (ML), and report calculated vibrational frequencies that could aid in the identification of these species in experiment. We further explore the effects on the binding energy when the adsorbate coverage is lowered to 1/9 and 1/16 ML.

  20. Synthesis of boron nitride powders

    NASA Astrophysics Data System (ADS)

    Dreissig, Dirk Horst

    2002-09-01

    In the materials science community there is much interest in the development of new, efficient approaches for preparing ceramic powders having properties or performance characteristics not found with powders produced by traditional metallurgical synthesis methods. In this regard, aerosol-based syntheses are finding general acceptance for the preparation of non-metal and metal oxide powders. In contrast, much less effort has been given to aerosol-type syntheses for non-oxide powders despite potentially useful benefits. This dissertation describes the application of two chemical systems in aerosol assisted vapor phase synthesis (AAVS) for the preparation of spherical morphology boron oxynitride, BNxOy, powders that are subsequently converted to spherical morphology boron nitride in a second nitridation step. Chapter 1 describes the AAVS synthesis of BNxOy powders using a reaction of an aqueous boric acid containing aerosol with ammonia at 1000°C. The effect of reactor tube material, total gas flow rate, ammonia concentration, boric acid concentration, and urea addition to the boric acid aerosol on the percent oxygen composition is described. The resulting BNxOy powders contain significant amounts of oxygen that require replacement in a second stage nitridation reaction at elevated temperature under ammonia. The influences of the reaction temperature profile, crucible geometry and transformation additive on final oxygen composition and powder crystallinity are described. Chapter 2 outlines the formation of BNxOy powders from an AAVS reaction between the boron precursor (MeO)3B and ammonia. The formation of the powders is studied as a function of total gas flow rate and ammonia concentration. In all cases the resulting powders contain lower levels of oxygen compared to powders produced from aqueous boric acid aerosols. The conversion of the BNxOy powders in the second stage nitridation reaction with ammonia is examined as a function of crucible geometry, temperature profile and ammonia flow rate. In support of this process, the molecular reaction between (MeO)3B and NH3 was reexamined. The adduct, (MeO)3B·NH3, was isolated and its molecular structure determined by single crystal X-ray diffraction techniques. The results of these studies provide guidance for more detailed studies that should result in industrial scale synthesis of spherical morphology BN which currently is not formed by standard metallurgical syntheses. This new material has potential applications in several areas including the formation of BN loaded organic polymer composites.

  1. Defences against ammonia toxicity in tropical air-breathing fishes exposed to high concentrations of environmental ammonia: a review.

    PubMed

    Ip, Y K; Chew, S F; Wilson, J M; Randall, D J

    2004-10-01

    In the tropics, air-breathing fishes can be exposed to environmental ammonia when stranded in puddles of water during the dry season, during a stay inside a burrow, or after agricultural fertilization. At low concentrations of environmental ammonia, NH(3) excretion is impeded, as in aerial exposure, leading to the accumulation of endogenous ammonia. At high concentrations of environmental ammonia, which results in a reversed NH(3) partial pressure gradient (DeltaP(NH3)), there is retention of endogenous ammonia and uptake of exogenous ammonia. In this review, several tropical air-breathing fishes (giant mudskipper, African catfish, oriental weatherloach, swamp eel, four-eyed sleeper, abehaze and slender African lungfish), which can tolerate high environmental ammonia exposure, are used as examples to demonstrate how eight different adaptations can be involved in defence against ammonia toxicity. Four of these adaptations deal with ammonia toxicity at branchial and/or epithelial surfaces: (1) active excretion of NH(4)(+); (2) lowering of environmental pH; (3) low NH(3) permeability of epithelial surfaces; and (4) volatilization of NH(3), while another four adaptations ameliorate ammonia toxicity at the cellular and subcellular levels: (5) high tolerance of ammonia at the cellular and subcellular levels; (6) reduction in ammonia production; (7) glutamine synthesis; and (8) urea synthesis. The responses of tropical air-breathing fishes to high environmental ammonia are determined apparently by behavioural adaptations and the nature of their natural environments. PMID:15316728

  2. Solid-state reaction synthesis of boron carbonitride nanotubes

    Microsoft Academic Search

    Libin Mo; Yongjun Chen; Lijie Luo

    2010-01-01

    In this study, a simple route for synthesis of ternary boron carbonitride (B–C–N) nanotubes was demonstrated, by heating ball-milled\\u000a mixture powders of amorphous boron and activated charcoal with a small amount of iron oxide (Fe2O3) at 1000–1200°C under a mixture gas flow of nitrogen (N2) and hydrogen (H2). The reduction of Fe2O3 by H2 at 650°C produced Fe nanoparticles, playing

  3. Synthesis of hydrophilic copper nanoparticles: effect of reaction temperature

    Microsoft Academic Search

    P. K. Khanna; Priyesh More; Jagdish Jawalkar; Yogesh Patil; N. Koteswar Rao

    2009-01-01

    Synthesis of hydrophilic copper nanoparticles with an additional coating of an hydrophilic polymer has been carried out by\\u000a use of hydrazine hydrate (HH) and sodium formaldehyde sulfoxylate (SFS) in aqueous medium. The effect of temperature on nanoparticles\\u000a when synthesized in aqueous medium has been studied. It is observed that an ideal temperature ranges some where between 70\\u000a and 80 °C. Nearly

  4. A new approach to the modeling of SHS reactions: Combustion synthesis of transition metal aluminides

    Microsoft Academic Search

    Silvia Gennari; Umberto Anselmi Tamburini; Filippo Maglia; Giorgio Spinolo; Zuhair A. Munir

    2006-01-01

    A recently developed numerical simulation of self-propagating high-temperature synthesis (SHS) using an approach based on microscopic reaction mechanisms and utilizing appropriate physical parameters is applied to the SHS of a fairly large group of transition metal aluminides. The model was utilized to analyze temperature profiles and wave instability and the results were interpreted in terms of chemical and thermal effects.

  5. Isoquinolone Synthesis through SNAr Reaction of 2-Halobenzonitriles with Ketones Followed by Cyclization.

    PubMed

    Mayo, Muhammad Shareef; Yu, Xiaoqiang; Feng, Xiujuan; Yamamoto, Yoshinori; Bao, Ming

    2015-04-17

    An efficient method for the synthesis of isoquinolones through base KO(t)Bu-promoted SNAr reaction of 2-halobenzonitriles with ketones followed by Lewis acid Cu(OAc)2-catalyzed cyclization is described. Isoquinolone derivatives were obtained in satisfactory to good yields. PMID:25798854

  6. A versatile synthesis of fused triazolo derivatives by sequential Ugi\\/alkyne-azide cycloaddition reactions

    Microsoft Academic Search

    Irini Akritopoulou-Zanze; Vijaya Gracias; Stevan W. Djuric

    2004-01-01

    We report a facile synthesis of fused dihydrotriazolo[1,5-a]pyrazinones and triazolobenzodiazepines by an Ugi\\/alkyne–azide cycloaddition synthetic sequence. The coupling of the Ugi multi-component reaction with the intramolecular alkyne–azide cycloaddition provides access to highly functionalized heterocyclic ring systems in two steps from easily available starting materials in excellent overall yields.

  7. One-pot synthesis of keto thioethers by palladium/gold-catalyzed click and pinacol reactions.

    PubMed

    Cadu, Alban; Watile, Rahul A; Biswas, Srijit; Orthaber, Andreas; Sjöberg, Per J R; Samec, Joseph S M

    2014-11-01

    An atom-efficient synthesis of keto thioethers was devised via tandem gold/palladium catalysis. The reaction proceeds through a regioselective thiol attack at the ?-position of the alcohol, followed by an alkyl, aryl, or benzyl 1,2-shift. Both acyclic and cyclic systems were studied, in the latter case leading to the ring expansion of cyclic substrates. PMID:25325145

  8. Action Reaction Learning: Analysis and Synthesis of Human Tony Jebara Alex Pentland

    E-print Network

    Jebara, Tony

    to the user's behaviour and performs it inter- actively. Thus, after analyzing human interaction in a pair is the ability to predict regularities in human behaviour using computational models trained with machineAction Reaction Learning: Analysis and Synthesis of Human Behaviour Tony Jebara Alex Pentland

  9. Action Reaction Learning: Analysis and Synthesis of Human Tony Jebara Alex Pentland

    E-print Network

    to the user's behaviour and performs it inter­ actively. Thus, after analyzing human interaction in a pair relevance is the ability to predict regularities in human behaviour using computational models trainedAction Reaction Learning: Analysis and Synthesis of Human Behaviour Tony Jebara Alex Pentland

  10. Enantioselective synthesis of 4-substituted phenylalanines by cross-coupling reactions

    Microsoft Academic Search

    Fariborz Firooznia; Candido Gude; Kenneth Chan; Nicholas Marcopulos; Yoshitaka Satoh

    1999-01-01

    The enantiomerically enriched BOC-protected (4-pinacolylborono)phenylalanine methyl ester (8) is produced via enzymatic resolution of the racemic material, or direct synthesis from the corresponding iodide (or triflate), and undergoes Suzuki-Miyaura coupling reactions with aromatic halides and triflates in the presence of catalytic amounts of PdCl2(dppf) to produce enantiomerically enriched 4-substituted phenylalanine derivatives.

  11. Multistep One-Pot Reactions Combining Biocatalysts and Chemical Catalysts for Asymmetric Synthesis

    E-print Network

    Zhao, Huimin

    Multistep One-Pot Reactions Combining Biocatalysts and Chemical Catalysts for Asymmetric Synthesis Carl A. Denard, John F. Hartwig,*, and Huimin Zhao*,,§ Department of Chemical and Biomolecular of chemical catalysts. Over the last 20 years, research in this area has provided us with proof of concept

  12. A novel rhodium-catalyzed domino-hydroformylation-reaction for the synthesis of sulphonamides.

    PubMed

    Dong, Kaiwu; Fang, Xianjie; Jackstell, Ralf; Beller, Matthias

    2015-03-25

    An efficient and highly selective method for the synthesis of sulphonamides by a domino hydroformylation-reductive sulphonamidation reaction has been developed. Various olefins and sulphonamides are converted into the desired products in good yields and with excellent selectivities in the presence of a rhodium/Naphos catalyst. PMID:25712242

  13. Synthesis of 6,7,8-trisubstituted purines via a copper-catalyzed amidation reaction.

    PubMed

    Ibrahim, Nada; Legraverend, Michel

    2009-01-01

    We report herein an efficient method for the synthesis of 6,7,8-trisubstituted purines via a copper-catalyzed amidation reaction from easily accessible starting materials. Furthermore, the resulting 6-benzylsulfanyl-substituted purine derivatives may be readily oxidized for substitution by nucleophiles to give access to 6,7,8-trisubstituted purines for biological screening purposes. PMID:19012431

  14. The Photochemical Synthesis, Kinetics, and Reactions of Nitrosomethane Dimer: A Physical-Organic Experiment.

    ERIC Educational Resources Information Center

    Kozubek, H.; And Others

    1982-01-01

    Provides background information procedures, and results for the photochemical synthesis and reactions of nitrosomethane dimer. The experiments described have shown a high degree of reliability with student use and are suggested to illustrate some problems of physical and organic photochemistry. (Author/JN)

  15. Preparation of Germanium Oxynitride Films in Ammonia

    Microsoft Academic Search

    I. G. Nakhutsrishvili; D. A. Dzhishiashvili; Z. I. Mkervalishvili

    2003-01-01

    The surface reaction of single-crystal germanium with ammonia was studied by microgravimetry. The results indicate that the forming germanium nitride vaporizes and then deposits in the form of germanium oxynitride on a substrate located in the cold zone of the reactor. The formation of the oxynitride film is due to the presence of small amounts of water vapor in ammonia.

  16. [Development of boomerang-type intramolecular cascade reactions and application to natural product synthesis].

    PubMed

    Takasu, K

    2001-12-01

    Intramolecular cascade reaction has received much attention as a powerful methodology to construct a polycyclic framework in organic synthesis. We have been developing "boomerang-type cascade reaction" to construct a variety of polycyclic skeletons efficiently. In the above reactions, a nucleophilic function of substrates changes the character into an electrophile after the initial reaction, and the electrophilic group acts as a nucleophile in the second reaction. That is, the reaction center stepwise moves from one functional group back to the same one via other functional groups. The stream of the electron concerning the cascade reaction is like a locus of boomerang. We show here three different boomerang-type reactions via ionic species or free radicals. 1) Diastereoselective Michael-aldol reaction based on the chiral auxiliary method and enantioselective Michael-aldol reaction by the use of external chiral sources. 2) Short and efficient total syntheses of longifolane sesquiterpenes utilizing intramolecular double Michael addition as a key step. 3) Development of boomerang-type radical cascade reaction of halopolyenes to construct terpenoid skeletons and its regioselectivity. PMID:11766403

  17. A Facile Synthesis of Functionalized Bis(arylethynyl)benzene Derivatives via Sila-Sonogashira Reaction

    Microsoft Academic Search

    Zhang-Lin Zhou; Lihua Zhao; Sean Zhang; Kent Vincent; Sity Lam; Dick Henze

    2011-01-01

    This paper describes a facile synthesis of a new series of symmetrical bis(arylethynyl)benzene derivatives via a one-pot coupling reaction between trialkylsilyl protected arylalkynyes and aryldihalides bearing both electron-withdrawing (EW) and electron-donating groups (ED) in the presence of PdCl2(PPh3)2(5%)\\/CuI\\/TBAF\\/TEA\\/THF (sila-Sonogashira reaction) at room temperature.One-pot coupling reactions of trimethylsilyl protected arylacetylenes with aryldihalides bearing both electron-withdrawing (EW) and\\/or electron-donating groups (ED) in

  18. Tricyanovinylalkynyl-metal complexes: synthesis and some reactions.

    PubMed

    Bruce, Michael I; Burgun, Aléxandre; Kramarczuk, Kathy A; Nicholson, Brian K; Parker, Christian R; Skelton, Brian W; White, Allan H; Zaitseva, Natasha N

    2009-01-01

    Reactions of Group 8 metal ethynyls with tetracyanoethene afford tricyanovinylethynyl-metal derivatives, M{C[triple bond]CC(CN)=C(CN)(2)}(PP)Cp' [2; M = Ru, Os; PP = (PPh(3))(2), dppe; Cp' = Cp, Cp*; not all combinations]; a similar reaction occurs with the vinylidene RuCl(=C=CHPh)(PPh(3))Cp. Further replacement of a CN group in occurs with nucleophiles, while homo- and hetero-metallic derivatives are obtained by coordination of one of the remaining CN groups to other metal-ligand fragments. PMID:19081968

  19. Modular Synthesis of Pyrazolones Using an Alkene Aminocarbonylation Reaction.

    PubMed

    Lavergne, Kaitlyn; Bongers, Amanda; Betit, Lyanne; Beauchemin, André M

    2015-07-17

    A variety of pyrazolones were synthesized from enol ethers and hydrazones using a reaction sequence involving aminocarbonylation of enol ethers followed by nucleophile-induced aromatization of the azomethine imines intermediates. Using bases to catalyze the in situ formation of imino isocyanates allowed alkene aminocarbonylation to proceed under milder conditions with reactive substrates and enabled aminocarbonylation reactions of sensitive enol ethers. Aromatization of the azomethine imines could be induced by reduction using NaBH4, or by addition of NH2OH to afford the parent (?)N-H products. PMID:26126788

  20. Synthesis of nanosized silicon particles by a rapid metathesis reaction

    Microsoft Academic Search

    C. W. Won; H. H. Nersisyan; H. I. Won; H. H. Lee

    2009-01-01

    A solid-state rapid metathesis reaction was performed in a bed of sodium silicofluoride (Na2SiF6) and sodium azide (NaN3) powders diluted with sodium fluoride (NaF), to produce silicon nanoparticles. After a local ignition of Na2SiF6+4NaN3+kNaF mixture (here k is mole number of NaF), the reaction proceeded in a self-sustaining combustion mode developing high temperatures (950–1000°C) on very short time scales (a

  1. Hydrothermal synthesis of anatase TiO2 nanorods with high crystallinity using ammonia solution as a solvent.

    PubMed

    Zhang, Dong Ri; Cha, Hyun Gil; Kang, Young Soo

    2011-07-01

    Anatase TiO2 nanorods with high crystallinity were synthesized using ammonia solution (28%) as a solvent by through the hydrothermal method. The X-ray diffraction pattern confirmed the product's anatase phase and high crystallinity, and the transmission electron microscope (TEM) image demonstrated the unique morphologies of the two ends of the TiO2 nanorods (two tringle-horn shapes and one round-horn shape), whose lengths and widths were within the ranges of 200-300 and 60-110 nm, respectively. The high-resolution TEM image clearly displayed the crystal lattices of the (101) planes lying along the direction of the lengthes of the TiO2 nanorods. The energy dispersive X-ray spectrum of a TiO2 nanorod revealed the presence of about 4 atm% nitrogen element as a trace in the anatase TiO2 nanorod. The Raman spectrum of the TiO2 nanorods also showed the typical bands of anatase TiO2 and very weak peaks resulting from the TiN first-order defect-induced Raman scattering. The UV-vis diffuse-reflectance spectra showed a slight red shift (about 3 nm) of the anatase TiO2 nanorods compared with P25, which probably resulted from the trace of TiN on the surfaces of the anatase TiO2 nanorods. A three-stage-process mechanism model is proposed for the formation of the nanorods: Rhombus crystallites bounded by four {101} faces are first formed through anisotropic growth, then longer rhombus crystallites are grown via oriented attachment, finally, nanorods with a unique morphology are self-assembled by Van Der Waals forces. PMID:22121648

  2. Oxacycle Synthesis via Intramolecular Reaction of Carbanions and Peroxides

    PubMed Central

    2015-01-01

    The intramolecular reaction of dialkyl peroxides with carbanions, generated via chemoselective metal-heteroatom exchange or deprotonation, provides a new approach to cyclic ethers. Applied in tandem with C–C bond formation, the strategy enables a one-step annelation to form oxaospirocycles. PMID:24702123

  3. MICROWAVE EFFECTS IN ORGANIC SYNTHESIS: MECHANISTIC AND REACTION MEDIUM CONSIDERATIONS

    EPA Science Inventory

    The scope of applications of microwave irradiation relates to a wide spectrum of organic syntheses with numerous benefits (reduction in reaction times, improved purity of products and better yields) encompassing advantages of both thermal and (or) specific non-purely thermal effe...

  4. Biomimetic flavin-catalysed reactions for organic synthesis.

    PubMed

    Iida, H; Imada, Y; Murahashi, S-I

    2015-07-28

    Using simple riboflavin related compounds as biomimetic catalysts, catalytic oxidation of various substrates with hydrogen peroxide or molecular oxygen can be performed selectively under mild conditions. The principle of these reactions is fundamental and will provide a wide scope for environmentally benign future practical methods. PMID:26077635

  5. Prebiotic synthesis of histidine

    NASA Technical Reports Server (NTRS)

    Shen, C.; Yang, L.; Miller, S. L.; Oro, J.

    1990-01-01

    The prebiotic formation of histidine (His) has been accomplished experimentally by the reaction of erythrose with formamidine followed by a Strecker synthesis. In the first step of this reaction sequence, the formation of imidazole-4-acetaldehyde took place by the condensation of erythrose and formamidine, two compounds that are known to be formed under prebiotic conditions. In a second step, the imidazole-4-acetaldehyde was converted to His, without isolation of the reaction products by adding HCN and ammonia to the reaction mixture. LC, HPLC, thermospray liquid chromatography-mass spectrometry, and tandem mass spectrometry were used to identify the product, which was obtained in a yield of 3.5% based on the ratio of His/erythrose. This is a new chemical synthesis of one of the basic amino acids which had not been synthesized prebiotically until now.

  6. Tandem reactions for streamlining synthesis: enantio- and diastereoselective one-pot generation of functionalized epoxy alcohols.

    PubMed

    Hussain, Mahmud M; Walsh, Patrick J

    2008-08-01

    [Reaction: see text] In 1980, Sharpless and Katsuki introduced the asymmetric epoxidation of prochiral allylic alcohols (the Sharpless-Katsuki asymmetric epoxidation), which enabled the rapid synthesis of highly enantioenriched epoxy alcohols. This reaction was a milestone in the development of asymmetric catalysis because it was the first highly enantioselective oxidation reaction. Furthermore, it provided access to enantioenriched allylic alcohols that are now standard starting materials in natural product synthesis. In 1981, Sharpless and co-workers made another seminal contribution by describing the kinetic resolution (KR) of racemic allylic alcohols. This work demonstrated that small-molecule catalysts could compete with enzymatic catalysts in KRs. For these pioneering works, Sharpless was awarded the 2001 Nobel Prize with Knowles and Noyori. Despite these achievements, the Sharpless KR is not an efficient method to prepare epoxy alcohols with high enantiomeric excess (ee). First, the racemic allylic alcohol must be prepared and purified. KR of the racemic allylic alcohol must be stopped at low conversion, because the ee of the product epoxy alcohol decreases as the KR progresses. Thus, better methods to prepare epoxy alcohols containing stereogenic carbinol carbons are needed. This Account summarizes our efforts to develop one-pot methods for the synthesis of various epoxy alcohols and allylic epoxy alcohols with high enantio-, diastereo-, and chemoselectivity. Our laboratory developed titanium-based catalysts for use in the synthesis of epoxy alcohols with tertiary carbinols. The catalysts are involved in the first step, which is an asymmetric alkyl or allyl addition to enones. The resulting intermediates are then subjected to a titanium-directed diastereoselective epoxidation to provide tertiary epoxy alcohols. Similarly, the synthesis of acyclic epoxy alcohols begins with asymmetric additions to enals and subsequent epoxidation. The methods described here enable the synthesis of skeletally diverse epoxy alcohols. PMID:18710197

  7. Mass Spectroscopy of Chemical Reaction of 3d Metal Clusters Involved in Chemical Vapor Deposition Synthesis of Carbon Nanotubes

    E-print Network

    Maruyama, Shigeo

    Mass Spectroscopy of Chemical Reaction of 3d Metal Clusters Involved in Chemical Vapor Deposition, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan The chemical reactions of transition metal importance. For example, these reactions are involved in the synthesis of single-walled carbon nanotubes

  8. Synthesis, structure and a nucleophilic coordination reaction of Germanetellurones.

    PubMed

    Li, Bin; Li, Yan; Zhao, Na; Chen, Yuefei; Chen, Yujue; Fu, Gang; Zhu, Hongping; Ding, Yuqiang

    2014-08-21

    ?-Diketiminato cyclopentadienyl and ferrocenylethynyl germylenes LGeR (L = HC[C(Me)N-2,6-iPr2C6H3]2, R = Cp () and C[triple bond, length as m-dash]CFc ()) were prepared and utilized to synthesize the Ge[double bond, length as m-dash]Te bond species. Reactions of , , and LGeC[triple bond, length as m-dash]CPh () with an excess of Te powder proceeded in toluene under reflux successfully yielded germanetellurone L(R)GeTe (R = Cp (), C[triple bond, length as m-dash]CFc (), and C[triple bond, length as m-dash]CPh ()). Further reaction of with GeCl2·dioxane at -78 °C resulted in L(Cp)GeTe(GeCl2) (), the first example of a germylene germanetellurone adduct. Both compounds and contain two isomers that are generated by the simultaneous 1,2-H- and 1,3-H-shifts over the Cp ring at the Ge atom. The reactions of L(Me)GeE with AuC6F5·SC4H8 at room temperature led to pentafluorophenyl gold(i) germanethione and germaneselone compounds L(Me)GeE(AuC6F5) (E = S () and Se ()). The formation of compounds exhibits a rare nucleophilic coordination reaction pathway by the Ge[double bond, length as m-dash]E (E = S, Se, Te) bond towards the metal-containing Lewis acidic species. The structures of compounds , , and are studied by the NMR and/or IR spectroscopy and X-ray crystallography. PMID:24985929

  9. Formation of apatite oxynitrides by the reaction between apatite-type oxide ion conductors, La 8+xSr 2-x(Si/Ge) 6O 26+x/2, and ammonia

    NASA Astrophysics Data System (ADS)

    Orera, A.; Headspith, D.; Apperley, D. C.; Francesconi, M. G.; Slater, P. R.

    2009-12-01

    Following growing interest in the use of ammonia as a fuel in solid oxide fuel cells (SOFCs), we have investigated the possible reaction between the apatite silicate/germanate electrolytes, La 8+xSr 2-x(Si/Ge) 6O 26+x/2, and NH 3 gas. We examine how the composition of the apatite phase affects the reaction with ammonia. For the silicate series, the results showed a small degree of N incorporation at 600 °C, while at higher temperatures (800 °C), substantial N incorporation was observed. For the germanate series, partial decomposition was observed after heating in ammonia at 800 °C, while at the lower temperature (600 °C), significant N incorporation was observed. For both series, the N content in the resulting apatite oxynitride was shown to increase with increasing interstitial oxide ion content ( x/2) in the starting oxide. The results suggest that the driving force for the nitridation process is to remove the interstitial anion content, such that for the silicates the total anion (O+N) content in the oxynitrides approximates to 26.0, the value for an anion stoichiometric apatite. For the germanates, lower total anion contents are observed in some cases, consistent with the ability of the germanates to accommodate anion vacancies. The removal of the mobile interstitial oxide ions on nitridation suggests problems with the use of apatite-type electrolytes in SOFCs utilising NH 3 at elevated temperatures.

  10. Synthesis of some †-lactams via enolate-imine reactions 

    E-print Network

    McElveen, Margaret Lynn

    1978-01-01

    ) of the desired thioimidate 26 which melted at 62-63 C (lit. mp 63-64'C); 30 NMR 42. 4 (broad singlet, 3H, -S-CH3), 6. 4-7. 8 (m, 10H, aryl). 34 and Hollandt was modified slightly. To a solution of 4. 8 mL 35 (54 asnol) of phenol (Fisher) and 7. 5 mL (54 mmol... 46 46 47 47 48 (+)-1, r-3, t-4-Triphenyl-3-hydroxyazetidin-2-one (Q) 48 1, r-3, t-4-Triphenylazetidin-2-one (41). 49 r-3-Benzoylamino-l, t-4-diphenylazetidin-2-one (42) . 49 TABLE OF CONTENTS (continued) Alternate synthesis of r-3...

  11. STM control of chemical reaction: single-molecule synthesis.

    PubMed

    Hla, Saw-Wai; Rieder, Karl-Heinz

    2003-01-01

    The fascinating advances in single atom/molecule manipulation with a scanning tunneling microscope (STM) tip allow scientists to fabricate atomic-scale structures or to probe chemical and physical properties of matters at an atomic level. Owing to these advances, it has become possible for the basic chemical reaction steps, such as dissociation, diffusion, adsorption, readsorption, and bond-formation processes, to be performed by using the STM tip. Complete sequences of chemical reactions are able to induce at a single-molecule level. New molecules can be constructed from the basic molecular building blocks on a one-molecule-at-a-time basis by using a variety of STM manipulation schemes in a systematic step-by-step manner. These achievements open up entirely new opportunities in nanochemistry and nanochemical technology. In this review, various STM manipulation techniques useful in the single-molecule reaction process are reviewed, and their impact on the future of nanoscience and technology are discussed. PMID:12626735

  12. Synthesis of layered sodium lanthanum selenide through ion exchange reactions

    SciTech Connect

    Butts, Laura J.; Strickland, Nicholas [Department of Chemistry, Texas State University - San Marcos, 601 University Drive, San Marcos, TX 78666 (United States); Martin, Benjamin R. [Department of Chemistry, Texas State University - San Marcos, 601 University Drive, San Marcos, TX 78666 (United States)], E-mail: bmartin@txstate.edu

    2009-04-02

    Layered hexagonal KLaSe2 ({alpha}-NaFeO{sub 2}-type) was synthesized using the reactive flux method and analyzed by powder XRD to determine its lattice constants (space group R-3m, a = 4.40508(5) A, c = 22.7838(5) A). NaLaSe{sub 2}, which normally crystallizes as a disordered rock salt structure with mixed Na+/La + 3 sites, was synthesized through a solid state ion exchange reaction at 585 deg. C from a 1:3 molar ratio mixture of KLaSe{sub 2}:NaI. The product of this reaction was hexagonally layered NaLaSe{sub 2} (space group R-3m, a = 4.3497(3) A, c = 20.808(2) A) isostructural to KLaSe{sub 2}. This product was analyzed by comparison with members of the set of solid solutions Na{sub (1-x)}K{sub (x)}LaSe{sub 2} to confirm that the extent ion exchange in this reaction was complete. Cubic (disordered) NaLaSe{sub 2} was also reacted with KI to yield the poorly crystalline hexagonally layered product with the approximate formula Na{sub 0.79}K{sub 0.21}LaSe{sub 2}.

  13. One-pot synthesis of core-shell Cu@SiO2 nanospheres and their catalysis for hydrolytic dehydrogenation of ammonia borane and hydrazine borane

    NASA Astrophysics Data System (ADS)

    Yao, Qilu; Lu, Zhang-Hui; Zhang, Zhujun; Chen, Xiangshu; Lan, Yaqian

    2014-12-01

    Ultrafine copper nanoparticles (Cu NPs) within porous silica nanospheres (Cu@SiO2) were prepared via a simple one-pot synthetic route in a reverse micelle system and characterized by SEM, TEM, EDX, XRD, N2 adsorption-desorption, CO-TPD, XPS, and ICP methods. The characterized results show that ultrafine Cu NPs with diameter of around 2 nm are effectively embedded in the center of well-proportioned spherical SiO2 NPs of about 25 nm in diameter. Compared to commercial SiO2 supported Cu NPs, SiO2 nanospheres supported Cu NPs, and free Cu NPs, the synthesized core-shell nanospheres Cu@SiO2 exhibit a superior catalytic activity for the hydrolytic dehydrogenation of ammonia borane (AB, NH3BH3) and hydrazine borane (HB, N2H4BH3) under ambient atmosphere at room temperature. The turnover frequencies (TOF) for the hydrolysis of AB and HB in the presence of Cu@SiO2 nanospheres were measured to be 3.24 and 7.58 mol H2 (mol Cu min)-1, respectively, relatively high values for Cu nanocatalysts in the same reaction. In addition, the recycle tests show that the Cu@SiO2 nanospheres are still highly active in the hydrolysis of AB and HB, preserving 90 and 85% of their initial catalytic activity even after ten recycles, respectively.

  14. One-pot synthesis of core-shell Cu@SiO2 nanospheres and their catalysis for hydrolytic dehydrogenation of ammonia borane and hydrazine borane.

    PubMed

    Yao, Qilu; Lu, Zhang-Hui; Zhang, Zhujun; Chen, Xiangshu; Lan, Yaqian

    2014-01-01

    Ultrafine copper nanoparticles (Cu NPs) within porous silica nanospheres (Cu@SiO2) were prepared via a simple one-pot synthetic route in a reverse micelle system and characterized by SEM, TEM, EDX, XRD, N2 adsorption-desorption, CO-TPD, XPS, and ICP methods. The characterized results show that ultrafine Cu NPs with diameter of around 2 nm are effectively embedded in the center of well-proportioned spherical SiO2 NPs of about 25 nm in diameter. Compared to commercial SiO2 supported Cu NPs, SiO2 nanospheres supported Cu NPs, and free Cu NPs, the synthesized core-shell nanospheres Cu@SiO2 exhibit a superior catalytic activity for the hydrolytic dehydrogenation of ammonia borane (AB, NH3BH3) and hydrazine borane (HB, N2H4BH3) under ambient atmosphere at room temperature. The turnover frequencies (TOF) for the hydrolysis of AB and HB in the presence of Cu@SiO2 nanospheres were measured to be 3.24 and 7.58 mol H2 (mol Cu min)(-1), respectively, relatively high values for Cu nanocatalysts in the same reaction. In addition, the recycle tests show that the Cu@SiO2 nanospheres are still highly active in the hydrolysis of AB and HB, preserving 90 and 85% of their initial catalytic activity even after ten recycles, respectively. PMID:25534772

  15. Basic distinctions between cold- and hot-fusion reactions in the synthesis of superheavy elements

    NASA Astrophysics Data System (ADS)

    Nasirov, A. K.; Muminov, A. I.; Giardina, G.; Mandaglio, G.

    2014-07-01

    Superheavy elements (SHE) of charge number in the range of Z = 106-112 were synthesized in so-called cold-fusion reactions. The smallness of the excitation energy of compound nuclei is the main advantage of cold-fusion reactions. However, the synthesis of SHEs of charge number in the region of Z ? 112 is strongly complicated in cold-fusion reactions by a sharp decrease in the cross section of a compound nucleus formation in the entrance channel because of superiority of quasifission in the competition with complete fusion. Two favorable circumstances contributed to the success of the experiments aimed at the synthesis of the Z = 113-118 elements and performed at the Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research: large cross sections for the production of a compound nucleus, which are characteristic of hot-fusion reactions, and an increase in the fission barrier for nuclei toward the stability island. The factor that complicates the formation of a compound nucleus in cold-fusion reactions is discussed.

  16. In-situ formation of {delta}-NiMo intermetallic by self-propagating reaction synthesis

    SciTech Connect

    Chou, T.C. [BOC Group Technical Center, Murray Hill, NJ (United States); Nieh, T.G. [Lawrence Livermore National Lab., CA (United States); Mardinly, J. [Intel Corp., Santa Clara, CA (United States)

    1995-08-01

    Synthesis of {delta}-NiMo intermetallic was achieved by self-propagating reactions at elevated temperatures. The samples studied were thin-film diffusion couples comprised of Mo film on Ni grid. Annealing of the samples in vacuum at 700 or 800 C produced two distinct reaction zones with a single-phase reaction product {delta}-NiMo. The reaction zones contained equiaxed small grains and columnar large single crystals, respectively. Growth direction of the single crystals was parallel to the direction of Ni diffusion flux. Reaction at 900 C was intense to result in a spider-web-like structure as a result of melting/agglomeration of the reaction product. Based upon a parabolic rate equation, the apparent interdiffusion coefficients in the subject system were calculated and found to be 4 to 5 orders of magnitude greater than literature data. The enhanced diffusion kinetics and anisotropic grain growth of {delta}-NiMo will be discussed on the basis of exothermic reaction during diffusional intermixing. The enthalpy of the formation of {delta}-NiMo was calculated and demonstrated to be sufficient to serve as the driving force for the self-propagating reaction. The amount of thermal energy influx substantiated interfacial melting of the reaction product. Comparison will be made between the results obtained from thin-film and bulk diffusion couples.

  17. Versatile Synthesis of Stable, Functional Polypeptides via Reaction with Epoxides.

    PubMed

    Gharakhanian, Eric G; Deming, Timothy J

    2015-06-01

    Methodology was developed for efficient alkylation of methionine residues using epoxides as a general strategy to introduce a wide range of functional groups onto polypeptides. Use of a spacer between epoxide and functional groups further allowed addition of sterically demanding functionalities. Contrary to other methods to alkylate methionine residues, epoxide alkylations allow the reactions to be conducted in wet protic media and give sulfonium products that are stable against dealkylation. These functionalizations are notable since they are chemoselective, utilize stable and readily available epoxides, and allow facile incorporation of an unprecedented range of functional groups onto simple polypeptides using stable linkages. PMID:25974116

  18. Sonocatalyzed synthesis of 2-phenylvaleronitrile under controlled reaction conditions--a kinetic study.

    PubMed

    Vivekanand, P A; Wang, Maw-Ling

    2011-09-01

    In the current study, kinetics of synthesis of 2-phenylvaleronitrile (PVN) was successfully carried out by selective C-alkylation of benzyl cyanide (BC) with n-bromopropane (BP) using aqueous KOH and catalyzed by TBAB under ultrasonic (300W) assisted organic solvent-free conditions. Selective monoalkylation of benzyl cyanide has been achieved by controlling the reaction conditions and has been followed using gas chromatogram. The effects of various parameters such as agitation speed, catalyst concentration, KOH concentration, benzyl cyanide concentration, volume of water, ultrasonic frequency and temperature were studied systematically to understand their influence on the rate of the reaction. The experimental observations are consistent with an interfacial-type process. Further the kinetic results demonstrate clearly, that ultrasonic assisted phase-transfer catalysis significantly increased the reaction rate when compared to silent reactions. PMID:21377400

  19. Semibullvalene and Diazasemibullvalene: Recent Advances in the Synthesis, Reaction Chemistry, and Synthetic Applications.

    PubMed

    Zhang, Shaoguang; Zhang, Wen-Xiong; Xi, Zhenfeng

    2015-07-21

    Semibullvalene (SBV) and its aza analogue 2,6-diazasemibullvalene (NSBV) are theoretically interesting and experimentally challenging organic molecules because of four unique features: highly strained ring systems, intramolecular skeletal rearrangement, extremely rapid degenerate (aza-)Cope rearrangement, and the predicted existence of neutral homoaromatic delocalized structures. SBV has received much attention in the past 50 years. In contrast, after NSBV was predicted in 1971 and the first in situ synthesis was realized in 1982, no progress on NSBV chemistry was made until our results in 2012. We have been interested in the reaction chemistry of 1,4-dilithio-1,3-butadienes (dilithio reagents for short), especially for their applications in the synthesis of SBV and NSBV, because (i) the cyclodimerization of dilithio reagents could provide the potential eight-carbon skeleton of SBV from four-carbon butadiene units and (ii) the insertion reaction of dilithio reagents with C?N bonds of two nitriles could provide a 6C + 2N skeleton that might be a good precursor for the synthesis of NSBV. Therefore, we initiated a journey into the synthesis and reaction chemistry of SBV and NSBV starting from dilithio reagents that has been ongoing since 2006. In this Account, we outline mainly our recent achievements in the synthesis, structural characterization, reaction chemistry, synthetic application, and theoretical/computational analysis of NSBV. Two efficient strategies for the synthesis of NSBV from dilithio reagents and nitriles via oxidant-induced C-N bond formation are described. Structural investigations of NSBV, including X-ray crystal structure analysis, determination of the activation barrier for the aza-Cope rearrangement, and theoretical analysis, show that the localized structure of NSBV is the predominant form and that the homoaromatic delocalized structure exists as a minor component in the equilibrium. We also discuss the reaction chemistry and synthetic applications of NSBV. Several novel reaction patterns have been explored, including thermolysis, C-N bond insertion, rearrangement-cycloaddition, oxidation, and nucleophilic ring-opening reactions. Diverse and interesting N-containing polycyclic skeletons can be constructed, such as nickelaazetidine, 1,5-diazatriquinacenes, and triazabrexadienes, which are not available by other means. Our results show that NSBV not only features a rapid aza-Cope rearrangement with a low activation barrier but also acts as unique synthetic reagent that is significantly different from aziridine. The strained rigid ring systems as a whole can be involved in the reactions. Our achievements highlight two significant advances: (i) the well-established efficient synthesis and isolation of NSBV has greatly accelerated the development of NSBV chemistry, and (ii) the previously unattainable molecules have become "normal" and routine starting materials for the synthesis of otherwise unavailable but interesting structures. We expect that our pursuits will inspire and help direct future chemical and physical research on NSBV. PMID:26061608

  20. Analysis of residual phases in nickel aluminide powders produced by reaction synthesis

    SciTech Connect

    McCoy, K.P.; Shaw, K.G. (Xform, Inc., Cohoes, NY (United States)); Trogolo, J.A. (Rensselaer Polytechnic Inst., Troy, NY (United States))

    1992-01-01

    The use of x-ray diffraction has been used to determine phases present after reaction synthesis of Ni[sub 3]Al powder. The complex diffraction spectra produced by the powder prompted the development of a simulator. The simlulator uses nonlinear regression to determine the weight percent of the phases present. The simulator also determines the broadening of each peak in the spectrum. The phases present in Ni[sub 3]Al powder produced by reaction synthesis has been determined with the simulator. The simulator has been used to monitor the progress of phase transformation during various thermal treatments of Ni[sub 3]Al powder. A thermal cycle of 1200[degrees]C for two hours has been shown to produce a phase-pure product. The activation energy for the interdiffusion of nickel and aluminum has been determined to be 260[plus minus]35 kJ/mole.

  1. Analysis of residual phases in nickel aluminide powders produced by reaction synthesis

    SciTech Connect

    McCoy, K.P.; Shaw, K.G. [Xform, Inc., Cohoes, NY (United States); Trogolo, J.A. [Rensselaer Polytechnic Inst., Troy, NY (United States)

    1992-12-31

    The use of x-ray diffraction has been used to determine phases present after reaction synthesis of Ni{sub 3}Al powder. The complex diffraction spectra produced by the powder prompted the development of a simulator. The simlulator uses nonlinear regression to determine the weight percent of the phases present. The simulator also determines the broadening of each peak in the spectrum. The phases present in Ni{sub 3}Al powder produced by reaction synthesis has been determined with the simulator. The simulator has been used to monitor the progress of phase transformation during various thermal treatments of Ni{sub 3}Al powder. A thermal cycle of 1200{degrees}C for two hours has been shown to produce a phase-pure product. The activation energy for the interdiffusion of nickel and aluminum has been determined to be 260{plus_minus}35 kJ/mole.

  2. Synthesis of most polyene natural product motifs using just 12 building blocks and one coupling reaction

    NASA Astrophysics Data System (ADS)

    Woerly, Eric M.; Roy, Jahnabi; Burke, Martin D.

    2014-06-01

    The inherent modularity of polypeptides, oligonucleotides and oligosaccharides has been harnessed to achieve generalized synthesis platforms. Importantly, like these other targets, most small-molecule natural products are biosynthesized via iterative coupling of bifunctional building blocks. This suggests that many small molecules also possess inherent modularity commensurate with systematic building block-based construction. Supporting this hypothesis, here we report that the polyene motifs found in >75% of all known polyene natural products can be synthesized using just 12 building blocks and one coupling reaction. Using the same general retrosynthetic algorithm and reaction conditions, this platform enabled both the synthesis of a wide range of polyene frameworks that covered all of this natural-product chemical space and the first total syntheses of the polyene natural products asnipyrone B, physarigin A and neurosporaxanthin ?-D-glucopyranoside. Collectively, these results suggest the potential for a more generalized approach to making small molecules in the laboratory.

  3. Benzannulation via the Reaction of Ynamides and Vinylketenes. Application to the Synthesis of Highly Substituted Indoles

    PubMed Central

    Lam, Tin Yiu; Wang, Yu-Pu

    2013-01-01

    A two-stage “tandem strategy” for the synthesis of indoles with a high level of substitution on the six-membered ring is described. Benzannulation based on the reaction of cyclobutenones with ynamides proceeds via a cascade of four pericyclic reactions to produce multiply substituted aniline derivatives in which the position ortho to the nitrogen can bear a wide range of functionalized substituents. In the second stage of the tandem strategy, highly substituted indoles are generated via acid-, base-, and palladium-catalyzed cyclization and annulation processes. PMID:23952525

  4. Synthesis of fullerene glycoconjugates via a copper-catalyzed Huisgen cycloaddition reaction.

    PubMed

    Isobe, Hiroyuki; Cho, Kaimei; Solin, Niclas; Werz, Daniel B; Seeberger, Peter H; Nakamura, Eiichi

    2007-10-25

    The synthesis of fullerene-carbohydrate conjugates using a copper-catalyzed [3+2] cycloaddition reaction to facilitate the union of an azido-functionalized sugar and a pentaalkynyl[60]fullerene is straightforward. Thus, fullerenes bearing five oligosaccharides such as Gb3-trisaccharide can be readily accessed. Nanometer-scale molecular architectures presenting as many as 15 sugar moieties in C5-symmetry are readily produced. The cycloaddition reaction proceeds quantitatively under mild conditions without the need to protect the sugar hydroxyl groups. PMID:17915889

  5. Synthesis of novel N-cyclopentenyl-lactams using the Aubé reaction

    PubMed Central

    Shinde, Madhuri V; Ople, Rohini S; Sangtani, Ekta; Gonnade, Rajesh

    2015-01-01

    Summary A novel and convenient method utilizing the Aubé reaction to access a new class of compounds that are similar to carbocyclic nucleosides is reported. The azido alcohol derived from Vince lactam undergoes the Aubé reaction with various cyclic ketones to give cyclopentenyl-substituted lactams. Upon dihydroxylation, this affords the N-cyclopentenyl-lactam compounds in racemic form. Given the numerous uses of nucleosides and related compounds, we were interested in the synthesis of carbocylic nucleoside mimics. The attempts and results are described herein. PMID:26199661

  6. Hydrogel nanofilms for biomedical applications: synthesis via polycondensation reactions.

    PubMed

    Pippig, Falko; Holländer, Andreas

    2010-09-01

    A new technique for the production of nanoscale polymer networks on surfaces is presented. Bifunctional oligomeric building blocks react with trifunctional linkers and couple to activated polymer surfaces. PEG diamines were used as branch molecules in the network which were linked by either a trifunctional epoxide or a trifunctional acid chloride. The network with mesh size of 22 nm and more contains amino and hydroxy or carboxylic-acid groups. The concentration can be varied by the preparation conditions and by adding other substances like amino acids or amine-functionalized biotin to the reaction system. As an example, FITC-tagged streptavidin was coupled to biotin in the network with a concentration of up to 37 pmol.cm(-2). PMID:20602415

  7. Asymmetric synthesis of fully substituted cyclopentane-oxindoles through an organocatalytic triple Michael domino reaction.

    PubMed

    Zou, Liang-Hua; Philipps, Arne R; Raabe, Gerhard; Enders, Dieter

    2015-01-12

    An efficient, highly stereoselective asymmetric synthesis of fully functionalized cyclopentanes bearing an oxindole moiety and several other functional groups in one pot has been developed. Key step is an organocatalytic triple Michael domino reaction forming three C-C bonds and six stereocenters, including a quaternary one. Starting from equimolar amounts of simple substrates, a high molecular complexity can be reached after a Wittig olefination in one pot. The new protocol can easily be scaled up to gram amounts. PMID:25470781

  8. Anisothermal reaction synthesis of garnets, ferrites, and spinels in microwave field

    Microsoft Academic Search

    Ramesh D. Peelamedu; Rustum Roy; Dinesh Agrawal

    2001-01-01

    The experimental achievement of reacting two phases that are held at two different temperatures—the anisothermal reaction condition—is a radical innovation in materials chemistry. Details on the synthesis of Yttrium Iron Garnet (Y3Fe5O12), Barium Ferrite (BaFe12O19), and Nickel Aluminate (NiAl2O4) in 1–10 min in a microwave field are provided. The starting precursor oxides were chosen such that they include a low

  9. Self-propagating reactions in finite pellets: Synthesis of titanium carbide

    Microsoft Academic Search

    Jean-Pascal Lebrat; Arvind Varma

    1993-01-01

    The preparation of advanced materials by self-propagating high-temperature synthesis (SHS) has attracted significant current interest. The basic concept is that once initiated, a highly exothermic reaction can become self-sustaining and will propagate through the mixture of initial reactants in the form of a combustion wave. The reactants are converted to the products as the combustion wave advances. Modeling of the

  10. Characteristics of self-propagating reaction in TiN combustion synthesis

    Microsoft Academic Search

    Hiroshi Kudo; Osamu Odawara

    1989-01-01

    The characteristics of the combustion synthesis of TiN are investigated through a self-propagating reaction of titanium powder compacts of specific packing density (40% to 60% theoretical one) in the presence of flowing nitrogen gas (0.01 m3 min-1) under atmospheric pressure. It was found that the propagating velocity of the combustion wave became slower with increasing packing density. The conversion ratio

  11. Hydrothermal synthesis of vanadium nitride and modulation of its catalytic performance for oxygen reduction reaction.

    PubMed

    Huang, Taizhong; Mao, Shun; Zhou, Guihua; Wen, Zhenhai; Huang, Xingkang; Ci, Suqin; Chen, Junhong

    2014-08-21

    A creative hydrothermal synthesis method followed by calcination for vanadium nitride (VN) is reported. The oxygen reduction reaction (ORR) study of the catalyst shows that VN possesses a comparable catalytic performance to commercial Pt/C catalyst. The ORR catalytic activity study of vanadium nitride, vanadium carbonitride, and vanadium carbide reveals that tuning anions offers a promising route for the activity enhancement of the non-precious metal catalysts. PMID:25029261

  12. A new synthesis of TATB using inexpensive starting materials and mild reaction conditions

    Microsoft Academic Search

    A. R. Mitchell; P. F. Pagoria; R. D. Schmidt

    1996-01-01

    TATB is currently manufactured in US by nitration of the expensive TCB to give 2,4,6-trichloro-1,3,5-trinitrobenzene which is then aminated to yield TATB. Elevated temperatures (150 C) are required for both reactions. There is a need for a more economical synthesis of TATB that also addresses current environmental issues. We have recently found that 1,1,1-trimethylhydrazinium iodide (TMHI) allows the amination of

  13. Synthesis of cobalt metal nanowire arrays and the interfacial reactions of cobalt nanowires on (001)Si

    Microsoft Academic Search

    S. L. Cheng; Y. P. Wei; C. H. Chung

    2011-01-01

    In this study, we report the successful synthesis of large-scale, well-aligned pure cobalt metal nanowire arrays by using the electrodeposition in conjunction with anodic aluminum oxide (AAO) templates technique, and the investigation of the interfacial reactions between the produced Co metal nanowires and (001)Si substrate after different heat treatments. The morphologies, crystal structures, and compositions of the as-synthesized Co nanowires

  14. H(3)PW(12)O(40)-catalyzed multicomponent reaction for efficient synthesis of highly substituted piperidines.

    PubMed

    Khaksar, Samad; Baghbanian, Seyed Meysam; Barsan, Nastaran

    2014-01-01

    A simple, diastereoselective, inexpensive, and efficient route for the synthesis of highly functionalized piperidines by the condensation of ?-keto-esters, aromatic aldehydes and anilines using H3PW12O40 as a catalyst is described. The catalyst could be easily recovered after completion of the reaction and reused without a considerable change in its activity. Furthermore, in most cases the piperidine precipitates out of solution. PMID:24372051

  15. Witting Reaction Using a Stabilized Phosphorus Ylid: An Efficient and Stereoselective Synthesis of Ethyl Trans-Cinnamate

    ERIC Educational Resources Information Center

    Speed, Traci J.; Mclntyre, Jean P.; Thamattoor, Dasan M.

    2004-01-01

    An instructive experiment for the synthesis of ethyl trans-cinnamate, a pleasant smelling ester used in perfumery and flavoring by the reaction of benzaldehyde with the stable ylid triphenylphosphorane is described. The synthesis, workup and characterization of trans-cinnamate may be accomplished in a single laboratory session with commonly…

  16. Synthesis gas production by zinc oxide reaction with methane: elimination of greenhouse gas emission from a metallurgical plant

    Microsoft Academic Search

    H. Ale Ebrahim; E. Jamshidi

    2004-01-01

    Most natural gas based petrochemical processes consist of catalytic reforming or partial oxidation units for producing synthesis gas. This research shows that it is possible to replace these units by the reaction of zinc oxide with methane, which produces metallic zinc and synthesis gas (CO+2H2) simultaneously. Therefore, by combination of the metallurgical and petrochemical units, it is possible to eliminate

  17. Samarium iodide-mediated Reformatsky reactions for the stereoselective preparation of ?-hydroxy-?-amino acids: synthesis of isostatine and dolaisoleucine.

    PubMed

    Nelson, Christopher G; Burke, Terrence R

    2012-01-01

    The synthesis of ?-hydroxy-?-amino acids via SmI(2)-mediated Reformatsky reactions of ?-chloroacetyloxazolidinones with aminoaldehydes is reported. Diastereoselective coupling is demonstrated to depend on the absolute configuration of the Evans chiral auxiliary employed in the reaction, allowing erythro or threo products to be obtained selectively. The potential utility of the methodology is exemplified by the facile synthesis of biologically relevant N-Boc-isostatine (2b) and N-Boc-dolaisoleucine (3c). PMID:22136325

  18. Influence of high gas pressure on combustion synthesis of the solid–solid reaction of NiAl compound

    Microsoft Academic Search

    R. M. Marin-Ayral; M. C. Dumez; J. C. Tédenac

    2000-01-01

    We show the advantage of using high gas pressure in the improvement of combustion synthesis conditions for NiAl compound synthesis. Experiments on high pressure of argon between 10 and 500 MPa showed that the exothermicity of Ni–Al reactions was considerably reduced, with a complete reaction giving NiAl compound. Thermodynamic and kinetic studies were carried out. The results indicate that pressure

  19. Applications of Skyrme energy-density functional to fusion reactions for synthesis of superheavy nuclei

    SciTech Connect

    Wang Ning; Scheid, Werner [Institute for Theoretical Physics at Justus-Liebig-University, D-35392 Giessen (Germany); Wu Xizhen; Liu Min [China Institute of Atomic Energy, Beijing 102413 (China); Li Zhuxia [China Institute of Atomic Energy, Beijing 102413 (China); Institute of Theoretical Physics, Chinese Academic of Science, Beijing 100080 (China); Nuclear Theory Center of National Laboratory of Heavy Ion Accelerator, Lanzhou 730000 (China)

    2006-10-15

    The Skyrme energy-density functional approach has been extended to study massive heavy-ion fusion reactions. Based on the potential barrier obtained and the parametrized barrier distribution the fusion (capture) excitation functions of a lot of heavy-ion fusion reactions are studied systematically. The average deviations of fusion cross sections at energies near and above the barriers from experimental data are less than 0.05 for 92% of 76 fusion reactions with Z{sub 1}Z{sub 2}<1200. For the massive fusion reactions, for example, the {sup 238}U-induced reactions and {sup 48}Ca+{sup 208}Pb, the capture excitation functions have been reproduced remarkably well. The influence of structure effects in the reaction partners on the capture cross sections is studied with our parametrized barrier distribution. By comparing the reactions induced by double-magic nucleus {sup 48}Ca and by {sup 32}S and {sup 35}Cl, the ''threshold-like'' behavior in the capture excitation function for {sup 48}Ca-induced reactions is explored and an optimal balance between the capture cross section and the excitation energy of the compound nucleus is studied. Finally, the fusion reactions with {sup 36}S, {sup 37}Cl, {sup 48}Ca, and {sup 50}Ti bombarding {sup 248}Cm, {sup 247,249}Bk, {sup 250,252,254}Cf, and {sup 252,254}Es, as well as the reactions leading to the same compound nucleus with Z=120 and N=182, are studied further. The calculation results for these reactions are useful for searching for the optimal fusion configuration and suitable incident energy in the synthesis of superheavy nuclei.

  20. Prebiotic synthesis of imidazole-4-acetaldehyde and histidine

    NASA Technical Reports Server (NTRS)

    Shen, Chun; Oro, J.; Yang, Lily; Miller, Stanley L.

    1987-01-01

    The prebiotic synthesis of imidazole-4-acetaldehyde and imidazole-4-glycol from erythrose and formamidine has been demonstrated as well as the prebiotic synthesis of imidazole-4-ethanol and imidazole-4-glycol from erythrose, formaldehyde, and ammonia. The maximum yields of imidazole-4-acetaldehyde, imidazole-4-ethanol, and imidazole-4-glycol obtained in these reactions are 1.6, 5.4, and 6.8 percent respectively, based on the erythrose. Imidazole-4-acetaldehyde would have been converted to histidine on the primitive earth by a Strecker synthesis, and several prebiotic reactions would convert imidazole-4-glycol and imidazole-4-ethanol to imidazole-4-acetaldehyde.

  1. Synthesis of triple-layered Ag@Co@Ni core-shell nanoparticles for the catalytic dehydrogenation of ammonia borane.

    PubMed

    Qiu, Fangyuan; Liu, Guang; Li, Li; Wang, Ying; Xu, Changchang; An, Cuihua; Chen, Chengcheng; Xu, Yanan; Huang, Yanan; Wang, Yijing; Jiao, Lifang; Yuan, Huatang

    2014-01-01

    Triple-layered Ag@Co@Ni core-shell nanoparticles (NPs) containing a silver core, a cobalt inner shell, and a nickel outer shell were formed by an in situ chemical reduction method. The thickness of the double shells varied with different cobalt and nickel contents. Ag0.04 @Co0.48 @Ni0.48 showed the most distinct core-shell structure. Compared with its bimetallic core-shell counterparts, this catalyst showed higher catalytic activity for the hydrolysis of NH3 BH3 (AB). The synergetic interaction between Co and Ni in Ag0.04 @Co0.48 @Ni0.48 NPs may play a critical role in the enhanced catalytic activity. Furthermore, cobalt-nickel double shells surrounding the silver core in the special triple-layered core-shell structure provided increasing amounts of active sites on the surface to facilitate the catalytic reaction. These promising catalysts may lead to applications for AB in the field of fuel cells. PMID:24302541

  2. Molybdenum catalyzed ammonia borane dehydrogenation: oxidation state specific mechanisms.

    PubMed

    Buss, Joshua A; Edouard, Guy A; Cheng, Christine; Shi, Jade; Agapie, Theodor

    2014-08-13

    Though numerous catalysts for the dehydrogenation of ammonia borane (AB) are known, those that release >2 equiv of H2 are uncommon. Herein, we report the synthesis of Mo complexes supported by a para-terphenyl diphosphine ligand, 1, displaying metal-arene interactions. Both a Mo(0) N2 complex, 5, and a Mo(II) bis(acetonitrile) complex, 4, exhibit high levels of AB dehydrogenation, releasing over 2.0 equiv of H2. The reaction rate, extent of dehydrogenation, and reaction mechanism vary as a function of the precatalyst oxidation state. Several Mo hydrides (Mo(II)(H)2, [Mo(II)(H)](+), and [Mo(IV)(H)3](+)) relevant to AB chemistry were characterized. PMID:25034459

  3. Flow-synthesis of carboxylate and phosphonate based metal-organic frameworks under non-solvothermal reaction conditions.

    PubMed

    Waitschat, Steve; Wharmby, Michael T; Stock, Norbert

    2015-06-28

    A continuous flow reactor was developed for the synthesis of porous metal-organic frameworks (MOFs) under mild reaction conditions. Commodity hardware was used to assemble the device, giving it a great degree of flexibility in its configuration. The use of paraffin to encapsulate reactions and also ultrasonic treatment were employed to prevent clogging of the reactor. Reactor design was optimised through studies of the synthesis of zirconium carboxylate framework UiO-66. Synthesis of the aluminium carboxylate CAU-13 was also performed, to demonstrate the versatility of the device. Finally the reactor was used to synthesise a new cadmium phosphonate framework, bearing the STA-12 network. PMID:26007604

  4. Synthesis of pyrrolidine derivatives by a platinum/brønsted acid relay catalytic cascade reaction.

    PubMed

    Galván, Alicia; Calleja, Jonás; Fañanás, Francisco J; Rodríguez, Félix

    2015-02-16

    A new catalytic reaction for the synthesis of pyrrolidine derivatives is presented. The method implies the coupling of N-Boc-protected alkynamine derivatives and appropriate alkenes or alkynes in a process catalysed by a platinum/triflic acid catalytic binary system. This reaction is believed to proceed through a cascade process implying an initial platinum-catalysed cycloisomerization of the alkynamine derivative followed by a triflic acid promoted nucleophilic addition of the alkene or alkyne and trapping of the cationic species formed by the Boc group. Not only simple alkenes and alkynes were used in this reaction but also allyltrimethylsilane and propargyltrimethylsilane. Particularly, when allyltrimethylsilane is used as the alkene counterpart interesting bicyclic compounds containing a trimethylsilane group are obtained. However, when propargyltrimethylsilane is used in the presence of water we observed the formation of a related bicyclic compound lacking the trimethylsilane group and containing an exocyclic carbon-carbon bond. PMID:25557076

  5. Methanol synthesis on ZnO(0001{sup ¯}). IV. Reaction mechanisms and electronic structure

    SciTech Connect

    Frenzel, Johannes, E-mail: johannes.frenzel@theochem.rub.de; Marx, Dominik [Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum (Germany)

    2014-09-28

    Methanol synthesis from CO and H{sub 2} over ZnO, which requires high temperatures and high pressures giving rise to a complex interplay of physical and chemical processes over this heterogeneous catalyst surface, is investigated using ab initio simulations. The redox properties of the surrounding gas phase are known to directly impact on the catalyst properties and thus, set the overall catalytic reactivity of this easily reducible oxide material. In Paper III of our series [J. Kiss, J. Frenzel, N. N. Nair, B. Meyer, and D. Marx, J. Chem. Phys. 134, 064710 (2011)] we have qualitatively shown that for the partially hydroxylated and defective ZnO(0001{sup ¯}) surface there exists an intricate network of surface chemical reactions. In the present study, we employ advanced molecular dynamics techniques to resolve in detail this reaction network in terms of elementary steps on the defective surface, which is in stepwise equilibrium with the gas phase. The two individual reduction steps were investigated by ab initio metadynamics sampling of free energy landscapes in three-dimensional reaction subspaces. By also sampling adsorption and desorption processes and thus molecular species that are in the gas phase but close to the surface, our approach successfully generated several alternative pathways of methanol synthesis. The obtained results suggest an Eley-Rideal mechanism for both reduction steps, thus involving “near-surface” molecules from the gas phase, to give methanol preferentially over a strongly reduced catalyst surface, while important side reactions are of Langmuir-Hinshelwood type. Catalyst re-reduction by H{sub 2} stemming from the gas phase is a crucial process after each reduction step in order to maintain the catalyst's activity toward methanol formation and to close the catalytic cycle in some reaction channels. Furthermore, the role of oxygen vacancies, side reactions, and spectator species is investigated and mechanistic details are discussed based on extensive electronic structure analysis.

  6. Synthesis and reactions of a nucleoside derivative of phosphoric sulfonic anhydride. Studies related to the mechanisms of coupling reactions in the chemical synthesis of oligodeoxyribonucleotides by phosphotriester procedures.

    PubMed Central

    Dabkowski, W; Skrzypczynski, Z; Michalski, J; Piel, N; McLaughlin, L W; Cramer, F

    1984-01-01

    The synthesis of a model compound, diphenylphosphoric toluene-p-sulfonic anhydride, an arylsubstituted phosphoric sulfonic mixed anhydride, is described. Using the same procedure a thymidyl substituted derivative was prepared. The phosphoric sulfonic anhydride is the presumed intermediate in oligonucleotide coupling reactions involving phosphodiester activation by arenesulfonyl derivatives. This mixed anhydride reacts with a variety of nucleophiles. It can be converted to phophotriester derivatives in the presence of simple alcohols. Phosphotriester formation using the 5'-hydroxyl of a thymidine derivative requires additionally a catalyst such as N-methylimidazole. The reactive intermediate produced upon the addition of N-methylimidazole to the phosphoric sulfonic anhydride has been observed spectroscopically using 31P-NMR. PMID:6549065

  7. In situ X-ray diffraction study of reduction processes of Fe{sub 3}O{sub 4}- and Fe{sub 1-x}O-based ammonia-synthesis catalysts

    SciTech Connect

    Zheng Yifan, E-mail: zhengyifan@zjut.edu.c [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China); Catalysis Institute, Zhejiang University of Technology, Hangzhou 310014 (China); Liu Huazhang; Liu Zongjian; Li Xiaonian [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China); Catalysis Institute, Zhejiang University of Technology, Hangzhou 310014 (China)

    2009-09-15

    The temperature-programmed reduction process of two types of industrial ammonia-synthesis catalysts, A110 and ZA-5, which are, respectively, based on Fe{sub 3}O{sub 4} and Fe{sub 1-x}O precursors, were studied by in situ X-ray power diffraction (XRD). It has been found that the ZA-5 has lower reduction temperature and faster reduction rate, and its active phase alpha-Fe possesses a higher value of lattice microstrain than A110. The simulation based on Rietveld refinement has also shown that the shape of alpha-Fe grain of ZA-5 has a mixed shape of cube and sphere with more exposing (111) and (211) planes, while that of A110 looks like a concave cube with more exposing (110) planes. Based on the results obtained, a growth model of alpha-Fe during the reduction of Fe{sub 3}O{sub 4}- and Fe{sub 1-x}O-based ammonia-synthesis catalysts is proposed, and the origins for the activity difference has been also discussed. - Graphical Abstract: A proposed growth model of active phase alpha-Fe during reduction. Due to H{sub 2} diffusing easily into the pores, reduction starts on outside and inside surface simultaneously to form 'microcrystalline film', and the particles shrink during reduction which results in breaking of the aggregated oxide particle.

  8. A New Reaction Manifold for the Barton Radical Intermediates: Synthesis of N-Heterocyclic Furanosides and Pyranosides via the Formation of the C1-C2

    E-print Network

    RajanBabu, T. V. "Babu"

    A New Reaction Manifold for the Barton Radical Intermediates: Synthesis of N of the corresponding xanthate and thiourethane derivatives (The Barton- McCombie reaction) is one of the most useful). The substrates with Scheme 1. Intermediates in the Barton Deoxygenation Reaction Scheme 2. Synthesis of Imidazole

  9. Metal-free transannulation reaction of indoles with nitrostyrenes: a simple practical synthesis of 3-substituted 2-quinolones.

    PubMed

    Aksenov, Alexander V; Smirnov, Alexander N; Aksenov, Nicolai A; Aksenova, Inna V; Frolova, Liliya V; Kornienko, Alexander; Magedov, Igor V; Rubin, Michael

    2013-10-18

    3-Substituted 2-quinolones are obtained via a novel, metal-free transannulation reaction of 2-substituted indoles with 2-nitroalkenes in polyphosphoric acid. The reaction can be used in conjunction with the Fisher indole synthesis offering a practical three-component heteroannulation methodology to produce 2-quinolones from arylhydrazines, 2-nitroalkenes and acetophenone. PMID:23999797

  10. Templated Synthesis of Peptide Nucleic Acids via Sequence-Selective Base-Filling Reactions

    PubMed Central

    2009-01-01

    The templated synthesis of nucleic acids has previously been achieved through the backbone ligation of preformed nucleotide monomers or oligomers. In contrast, here we demonstrate templated nucleic acid synthesis using a base-filling approach in which individual bases are added to abasic sites of a peptide nucleic acid (PNA). Because nucleobase substrates in this approach are not self-reactive, a base-filling approach may reduce the formation of nontemplated reaction products. Using either reductive amination or amine acylation chemistries, we observed efficient and selective addition of each of the four nucleobases to an abasic site in the middle of the PNA strand. We also describe the addition of single nucleobases to the end of a PNA strand through base filling, as well as the tandem addition of two bases to the middle of the PNA strand. These findings represent an experimental foundation for nonenzymatic information transfer through base filling. PMID:19722647

  11. A general strategy for nanohybrids synthesis via coupled competitive reactions controlled in a hybrid process.

    PubMed

    Wang, Rongming; Yang, Wantai; Song, Yuanjun; Shen, Xiaomiao; Wang, Junmei; Zhong, Xiaodi; Li, Shuai; Song, Yujun

    2015-01-01

    A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process. The latent time of nucleation and the growth of nanohybrids can be well controlled due to the formation of controllable intermediates in the coupled competitive reactions. Thus, spatiotemporal-resolved synthesis can be realized by the hybrid process, which enables us to investigate nanohybrid formation at each stage through their solution color changes and TEM images. By adjusting the bi-channel solvents and kinetic parameters of each stage, the primary components of alloyed cores and the second components of transition metal doping ZnO or Al2O3 as surface coatings can be successively formed. The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components. Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission). PMID:25818342

  12. Self-propagating reactions in finite pellets: Synthesis of titanium carbide

    SciTech Connect

    Lebrat, J.P.; Varma, A. (Univ. of Notre Dame, IN (United States). Dept. of Chemical Engineering)

    1993-10-01

    The preparation of advanced materials by self-propagating high-temperature synthesis (SHS) has attracted significant current interest. The basic concept is that once initiated, a highly exothermic reaction can become self-sustaining and will propagate through the mixture of initial reactants in the form of a combustion wave. The reactants are converted to the products as the combustion wave advances. Modeling of the SHS technique is necessary to develop time and space relationships between process characteristics and physicochemical parameters of the reacting systems, and for subsequent process scale-up and optimization. To date, most mathematical analyses of SHS have treated infinitely long systems, which lead to analytical expressions of the velocity of the combustion front as a function of various system parameters, such as activation energy and pellet thermal conductivity, but which are independent of position within the pellet. However, as one can expect from physical intuition, for pellets of finite length the reaction front movement should be influenced by boundary conditions at the ends. The propagation rate of the reaction front should therefore be a function of position: that is, a constant-pattern behavior should not exist for finite systems. In this note, results of an experimental study of TiC synthesis are described, in which an attempt was made to verify the theoretical predictions and to assess the effects of boundary conditions on the propagation of the combustion wave.

  13. A General Strategy for Nanohybrids Synthesis via Coupled Competitive Reactions Controlled in a Hybrid Process

    PubMed Central

    Wang, Rongming; Yang, Wantai; Song, Yuanjun; Shen, Xiaomiao; Wang, Junmei; Zhong, Xiaodi; Li, Shuai; Song, Yujun

    2015-01-01

    A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process. The latent time of nucleation and the growth of nanohybrids can be well controlled due to the formation of controllable intermediates in the coupled competitive reactions. Thus, spatiotemporal-resolved synthesis can be realized by the hybrid process, which enables us to investigate nanohybrid formation at each stage through their solution color changes and TEM images. By adjusting the bi-channel solvents and kinetic parameters of each stage, the primary components of alloyed cores and the second components of transition metal doping ZnO or Al2O3 as surface coatings can be successively formed. The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components. Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission). PMID:25818342

  14. Low-cost anodes for ammonia electrooxidation

    NASA Astrophysics Data System (ADS)

    Selverston, Steven M.

    This research focused on the development of low-cost electrodes for the electrochemical oxidation of ammonia to nitrogen, a reaction that has possible applications in hydrogen generation, direct ammonia fuel cells, water treatment, and sensors. Statistical design of experiments was used to help develop an efficient and scalable process for electrodeposition of platinum with a specific electrochemical surface area of over 25 m2 /g. Catalyst surface area and activity were evaluated using cyclic voltammetry, and the material microstructure and morphology were investigated using x-ray diffraction and scanning electron microscopy. The synthesized electrodes were found to be active toward the ammonia electrooxidation reaction, particularly when supporting electrolyte was added. However, supporting electrolyte was not required in order to oxidize the ammonia. As proof of concept, a homemade direct ammonia fuel cell employing a commercial anion exchange membrane was tested at room temperature with gravity-fed fuel and without supporting electrolyte. At room temperature, with passive reactant supply and using dissolved oxygen at the cathode, the cell produced about one quarter the power of a direct methanol fuel cell that used active transport of humidified oxygen and preheated (50 °C) methanol. With continued development of the membrane, cathode and membrane electrode assembly, the passive direct ammonia fuel cell using anion exchange membrane could have performance similar to the equivalent direct methanol fuel cell, and it could benefit from many advantages of ammonia over methanol such as lower cost, higher energy density, and reduced greenhouse gas emissions.

  15. Asymmetric aza-Mannich reactions of sulfinimines: scope and application to the total synthesis of a bromopyrrole alkaloid.

    PubMed

    Lanter, James C; Chen, Hongfeng; Zhang, Xuqing; Sui, Zhihua

    2005-12-22

    [reaction: see text] An asymmetric intermolecular aza variant of the Mannich reaction is reported utilizing chiral sulfinimine anions as the nucleophile and N-sulfonyl aldimines as the electrophilic component. A wide range of nucleophiles and electrophiles are tolerated by the reaction conditions, delivering the condensation products in good to excellent yield with a high degree of stereocontrol. Application of this methodology to the total synthesis of a natural product is reported. PMID:16354096

  16. Magnetic properties of Ni-Zn ferrite powders formed by self-propagating high temperature synthesis reaction

    Microsoft Academic Search

    Yong Choi; Nam Ihn Cho; H. C. Kim; Y. D. Hahn

    2000-01-01

    The ferrite compositions of NixZnxFe2O4 were synthesized by self-propagating high temperature synthesis reaction with various contents of iron, iron oxide, nickel oxide and zinc oxide at oxygen partial pressures varying between 0.05 to 5.0 MPa. The oxygen pressure promoted the combustion reaction, while the compacting pressure retarded the reaction. The rate equation of ferrite formation is shown to be v

  17. Stereo-controlled synthesis of polyheterocycles via the diene-transmissive hetero-Diels-Alder reaction of ?,?-unsaturated ?-keto esters.

    PubMed

    Otani, Takashi; Tamai, Yumiko; Seki, Kazunori; Kikuchi, Tomohiro; Miyazawa, Taiichiro; Saito, Takao

    2015-05-19

    We describe the stereoselective synthesis of polyring-fused heterocyclic compounds based on diene-transmissive hetero-Diels-Alder reactions utilizing ?,?-unsaturated ?-keto esters. This protocol involves the initial endo- or exo-selective Diels-Alder (DA) reactions with electron-rich dienophiles, methylenation of the ester carbonyl groups with the Tebbe reagent, and a stereoselective second DA reaction with electron-deficient dienophiles. The use of enantioselective DA reactions in the initial reaction enables access to chiral polyring-fused heterocyclic compounds with multiple chiral centres. PMID:25920697

  18. Ignition phenomena and reaction mechanisms of the self-propagating high-temperature synthesis reaction in the Ti+C system

    Microsoft Academic Search

    Wei-Chang Lee; Shyan-Lung Chung

    1995-01-01

    The ignition phenomena and the reaction mechanism of the self-propagating high-temperature synthesis reaction of titanium and carbon powders were experimentally investigated. When using coarse graphite powders (<325 mesh) as the carbon source, the ignition temperature ranged from 1650–1720‡C and was independent of the C\\/Ti ratio. The ignition temperature could be significantly lowered by using finer graphite powders (e.g. 1400‡C for

  19. Fusion reactions and experimental approaches to the synthesis of superheavy nuclei

    SciTech Connect

    Yeremin, A. V.; Utyonkov, V. K.; Oganessian, Yu. Ts. [Flerov Laboratory of Nuclear Reactions, JINR, 141 980 Dubna, Moscow region (Russian Federation)

    1998-02-15

    The question whether the asymmetric actinide based heavy ion reactions could be used for the synthesis of heavy (Z{>=}106) nuclides is essential from the point of view of the study of limitation on fusion, it is also important in such reactions new nuclides close to the magic number N=162 can be produced. Thus as the problem of a hindrance to fusion still remains unsolved the high excitation energy of the compound nucleus looks to be an obvious obstacle to using these reactions. Using the gas-filled recoil separator and electrostatic recoil separator VAS-SILISSA installed at the beam lines of the U-400 heavy ion cyclotron of the FLNR JINR we investigated the fusion reactions leading to 102, 103, 104, 105 and heaviest isotopes of the 106, 108 and 110 elements. The analysis of the measured cross-sections did not reveal any evidence of a hindrance to fusion at the ion bombarding energy close to the Coulomb barrier. {sup 48}Ca+{sup 232}Th{yields}{sup 280}110*, {sup 48}Ca+{sup 238}U{yields}{sup 286}112*, {sup 48}Ca+{sup 244}Pu{yields}{sup 292}114* appear to be the best reactions from the point of view of their cross-sections.

  20. Neutral and Cationic Alkyl Tantalum Imido Complexes: Synthesis and Migratory Insertion Reactions

    PubMed Central

    Anderson, Laura L.; Schmidt, Joseph A. R.; Arnold, John; Bergman, Robert G.

    2008-01-01

    The synthesis and reactivity of dibenzyl cationic tantalum imido complexes is described. The trialkyl tantalum imido compounds Bn3Ta=NCMe3 (1) and Np3Ta=NCMe3 (2) were synthesized as starting materials for the study of dialkyl cationic tantalum imido complexes. Compound 1 undergoes insertion reactions with diisopropylcarbodiimide and 2,6-dimethylphenylisocyanide to give (bisamidinate)imido complex 5 and (bisimino-acyl)imido complex 6, respectively. Treatment of compound 1 with B(C6F5)3 gives the zwitterionic tantalum complex [Bn2Ta=NCMe3][BnB(C6F5)3] (7) which is stabilized by ?6-coordination of the benzyl triaryl borate anion. Coordination of the aryl anion can be displaced by three equivalents of pyridine to give the Lewis base complex 8. Treatment of compound 1 with [Ph3C][B(C6F5)4] gives the cationic tantalum imido complex [Bn2Ta=NCMe3][B(C6F5)4] (3). This salt forms insoluble aggregates unless trapped by THF coordination or an insertion reaction with an alkyne or an alkene. Cation 3 undergoes migratory insertion reactions with diphenylacetylene, phenylacetylene, norbornene, and cis-cyclooctene to give the corresponding alkenyl or modified alkyl imido complexes. The characterization of these products and the significance of these insertion reactions with respect to Ziegler-Natta polymerizations and hydroamination reactions are described. PMID:19079787

  1. Neutral and Cationic Alkyl Tantalum Imido Complexes: Synthesis and Migratory Insertion Reactions.

    PubMed

    Anderson, Laura L; Schmidt, Joseph A R; Arnold, John; Bergman, Robert G

    2006-07-01

    The synthesis and reactivity of dibenzyl cationic tantalum imido complexes is described. The trialkyl tantalum imido compounds Bn(3)Ta=NCMe(3) (1) and Np(3)Ta=NCMe(3) (2) were synthesized as starting materials for the study of dialkyl cationic tantalum imido complexes. Compound 1 undergoes insertion reactions with diisopropylcarbodiimide and 2,6-dimethylphenylisocyanide to give (bisamidinate)imido complex 5 and (bisimino-acyl)imido complex 6, respectively. Treatment of compound 1 with B(C(6)F(5))(3) gives the zwitterionic tantalum complex [Bn(2)Ta=NCMe(3)][BnB(C(6)F(5))(3)] (7) which is stabilized by eta(6)-coordination of the benzyl triaryl borate anion. Coordination of the aryl anion can be displaced by three equivalents of pyridine to give the Lewis base complex 8. Treatment of compound 1 with [Ph(3)C][B(C(6)F(5))(4)] gives the cationic tantalum imido complex [Bn(2)Ta=NCMe(3)][B(C(6)F(5))(4)] (3). This salt forms insoluble aggregates unless trapped by THF coordination or an insertion reaction with an alkyne or an alkene. Cation 3 undergoes migratory insertion reactions with diphenylacetylene, phenylacetylene, norbornene, and cis-cyclooctene to give the corresponding alkenyl or modified alkyl imido complexes. The characterization of these products and the significance of these insertion reactions with respect to Ziegler-Natta polymerizations and hydroamination reactions are described. PMID:19079787

  2. Biochemical Characterization of the Arabidopsis Biotin Synthase Reaction. The Importance of Mitochondria in Biotin Synthesis1

    PubMed Central

    Picciocchi, Antoine; Douce, Roland; Alban, Claude

    2001-01-01

    Biotin synthase, encoded by the bio2 gene in Arabidopsis, catalyzes the final step in the biotin biosynthetic pathway. The development of radiochemical and biological detection methods allowed the first detection and accurate quantification of a plant biotin synthase activity, using protein extracts from bacteria overexpressing the Arabidopsis Bio2 protein. Under optimized conditions, the turnover number of the reaction was >2 h?1 with this in vitro system. Purified Bio2 protein was not efficient by itself in supporting biotin synthesis. However, heterologous interactions between the plant Bio2 protein and bacterial accessory proteins yielded a functional biotin synthase complex. Biotin synthase in this heterologous system obeyed Michaelis-Menten kinetics with respect to dethiobiotin (Km = 30 ?m) and exhibited a kinetic cooperativity with respect to S-adenosyl-methionine (Hill coefficient = 1.9; K0.5 = 39 ?m), an obligatory cofactor of the reaction. In vitro inhibition of biotin synthase activity by acidomycin, a structural analog of biotin, showed that biotin synthase reaction was the specific target of this inhibitor of biotin synthesis. It is important that combination experiments using purified Bio2 protein and extracts from pea (Pisum sativum) leaf or potato (Solanum tuberosum) organelles showed that only mitochondrial fractions could elicit biotin formation in the plant-reconstituted system. Our data demonstrated that one or more unidentified factors from mitochondrial matrix (pea and potato) and from mitochondrial membranes (pea), in addition to the Bio2 protein, are obligatory for the conversion of dethiobiotin to biotin, highlighting the importance of mitochondria in plant biotin synthesis. PMID:11706201

  3. One-Pot Protection-Glycosylation Reactions for Synthesis of Lipid II Analogues

    PubMed Central

    Mitachi, Katsuhiko; Mohan, Priya; Siricilla, Shajila

    2014-01-01

    (2,6-Dichloro-4-methoxyphenyl)(2,4-dichlorophenyl) methyl trichloroacetimidate (3) and its polymer-supported reagent 4 can be successfully applied to a one-pot protection-glycosylation reaction to form the disaccharide derivative 7d for the synthesis of lipid II analogues. The temporary protecting group or linker at the C-6 position and N-Troc protecting group of 7d can be cleaved simoultaneousely via a reductive condition. Overall yield of syntheses of lipid II, 1 and neryl-lipid II-N?-dansylthiourea are significantly improved via the described methods. PMID:24623584

  4. Formal Synthesis of (+)-Brefeldin A: Application of a Zinc-mediated Ring Expansion Reaction

    PubMed Central

    Lin, Weimin; Zercher, Charles K.

    2008-01-01

    An efficient formal synthesis of (+)-brefeldin A was accomplished through a synthetic approach that relied upon three keys steps. The five-membered ring was generated in a stereocontrolled fashion through application of a tandem conjugate addition-intramolecular cyclization method developed by Toru. Ring-closing metathesis provided access to a twelve-membered ?-keto lactone, which was ring-expanded to the ?,?-unsaturated-?-keto lactone through a zinc carbenoid-mediated reaction. Conversion of this lactone to (+)-brefeldin A has been reported previously. PMID:17497923

  5. Laser-induced self-propagating reaction synthesis of Ti–Fe alloys

    Microsoft Academic Search

    C. S. Wang; K. S. Zhang; H. J. Pang; Y. Z. Chen; C. Dong

    2008-01-01

    Ti70.5Fe29.5 alloy is synthesized using laser-induced self-propagating reaction synthesis (LSRS). The product mainly consists of ?-Ti + TiFe\\u000a eutectic. However, a given amount of oxygen-stabilized Ti2Fe phase is also found in the product due to high cooling rate and oxygen existence. The formation of the fine eutectic structure\\u000a makes the alloy exhibit high hardness (9.34 GPa), high compressive strength (2609 MPa), and good relative

  6. Preparation of molybdenum borides by combustion synthesis involving solid-phase displacement reactions

    Microsoft Academic Search

    C. L. Yeh; W. S. Hsu

    2008-01-01

    Preparation of molybdenum borides of five different phases in the Mo–B binary system (including Mo2B, MoB, MoB2, Mo2B5, and MoB4) was performed by self-propagating high-temperature synthesis (SHS) with two kinds of the reactant samples. When elemental powder compacts with an exact stoichiometry corresponding to the boride phase were employed, self-sustaining reaction was only achieved in the sample with Mo:B=1:1 and

  7. Synthesis and decomposition reactions of metal amides in metal–N–H hydrogen storage system

    Microsoft Academic Search

    H. Y. Leng; T. Ichikawa; S. Hino; N. Hanada; S. Isobe; H. Fujii

    2006-01-01

    The synthesis and decomposition properties of some metal amides M(NH2)x such as LiNH2, NaNH2, Mg(NH2)2 and Ca(NH2)2 were investigated, which play important roles for designing a new family of metal–N–H hydrogen storage systems. Both the gas chromatographic examination and X-ray diffraction measurement indicated that the reaction between alkali or alkaline earth metal hydride MHx (such as LiH, NaH, MgH2 and

  8. Self-propagating high-temperature synthesis and solid-phase reactions in bilayer thin films

    Microsoft Academic Search

    V. G. Myagkov; V. S. Zhigalov; L. E. Bykova; V. K. Mal’tsev

    1998-01-01

    Self-propagating high-temperature synthesis (SHS) in Al\\/Ni, Al\\/Fe, and Al\\/Co bilayer thin films is investigated. It is established\\u000a that SHS is achieved in thin films at initiation temperatures 300–350 lower than in powders. The mechanism of SHS in thin\\u000a films is similar to the process of explosive crystallization. It is shown that at the initial stage solid-phase reactions\\u000a arising on the

  9. Fischer-Tropsch synthesis in supercritical reaction media. Progress report, January 1, 1993--March 31, 1993

    SciTech Connect

    Subramaniam, B.; Bochniak, D.; Snavely, K.

    1993-04-01

    The reactor configuration has been modified to handle tows both in the upflow and downflow directions. For comparison to bubble column operation, an upflow mode of operation will be used. For comparison to trickle-bed operation, a downflow mode will be employed. Thus, this modification allows the most flexibility for studying the effects of liquid and supercritical reaction media on the Fischer-Tropsch synthesis reaction and permits comparisons of our experimental results with previous work. A stainless steel reactor tube was ordered. This unit along with three other pieces of tubing (greater than 1/4in. i. d.) are to be sent to Alon Processing Co. for alonizing (passivating) the internal surface. This process had been employed by Huff and Satterfield (1983) to ensure that the stainless steel surfaces are catalytically inert at high temperatures (> 200{degree}C).

  10. Modeling of reaction kinetics for reactor selection in the case of L-erythrulose synthesis.

    PubMed

    Vasic-Racki, D; Bongs, J; Schörken, U; Sprenger, G A; Liese, A

    2003-03-01

    To choose the most effective process design in enzyme process development it is important to find the most effective reactor mode of operation. This goal is achieved by modeling of the reaction kinetics as a tool of enzyme reaction engineering. With the example of the transketolase catalyzed L-erythrulose synthesis we demonstrate how the most effective reactor mode can be determined by kinetic simulations. This is of major importance if the biocatalyst deactivation is caused by one of the substrates as in this case by glycolaldehyde. The cascade of two membrane reactors in series with soluble enzyme is proposed as a solution for the enzyme deactivation by one of the substrates. PMID:14505172

  11. Low-temperature synthesis of actinide tetraborides by solid-state metathesis reactions

    DOEpatents

    Lupinetti, Anthony J. (Los Alamos, NM); Garcia, Eduardo (Los Alamos, NM); Abney, Kent D. (Los Alamos, NM)

    2004-12-14

    The synthesis of actinide tetraborides including uranium tetraboride (UB.sub.4), plutonium tetraboride (PuB.sub.4) and thorium tetraboride (ThB.sub.4) by a solid-state metathesis reaction are demonstrated. The present method significantly lowers the temperature required to .ltoreq.850.degree. C. As an example, when UCl.sub.4 is reacted with an excess of MgB.sub.2, at 850.degree. C., crystalline UB.sub.4 is formed. Powder X-ray diffraction and ICP-AES data support the reduction of UCl.sub.3 as the initial step in the reaction. The UB.sub.4 product is purified by washing water and drying.

  12. Facile synthesis of ultrathin magnetic iron oxide nanoplates by Schikorr reaction

    PubMed Central

    2013-01-01

    In this work, a very facile one-pot hydrothermal synthesis approach has been developed for the preparation of ultrathin magnetite nanoplates. The hydrothermal procedure was performed by aging ferrous hydroxide under anaerobic conditions, which is known as Schikorr reaction. Ethylene glycol (EG), which was introduced to the reaction as another solvent, played a critical role in the formation process of these nanoplates. Typically, hexagonal Fe3O4 nanoplates with a thickness of 10 to 15 nm and a side length of 150 to 200 nm have been synthesized with EG/H2O = 1:1 in experiments. Our data suggest that the thickness of Fe3O4 nanoplates decreases, and the shape of the nanoplate becomes more irregular when the concentration of EG increases. The as-prepared Fe3O4 nanoplates were highly crystallized single crystals and exhibited large coercivity and specific absorption rate coefficient. PMID:23294626

  13. Hydrophobic Encapsulated Phosphonium Salts-Synthesis of Weakly Coordinating Cations and their Application in Wittig Reactions.

    PubMed

    Moritz, Ralf; Wagner, Manfred; Schollmeyer, Dieter; Baumgarten, Martin; Müllen, Klaus

    2015-06-15

    Large and rigid tetraarylphosphonium tetrafluoroborate salts have been synthesized representing weakly coordinating cations with diameters of several nanometers. Divergent dendritic growth by means of thermal Diels-Alder cycloaddition was employed for the construction of the hydrophobic polyphenylene framework up to the third generation. X-ray crystal structure analysis of first-generation phosphonium tetrafluoroborate supported the rigidity of the non-collapsible shell around the phosphorus center and gave insight into solid-state packing and cation-anion distances. Copper(I)-catalyzed azide-alkyne ligation served as reliable method for the preparation of a first-generation triazolylphenyl hybrid phosphonium cation under mild reaction conditions. Furthermore, from the synthesis of triarylbenzylphosphonium bromides, Wittig precursors with unprecedented bulky substituents in the ?-position were accessible. Employment of these precursors under Wittig conditions by treatment with base and subsequent reaction with aldehydes preferentially provided (Z)-olefins with bulky polyphenylene substituents. PMID:25965029

  14. Is inhaled ammonia

    Microsoft Academic Search

    Kaye H. Kilburn

    Describes how a large ammonia release exposed about 150 nearby residents to this irritating gas and sent seven to hospital emergency rooms. Six weeks later the 41 most symptomatic people completed questionnaires and had physical examinations. The 12 most impaired had subsequent neurobehavioral testing to see if exogenous ammonia was toxic to the brain as is endogenous ammonia in hepatic

  15. Catalytic formation of monosaccharides: from the formose reaction towards selective synthesis.

    PubMed

    Delidovich, Irina V; Simonov, Alexandr N; Taran, Oxana P; Parmon, Valentin N

    2014-07-01

    The formose reaction (FR) has been long the focus of intensive investigations as a simple method for synthesis of complex biologically important monosaccharides and other sugar-like molecules from the simplest organic substrate-formaldehyde. The fundamental importance of the FR is predominantly connected with the ascertainment of plausible scenarios of chemical evolution which could have occurred on the prebiotic Earth to produce the very first molecules of carbohydrates, amino- and nucleic acids, as well as other vitally important substances. The practical importance of studies on the FR is the elaboration of catalytic methods for the synthesis of rare and non-natural monosaccharides and polyols. This Minireview considers the FR from the point of view of chemists working in the field of catalysis with emphasis on the mechanisms of numerous parallel and consequent catalytic transformations that take place during the FR. Based on its kinetics, the FR may be considered as a non-radical chain process with degenerate branching. The Minireview also considers different approaches to the control of selectivity of carbohydrate synthesis from formaldehyde and lower monosaccharides. PMID:24930572

  16. Organocatalytic three-component cascade reaction for the synthesis of spiro[indeno[1,2-b]furan]-triones.

    PubMed

    Ahadi, Somayeh; Abaszadeh, Maryam; Bazgir, Ayoob

    2012-05-01

    New methods for the synthesis of spiro compounds containing dihydrofuran and coumarin moieties from 3-bromo-4-hydroxycoumarins as cyclic ?-halo compound based on a pyridinium-ylide-assisted three-component tandem reaction is investigated. To the best of our knowledge, employing cyclic ?-halo compounds for the synthesis of dihydrofuran-fused coumarin via a pyridinium ylide has not been reported yet. PMID:22419122

  17. Catalytic dehydrocoupling/dehydrogenation of N-methylamine-borane and ammonia-borane: synthesis and characterization of high molecular weight polyaminoboranes.

    PubMed

    Staubitz, Anne; Sloan, Matthew E; Robertson, Alasdair P M; Friedrich, Anja; Schneider, Sven; Gates, Paul J; Schmedt auf der Günne, Jörn; Manners, Ian

    2010-09-29

    The catalytic dehydrocoupling/dehydrogenation of N-methylamine-borane, MeNH(2)·BH(3) (7), to yield the soluble, high molecular weight poly(N-methylaminoborane) (8a), [MeNH-BH(2)](n) (M(W) > 20?000), has been achieved at 20 °C using Brookhart's Ir(III) pincer complex IrH(2)POCOP (5) (POCOP = [?(3)-1,3-(OPtBu(2))(2)C(6)H(3)]) as a catalyst. The analogous reaction with ammonia-borane, NH(3)·BH(3) (4), gave an insoluble product, [NH(2)-BH(2)](n) (8d), but copolymerization with MeNH(2)·BH(3) gave soluble random copolymers, [MeNH-BH(2)](n)-r-[NH(2)-BH(2)](m) (8b and 8c). The structures of polyaminoborane 8a and copolymers 8b and 8c were further analyzed by ultrahigh resolution electrospray mass spectrometry (ESI-MS), and 8a, together with insoluble homopolymer 8d, was also characterized by (11)B and (1)H solid-state NMR, IR, and wide-angle X-ray scattering (WAXS). The data indicate that 8a-8c are essentially linear, high molecular weight materials and that the insoluble polyaminoborane 8d possesses a similar structure but is of lower molecular weight (ca. 20 repeat units), presumably due to premature precipitation during its formation. The yield and molecular weight of polymer 8a was found to be relatively robust toward the influence of different temperatures, solvents, and adduct concentrations, while higher catalyst loadings led to higher molecular weight materials. It was therefore unexpected that the polymerization of 7 using 5 was found to be a chain-growth rather than a step-growth process, where high molecular weights were already attained at about 40% conversion of 7. The results obtained are consistent with a two stage polymerization mechanism where, first, the Ir catalyst 5 dehydrogenates 7 to afford the monomer MeNH?BH(2) and, second, the same catalyst effects the subsequent polymerization of this species. A wide range of other catalysts based on Ru, Rh, and Pd were also found to be effective for the transformation of 7 to polyaminoborane 8a. For example, polyaminoborane 8a was even isolated from the initial stage of the dehydrocoupling/dehydrogenation of 7 with [Rh(?-Cl)(1,5-cod)](2) (2) as the catalyst at 20 °C, a reaction reported to give the N,N,N-trimethyl borazine, [MeN-BH](3), under different conditions (dimethoxyethane, 45 °C). The ability to use a variety of catalysts to prepare polyaminoboranes suggests that the synthetic strategy should be applicable to a broad range of amine-borane precursors and is a promising development for this new class of inorganic polymers. PMID:20806956

  18. Regiocontrol by remote substituents. An enantioselective total synthesis of frenolicin B via a highly regioselective Diels-Alder reaction

    SciTech Connect

    Kraus, G.A.; Li, J. (Iowa State Univ., Ames (United States)); Gordon, M.S.; Jensen, J.H. (Ames Lab. US-DOE, IA (United States))

    1993-06-30

    The quinone subunit is contained in a broad range of biologically important natural products such as frenolicin B, which is a member of the pyranonaphthoquinone family. The diverse biological activity of quinones has led to the development of several new synthetic methods for quinones. Among the pathways featuring a cycloaddition reaction, one of the most general methods for the regiospecific synthesis of substituted quinones was pioneered by H.J. Rapoport and others. This method involves the Diels-Alder reaction of a substituted quinone. As part of a program to evaluate the directing effects of functional groups not directly attached to the atoms undergoing Diels-Alder cycloaddition, we now report that remote substituents on a dienophile can confer excellent regioselectivity in Diels-Alder reactions. This work has led to an extremely direct synthesis of the pyranonaphthoquinone framework and to the first synthesis of frenolicin B (1). 19 refs., 1 fig.

  19. Elucidating the Reaction Pathways in the Synthesis of Organolead Trihalide Perovskite for High-Performance Solar Cells

    PubMed Central

    Wang, Baohua; Young Wong, King; Xiao, Xudong; Chen, Tao

    2015-01-01

    The past two years have witnessed unprecedentedly rapid development of organic–inorganic halide perovskite–based solar cells. The solution–processability and high efficiency make this technology extraordinarily attractive. The intensive investigations have accumulated rich experiences in the perovskite fabrication; while the mechanism of the chemical synthesis still remains unresolved. Here, we set up the chemical equation of the synthesis and elucidate the reactions from both thermodynamic and kinetic perspectives. Our study shows that gaseous products thermodynamically favour the reaction, while the activation energy and “collision” probability synergistically determine the reaction rate. These understandings enable us to finely tune the crystal size for high-quality perovskite film, leading to a record fill factor among similar device structures in the literature. This investigation provides a general strategy to explore the mechanism of perovskite synthesis and benefits the fabrication of high–efficiency perovskite photoactive layer. PMID:26020476

  20. Elucidating the reaction pathways in the synthesis of organolead trihalide perovskite for high-performance solar cells.

    PubMed

    Wang, Baohua; Young Wong, King; Xiao, Xudong; Chen, Tao

    2015-01-01

    The past two years have witnessed unprecedentedly rapid development of organic-inorganic halide perovskite-based solar cells. The solution-processability and high efficiency make this technology extraordinarily attractive. The intensive investigations have accumulated rich experiences in the perovskite fabrication; while the mechanism of the chemical synthesis still remains unresolved. Here, we set up the chemical equation of the synthesis and elucidate the reactions from both thermodynamic and kinetic perspectives. Our study shows that gaseous products thermodynamically favour the reaction, while the activation energy and "collision" probability synergistically determine the reaction rate. These understandings enable us to finely tune the crystal size for high-quality perovskite film, leading to a record fill factor among similar device structures in the literature. This investigation provides a general strategy to explore the mechanism of perovskite synthesis and benefits the fabrication of high-efficiency perovskite photoactive layer. PMID:26020476

  1. Synthesis and reaction temperature-tailored self-assembly of copper sulfide nanoplates

    NASA Astrophysics Data System (ADS)

    Wu, Haibin; Chen, Wei

    2011-12-01

    Nanostructured copper sulfides have attracted much attention due to their unique electronic and optical properties and potential applications in many areas. This article presents a high-temperature precursor-injection method to synthesize covellite copper sulfide (CuS) nanoplates by using oleylamine as capping ligands. The synthesized CuS nanoplates were found to be self-assembled into face-to-face one-dimensional columnar arrays with the longest column of 0.75 ?m. Further studies showed that the reaction temperature has strong effects on the size, size distribution and the self-assembly behaviors of the CuS nanoplates. The self-assembly behaviors were found to be tuned by the reaction temperature. In the range of 140-180 °C, the face-to-face self-assembly is formed over the entire substrate, whereas only edge-to-edge arrangements were observed at the reaction temperature of 200 °C. As the temperature further increases, the product exhibits a mixture of large and small nanocrystals and there is not any presence of self-assembly. The present study highlights the size-controlled synthesis of copper sulfide nanoplates and their self-assembly behaviors dependent on reaction temperature.

  2. Concise synthesis of the C15-C38 fragment of okadaic acid: application of the Suzuki-Miyaura reaction to spiroacetal synthesis.

    PubMed

    Fuwa, Haruhiko; Sakamoto, Keita; Muto, Takashi; Sasaki, Makoto

    2015-01-16

    A concise synthetic entry to the C15-C38 fragment of okadaic acid by exploiting a Suzuki-Miyaura reaction for the rapid assembly of the spiroacetal substructures has been developed. The present synthesis was completed in 19 linear steps from a commercially available material, showcasing the efficiency of our synthetic strategy. PMID:25544331

  3. Ammonia-based hydrogen source for fuel cell applications

    Microsoft Academic Search

    Lixiong Li; James A. Hurley

    2007-01-01

    Generation of hydrogen from the reaction of ammonia (NH3) with magnesium hydride (MgH2) was studied. Experiments were conducted at near ambient temperatures (75–150?C), which are lower than that required by ammonia cracking and\\/or metal hydride thermal decomposition reactions. Effects of selected catalysts\\/promoters for the production of hydrogen by the NH3–MgH2 reaction were evaluated. Addition of ammonium chloride (NH4Cl) accelerated the

  4. Synthesis of functionalized ?-lactams and pyrrolidine-2,5-diones through a metal-free sequential Ugi-4CR/cyclization reaction.

    PubMed

    Ghabraie, Elmira; Balalaie, Saeed; Mehrparvar, Saber; Rominger, Frank

    2014-09-01

    An efficient approach for the synthesis of functionalized ?-lactams and pyrrolidine-2,5-diones was achieved through a sequential Ugi-4CR/cyclization reaction. Diversity-oriented synthesis, good to high yields, easy workup, and short reaction times are advantages of this procedure. PMID:25105212

  5. Thermo-electrochemical modeling of ammonia-fueled solid oxide fuel cells considering ammonia thermal decomposition in the anode

    Microsoft Academic Search

    Meng Ni

    2011-01-01

    Ammonia (NH3) is a promising hydrogen carrier and a possible fuel for use in Solid Oxide Fuel Cells (SOFCs). In this study, a 2D thermo-electrochemical model is developed to investigate the heat\\/mass transfer, chemical (ammonia thermal decomposition) and electrochemical reactions in a planar SOFC running on ammonia. The model integrates three sub-models: (1) an electrochemical model relating the current density–voltage

  6. Synthesis of titanium carbide by self-propagating powder reactions. 1: Enthalpy of formation of TiC

    Microsoft Academic Search

    D. L. Vrel; J. M. Lihrmann; J. P. Petitet

    2009-01-01

    In order to solve the heat equation which describes self-propagating high temperature synthesis (SHS) of refractory materials, a set of experiments have been performed to measure the enthalpy of reaction which accompanies the formation of titanium carbide in direct powder reactions. In air, the measured value is [minus]139 [+-] 6 kJ\\/mol, whereas in argon it becomes [minus]129 [+-] 6 kJ\\/mol

  7. Laser-induced self-propagating reaction synthesis of amorphous-based composite Zr-Al-Ni-Cu alloys

    Microsoft Academic Search

    Cunshan Wang; Linhui Gao; Gang Li; Yanfang Wang; Yuanliang Xia; S. Bysakh; Chuang Dong

    2003-01-01

    Strong exothermic reaction due to large negative enthalpy of mixing can occur among major components of bulk metallic glass forming alloy systems. Based on this idea, we developed a new technique to fabricate amorphous-based composite materials using Laser-induced Self-propagating Reaction Synthesis (LSRS). The LSRS of the Zr55Al10Ni5Cu30 alloy shows that the products mainly consist of the amorphous, Zr3Al2 and Zr2Cu

  8. Scale-up synthesis of zinc borate from the reaction of zinc oxide and boric acid in aqueous medium

    Microsoft Academic Search

    Mert Kilinç; Gaye Ö. Çakal; Sertan Yesil; Göknur Bayram; Inci Eroglu; Saim Özkar

    2010-01-01

    Synthesis of zinc borate was conducted in a laboratory and a pilot scale batch reactor to see the influence of process variables on the reaction parameters and the final product, 2ZnO·3B2O3·3.5H2O. Effects of stirring speed, presence of baffles, amount of seed, particle size and purity of zinc oxide, and mole ratio of H3BO3:ZnO on the zinc borate formation reaction were

  9. Densification process of TiCx–Ni composites formed by self-propagating high-temperature synthesis reaction

    Microsoft Academic Search

    YONG CHOI; J. K. LEE; M. E MULLINS

    1997-01-01

    Densification behaviour of the TiC-Ni system formed by self-propagating high-temperature synthesis (SHS) were studied to develop\\u000a the structural metal-matrix composites. The composites were prepared by two routes: (1) consolidation during the SHS reaction,\\u000a and (2) consolidation process after the SHS reaction. The final phases of the stoichiometric reactant mixture of titanium\\u000a and graphite with 50 wt% nickel produced by simultaneous

  10. One-pot synthesis of acyclic nucleosides from carbohydrate derivatives, by combination of tandem and sequential reactions.

    PubMed

    Boto, Alicia; Hernández, Dácil; Hernández, Rosendo; Alvarez, Eleuterio

    2007-12-01

    The design of processes which combine tandem and sequential reactions allows the transformation of readily available precursors into high-profit products. This strategy is illustrated by the one-pot synthesis of acyclic nucleosides, which are potential antiviral compounds, from readily available carbohydrates. The reaction conditions are mild, compatible with most functional groups. Depending on the starting sugar, both common and uncommon acyclic chains can be prepared. These polyhydroxylated chains can be combined with different bases to generate diversity. PMID:17985924

  11. Biotransformations Utilizing ?-Oxidation Cycle Reactions in the Synthesis of Natural Compounds and Medicines

    PubMed Central

    Œwizdor, Alina; Panek, Anna; Milecka-Tronina, Natalia; Ko?ek, Teresa

    2012-01-01

    ?-Oxidation cycle reactions, which are key stages in the metabolism of fatty acids in eucaryotic cells and in processes with a significant role in the degradation of acids used by microbes as a carbon source, have also found application in biotransformations. One of the major advantages of biotransformations based on the ?-oxidation cycle is the possibility to transform a substrate in a series of reactions catalyzed by a number of enzymes. It allows the use of sterols as a substrate base in the production of natural steroid compounds and their analogues. This route also leads to biologically active compounds of therapeutic significance. Transformations of natural substrates via ?-oxidation are the core part of the synthetic routes of natural flavors used as food additives. Stereoselectivity of the enzymes catalyzing the stages of dehydrogenation and addition of a water molecule to the double bond also finds application in the synthesis of chiral biologically active compounds, including medicines. Recent advances in genetic, metabolic engineering, methods for the enhancement of bioprocess productivity and the selectivity of target reactions are also described. PMID:23443116

  12. A concise synthesis of benzimidazoles via the microwave-assisted one-pot batch reaction of amino acids up to a 10-g scale.

    PubMed

    Peng, Pai; Xiong, Jin-Feng; Mo, Guang-Zhen; Zheng, Jia-Li; Chen, Ren-Hong; Chen, Xiao-Yun; Wang, Zhao-Yang

    2014-10-01

    An efficient method for the synthesis of aminomethyl benzimidazoles is developed by using a one-pot batch reaction between amino acids and o-phenylenediamines. This reaction proceeds smoothly in an unmodified household microwave oven, even though scale-up is to 10 g. A desirable method for the quick synthesis of benzimidazoles, which are used as a kind of important intermediates in drug synthesis, is provided by the scale-up utilization of amino acid resource. PMID:25030664

  13. Simultaneous Light-Directed Synthesis of Mirror-Image Microarrays in a Photochemical Reaction Cell with Flare Suppression

    PubMed Central

    2013-01-01

    The use of photolabile protecting groups is a versatile and well-established means of synthesizing high complexity microarrays of biopolymers, such as nucleic acids and peptides, for high-throughput analysis. The synthesis takes place in a photochemical reaction cell which positions the microarray substrate at the focus of the optical system delivering the light and which can be connected to a fluidics system which delivers appropriate reagents to the surface in synchrony with the light exposure. Here we describe a novel photochemical reaction cell which allows for the simultaneous synthesis of microarrays on two substrates. The reaction cell positions both substrates within the limited depth-of-focus of the optical system while maintaining the necessary reagent flow conditions. The resulting microarrays are mirror images of each other but otherwise essentially identical. The new reaction cell doubles the throughput of microarray synthesis without increasing the consumption of reagents. In addition, a secondary flow chamber behind the reaction cell can be filled with an absorbent and index-matching fluid to eliminate reflections from light exiting the reaction cell assembly, greatly reducing unintended light exposure that reduces the sequence fidelity of the microarray probes. PMID:23968455

  14. Determination of Ammonia in Household Cleaners: An Instrumental Analysis Experiment.

    ERIC Educational Resources Information Center

    Graham, Richard C.; DePew, Steven

    1983-01-01

    Briefly discusses three techniques for assessing amount of ammonia present in household cleaners. Because of disadvantages with these methods, the thermometric titration technique is suggested in which students judge the best buy based on relative cost of ammonia present in samples. Laboratory procedures, typical results, and reactions involved…

  15. An organocatalytic Mannich/denitration reaction for the asymmetric synthesis of 3-ethylacetate-substitued 3-amino-2-oxindoles: formal synthesis of AG-041R.

    PubMed

    Zhao, Kun; Shu, Tao; Jia, Jiaqi; Raabe, Gerhard; Enders, Dieter

    2015-03-01

    The highly enantioselective organocatalytic addition of ethyl nitroacetate to isatin-derived N-Boc ketimines (Boc = tert-butoxycarbonyl), followed by the removal of the nitro group, is described. The scalable reaction sequence leads to the title compounds as important intermediates of pyrroloindoline alkaloids and related drugs in excellent yields and enantioselectivities. The synthesis of the hexahydrofurano[2,3-b]indole skeleton, the spirocarbamate oxindole unit, and the formal synthesis of AG-041R have been carried out to demonstrate the synthetic utility of this protocol. PMID:25630891

  16. Photochemical Synthesis and Ligand Exchange Reactions of Ru(CO)[subscript 4] (Eta[superscript 2]-Alkene) Compounds

    ERIC Educational Resources Information Center

    Cooke, Jason; Berry, David E.; Fawkes, Kelli L.

    2007-01-01

    The photochemical synthesis and subsequent ligand exchange reactions of Ru(CO)[subscript 4] (eta[superscript2]-alkene) compounds has provided a novel experiment for upper-level inorganic chemistry laboratory courses. The experiment is designed to provide a system in which the changing electronic properties of the alkene ligands could be easily…

  17. Microwave-Enhanced Organic Syntheses for the Undergraduate Laboratory: Diels-Alder Cycloaddition, Wittig Reaction, and Williamson Ether Synthesis

    ERIC Educational Resources Information Center

    Baar, Marsha R.; Falcone, Danielle; Gordon, Christopher

    2010-01-01

    Microwave heating enhanced the rate of three reactions typically performed in our undergraduate organic chemistry laboratory: a Diels-Alder cycloaddition, a Wittig salt formation, and a Williamson ether synthesis. Ninety-minute refluxes were shortened to 10 min using a laboratory-grade microwave oven. In addition, yields improved for the Wittig…

  18. Lewis Acid and/or Lewis Base catalyzed [3+2] cycloaddition reaction: Synthesis of pyrazoles and pyrazolines

    E-print Network

    Paris-Sud XI, Université de

    1 Lewis Acid and/or Lewis Base catalyzed [3+2] cycloaddition reaction: Synthesis of pyrazoles-Hillman adducts, activated and simple alkynes to afford 3,5-disubstituted pyrazolines and pyrazoles respectively trichloride, activated olefins, Baylis- Hillman adducts, pyrazolines, pyrazoles. Formation of heterocycles

  19. Thermodynamic analysis of self-propagating reaction of alkaline-and rare-earth metal oxide synthesis

    Microsoft Academic Search

    V. S. Sudavtsova; A. M. Sych; V. G. Kudin

    1999-01-01

    A thermodynamic method is proposed to determine the optimal conditions for the synthesis of complex oxides employing self-propagating\\u000a reactions. This permits estimation of heat effects and changes in Gibbs energy and entropy with the aid of standard thermodynamic\\u000a functions, and also calculation of the temperatures of synthesized products in the adiabatic approximation.

  20. Synthesis of polyhydroxylated piperidine and pyrrolidine peptidomimetics via one-pot sequential lactam reduction/Joullié-Ugi reaction.

    PubMed

    Szcze?niak, Piotr; Maziarz, El?bieta; Stecko, Sebastian; Furman, Bart?omiej

    2015-04-01

    A direct approach to the synthesis of polyhydroxylated piperidine and pyrrolidine peptidomimetics is described. The presented strategy is based on one-pot reduction of sugar-derived lactams with Schwartz's reagent followed by a multicomponent Ugi-Joullié reaction. PMID:25768203

  1. Synthesis of novel tryptamine-based macrocycles using an Ugi 4-CR/microwave assisted click-cycloaddition reaction protocol.

    PubMed

    Chavez-Acevedo, Lizbeth; Miranda, Luis D

    2015-04-21

    A practical synthesis of novel tryptamine-based macrocycles using an Ugi 4-CR/click-cycloaddition sequential reaction protocol is described. The main features of the macrocyclic scaffolds are a peptoid moiety, a 1,3-substituted indole nucleus, and a triazole ring. PMID:25766574

  2. Synthesis of Heterocycles Through Classical Ugi and Passerini Reactions Followed by Secondary Transformations Involving One or Two Additional Functional Groups

    NASA Astrophysics Data System (ADS)

    Banfi, Luca; Basso, Andrea; Riva, Renata

    The combination of classical isocyanide-based multicomponent reactions (Ugi and Passerini) with a variety of post-condensation transformations, which take advantage of suitably positioned additional functional groups, allows the straightforward synthesis, often in 1-2 synthetic steps, of many diverse nitrogen-containing heterocycles. This review will cover all the applications of this strategy reported to date (September 2009).

  3. N-Heterocyclic carbene-catalyzed diastereoselective synthesis of ?-lactone-fused cyclopentanes using homoenolate annulation reaction.

    PubMed

    Mukherjee, Subrata; Mondal, Santigopal; Patra, Atanu; Gonnade, Rajesh G; Biju, Akkattu T

    2015-05-26

    NHC-catalyzed annulation of enals with 2-enoylpyridines or 2-enoylpyridine N-oxides leading to the diastereoselective synthesis of ?-lactone-fused cyclopentanes is reported. The reaction proceeds via the generation of homoenolate equivalent intermediates and tolerates a broad range of functional groups. PMID:25972189

  4. Development of an Asymmetric Trimethylenemethane Cycloaddition Reaction: Application in the Enantioselective Synthesis of Highly Substituted Carbocycles

    PubMed Central

    Trost, Barry M.; Silverman, Steven M.; Stambuli, James P.

    2011-01-01

    A protocol for the enantioselective [3+2] cycloaddition of trimethylenemethane with electron-deficient olefins has been developed. The synthesis of novel phosphoramidite ligands was critical in this effort, and the preparation and reactivity of these ligands is detailed. The evolution of the ligand design, commencing with acyclic amine-derived phosphoramidites and leading to cyclic pyrrolidine and azetidine structures is discussed. The conditions developed to effect an asymmetric TMM reaction using 2-trimethylsilylmethyl allyl acetate were shown to be tolerant of a wide variety of alkene acceptors, providing the desired methylenecyclopentanes with high levels of enantioselectivity. The donor scope was also explored and substituted systems were tolerated, including one bearing a nitrile moiety. These donors were reactive with unsaturated acylpyrroles, giving the product cyclopentane rings bearing three stereocenters in high enantioselectivity and complete diastereoselectivity. PMID:21936576

  5. A new synthesis of TATB using inexpensive starting materials and mild reaction conditions

    SciTech Connect

    Mitchell, A.R.; Pagoria, P.F.; Schmidt, R.D.

    1996-04-01

    TATB is currently manufactured in US by nitration of the expensive TCB to give 2,4,6-trichloro-1,3,5-trinitrobenzene which is then aminated to yield TATB. Elevated temperatures (150 C) are required for both reactions. There is a need for a more economical synthesis of TATB that also addresses current environmental issues. We have recently found that 1,1,1-trimethylhydrazinium iodide (TMHI) allows the amination of nitroarenes at ambient temperature via Vicarious Nucleophilic Substitution of hydrogen. TMHI reacts with picramide in presence of strong base (NaOMe or t-BuOK) to give TATB in over 95% yield. TMHI and picramide can be obtained from either inexpensive starting materials or surplus energetic materials from demilitarization activities, such as the 30,000 metric tons of UDMH (surplus rocket propellant) from the former Soviet Union.

  6. Construction materials for reaction unit in the liquid-phase synthesis of propylene oxide

    SciTech Connect

    Zaritskii, V.I.D.

    1987-09-01

    The main components of the reaction medium in equipment for the synthesis of propylene oxide by liquid-phase oxidation of gaseous propylene with peracetic acid are propylene, peracetic acid, ethyl acetate, acetic acid, propylene oxide, carbon dioxide, oxygen, methane, and propylene glycol acetates. The operating conditions of the equipment and content of the main components of the medium are shown. Results are given for the investigation of the corrosion behavior of 12Kh18N10T, 10Kh17N13M2T, 08Kh22N6T, and 08Kh21N6M2T steels, AD0 and AD1 aluminum, and VT1-0 titanium. VSt3 carbon steel was tested for comparison.

  7. Nickel-alumina composites: In situ synthesis by a displacement reaction, and mechanical properties

    SciTech Connect

    Jones, S.A.; Burlitch, J.M.; Uestuendag, E.; Yoo, J.; Zehnder, A.T. [Cornell Univ., Ithaca, NY (United States)

    1995-10-01

    Nickel-alumina composites have the potential to be high performance materials. Alumina, with its excellent oxidation resistance, combined with a ductile phase such as nickel may provide a tough material with a lower density and higher Young`s modulus, overall, a higher specific modulus than typical Superalloys. Dense, interpenetrating Ni-Al{sub 2}O{sub 3} composites were synthesized using a displacement reaction between NiO and aluminum. The resulting composites were characterized in terms of their mechanical properties such as hardness, flexure strength, fracture toughness and elastic constants. The synthesis, characterization, and mechanical properties, as well as the effect of the interpenetrating microstructure on the toughening mechanisms and other properties will be discussed.

  8. Reaction Behavior and Mechanism during Self-Propagating High-Temperature Synthesis Reaction in an Al-TiO2-B4C System

    NASA Astrophysics Data System (ADS)

    Zou, Binglin; Shen, Ping; Yin, Shiqiang; Jiang, Qichuan

    2008-08-01

    The reaction behavior and mechanism during self-propagating high-temperature synthesis (SHS) in an Al-TiO2-B4C system were investigated. The result shows that the reaction could be self-sustaining for the Al content no more than 58.4 wt pct in the reactants. With the increase in Al, the combustion temperature decreases monotonically, the ignition delay time first decreases and then increases, while the combustion wave velocity displays an opposite behavior. The reaction mechanisms are somewhat dependent on the Al content, while the resultant types of the final products are independent. The desired reaction products make the Al-TiO2-B4C system ideal for producing the ( ?-Al2O3-TiC-TiB2)/Al composites using the SHS technique.

  9. Applications of Click Chemistry Reactions to the Synthesis of Functional Materials

    NASA Astrophysics Data System (ADS)

    Accurso, Adrian A.

    This body of work focuses on the production of functional materials using the most reliable carbon-hetoratom bond-forming processes available, which are widely termed "click chemistry" reactions in the literature. This focus on function is enabled by a basis in synthetic chemistry, and where appropriate, brings in techniques from the related fields of materials science and biology to address current needs in those areas. Chapter 1 concerns the in situ production of azide and alkyne-based click chemistry adhesive polymers. Screening of a library of multivalent azides and alkynes was accomplished on a custom-built highthroughput instrument and followed up on a lap-shear testing apparatus. The conductivity of composites made of the adhesive was also explored according to standard methods. The second and third chapters explore the synthesis and function of a family of related [3.3.1]-bicyclononane dichlorides, which we have termed "WCL" electrophiles, and their potential applications for surface functionalization, the synthesis of polycations, and candidate membrane disruptive compounds. The rates of consumption of dichlorides and hydrolysis of model compounds were also explored using NMR, GC-MS, and HPLC-based methods.

  10. Fischer-Tropsch synthesis in supercritical reaction media. Progress report, October 1, 1993--December 31, 1993

    SciTech Connect

    Subramaniam, B.; Bochniak, D.; Snavely, K.

    1994-01-01

    Construction of the automated high pressure reactor unit was completed. Testing of the reactor and trial runs are currently in progress. An HP 5890 GC/FID system interfaced with an BP 3365 Chemstation is now in place for analysis of F-T synthesis products. Calibration methods are currently under development. The pressure transducers were successfully calibrated using high precision Heise gauges. Figure 1 shows the linearity of the transducer response. The HPLC pump, used for pumping n-hexane was also tested and calibrated. The agitated sand bath surrounding the reactor (meant for absorbing the high heat of reaction produced in Fischer-Tropsch synthesis) was assembled in place and successfully tested. The entire system was tested to withstand the operating pressures and to be free of leaks. A cold wax trap was fabricated and added to the existing setup. This is similar in nature to the hot wax trap and will serve to collect condensables from the product stream not collected in the hot wax trap and from the GC exhaust stream. Pressure control (using the stepping-motor-driven micrometering valve) and temperature control tests are currently in progress aimed at establishing the control parameters. Thereafter, the experimental investigations consisting of the blank runs and sub-, near-, and supercritical experiments will be commenced. Progress was made in the development of both on-line and off-line analyses. Off-line analysis determines retention times (compound identification) and response factors (quantitative analysis).

  11. Control of chemical reactions and synthesis by low-energy electrons.

    PubMed

    Böhler, Esther; Warneke, Jonas; Swiderek, Petra

    2013-12-21

    Controlling the outcome of reactions is a central issue of chemical research. Physical tools can achieve this if they are able to precisely dissociate specific bonds of a molecule. However, to control synthesis, such tools must induce the formation of new bonds between two reactants to yield a more complex product. In the ideal case of an atom efficient synthesis, this product would contain all or at least most of the initial material. An electron beam is a physical tool that is capable of preparing molecules in reactive states or, at low electron energies, of initiating highly selective bond dissociation. The resulting fragments in turn can react with other molecules to yield stable products. This tutorial review focuses in particular on such low-energy electron-initiated molecular syntheses and their applications in the modification of surfaces. It thus emphasizes strategies towards the controlled and predictable formation of more complex products from small reactants initiated by interaction with low-energy electrons either through selective bond dissociation or formation of specific reactive molecular species. However, selective bond dissociation is not always desirable. This is briefly illustrated by the case of electron beam induced deposition where additional strategies may be required to control product formation. PMID:24088739

  12. Synthesis of isotopically labeled P-site substrates for the ribosomal peptidyl transferase reaction

    PubMed Central

    Zhong, Minghong

    2010-01-01

    Isotopomers of the ribosomal P-site substrate, the trinucleotide peptide conjugate CCA-pcb,1 have been designed and synthesized in 26–350020steps. These include individual isotopic substitution at the ?-proton, carbonyl carbon, and carbonyl oxygen of the amino acid, the O2' and O3' of the adenosine, and a remote label in the N3 and N4 of both cytidines. These isotopomers were synthesized by coupling cytidylyl-(3'5')-cytidine phosphoramidite isotopomers, as the common synthetic intermediates, with isotopically substituted A-Phe-cap-biotin (A-pcb). The isotopic enrichment is higher than 99% for 1-13C (Phe), 2-2H (Phe), and 3,4-15N2 (cytidine), 93% for 2'/3'- 18O (adenosine), and 64% for 1-18O (Phe). A new synthesis of highly enriched [1-18O2] phenylalanine has been developed. The synthesis of [3'-18O] adenosine was improved by Lewis acid aided regioselective ring opening of the epoxide and by an economical SN2-SN2 method with high isotopic enrichment (93%). Such substrates are valuable for studies of the ribosomal peptidyl transferase reaction by complete kinetic isotope effect analysis and of other biological processes catalyzed by nucleic acid related enzymes, including polymerases, reverse transcriptases, ligases, nucleases, and ribozymes. PMID:18081346

  13. Synthesis and characterization of isomaltulose-derived oligosaccharides produced by transglucosylation reaction of Leuconostoc mesenteroides dextransucrase.

    PubMed

    Barea-Alvarez, Montserrat; Benito, Maria Teresa; Olano, Agustín; Jimeno, Maria Luisa; Moreno, F Javier

    2014-09-17

    This paper reports the efficient enzymatic synthesis of a homologous series of isomaltulose-derived oligosaccharides with degrees of polymerization ranging from 3 to 9 through the transglucosylation reaction using a dextransucrase from Leuconostoc mesenteroides B-512F. The total oligosaccharide yield obtained under optimal conditions was 41-42% (in weight with respect to the initial amount of isomaltulose) after 24-48 h of reaction. Nuclear magnetic resonance (NMR) structural characterization indicated that dextransucrase specifically transferred glucose moieties of sucrose to the C-6 of the nonreducing glucose residue of isomaltulose. Likewise, monitoring the progression of the content of each individual oligosaccharide indicated that oligosaccharide acceptor products of low molecular weight acted in turn as acceptors for further transglucosylation to yield oligosaccharides of a higher degree of polymerization. The produced isomaltulose-derived oligosaccharides can be considered as isomalto-oligosaccharides (IMOs) because they are linked by only ?-(1?6) bonds. In addition, having isomaltulose as the core structure, these IMO-like structures could possess appealing bioactive properties that could find potential applications as functional food ingredients. PMID:25175804

  14. Modelling the reaction course of N -acetylneuraminic acid synthesis from N -acetyl- d -glucosamine—new strategies for the optimisation of neuraminic acid synthesis

    Microsoft Academic Search

    Vera Zimmermann; Hans-Georg Hennemann; Thomas Daußmann; Udo Kragl

    2007-01-01

    In this work, a model describing the complete enzyme catalysed synthesis of N-acetylneuraminic acid (Neu5Ac) from N-acetyl-d-glucosamine (GlcNAc) is presented. It includes the combined reaction steps of epimerisation from GlcNAc to N-acetyl-d-mannosamine (ManNAc) and the aldol condensation of ManNAc with sodium pyruvate yielding Neu5Ac. The model is expedient to\\u000a predict the reaction course for various initial and feed concentrations and

  15. Process for the elimination of ammonia in coke plant waste waters

    SciTech Connect

    Wagener, D.; Laue, K.H.; Sander, Th.

    1984-05-08

    A process for the elimination of ammonia in waste waters from a coke oven battery wherein ammonia-containing waste water or ammonia-containing vapor obtained by means of ammonia separation from the waste water are mixed with flue gas from the coke oven battery and sprayed into a NO /SUB x/ reactor at an elevated temperature with the resulting mixture being subjected to a catalytic redox reaction.

  16. Formation of simple C-labelled molecules by the nuclear reaction N(p,?) C in nitrogen containing solids

    Microsoft Academic Search

    K. Rössler; M. Vogt; H. Lattke

    1982-01-01

    Simple C-labelled molecules which are formed by hot processes following the N(p, a) C nuclear reactions with 13 MeV protons in cyclotron targets are of interest as precursors for the synthesis of C-radiopharma-ceuticals. Solid targets show the advantage of greater stability against radiolysis and heat and a greater variability of chemical reactions. Frozen ammonia NH3, ammonium halides NH4X (X =

  17. Homochiral Selectivity in RNA Synthesis: Montmorillonite-catalyzed Quaternary Reactions of D, L-Purine with D, L- Pyrimidine Nucleotides

    NASA Astrophysics Data System (ADS)

    Joshi, Prakash C.; Aldersley, Michael F.; Ferris, James P.

    2011-06-01

    Selective adsorption of D, L-ImpA with D, L-ImpU on the platelets of montmorillonite demonstrates an important reaction pathway for the origin of homochirality in RNA synthesis. Our earlier studies have shown that the individual reactions of D, L-ImpA or D, L-ImpU on montmorillonite catalyst produced oligomers which were only partially inhibited by the incorporation of both D- and L-enantiomers. Homochirality in these reactions was largely due to the formation of cyclic dimers that cannot elongate. We investigated the quaternary reactions of D, L-ImpA with D, L-ImpU on montmorillonite. The chain length of these oligomers increased from 9-mer to 11-mer as observed by HPLC, with a concominant increase in the yield of linear dimers and higher oligomers in the reactions involving D, L-ImpA with D, L-ImpU as compared to the similar reactions carried out with D-enantiomers only. The formation of cyclic dimers of U was completely inhibited in the quaternary reactions. The yield of cyclic dimers of A was reduced from 60% to 10% within the dimer fraction. 12 linear dimers and 3 cyclic dimers were isolated and characterized from the quaternary reaction. The homochirality and regioselectivity of dimers were 64.1% and 71.7%, respectively. Their sequence selectivity was shown by the formation of purine-pyrimidine (54-59%) linkages, followed by purine-purine (29-32%) linkages and pyrimidine-pyrimidine (9-13%) linkages. Of the 16 trimers detected, 10 were homochiral with an overall homochirality of 73-76%. In view of the greater homochirality, sequence- and regio- selectivity, the quaternary reactions on montmorillonite demonstrate an unexpectedly favorable route for the prebiotic synthesis of homochiral RNA compared with the separate reactions of enantiomeric activated mononucleotides.

  18. Development of a Suzuki Cross-Coupling Reaction between 2-Azidoarylboronic Pinacolate Esters and Vinyl Triflates To Enable the Synthesis of [2,3]-Fused Indole Heterocycles

    PubMed Central

    2015-01-01

    The scope and limitations of a Suzuki reaction between 2-azidoarylboronic acid pinacolate esters and vinyl triflates are reported. This cross-coupling reaction enables the regioselective synthesis of indoles after a subsequent RhII2-catalyzed sp2-C–H bond amination reaction. PMID:24571492

  19. Sugar-Driven Prebiotic Synthesis of 3,5(6)-Dimethylpyrazin-2-one: A Possible Nucleobase of a Primitive Replication Process

    Microsoft Academic Search

    Arthur L. Weber

    2008-01-01

    Reaction of glyceraldehyde with alanine amide (or ammonia) under anaerobic aqueous conditions yielded 3,5(6)-dimethylpyrazin-2-one\\u000a that is considered a possible complementary residue of a primitive replicating molecule that preceded RNA. Synthesis of the\\u000a dimethylpyrazin-2-one isomers under mild aqueous conditions (65°C, pH 5.5) from 100 mM glyceraldehyde and alanine amide (or\\u000a ammonia) was complete in about 5 days. This synthesis using 25 mM glyceraldehyde and alanine

  20. Five-membered cyclic metal carbyne: synthesis of osmapentalynes by the reactions of osmapentalene with allene, alkyne, and alkene.

    PubMed

    Zhu, Congqing; Yang, Yuhui; Wu, Jingjing; Luo, Ming; Fan, Jinglan; Zhu, Jun; Xia, Haiping

    2015-06-01

    The synthesis of small cyclic metal carbynes is challenging due to the large angle strain associated with the highly distorted nonlinear triple bonds. Herein, we report a general route for the synthesis of five-membered cyclic metal carbyne complexes, osmapentalynes, by the reactions of an osmapentalene derivative with allene, alkyne, and alkene. Experimental observations and theoretical calculations document the aromaticity in the fused five-membered rings of osmapentalynes. The realization of transforming osmapentalene to osmapentalyne through this general route would not only allow further exploration of metallapentalyne chemistry but also show promising applications of this novel aromatic system with broad absorption band and high molar absorption coefficient. PMID:25917530

  1. Chemical pathways for the formation of ammonia in Hanford wastes

    SciTech Connect

    Stock, L.M.; Pederson, L.R.

    1997-09-01

    This report reviews chemical reactions leading to the formation of ammonia in Hanford wastes. The general features of the chemistry of the organic compounds in the Hanford wastes are briefly outlined. The radiolytic and thermal free radical reactions that are responsible for the initiation and propagation of the oxidative degradation reactions of the nitrogen-containing complexants, trisodium HEDTA and tetrasodium EDTA, are outlined. In addition, the roles played by three different ionic reaction pathways for the oxidation of the same compounds and their degradation products are described as a prelude to the discussion of the formation of ammonia. The reaction pathways postulated for its formation are based on tank observations, laboratory studies with simulated and actual wastes, and the review of the scientific literature. Ammonia derives from the reduction of nitrite ion (most important), from the conversion of organic nitrogen in the complexants and their degradation products, and from radiolytic reactions of nitrous oxide and nitrogen (least important). Reduction of nitrite ions is believed to be the most important source of ammonia. Whether by radiolytic or thermal routes, nitrite reduction reactions proceed through nitrogen dioxide, nitric oxide, the nitrosyl anion, and the hyponitrite anion. Nitrite ion is also converted into hydroxylamine, another important intermediate on the pathway to form ammonia. These reaction pathways additionally result in the formation of nitrous oxide and molecular nitrogen, whereas hydrogen formation is produced in a separate reaction sequence.

  2. Modeling ammonia removal in aerated facultative lagoons.

    PubMed

    Houweling, C D; Kharoune, L; Escalas, A; Comeau, Y

    2005-01-01

    A mechanistic model has been developed to model ammonia removal in aerated facultative lagoons. Flow is modeled through the water column by a continuously stirred tank reactor and exchanges between the sludge layer and the water column are simulated by a solids separator. The biological model is based on an activated sludge model with reactions added for anaerobic bacterial growth and degradation of inert organic material. Results show that the model is able to predict seasonal variation in ammonia removal as well as sludge accumulation in the lagoons. PMID:16114676

  3. Abiotic synthesis of high-molecular-weight organics from an inorganic gas mixture of carbon monoxide, ammonia, and water by 3 MeV proton irradiation

    NASA Astrophysics Data System (ADS)

    Takano, Yoshinori; Ohashi, Akihiro; Kaneko, Takeo; Kobayashi, Kensei

    2004-02-01

    The abiotic formation of high-molecular-weight organics from an inorganic gas mixture of carbon monoxide, ammonia, and water as a result of 3 MeV proton irradiation from a Van de Graaff accelerator was experimentally verified. The inorganic gas mixture was simulated for representative of interstellar medium. The irradiation products included amino acid (AA) precursors, and the molecular weight distribution ranged from several hundred to a maximum of 3000 Da. Both proteinous and nonproteinous AAs were detected after acid hydrolysis. Thus, the primary irradiation products were not free AA analogs, but were AA precursors having high molecular weight. The present results have significant implications regarding the extraterrestrial origins of AA precursors, such as meteoritic organic compounds and the organic composition of interstellar dust particles.

  4. Nitrogen and Hydrogen on a Palladium-covered proton conductor: a first principle study of Ammonia catalysis

    NASA Astrophysics Data System (ADS)

    Paulatto, Lorenzo; de Gironcoli, Stefano

    2009-03-01

    Being liquid at ambient conditions Ammonia would be an ideal Hydrogen vector. However, the industrial Haber process for Ammonia synthesis involves high pressures ( 100 bar) and temperatures (450-500 ^oC), making the process very expensive. Recently, ambient pressure Ammonia production, in the 570-750 ^oC temperature range, has been reported at the Palladium cathode of a proton conducting cell-reactor [1]. The rate limiting step in the Haber process is N2 dissociation, while the observed limiting factor in Ref. [1] appears to be the proton transfer through the conductor and it has been proposed that Nitrogen hydrogenation may in this case precede dissociation. We use first-principles techniques to study Nitrogen, Hydrogen and Ammonia interaction with flat and stepped Pd surfaces, in presence of external electric fields. Our aim is to study the effect of electrochemically provided protons on the catalysis of the reaction. [1]G. Marnellos and M. Stoukides, Science 282, 98 (1998); G. Marnellos, S. Zisekas, and M. Stoukides, J. of Catalysis 193, 80-87 (2000)

  5. Chemical pathways for the formation of ammonia in Hanford wastes

    SciTech Connect

    Stock, L.M.; Pederson, L.R.

    1997-12-01

    This report reviews chemical reactions leading to the formation of ammonia in Hanford wastes. The general features of the chemistry of the organic compounds in the Hanford wastes are briefly outlined. The radiolytic and thermal free radical reactions that are responsible for the initiation and propagation of the oxidative degradation reactions of the nitrogen-containing complexants, trisodium HEDTA and tetrasodium EDTA, are outlined. In addition, the roles played by three different ionic reaction pathways for the oxidation of the same compounds and their degradation products are described as a prelude to the discussion of the formation of ammonia. The reaction pathways postulated for its formation are based on tank observations, laboratory studies with simulated and actual wastes, and the review of the scientific literature. Ammonia derives from the reduction of nitrite ion (most important), from the conversion of organic nitrogen in the complexants and their degradation products, and from radiolytic reactions of nitrous oxide and nitrogen (least important).

  6. Synthesis of Unsymmetrical Diarylureas via Pd-Catalyzed C–N Cross-Coupling Reactions

    E-print Network

    Breitler, Simon

    A facile synthesis of unsymmetrical N,N?-diarylureas is described. The utilization of the Pd-catalyzed arylation of ureas enables the synthesis of an array of diarylureas in good to excellent yields from benzylurea via a ...

  7. Observation of intermetallic Ni{sub 3}Ti whiskers during combustion synthesis reactions in the Ni-Ti-C system

    SciTech Connect

    Chrysanthou, A.; Kassim, K.H. [Univ. of Nottingham (United Kingdom). Dept. of Materials Engineering and Materials Design] [Univ. of Nottingham (United Kingdom). Dept. of Materials Engineering and Materials Design

    1995-10-01

    The term self-propagating high-temperature synthesis (SHS) describes a process reaction where, once ignited, the reactants spontaneously transform into products due to the exothermic nature of the reaction. The work which is reported here was part of a program of research studying the potential of the SHS process for the production of metal-matrix composites for wear-resistant applications based on TiC in a nickel matrix. Self-propagating reactions between titanium and carbon black, generating 30--90% TiC by weight in Ni, were studied. Although SHS reactions for this particular system have been studied by other researchers, the observation of whisker growth while using this technique has not previously been reported.

  8. Molecular Structure of Ammonia

    NSDL National Science Digital Library

    2006-05-02

    Ammonia is a non-ionic colorless gas at ambient temperatures and a hydrogen bonding liquid at 240 Kelvin that has the remarkable ability to dissolve alkali metals. Ammonia is a Lewis base and is readily absorbed by water to form small amounts of ammonium hydroxide (pKb = 4.74). Naturally, ammonia has its sources in the biosphere (the nitrogen cycle) and is a trace gas in air and a source of ammonium ions in rain and atmospheric aerosols. Ammonia is prepared industrially by the Haber-Bosch process in quantities exceeding 120 million metric tons per year. In this process, ammonia gas is formed when hydrogen and nitrogen (3:1) are compressed to pressures of 200 atm and passed over an iron catalyst at 380-450 degrees C. Much of the ammonia produced this way (85%) is used as fertilizers on crops, a significant portion of which leaches from croplands into streams causing nitrate pollution and eutrophication of waterways (e.g., dead-zone in the Gulf of Mexico). Other sources of ammonia include combustion (coal and biomass burning) and from bacterial decomposition of animal excreta.

  9. Synthesis of ultrastable copper sulfide nanoclusters via trapping the reaction intermediate: potential anticancer and antibacterial applications.

    PubMed

    Wang, Hong-Yin; Hua, Xian-Wu; Wu, Fu-Gen; Li, Bolin; Liu, Peidang; Gu, Ning; Wang, Zhifei; Chen, Zhan

    2015-04-01

    Copper-based nanomaterials have broad applications in electronics, catalysts, solar energy conversion, antibiotics, tissue imaging, and photothermal cancer therapy. However, it is challenging to prepare ultrasmall and ultrastable CuS nanoclusters (NCs) at room temperature. In this article, a simple method to synthesize water-soluble, monodispersed CuS NCs is reported based on the strategy of trapping the reaction intermediate using thiol-terminated, alkyl-containing short-chain poly(ethylene glycol)s (HS-(CH2)11-(OCH2CH2)6-OH, abbreviated as MUH). The MUH-coated CuS NCs have superior stability in solutions with varied pH values and are stable in pure water for at least 10 months. The as-prepared CuS NCs were highly toxic to A549 cancer cells at a concentration of higher than 100 ?M (9.6 ?g/mL), making them be potentially applicable as anticancer drugs via intravenous administration by liposomal encapsulation or by direct intratumoral injection. Besides, for the first time, CuS NCs were used for antibacterial application, and 800 ?M (76.8 ?g/mL) CuS NCs could completely kill the E. coli cells through damaging the cell walls. Moreover, the NCs synthesized here have strong near-infrared (NIR) absorption and can be used as a candidate reagent for photothermal therapy and photoacoustic imaging. The method of trapping the reaction intermediate for simple and controlled synthesis of nanoclusters is generally applicable and can be widely used to synthesize many metal-based (such as Pt, Pd, Au, and Ag) nanoclusters and nanocrystals. PMID:25785786

  10. Reaction Routes for the Synthesis of CuInSe2 Using Bilayer Compound Precursors

    SciTech Connect

    Krishnan, Rangarajan [University of Florida; Wood, David [University of Florida; Chaudhari, Vaibhav U. [University of Florida; Payzant, E Andrew [ORNL; Noufi, Rommel [National Renewable Energy Laboratory (NREL); Rozeveld, Steve [Dow Chemical Company, The; Kim, Woo Kyoung [Yeungnam University, Korea; Anderson, Timothy J [University of Florida

    2012-01-01

    The reaction pathways and phase evolution during synthesis of CuInSe{sub 2} (CIS) by a novel bilayer approach were investigated using in situ high-temperature X-ray diffraction. Two bilayer precursor structures, glass/Mo/{gamma}-In{sub 2}Se{sub 3}/{beta}-CuSe + {beta}-Cu{sub 2}Se/Se and glass/Mo/{gamma}-In{sub 2}Se{sub 3}/{beta}-Cu{sub 2}Se/Se, were examined in this study. Temperature ramp experiments revealed that the phase transformation sequence for each bilayer precursor qualitatively follows that predicted by the phase diagram and that the onset temperatures for decomposition of the sub-binary compounds depend on the Se partial pressure. Measurement of the isothermal rate of formation of CuInSe{sub 2} at six temperatures in the range 260 to 310 C for the {gamma}-In{sub 2}Se{sub 3}/{beta}-CuSe + {beta}-Cu{sub 2}Se/Se bilayer suggests relatively slow nucleation followed by diffusion-limited reaction with estimated activation energy of 162({+-}7) and 225 ({+-}16) kJ/mol from Avrami and parabolic models, respectively. Interestingly, the measured activation energy for the same precursor in a 4 mol % H{sub 2}/He ambient (108 ({+-}8) kJ/mol) was lower than that observed in pure N{sub 2} (158 ({+-}16) kJ/mol). The results of isothermal measurements in the temperature range 250 to 300 C for the {gamma}-In{sub 2}Se{sub 3}/{beta}-Cu{sub 2}Se/Se precursor film in an inert ambient are consistent with one-dimensional diffusion-limited growth with estimated activation energy from the Avrami and parabolic models of 194 ({+-}10) and 203 ({+-}12) kJ/mol, respectively.

  11. Synthesis of Al4SiC4 powders from kaolin grog, aluminum and carbon black by carbothermal reaction

    NASA Astrophysics Data System (ADS)

    Yuan, Wenjie; Yu, Chao; Deng, Chengji; Zhu, Hongxi

    2013-12-01

    In this paper, the synthesis of Al4SiC4 used as natural oxide materials by carbothermal reduction was investigated in order to explore the synthesis route with low costs. The samples were calcined by using kaolin grog, aluminum and carbon black as raw materials with the selected proportion at the temperature from 1500 to 1800 ° C for 2 hours under flow argon atmosphere. The phase composition of reaction products were determined by X-ray diffraction. The microstructure and elemental composition of different phases were observed and identified by scanning electron microscopy and energy dispersive spectroscopy. The mechanism of reaction processing was discussed. The results show that Al4SiC4 powders composed of hexagonal plate-like particulates with various sizes and the thickness of less than 20 ?m are obtained when the temperature reaches 1800 °C.

  12. Synthesis of Cu3Sn alloy nanocrystals through sequential reduction induced by gradual increase of the reaction temperature.

    PubMed

    Cho, Sanghun; Shin, Dong-Hun; Yin, Zhenxing; Lee, Chaedong; Park, Si Yun; Yoo, Jeeyoung; Piao, Yuanzhe; Kim, Youn Sang

    2015-04-27

    Cu3Sn alloy nanocrystals are synthesized by sequential reduction of Cu and Sn precursors through a gradual increase of the reaction temperature. By transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), UV/Vis spectroscopy, and X-ray diffraction (XRD) analyses, the alloy formation mechanism of Cu3Sn nanocrystals has been studied. The incremental increase of the reaction temperature sequentially induces the reduction of Sn, the diffusion of Sn into the preformed Cu nanocrystals, resulting in the intermediate phase of Cu-Sn alloy nanocrystals, and then the formation of Cu3Sn alloy nanocrystals. We anticipate that the synthesis of Cu3Sn alloy nanocrystals encourages studies toward the synthesis of various alloy nanomaterials. PMID:25777248

  13. Ignition phenomena and reaction mechanisms of the self-propagating high-temperature synthesis reaction in the titanium-carbon-aluminum system

    SciTech Connect

    Lee, W.C.; Chung, S.L. [National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Chemical Engineering

    1997-01-01

    The effect of the addition of aluminum on the ignition and self-propagating high-temperature synthesis (SHS) reaction between titanium and carbon was experimentally investigated. Although TiC was the only product compound in the final product, the reaction between titanium and aluminum was believed to occur before the ignition of the reaction between titanium and carbon, as evidenced by a hump that appeared in the temperature profile during heating. The ignition temperature of the reaction between titanium and carbon was significantly decreased by the addition of aluminum. This was explained by the fact that the aluminum provides an easier route for reactant mass transfer, thus significantly increasing the reaction rate of the reaction between titanium and carbon. As the temperature was increased to beyond the melting point of aluminum during heating, aluminum melted and titanium dissolved into it. As the temperature was increased to beyond the melting point of aluminum during heating, aluminum melted and titanium dissolved into it. As the temperature was increased further (>1,050 C), the titanium-containing aluminum spread over the carbon particles. Ignition is believed to have occurred by the reaction of titanium and carbon at the interface by the diffusion of titanium through the aluminum melt to the interface. The rate of heating and the density of the reactant compact also affected the ignition temperature. These were explained by their influence on the extent of the capillary spreading of the titanium-containing aluminum melt on the carbon particles or by the formation of a TiAl{sub x} layer at the interface between the aluminum melt and the titanium particles. Fracture surfaces of the product showed three different types of morphology. A possible reaction mechanism was proposed that describes the ignition process and explains the formation of each type of product.

  14. Unusual regioselection in the Mitsunobu reactions of syn-2,3-dihydroxy esters: synthesis of statine and its diastereomer.

    PubMed

    Ko, Soo Y

    2002-04-19

    Mitsunobu reactions of syn-2,3-dihydroxy esters exhibit a complete regioselection for the beta-hydroxyl group. Benzoylation, azidation, and tosylation have been performed under these conditions. Beta-functionalizations of syn-2,3-dihydroxy esters are uncommon, and the Mitsunobu reactions are complementary to other diol chemistries in the regioselection. In addition, the configurational inversion accompanying the Mitsunobu protocol offers a means for diastereochemical diversity, as exemplified by a synthesis of statine and its anti diastereomer. These findings will further expand the synthetic utilities of the Sharpless AD process. PMID:11950319

  15. Synthesis of a Library of “Lead-Like” ?-Lactams by a One Pot, Four-Component Reaction

    PubMed Central

    Martin, Kevin S.; Di Maso, Michael J.; Fettinger, James C.

    2013-01-01

    The synthesis of a pilot scale library of 116 structurally diverse ?-lactams is reported. The library core structure emanates from a ?-lactam forming one-pot, four-component reaction of ammonium acetate, p-methoxythiophenol, p-methoxybenzaldehyde and maleic anhydride. Structural diversity then arises from amide coupling, thioaryl cleavage, N-functionalization and heterocycle forming reactions on this core structure. Computational analysis reveals that the library contains molecular properties and shape diversity suitable for drug lead and biological probe discovery. PMID:23682712

  16. Enantioselective nickel-catalyzed reductive coupling reactions of alkynes and aldehydes. Synthesis of amphidinolides T1 and T4 via catalytic, stereoselective macrocyclizations

    E-print Network

    Colby Davie, Elizabeth A. (Elizabeth Anne)

    2005-01-01

    I. Enantioselective Nickel-Catalyzed Reductive Couplings of Alkynes and Aldehydes Allylic alcohol synthesis via a nickel-catalyzed reductive coupling reaction of alkylsubstituted alkynes and aldehydes was studied for ligand ...

  17. Use of a Tandem Prins/Friedel-Crafts Reaction in the Construction of the Indeno-Tetrahydropyridine Core of the Haouamine Alkaloids: Formal Synthesis of (?)-Haouamine A

    PubMed Central

    Fenster, Erik; Fehl, Charlie; Aubé, Jeffrey

    2011-01-01

    A tandem Prins/Friedel-Crafts reaction useful for the construction of the indeno-tetrahydropyridine core of the haouamine alkaloids and a formal synthesis of (?)-haouamine A are described. PMID:21517105

  18. Total synthesis of peloruside A via kinetic lactonization and relay RCM cyclization reactions (and identification of iso-peloruside A)

    PubMed Central

    Hoye, Thomas R.; Jeon, Junha; Kopel, Lucas C.; Ryba, Troy D.; Tennakoon, Manomi A.; Wang, Yini

    2013-01-01

    A convergent total synthesis of peloruside A (1) is described. The key strategic features are a diastereoselective lactonization to generate a C5-C9 valerolactone from the C2-symmetric ketone 4, which comprises C1–C9 of 1, and a relay ring closing metathesis (RRCM) reaction to produce a dehydrovalerolactone 20, which embodies C13–C19. A new isomer of 1, the valerolactone iso-peloruside A (iso-1), was identified. PMID:20645374

  19. Synthetic studies of the lichen macrolide lepranthin. Stereoselective synthesis of the diolide framework based on regioselective epoxide-opening reactions.

    PubMed

    Takada, Hisashi; Nagumo, Shinji; Yasui, Eiko; Mizukami, Megumi; Miyashita, Masaaki

    2011-01-01

    Stereoselective synthesis of the 16-membered diolide 27, a fully functionalized congener of lepranthin (1), is described. The requisite five asymmetric carbon centers in monomer 23 were constructed in a highly stereoselective manner by using different epoxide-opening reactions of ?,?-unsaturated ?,?-epoxy esters and epoxy alcohol derivatives as the key steps. The monomer 23 was successfully transformed into the MOM protected diolide 27 by Yamaguchi macrolactonization. PMID:21467690

  20. Production of Ni3Ti-TiC x intermetallic-ceramic composites employing combustion synthesis reactions

    Microsoft Academic Search

    Douglas E. Burkes; Guglielmo Gottoli; John J. Moore; Hu Chun Yi

    2006-01-01

    Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi-TiC (stoichiometric) or Ni3Ti-TiC x (nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be synthesized. The stoichiometry of TiC x , for

  1. Synthesis of Heterocycles Through Classical Ugi and Passerini Reactions Followed by Secondary Transformations Involving One or Two Additional Functional Groups

    Microsoft Academic Search

    Luca Banfi; Andrea Basso; Renata Riva

    2010-01-01

    \\u000a The combination of classical isocyanide-based multicomponent reactions (Ugi and Passerini) with a variety of post-condensation\\u000a transformations, which take advantage of suitably positioned additional functional groups, allows the straightforward synthesis,\\u000a often in 1–2 synthetic steps, of many diverse nitrogen-containing heterocycles. This review will cover all the applications\\u000a of this strategy reported to date (September 2009).

  2. Recent developments in the synthesis of heterocyclic derivatives by PdI 2-catalyzed oxidative carbonylation reactions

    Microsoft Academic Search

    Bartolo Gabriele; Giuseppe Salerno; Mirco Costa; Gian Paolo Chiusoli

    2003-01-01

    A simple catalytic system, consisting of PdI2 in conjunction with an excess of KI, has proven to be very valuable for the direct one-step synthesis of a variety of heterocyclic derivatives by oxidative carbonylation of suitably functionalized alkynes. The same catalyst also promoted the oxidative carbonylation of ?-amino alcohols to oxazolidin-2-ones with unprecedented catalytic efficiencies for this kind of reaction.

  3. Myocardial synthesis of prostaglandin-like substances and coronary reactions to cardiostimulation and to hypoxia.

    PubMed Central

    Sunahara, F A; Talesnik, J

    1979-01-01

    1 Continuous recording of cardiac contractions and coronary flow from isolated perfused hearts of rats permitted the study of coronary reactions to: (a) cardiostimulation induced by single doses or slow infusions of noradrenaline, CaCl2, glucagon or electrically induced tachycardia; (b) short interruptions of coronary inflow (hypoxia). 2 Except during tachycardia the heart rate was kept constant at 210 beats/min by electrical pacing. 3 Metabolic coronary vasodilatation (MCD) resulting from cardiac hyperactivity induced by noradrenaline, Ca2+, tachycardia or glucagon was inhibited by administration of prostaglandin E2. Reactive hyperaemia response to hypoxia was unaffected by prostaglandin administration. 4 Inhibition of MCD could also be obtained by prolonged infusion with arachidonic acid (1.6 X 10(-7) M), presumably by its conversion into prostaglandin-like substance since arachidonic acid failed to block MCD in hearts from rats pretreated with non-steroidal anti-inflammatory drugs (indomethacin, naproxen, phenylbutazone). 5 Reactive hyperaemia was unaffected either by arachidonic acid or by blockade of the synthesis of prostaglandin-like substances by anti-inflammatory drugs. 6 Since prostaglandin synthetase inhibition does not prevent but may enhance MCD, we do not advocate prostaglandin-like substances as agents directly responsible for the coronary vasodilatation that follows cardiac hyperactivity. 7 We postulate that cardiac overproduction of prostaglandins may lead to a failure in the adaptive coronary flow response to cardiac hyperactivity (coronary insufficiency?). PMID:760893

  4. Prediction of Reaction Kinetic in Mechanically Activated Self-Propagating High-Temperature Synthesis Process

    NASA Astrophysics Data System (ADS)

    Razavi, Mansour

    2012-12-01

    In this paper we have tried to develop a semi-empirical formula for estimation of starting time of reactions during mechanical alloying process according to self-propagating high temperature synthesis (SHS) mechanism. For this purpose, three SHS systems containing Ti-C, Mo-Si and Si-C were selected and their behaviors were observed. Aforementioned systems were milled in a planetary ball mill equipped with temperature sensor detector of cups. Samplings were done at different times of discontinuously milling. To change mills' energy, stainless steel and tungsten carbide balls were used. In order to detect the phases and characterizations of milled powder, XRD instrument was utilized. Results showed that all productions were synthesized after sudden increase in temperature. Maximum measured temperature and critical time had up and downtrends for production of TiC, MoSi2 and SiC, respectively. Crystalline size of milled powder had nano-meter scale. By using experimental data along with theoretical equations, a semi-empirical formula between critical time for transformation of raw materials to productions, type of milled system and ball mill parameter can be presented with high accuracy. According to calculated formula, critical time was related to ball mill energy and Gibbs free energy of milled system with direct and inverse proportionality, respectively.

  5. Microwave (MW) irradiated Ugi four-component reaction (Ugi-4CR): Expedited synthesis of steroid-amino acid conjugates - A novel class of hybrid compounds.

    PubMed

    Borah, Preetismita; Borah, Juri Moni; Chowdhury, Pritish

    2015-06-01

    Microwave (MW) assisted chemical reactions are currently gaining considerable importance in organic synthesis to contribute in green technology. Considering the importance of peptidomimetic steroid-amino acid conjugates - a novel class of hybrid compounds having diverse biological properties, we report here synthesis of these compounds of alanine and valine methyl esters with seco-steroids (A, B and D ring cleavage) in expedited way by MW promoted Ugi-four-component reaction (Ugi-4CR). PMID:25701096

  6. Method for the Synthesis of Phenothiazines via a Domino Iron-Catalyzed C-S/C-N Cross-Coupling Reaction.

    PubMed

    Hu, Weiye; Zhang, Songlin

    2015-06-19

    An environmentally benign and efficient method has been developed for the synthesis of phenothiazines via a tandem iron-catalyzed C-S/C-N cross-coupling reaction. Some of the issues typically encountered during the synthesis of phenothiazines in the presence of palladium and copper catalysts, including poor substrate scope, long reaction times and poor regioselectivity, have been addressed using this newly developed iron-catalyzed method. PMID:26028127

  7. Ammonia Release on ISS

    NASA Technical Reports Server (NTRS)

    Macatangay, Ariel

    2009-01-01

    Crew: Approximately 53% metabolic load Product of protein metabolism Limit production of ammonia by external regulation NOT possbile Payloads Potential source Scientific experiments Thorough safety review ensures sufficient levels of containment

  8. Ammonia and sediment toxicity

    SciTech Connect

    Ogle, R.S.; Hansen, S.R. [S.R. Hansen and Associates, Concord, CA (United States)

    1994-12-31

    Ammonia toxicity to aquatic organisms has received considerable study, with most of these studies focusing on water column organisms. However, with the development and implementation of sediment (and pore water) toxicity tests, the toxicity of ammonia to benthic infauna and other sediment toxicity test organisms has become important, especially since sediment/porewater ammonia occurs at higher concentrations than in the water column. Unfortunately, there has been very little of this type information, especially for marine/estuarine organisms. This laboratory determined the toxicity of ammonia to three key marine/estuarine test organisms: the amphipod Eohaustorius estuarius, the bivalve Mytilus edulis, and the echinoderm Strongylocentrotus purpuratus. Because sediment/porewater pH can differ substantially from typical seawater pH, the toxicity evaluations covered a range of pH levels (6, 7, 8, and 9). Eohaustorius results indicate that while Total Ammonia increased in toxicity (measured as EC50) as pH increased (from 460 mg/L at pH 6, to 13 mg/L at pH 9), unionized ammonia toxicity decreased from 0.13 mg/L at pH 6 to 2.8 mg/L at pH 9. The amphipod was much less sensitive to ammonia than were the bivalve and echinoderm, with an unionized ammonia EC50 at pH 8 of 2.14 mg/L relative to 0.43 mg/L for the mussel and 0.13 mg/L for the purple urchin. These results are discussed with respect to design and interpretation of sediment toxicity test results, including an interpretation approach based on partitioning of Toxic Units (TU).

  9. Ammonia Clouds on Jupiter

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Click on the image for movie of Ammonia Ice Clouds on Jupiter

    In this movie, put together from false-color images taken by the New Horizons Ralph instrument as the spacecraft flew past Jupiter in early 2007, show ammonia clouds (appearing as bright blue areas) as they form and disperse over five successive Jupiter 'days.' Scientists noted how the larger cloud travels along with a small, local deep hole.

  10. Titan's Ammonia Feature

    NASA Technical Reports Server (NTRS)

    Smythe, W.; Nelson, R.; Boryta, M.; Choukroun, M.

    2011-01-01

    NH3 has long been considered an important component in the formation and evolution of the outer planet satellites. NH3 is particularly important for Titan, since it may serve as the reservoir for atmospheric nitrogen. A brightening seen on Titan starting in 2004 may arise from a transient low-lying fog or surface coating of ammonia. The spectral shape suggests the ammonia is anhydrous, a molecule that hydrates quickly in the presence of water.

  11. Stereoselective synthesis of unsaturated and functionalized L-NHBoc amino acids, using Wittig reaction under mild phase-transfer conditions.

    PubMed

    Rémond, Emmanuelle; Bayardon, Jérôme; Ondel-Eymin, Marie-Joëlle; Jugé, Sylvain

    2012-09-01

    The stereoselective synthesis of a new amino acid phosphonium salt was described by quaternization of melting triphenylphosphine with the ?-iodo NHBoc-amino ester, derived from L-aspartic acid. The deprotection of the carboxylic acid function to afford the phosphonium salt with a free carboxylic acid group was achieved by a palladium-catalyzed desallylation reaction. This phosphonium salt was used in the Wittig reaction with aromatic or aliphatic aldehydes and trifluoroacetophenone, under solid-liquid phase-transfer conditions in chlorobenzene and in the presence of K(3)PO(4) as weak base, to afford the corresponding unsaturated amino acids without racemization. Thus, the reaction with substituted aldehydes allows to graft various functionalized groups on the lateral chain of the amino acid, such as trifluoromethyl, cyano, nitro, ferrocenyl, boronato, or azido. In addition, the reaction of the amino acid Wittig reagent with ?,?-unsaturated aldehydes leads to amino acids bearing a diene on the lateral chain. Finally, this amino acid phosphonium salt appears to be a new powerful tool for the preparation of unsaturated and non-proteinogenic ?-amino acids, directly usable for the synthesis of customized peptides. PMID:22870957

  12. Trapping in water - an important prerequisite for complex reactivity in astrophysical ices: the case of acetone (CH3)2C = O and ammonia NH3

    NASA Astrophysics Data System (ADS)

    Fresneau, Aurélien; Danger, Grégoire; Rimola, Albert; Theule, Patrice; Duvernay, Fabrice; Chiavassa, Thierry

    2014-10-01

    Water is the most abundant compound in interstellar and cometary ices. Laboratory experiments on ice analogues have shown that water has a great influence on the chemical activity of these ices. In this study, we investigated the reactivity of acetone-ammonia ices, showing that water is an essential component in chemical reactions with high activation energies. In a water-free binary ice, acetone and ammonia do not react due to high activation energy, as the reactants desorb before reacting (at 120 and 140 K, respectively). By contrast, our study shows that under experimental conditions of ˜150 K, this reaction does occur in the presence of water. Here, water traps reactants in the solid phase above their desorption temperatures, allowing them to gather thermal energy as the reaction proceeds. Using infrared spectroscopy and mass spectrometry associated with isotopic labelling, as well as quantum chemical calculations, 2-aminopropan-2-ol (2HN-C(CH3)2-OH) was identified as the acetone-ammonia reaction product. The formation of this product may represent the first step towards formation of 2-aminoisobutyric acid (AIB) in the Strecker synthesis. The activation energy for the formation of 2-aminopropan-2-ol was measured to be 42 ± 3 kJ mol-1, while its desorption energy equalled 61.3 ± 0.1 kJ mol-1. Our work demonstrates that astrophysical water, rather than being a non-thermally reactive species, is crucial for the evolution of complex chemistry occurring in the Universe.

  13. Analysis of ammonia decomposition reactor to generate hydrogen for fuel cell applications

    Microsoft Academic Search

    Vyjayanthi Alagharu; Srinivas Palanki; Kevin N. West

    2010-01-01

    In this paper, reaction engineering principles are utilized to analyze process conditions for producing sufficient hydrogen in an ammonia decomposition reactor for generating net power of 100W in a fuel cell. It is shown that operating the reactor adiabatically results in a sharp decrease in temperature due to endothermic reaction, which results in low conversion of ammonia. For this reason,

  14. Endothermic reactors for an ammonia based thermochemical solar energy storage and transport system

    Microsoft Academic Search

    K. Lovegrove; A. Luzzi

    1996-01-01

    The ammonia dissociation reaction is one of a number of reactions which has been investigated for use in closed loop solar thermochemical energy storage systems, over a period of nearly two decades. A recent series of experiments with an electrically heated high pressure ammonia dissociation reactor has validated a two dimensional pseudo-homogenous theoretical reactor model, established rate parameters for the

  15. Ammonia in comet P/Halley

    NASA Technical Reports Server (NTRS)

    Meier, R.; Eberhardt, P.; Krankowsky, D.; Hodges, R. R.

    1994-01-01

    In comet P/Halley the abundances of ammonia relative to water reported in the literature differ by about one order of magnitude from roughly 0.1% up to 2%. Different observational techniques seem to have inherent systematic errors. Using the ion mass channels m/q = 19 amu/e, 18 amu/e and 17 amu/e of the Neutral Mass Spectrometer experiment aboard the spacecraft Giotto, we derive a production rate of ammonia of (1.5(sub -0.7)(sup +0.5))% relative to water. Inside the contact surface we can explain our data by a nuclear source only. The uncertainty in our abundance of ammonia is primarily a result of uncertainties in some key reaction coefficients. We discuss in detail these reactions and the range of error indicated results from extreme assumptions in the rate coefficients. From our data, even in the worst case, we can exclude the ammonia abundance to be only of the order of a few per mill.

  16. Synthesis of Spirocyclic Indolines by Interruption of the Bischler–Napieralski Reaction

    E-print Network

    Medley, Jonathan William

    The development of a versatile method for the synthesis of spirocyclic pyrrolidinoindolines is discussed. Treatment of N-acyltryptamines with trifluoromethanesulfonic anhydride–2-chloropyridine reagent combination affords ...

  17. Tissue glutamine synthetase associated with ammonia detoxication and nitrogen metabolism in Clarias batrachus.

    PubMed

    Singh, R A; Singh, S N

    1989-04-01

    The composition of reaction mixture of glutamine synthetase (GS) assay system was perfected and utilized to determine the activity of this enzyme spectrophotometrically in selected tissues of the freshwater teleostean fish, Clarias batrachus. Of these tissues, brain was found to contain comparatively a very high activity representing a rapid role of GS in ammonia detoxication and synthesis of essential neurotransmitter substance in this tissue. Of other tissues, liver, kidney and gill were found to contain significant activities in the order representing their relative metabolic activities. The study was extended by examining the brain (neural) and liver (non-neural) GS system in more detail with a view to see the alterations (if any). GS activity of both, neural and non-neural tissues was found to be the same and also in the range reported for other Vertebrates. Observations regarding kinetic, physical and chemical properties of the enzyme are reported. Maximum enzyme activity was observed at pH 7.2 to 7.4 and temperature 35 degrees C. The enzyme was found to be more stable at 25 degrees C while activity decreased at higher temperatures (above 40 degrees C) and showed no activity at 60 degrees C (liver) and 70 degrees C (brain). A comparison and possible physiological roles of the enzyme for the concept of ammonia excretion, protein synthesis and nitrogen metabolism in teleostean fish tissues are discussed. PMID:2476092

  18. Spin-state chemistry of deuterated ammonia

    E-print Network

    Sipilä, O; Caselli, P; Schlemmer, S

    2015-01-01

    Aims. We aim to develop a chemical model that contains a consistent description of spin-state chemistry in reactions involving chemical species with multiple deuterons. We apply the model to the specific case of deuterated ammonia, to derive values for the various spin-state ratios. Methods. We apply symmetry rules in the complete scrambling assumption to calculate branching ratio tables for reactions between chemical species that include multiple protons and/or deuterons. Reaction sets for both gas-phase and grain-surface chemistry are generated using an automated routine that forms all possible spin-state variants of any given reaction with up to six H/D atoms. Single-point and modified Bonnor-Ebert models are used to study the density and temperature dependence of ammonia and its isotopologs, and the associated spin-state ratios. Results. We find that the spin-state ratios of the ammonia isotopologs are, at late times, very different from their statistical values. The ratios are rather insensitive to varia...

  19. Scale-up synthesis of zinc borate from the reaction of zinc oxide and boric acid in aqueous medium

    NASA Astrophysics Data System (ADS)

    K?l?nç, Mert; Çakal, Gaye Ö.; Ye?il, Sertan; Bayram, Göknur; Ero?lu, ?nci; Özkar, Saim

    2010-11-01

    Synthesis of zinc borate was conducted in a laboratory and a pilot scale batch reactor to see the influence of process variables on the reaction parameters and the final product, 2ZnO·3B 2O 3·3.5H 2O. Effects of stirring speed, presence of baffles, amount of seed, particle size and purity of zinc oxide, and mole ratio of H 3BO 3:ZnO on the zinc borate formation reaction were examined at a constant temperature of 85 °C in a laboratory (4 L) and a pilot scale (85 L) reactor. Products obtained from the reaction in both reactors were characterized by chemical analysis, X-ray diffraction, particle size distribution analysis, thermal gravimetric analysis and scanning electron microscopy. The kinetic data for the zinc borate production reaction was fit by using the logistic model. The results revealed that the specific reaction rate, a model parameter, decreases with increase in particle size of zinc oxide and the presence of baffles, but increases with increase in stirring speed and purity of zinc oxide; however, it is unaffected with the changes in the amount of seed and reactants ratio. The reaction completion time is unaffected by scaling-up.

  20. NH4I-mediated three-component coupling reaction: metal-free synthesis of ?-alkoxy methyl sulfides from DMSO, alcohols, and styrenes.

    PubMed

    Gao, Xiaofang; Pan, Xiaojun; Gao, Jian; Jiang, Huanfeng; Yuan, Gaoqing; Li, Yingwei

    2015-02-20

    A novel synthesis recipe for ?-alkoxy methyl sulfides was developed via NH4I-mediated three-component oxysulfenylation reaction of styrenes with DMSO and alcohols. This method features simple operation and readily available starting materials, and it provides an alternative sulfenylating agent generated from DMSO for oxysulfenylation reactions. PMID:25671345

  1. A facile one-pot synthesis of functionalized 1,3-oxathiolan-2-yliden derivatives: multicomponent reaction of oxiranes in water.

    PubMed

    Rostami-Charati, Faramarz; Hosseini-Tabatabaei, Mohammad R; Shahraki, Mehdi

    2014-01-01

    An efficient synthesis of 1,3-oxathiolan-2-yliden derivatives is described via a simple reactions between CHacids, CS2 and oxiranes in the presence of triethylamine at 70° C in water as the solvent. The mild reaction conditions and high yields of the products exhibit the good synthetic advantage of this method. PMID:23755720

  2. Formation of Hydroxylamine (NH2OH) in Electron-Irradiated Ammonia-Water Ices Weijun Zheng,,

    E-print Network

    Kaiser, Ralf I.

    ), molecular oxygen (O2), hydrazine (N2H4), and hydrogen peroxide (H2O2), which was also monitored in previous in electron- irradiated ammonia-water ices. The synthesis of molecular hydrogen (H2), molecular nitrogen (N2

  3. Design and synthesis of chiral Zn2+ complexes mimicking natural aldolases for catalytic C-C bond forming reactions in aqueous solution.

    PubMed

    Itoh, Susumu; Sonoike, Shotaro; Kitamura, Masanori; Aoki, Shin

    2014-01-01

    Extending carbon frameworks via a series of C-C bond forming reactions is essential for the synthesis of natural products, pharmaceutically active compounds, active agrochemical ingredients, and a variety of functional materials. The application of stereoselective C-C bond forming reactions to the one-pot synthesis of biorelevant compounds is now emerging as a challenging and powerful strategy for improving the efficiency of a chemical reaction, in which some of the reactants are subjected to successive chemical reactions in just one reactor. However, organic reactions are generally conducted in organic solvents, as many organic molecules, reagents, and intermediates are not stable or soluble in water. In contrast, enzymatic reactions in living systems proceed in aqueous solvents, as most of enzymes generally function only within a narrow range of temperature and pH and are not so stable in less polar organic environments, which makes it difficult to conduct chemoenzymatic reactions in organic solvents. In this review, we describe the design and synthesis of chiral metal complexes with Zn2+ ions as a catalytic factor that mimic aldolases in stereoselective C-C bond forming reactions, especially for enantioselective aldol reactions. Their application to chemoenzymatic reactions in aqueous solution is also presented. PMID:24481060

  4. The swamp eel Monopterus albus reduces endogenous ammonia production and detoxifies ammonia to glutamine during 144 h of aerial exposure.

    PubMed

    Tay, Angeline S L; Chew, Shit F; Ip, Yuen K

    2003-07-01

    The swamp eel Monopterus albus inhabits muddy ponds, swamps, canals and rice fields, where it can burrow within the moist earth during the dry summer season, thus surviving for long periods without water. This study aimed to elucidate the strategies adopted by M. albus to defend against endogenous ammonia toxicity when kept out of water for 144 h (6 days). Like any other fish, M. albus has difficulties in excreting ammonia during aerial exposure. In fact, the rates of ammonia and urea excretions decreased significantly in specimens throughout the 144 h of aerial exposure. At 144 h, the ammonia and urea excretion rates decreased to 20% and 25%, respectively, of the corresponding control values. Consequently, ammonia accumulated to high levels in the tissues and plasma of the experimental specimens. Apparently, M. albus has developed relatively higher ammonia tolerance at the cellular and subcellular levels compared with many other teleost fish. Since the urea concentration in the tissues of specimens exposed to air remained low, urea synthesis was apparently not adopted as a strategy to detoxify endogenous ammonia during 144 h of aerial exposure. Instead, ammonia produced through amino acid catabolism was detoxified to glutamine, leading to the accumulation of glutamine in the body during the first 72 h of aerial exposure. Complementing the increased glutamine formation was a significant increase in glutamine synthetase activity in the liver of specimens exposed to air for 144 h. Formation of glutamine is energetically expensive. It is probably because M. albus remained relatively inactive on land that the reduction in energy demand for locomotory activity facilitated its exploitation of glutamine formation to detoxify endogenous ammonia. There was a slight decrease in the glutamine level in the body of the experimental animals between 72 h and 144 h of aerial exposure, which indicates that glutamine might not be the end product of nitrogen metabolism. In addition, these results suggest that suppression of endogenous ammonia production, possibly through reductions in proteolysis and amino acid catabolism, acts as the major strategy to avoid ammonia intoxication in specimens exposed to air for >/=72 h. It is concluded that glutamine formation and reduction in ammonia production together served as effective strategies to avoid the excessive accumulation of ammonia in the body of M. albus during 144 h of aerial exposure. However, these strategies might not be adequate to sustain the survival of M. albus in the mud for longer periods during drought because ammonia and glutamine concentrations had already built up to high levels in the body of specimens exposed to air for 144 h. PMID:12796462

  5. Synthesis of Pyrroloquinones via a CAN Mediated Oxidative Free Radical Reaction of 1,3-Dicarbonyl Compounds with Aminoquinones

    PubMed Central

    Nguyen, Thao; Nadkarni, Dwayaja; Dutta, Shilpa; Xu, Su; Kim, Sanghun; Murugesan, Srinivasan; Velu, Sadanandan

    2015-01-01

    Pyrroloquinone ring systems are important structural units present in many biologically active molecules including a number of marine alkaloids. For example, they are found in a series of marine metabolites, such as tsitsikammamines, zyzzyanones, wakayin, and terreusinone. Several of these alkaloids have exhibited antimicrobial, antimalarial, antifungal, antitumor, and photoprotecting activities. Synthesis of pyrroloquinone unit is the key step in the synthesis of many of these important organic molecules. Here, we present a ceric (IV) ammonium nitrate (CAN) mediated oxidative free radical cyclization reaction of 1,3-dicarbonyl compounds with aminoquinones as a facile methodology for making various substituted pyrroloquinones. 1,3-dicarbonyl compounds used in this study are ethyl acetoacetate, acetylacetone, benzoyl acetone, and N,N-dimethyl acetoacetamide. The aminoquinones used in this study are 2-(benzylamino)naphthalene-1,4-dione and 6-(benzylamino)-1-tosyl-1H-indole-4,7-dione. The yields of the synthesized pyrroloquinones ranged from 23–91%. PMID:25705550

  6. Synthesis of complex benzenoids via the intermediate generation of o-benzynes through the hexadehydro-Diels–Alder reaction

    PubMed Central

    Baire, Beeraiah; Niu, Dawen; Willoughby, Patrick H.; Woods, Brian P.; Hoye, Thomas R.

    2014-01-01

    The hexadehydro-Diels–Alder (HDDA) cascade enables the synthesis of complex benzenoid products with various substitution patterns via aryne intermediates. The first stage of this cascade involves generation of a highly reactive ortho-benzyne intermediate by a net [4+2] cycloisomerization of a triyne substrate. The benzyne can be rapidly ‘trapped’ either intra- or intermolecularly with a myriad of nucleophilic or ?-bond-donating reactants. As a representative example of a general procedure to synthesize highly substituted benzenoids, this protocol describes the synthesis of a typical triyne substrate and its use as the reactant in an HDDA cascade to form a phthalide. The synthetic procedure detailed herein (four chemical reactions) takes 16–20 h of active effort over a several day period for preparation of the triyne precursor and ~2 h of active effort over a 3-day period for generation and trapping of the benzyne and isolation of the phthalide product. PMID:23411632

  7. Toluene dioxygenase-catalyzed synthesis and reactions of cis-diol metabolites derived from 2- and 3-methoxyphenols.

    PubMed

    Boyd, Derek R; Sharma, Narain D; Malone, John F; McIntyre, Peter B A; McRoberts, Colin; Floyd, Stewart; Allen, Christopher C R; Gohil, Amit; Coles, Simon J; Horton, Peter N; Stevenson, Paul J

    2015-04-01

    Using toluene dioxygenase as biocatalyst, enantiopure cis-dihydrodiol and cis-tetrahydrodiol metabolites, isolated as their ketone tautomers, were obtained from meta and ortho methoxyphenols. Although these isomeric phenol substrates are structurally similar, the major bioproducts from each of these biotransformations were found at different oxidation levels. The relatively stable cyclohexenone cis-diol metabolite from meta methoxyphenol was isolated, while the corresponding metabolite from ortho methoxyphenol was rapidly bioreduced to a cyclohexanone cis-diol. The chemistry of the 3-methoxycyclohexenone cis-diol product was investigated and elimination, aromatization, hydrogenation, regioselective O-exchange, Stork-Danheiser transposition and O-methylation reactions were observed. An offshoot of this technology provided a two-step chemoenzymatic synthesis, from meta methoxyphenol, of a recently reported chiral fungal metabolite; this synthesis also established the previously unassigned absolute configuration. PMID:25756661

  8. Imaging and controlling intracellular reactions: Lysosome transport as a function of diameter and the intracellular synthesis of conducting polymers

    NASA Astrophysics Data System (ADS)

    Payne, Christine

    2014-03-01

    Eukaryotic cells are the ultimate complex environment with intracellular chemical reactions regulated by the local cellular environment. For example, reactants are sequestered into specific organelles to control local concentration and pH, motor proteins transport reactants within the cell, and intracellular vesicles undergo fusion to bring reactants together. Current research in the Payne Lab in the School of Chemistry and Biochemistry at Georgia Tech is aimed at understanding and utilizing this complex environment to control intracellular chemical reactions. This will be illustrated using two examples, intracellular transport as a function of organelle diameter and the intracellular synthesis of conducting polymers. Using single particle tracking fluorescence microscopy, we measured the intracellular transport of lysosomes, membrane-bound organelles, as a function of diameter as they underwent transport in living cells. Both ATP-dependent active transport and diffusion were examined. As expected, diffusion scales with the diameter of the lysosome. However, active transport is unaffected suggesting that motor proteins are insensitive to cytosolic drag. In a second example, we utilize intracellular complexity, specifically the distinct micro-environments of different organelles, to carry out chemical reactions. We show that catalase, found in the peroxisomes of cells, can be used to catalyze the polymerization of the conducting polymer PEDOT:PSS. More importantly, we have found that a range of iron-containing biomolecules are suitable catalysts with different iron-containing biomolecules leading to different polymer properties. These experiments illustrate the advantage of intracellular complexity for the synthesis of novel materials.

  9. Biogenic synthesis of palladium nanoparticles using Pulicaria glutinosa extract and their catalytic activity towards the Suzuki coupling reaction.

    PubMed

    Khan, Mujeeb; Khan, Merajuddin; Kuniyil, Mufsir; Adil, Syed Farooq; Al-Warthan, Abdulrahman; Alkhathlan, Hamad Z; Tremel, Wolfgang; Tahir, Muhammad Nawaz; Siddiqui, Mohammed Rafiq H

    2014-06-28

    Green synthesis of nanomaterials finds the edge over chemical methods due to its environmental compatibility. Herein, we report a facile and eco-friendly method for the synthesis of palladium (Pd) nanoparticles (NPs) using an aqueous solution of Pulicaria glutinosa, a plant widely found in a large region of Saudi Arabia, as a bioreductant. The as-prepared Pd NPs were characterized using ultraviolet-visible (UV-vis) spectroscopy, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform-infrared spectroscopy (FT-IR). The hydroxyl groups of the plant extract (PE) molecules were found mainly responsible for the reduction and growth of Pd NPs. FT-IR analysis confirmed the dual role of the PE, both as a bioreductant as well as a capping ligand, which stabilizes the surface of Pd NPs. The crystalline nature of the Pd NPs was identified using XRD analysis which confirmed the formation of a face-centered cubic structure (JCPDS: 87-0641, space group: Fm3m (225)). Furthermore, the as-synthesized Pd NPs demonstrated excellent catalytic activity towards the Suzuki coupling reaction under aqueous and aerobic conditions. Kinetic studies of the catalytic reaction monitored using GC confirmed that the reaction completes in less than 5 minutes. PMID:24619034

  10. Reactions of N-alkylazinium cations. 3. Quaternary pteridinium salts. Synthesis, structure, and reactions with simple nucleophiles

    SciTech Connect

    Kazantseva, I.V.; Charushin, V.N.; Chuapkhin, O.N.; Chernyshev, A.I.; Esipov, S.E.

    1986-03-01

    4-Morpholinopteridine reacts with triethyloxonium tetra-fluoroborate to give two types of isomeric quaternary salts, viz., 1-ethyl- and 8-ethyl-4-morpholinopteridinium tetrafluoroborates. The structures of the pteridinium cations were provided by the /sup 1/H and /sup 13/C NMR spectra and also by chemical transformations in reactions with simple nucleophiles.

  11. The formation of TiC\\/Al2O3 microstructures by a self-propagating high-temperature synthesis reaction

    Microsoft Academic Search

    C. R. Bowen; B. Derby

    1996-01-01

    The effect of processing variables on reaction rate and ceramic microstructure are examined for the self-propagating high-temperature synthesis reaction 3TiO2+4Al+3C ? 3TiC+2Al2O3. Reaction controlling methods used are reactant particle size, the use of diluents (to lower the combustion temperature) and the use of reactant preheating (to increase the combustion temperature). The ceramic microstructure has an unusual laminar structure which is

  12. Synthesis of superheavy element 120 via {sup 50}Ti+{sup A}Cf hot fusion reactions

    SciTech Connect

    Liu, Z. H. [China Institute of Atomic Energy, Beijing 102413 (China); Bao Jingdong [Department of Physics, Beijing Normal University, Beijing 100875 (China); Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 730000 (China)

    2009-11-15

    Synthesis of superheavy element 120 in terms of the {sup 50}Ti+{sup 249-252}Cf fusion-evaporation reactions is evaluated and discussed. It is found that the reactions of {sup 250,251}Cf({sup 50}Ti,3n){sup 297,298}120 and {sup 251,252}Cf({sup 50}Ti,4n){sup 297,298}120 are relatively favorable with the maximum evaporation-residue cross sections of 0.12, 0.09, 0.11, and 0.25 pb, respectively. However, {sup 252}Cf may be difficult to be target because its spontaneous fission will bring about serious background in the experiment. Fusion probabilities for different target-projectile combinations leading to the formation of surperheavy nucleus {sup 302}120 are estimated with the ''fusion-by-diffusion'' model and presented as a function of the Coulomb parameter Z{sub 1}Z{sub 2}/(A{sub 1}{sup 1/3}+A{sub 2}{sup 1/3}). Among the reactions {sup 50}Ti+{sup 252}Cf, {sup 54}Cr+{sup 248}Cm, {sup 58}Fe+{sup 244}Pu, and {sup 64}Ni+{sup 238}U, the reaction {sup 50}Ti+{sup 252}Cf has the largest fusion probability. Synthesis of superheavy element 120 is of essential importance for determining whether the magic proton shell should be at Z=114 or at higher proton numbers Z=120-126. Therefore, the experiment to produce isotopes with Z=120 in the fusion reactions {sup 50}Ti+{sup 250,251}Cf is of great interest.

  13. Reaction of the CoII-Substrate Radical Pair Catalytic Intermediate in Coenzyme B12-Dependent Ethanolamine Ammonia-Lyase in Frozen Aqueous Solution from 190 to 217 K

    PubMed Central

    Zhu, Chen; Warncke, Kurt

    2008-01-01

    The decay kinetics of the aminoethanol-generated CoII-substrate radical pair catalytic intermediate in ethanolamine ammonia-lyase from Salmonella typhimurium have been measured on timescales of <105 s in frozen aqueous solution from 190 to 217 K. X-band continuous-wave electron paramagnetic resonance (EPR) spectroscopy of the disordered samples has been used to continuously monitor the full radical pair EPR spectrum during progress of the decay after temperature step reaction initiation. The decay to a diamagnetic state is complete and no paramagnetic intermediate states are detected. The decay exhibits three kinetic regimes in the measured temperature range, as follows. i), Low temperature range, 190 ? T ? 207 K: the decay is biexponential with constant fast (0.57 ± 0.04) and slow (0.43 ± 0.04) phase amplitudes. ii), Transition temperature range, 207 < T < 214 K: the amplitude of the slow phase decreases to zero with a compensatory rise in the fast phase amplitude, with increasing temperature. iii), High temperature range, T ? 214 K: the decay is monoexponential. The observed first-order rate constants for the monoexponential (kobs,m) and the fast phase of the biexponential decay (kobs,f) adhere to the same linear relation on an lnk versus T?1 (Arrhenius) plot. Thus, kobs,m and kobs,f correspond to the same apparent Arrhenius prefactor and activation energy (logAapp,f (s?1) = 13.0, Ea,app,f = 15.0 kcal/mol), and therefore, a common decay mechanism. We propose that kobs,m and kobs,f represent the native, forward reaction of the substrate through the radical rearrangement step. The slow phase rate constant (kobs,s) for 190 ? T ? 207 K obeys a different linear Arrhenius relation (logAapp,s (s?1) = 13.9, Ea,app,s = 16.6 kcal/mol). In the transition temperature range, kobs,s displays a super-Arrhenius increase with increasing temperature. The change in Ea,app,s with temperature and the narrow range over which it occurs suggest an origin in a liquid/glass or dynamical transition. A discontinuity in the activation barrier for the chemical reaction is not expected in the transition temperature range. Therefore, the transition arises from a change in the properties of the protein. We propose that a protein dynamical contribution to the reaction, which is present above the transition temperature, is lost below the transition temperature, owing to an increase in the activation energy barrier for protein motions that are coupled to the reaction. For both the fast and slow phases of the low temperature decay, the dynamical transition in protein motions that are obligatorily coupled to the reaction of the CoII-substrate radical pair lies below 190 K. PMID:18805934

  14. Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

    PubMed Central

    Kocsis, Laura S.; Benedetti, Erica; Brummond, Kay M.

    2013-01-01

    Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable. The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts. The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields. PMID:23609566

  15. A green synthesis of a layered titanate, potassium lithium titanate; lower temperature solid-state reaction and improved materials performance

    SciTech Connect

    Ogawa, Makoto, E-mail: waseda.ogawa@gmail.com [Graduate School of Creative Science and Engineering, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo 169-8050 (Japan); Department of Earth Sciences, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo 169-8050 (Japan); Morita, Masashi, E-mail: m-masashi@y.akane.waseda.jp [Graduate School of Creative Science and Engineering, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo 169-8050 (Japan); Igarashi, Shota, E-mail: uxei_yoshi_yoshi@yahoo.co.jp [Graduate School of Creative Science and Engineering, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo 169-8050 (Japan); Sato, Soh, E-mail: rookie_so_sleepy@yahoo.co.jp [Graduate School of Creative Science and Engineering, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo 169-8050 (Japan)

    2013-10-15

    A layered titanate, potassium lithium titanate, with the size range from 0.1 to 30 µm was prepared to show the effects of the particle size on the materials performance. The potassium lithium titanate was prepared by solid-state reaction as reported previously, where the reaction temperature was varied. The reported temperature for the titanate preparation was higher than 800 °C, though 600 °C is good enough to obtain single-phase potassium lithium titanate. The lower temperature synthesis is cost effective and the product exhibit better performance as photocatalysts due to surface reactivity. - Graphical abstract: Finite particle of a layered titanate, potassium lithium titanate, was prepared by solid-state reaction at lower temperature to show modified materials performance. Display Omitted - Highlights: • Potassium lithium titanate was prepared by solid-state reaction. • Lower temperature reaction resulted in smaller sized particles of titanate. • 600 °C was good enough to obtain single phased potassium lithium titanate. • The product exhibited better performance as photocatalyst.

  16. Preventing Theft of Anhydrous Ammonia 

    E-print Network

    Smith, David

    2004-09-16

    Anhydrous ammonia is widely used as a fertilizer. The theft of anhydrous ammonia for use in producing illegal drugs is a growing problem. This publication describes how thieves operate and how farmers and agricultural dealers can protect themselves...

  17. Liberation of ammonia by cyanobacteria

    SciTech Connect

    Newton, J.W.

    1986-04-01

    Photoheterotrophic nitrogen-fixing cyanobacteria release ammonia when treated with methionine sulfoximine (MSX) to inhibit nitrogen incorporation into protein. This released ammonia can be derived from recently fixed nitrogen (nitrogen atmosphere) or endogenous reserves (argon atmosphere). Anaerobic ammonia release requires light and is stimulated by the photosystem II herbicides DCMU and Atrazine, regardless of the source of ammonia. As much as one quarter of the total cellular nitrogen can be released as ammonia by cyanbacteria treated with MSX and DCMU under argon in light. Chromatography of cell extracts indicates that virtually all cellular proteins are degraded. DCMU and Atrazine, at very low concentration, inhibit sustained uptake of the ammonia analog /sup 14/C methylamine. These data indicate that the herbicides interrupt ammonia uptake and retention by the cells, and support a role for photosystem II in ammonia metabolism.

  18. The Ammonia-Soda Process.

    ERIC Educational Resources Information Center

    Tingle, M.

    1979-01-01

    This article is a condensed version of a commentary written to accompany a set of slides which describes the ammonia-soda process used by the ammonia-soda plant at Northwich of the United Kingdom. (HM)

  19. Direct synthesis of ZnO nanoparticles by a solution-free mechanochemical reaction

    Microsoft Academic Search

    Liming Shen; Ningzhong Bao; Kazumichi Yanagisawa; Kazunari Domen; Arunava Gupta; Craig A. Grimes

    2006-01-01

    This paper presents a study on the synthesis and characterization of ZnO nanoparticles by a two-step synthesis procedure. The first step is the solution-free mechanochemical synthesis of ZnC2O4·2H2O nanoparticles by grinding a powder mixture of Zn(CH3COO)2 and H2C2O4·2H2O at room temperature for a certain time. The second step is the thermal decomposition of ZnC2O4·2H2O nanoparticles at 450 °C to form

  20. Multiple self-propagating high-temperature synthesis and solid-phase reactions in thin films

    Microsoft Academic Search

    V. G. Myagkov; L. E. Bykova; G. N. Bondarenko

    1999-01-01

    A variety of self-propagating high-temperature synthesis in thin films has been found and investigated. This modification,\\u000a called multiple self-propagating high-temperature synthesis, occurs in the solid phase and is a reversible phase transition.\\u000a Multiple self-propagating high-temperature synthesis is similar in many respects to a metal—insulator phase transition. It\\u000a is shown that for eutectic systems it is equivalent to a repeated transition

  1. Solution-Phase Synthesis of a Tricyclic Pyrrole-2-Carboxamide Discovery Library Applying a Stetter-Paal-Knorr Reaction Sequence

    PubMed Central

    Iyer, Pravin S.; Fodor, Matthew D.; Coleman, Claire M.; Twining, Leslie A.; Mitasev, Branko

    2012-01-01

    The solution phase synthesis of a discovery library of 178 tricyclic pyrrole-2-carboxamides was accomplished in nine steps and seven purifications starting with three benzoyl protected amino acid methyl esters. Further diversity was introduced by two glyoxaldehydes and forty-one primary amines. The combination of Pauson-Khand, Stetter and microwave assisted Paal Knorr reactions was applied as a key sequence. The discovery library was designed with the help of QikProp 2.1 and physicochemical data are presented for all pyrroles. Library members were synthesized and purified in parallel and analyzed by LC-MS. Selected compounds were fully characterized. PMID:16677007

  2. Synthesis of pyrazole containing ?-amino acids via a highly regioselective condensation/aza-Michael reaction of ?-aryl ?,?-unsaturated ketones.

    PubMed

    Gilfillan, Lynne; Artschwager, Raik; Harkiss, Alexander H; Liskamp, Rob M J; Sutherland, Andrew

    2015-04-21

    A synthetic approach for the preparation of a new class of highly conjugated unnatural ?-amino acids bearing a 5-arylpyrazole side-chain has been developed. Horner-Wadsworth-Emmons reaction of an aspartic acid derived ?-keto phosphonate ester with a range of aromatic aldehydes gave ?-aryl ?,?-unsaturated ketones. Treatment of these with phenyl hydrazine followed by oxidation allowed the regioselective synthesis of pyrazole derived ?-amino acids. As well as evaluating the fluorescent properties of the ?-amino acids, their synthetic utility was also explored with the preparation of a sulfonyl fluoride derivative, a potential probe for serine proteases. PMID:25774874

  3. Production of Ni 3 Ti-TiC x intermetallic-ceramic composites employing combustion synthesis reactions

    Microsoft Academic Search

    Douglas E. Burkes; John J. Moore; Guglielmo Gottoli; Hu Chun Yi

    2006-01-01

    Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi-TiC (stoichiometric)\\u000a or Ni3Ti-TiC\\u000a x\\u000a (nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be\\u000a synthesized. The stoichiometry of TiC\\u000a x\\u000a , for

  4. Production of Ni 3 Ti?TiC x intermetallic-ceramic composites employing combustion synthesis reactions

    Microsoft Academic Search

    Douglas E. Burkes; Guglielmo Gottoli; John J. Moore; Hu Chun Yi

    2006-01-01

    Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi?TiC (stoichiometric)\\u000a or Ni3Ti?TiC\\u000a x\\u000a (nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be\\u000a synthesized. The stoichiometry of TiC\\u000a x\\u000a , for

  5. Hydrothermal reactions: From the synthesis of ligand to new lanthanide 3D-coordination polymers

    SciTech Connect

    Silva, Fausthon Fred da; Fernandes de Oliveira, Carlos Alberto; Lago Falcão, Eduardo Henrique [Laboratório de Terras Raras, Departamento de Química Fundamental, Universidade Federal de Pernambuco (DQF-UFPE), 50590-470 Recife, PE (Brazil); Gatto, Claudia Cristina [Laboratório de Síntese Inorgânica e Cristalografia, Instituto de Química, Universidade de Brasília (IQ-UnB), 70904-970 Brasilia, DF (Brazil); Bezerra da Costa, Nivan; Oliveira Freire, Ricardo [Pople Computational Chemistry Laboratory, Departamento de Química, Universidade Federal de Sergipe, São Cristóvão-SE 49100-000 (Brazil); Chojnacki, Jaros?aw [Department of Inorganic Chemistry, Gdansk University of Technology, 80-233 Gdansk (Poland); Alves Júnior, Severino, E-mail: salvesjr@ufpe.br [Laboratório de Terras Raras, Departamento de Química Fundamental, Universidade Federal de Pernambuco (DQF-UFPE), 50590-470 Recife, PE (Brazil)

    2013-11-15

    The organic ligand 2,5-piperazinedione-1,4-diacetic acid (H{sub 2}PDA) was synthesized under hydrothermal conditions starting from the iminodiacetic acid and catalyzed by oxalic acid. The X-ray powder diffraction data indicates that the compound crystallizes in the P2{sub 1}/c monoclinic system as reported in the literature. The ligand was also characterized by elemental analysis, magnetic nuclear resonance, infrared spectroscopy and thermogravimetric analysis. Two new coordination networks based on lanthanide ions were obtained with this ligand using hydrothermal reaction. In addition to single-crystal X-ray diffraction, the compounds were characterized by infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and elemental analysis. Single-crystal XRD showed that the compounds are isostructural, crystallizing in P2{sub 1}/n monoclinic system with chemical formula [Ln(PDA){sub 1.5}(H{sub 2}O)](H{sub 2}O){sub 3} (Ln=Gd{sup 3+}(1) and Eu{sup 3+}(2)).The luminescence properties of both compounds were studied. In the compound (1), a broad emission band was observed at 479 nm, redshifted by 70 nm in comparison of the free ligand. In (2), the typical f–f transition was observed with a maximum peak at 618 nm, related with the red emission of the europium ions. Computational methods were performed to simulate the crystal structure of (2). The theoretical calculations of the intensity parameters are in good agreement with the experimental values. - Graphical abstract: Scheme of obtaining the ligand 2,5-piperazinedione-1,4-diacetic acid (H{sub 2}PDA) and two new isostructural 3D-coordination polymers [Ln(PDA){sub 1.5}(H{sub 2}O)](H{sub 2}O){sub 3} (Ln=Gd{sup 3+} and Eu{sup 3+}) by hydrothermal synthesis. Display Omitted - Highlights: • The ligand 2,5-piperazinedione-1,4-diacetic acid was synthetized using the hydrothermic method and characterized. • Two new 3D-coordination polymers with this ligand containing Gd{sup 3+} and Eu{sup 3+} ions were also obtained. • The compounds are isostructural and the typical luminescent properties were observed in both structures.

  6. 5, 25052540, 2008 Modeling ammonia

    E-print Network

    Paris-Sud XI, Université de

    BGD 5, 2505­2540, 2008 Modeling ammonia interactions with measured leaf wetness in grassland J of atmospheric ammonia and other trace gases with measured leaf surface wetness in a managed grassland canopy J, 2505­2540, 2008 Modeling ammonia interactions with measured leaf wetness in grassland J. Burkhardt et

  7. Nucleophilic aromatic substitution reactions of meso-bromosubporphyrin: synthesis of a thiopyrane-fused subporphyrin.

    PubMed

    Shimizu, Daiki; Mori, Hirotaka; Kitano, Masaaki; Cha, Won-Young; Oh, Juwon; Tanaka, Takayuki; Kim, Dongho; Osuka, Atsuhiro

    2014-12-01

    meso-Bromosubporphyrin undergoes nucleophilic aromatic substitution (SN Ar) reactions with arylamines, diarylamines, phenols, ethanol, thiophenols, and n-butanethiol in the presence of suitable bases to provide the corresponding substitution products. The SN Ar reactions also proceed well with pyrrole, indole, and carbazole to provide substitution products in moderate to good yields. Finally, the SN Ar reaction with 2-bromothiophenol and subsequent intramolecular peripheral arylation reaction affords a thiopyrane-fused subporphyrin. PMID:25336122

  8. The Ene-Reaction of Phosphaalkynes-Application for the Synthesis of Phosphiranes

    Microsoft Academic Search

    M. Regitz; U. Annen; E. P. O. Fuchs

    1990-01-01

    1,3-Butadienes 1 and 6-Methyl-2H-pyran-2-ones 6 react with two equivalents of phosphaalkynes 2 in a domino-reaction to the diphosphiranes 5 and 9 respectively. Diels-Alder-reaction of 1 with 2 leads to 3 which cannot be isolated. An Ene-reaction of the phosphacyclohexa-1,4-diene 3 with additional 2 gives 4 followed by an intramolecular Diels-Alder-reaction yielding the stable diphosphatricyclooctenes 5.

  9. Regioselective Synthesis of Highly Substituted Imidazoles via the Sequential Reaction of Allenyl Sulfonamides and Amines.

    PubMed

    Yu, Lian; Deng, Yuan; Cao, Jian

    2015-05-01

    A novel synthesis of imidazoles from electron-withdrawing group-substituted allenyl sulfonamides with amines was developed. The 4- and 5-functionalized imidazoles were constructed regioselectively, which depended on the substituents on the nitrogen atoms. PMID:25853897

  10. Novel reactions of a neutral organic reductant : reductive coupling and nanoparticle synthesis

    E-print Network

    Mork, Anna Jolene

    2012-01-01

    A recently developed bis-pyridinylidene neutral organic electron donor captured our interest as a potential source of new chemistries for reductive coupling and the synthesis of group IV nanoparticles. This super electron ...

  11. A novel oxy-oxonia(azonia)-cope reaction: serendipitous discovery and its application to the synthesis of macrocyclic musks.

    PubMed

    Zou, Yue; Zhou, Lijun; Ding, Changming; Wang, Quanrui; Kraft, Philip; Goeke, Andreas

    2014-10-01

    This brief review, including new experimental results, is the summary of a talk at the GDCh conference 'flavors & fragrances 2013' in Leipzig, Germany, 11th-13th September, 2013. Musk odorants are indispensable in perfumery to lend sensuality to fine fragrances, a nourishing effect to cosmetics, and a comforting feeling to laundry. We have recently found serendipitously a new oxy-oxonia-Cope rearrangement. In this account, we review the background of oxonia-sigmatropic rearrangements and the discovery of this novel reaction. Special attention is focused on the versatile lactone and lactam formation reactions via [n+4] ring enlargement and the macrocyclization in the synthesis of new macrocyclic musks. The synthesized structures provide new insights into the structure-odor relationships of musks. PMID:25329787

  12. Facile synthesis of magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals via a cation-exchange reaction.

    PubMed

    Ning, Jiajia; Xiao, Guanjun; Wang, Li; Zou, Bo; Liu, Bingbing; Zou, Guangtian

    2011-02-01

    Magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals with small size and uniform size distribution are synthesized via a cation-exchange reaction. Two experimental stages are included in the synthesis of metal oxides nanocrystals. Firstly, Cu(OH)2 decomposes to CuO nanocrystals, induced by free metal cations. Compared to CuO nanocrystals produced without any free metal cation, the free metal cation has an important influence on the shape and size of CuO. Secondly, free metal cations exchange with the Cu2+ cation in the CuO nanocrystals to get Mn3O4, Fe2O3, CoO and NiO nanocrystals by cation-exchange reactions. The magnetic properties of these metal oxides nanocrystals have been investigated, all the nanocrystals are superparamagnetic at room temperature. PMID:21109892

  13. Plasma-enhanced microwave solid-state synthesis of cadmium sulfide: reaction mechanism and optical properties.

    PubMed

    Du, Ke-Zhao; Chaturvedi, Apoorva; Wang, Xing-Zhi; Zhao, Yi; Zhang, Ke-Ke; Iqbal Bakti Utama, M; Hu, Peng; Jiang, Hui; Xiong, Qi-Hua; Kloc, Christian

    2015-07-21

    CdS synthesis by plasma-enhanced microwave physical vapor transport (PMPVT) has been developed in this work. The photoluminescence (PL), absorbance, Raman spectra and the mechanism of CdS crystal growth have been investigated. Furthermore, plasma-enhanced microwave chemical vapour transport (PMCVT) synthesis of CdS with additional chemical transport agents has been explored. In addition, other II-VI chalcogenides were also synthesized by PMPVT. PMID:26151570

  14. Ammonia Anabolism in Ruminants

    Microsoft Academic Search

    Sadao Hoshino; Katsuharu Sarumaru; Kazuwo Morimoto

    1966-01-01

    Ruminal concentrations of ammonia, alpha-ketoglutaric acid, glntamic acid, and glutamine were determined in two feeding periods (alfalfa pellet only and alfalfa pellet + urea) by using fistulated Cor- riedal sheep. By addition of urea, the am- monia concentration exhibited significant increases. Glutamic acid decreased in con- trast to glutamine in concentration, but the differences between the rations were not significant.

  15. Combustion synthesis of TiN–TiB 2 composites in Ti\\/BN\\/N 2 and Ti\\/BN\\/B reaction systems

    Microsoft Academic Search

    C. L. Yeh; G. S. Teng

    2006-01-01

    An experimental study on in situ formation of TiN–TiB2 composites with a wide range of compositions by self-propagating high-temperature synthesis (SHS) was conducted in two reaction systems. Combustion of sample compacts made up of titanium (Ti) and boron nitride (BN) powders was initiated under nitrogen pressure for the synthesis of composites with TiN contents of 75–87.5mol%. Experiments with reactant compacts

  16. Mass Spectroscopy of Chemical Reaction of 3d Metal Clusters Involved in Chemical Vapor Deposition Synthesis of Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Inoue, Shuhei; Maruyama, Shigeo

    2008-04-01

    The chemical reactions of transition metal clusters in the gas phase have aroused considerable scientific interest and are also of critical scientific importance. For example, these reactions are involved in the synthesis of single-walled carbon nanotubes, which are considered ideal materials because of their outstanding properties. Alcohol catalytic chemical vapor deposition (ACCVD) is one of the best synthetic processes for carbon nanotubes (CNTs); however, even the initial growth mechanism is still unclear, unlike those of other synthetic processes. In this study, we used a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer to determine the initial reactions of transition metal cluster ions (iron, cobalt, and nickel) that are typically adopted in the alcohol CVD process. Metal clusters with approximately 10-25 atoms each, generated by a pulsed laser ablation system in a supersonic-expansion cluster beam source, were directly carried into the FT-ICR cell. Subsequently, ethanol was introduced into the ICR cell. We observed two different results: one was simple chemisorption observed in the iron cluster and the other was dehydrogenated chemisorption observed in the nickel cluster; however, cobalt clusters exhibited both patterns, and a sequential reaction was observed. Furthermore, the dehydrogenation of ethanol on the cobalt cluster is fully described from isotope-labeled experiments.

  17. Efficient synthesis of secondary alkyl fluorides via Suzuki cross-coupling reaction of 1-halo-1-fluoroalkanes.

    PubMed

    Jiang, Xiaojian; Sakthivel, Sekarpandi; Kulbitski, Kseniya; Nisnevich, Gennady; Gandelman, Mark

    2014-07-01

    Organofluorine compounds have found extensive applications in various areas of science. Consequently, the development of new efficient and selective methods for their synthesis is an important goal in organic chemistry. Here, we present the first Suzuki cross-coupling reaction which utilizes dihalo compounds for the preparation of secondary alkyl fluorides. Namely, an unprecedented use of simple 1-halo-1-fluoroalkanes as electrophiles in C(sp(3))-C(sp(3)) and C(sp(3))-C(sp(2)) cross-couplings allows for the formal site-selective incorporation of F-group in the alkyl chain with no adjacent activating functional groups. Highly effective approach to the electrophilic substrates, 1-halo-1-fluoroalkanes, via iododecarboxylation of the corresponding ?-fluorocarboxylic acids is also presented. The conceptually new route to organofluorides was used for the facile preparation of biomedically valuable compounds. In addition, we demonstrated that an asymmetric version of the developed reaction for the stereoconvergent synthesis of chiral secondary alkyl fluorides is feasible. PMID:24958322

  18. Energy metabolism in brain cells: effects of elevated ammonia concentrations.

    PubMed

    Hertz, Leif; Kala, Geeta

    2007-12-01

    Both neurons and astrocytes have high rates of glucose utilization and oxidative metabolism. Fully 20% of glucose consumption is used for astrocytic production of glutamate and glutamine, which during intense glutamatergic activity leads to an increase in glutamate content, but at steady state is compensated for by an equally intense oxidation of glutamate. The amounts of ammonia used for glutamine synthesis and liberated during glutamine hydrolysis are large, compared to the additional demand for glutamine synthesis in hyperammonemic animals and patients with hepatic encephalopathy. Nevertheless, elevated ammonia concentrations lead to an increased astrocytic glutamine production and an elevated content of glutamine combined with a decrease in glutamate content, probably mainly in a cytosolic pool needed for normal activity of the malate-asparate shuttle (MAS); another compartment generated by glutamine hydrolysis is increased. As a result of reduced MAS activity the pyruvate/lactate ratio is decreased in astrocytes but not in neurons and decarboxylation of pyruvate to form acetyl coenzyme A is reduced. Elevated ammonia concentrations also inhibit decarboxylation of alpha-ketoglutarate in the TCA cycle. This effect occurs in both neurons and astrocytes, is unrelated to MAS activity and seen after chronic treatment with ammonia even in the absence of elevated ammonia concentrations. PMID:17882538

  19. Raman spectroscopy as a tool for monitoring mesoscale continuous-flow organic synthesis: Equipment interface and assessment in four medicinally-relevant reactions

    PubMed Central

    Hamlin, Trevor A

    2013-01-01

    Summary An apparatus is reported for real-time Raman monitoring of reactions performed using continuous-flow processing. Its capability is assessed by studying four reactions, all involving formation of products bearing ?,?-unsaturated carbonyl moieties; synthesis of 3-acetylcoumarin, Knoevenagel and Claisen–Schmidt condensations, and a Biginelli reaction. In each case it is possible to monitor the reactions and also in one case, by means of a calibration curve, determine product conversion from Raman spectral data as corroborated by data obtained using NMR spectroscopy. PMID:24062851

  20. Carboxymethyl Chinese yam starch: synthesis, characterization, and influence of reaction parameters

    Microsoft Academic Search

    Wang Yanli; Gao Wenyuan; Li Xia

    2009-01-01

    Carboxymethyl starch (CMS) was obtained as a product of the reaction of starch and monochloroacetic acid (MCA) in the presence of sodium hydroxide. The influence of the molar ratio of NaOH\\/AGU, the molar ratio of MCA\\/AGU, the reaction time, reaction temperature, and the water content on the degree of substitution (DS) was studied. The optimal molar ratio of NaOH\\/AGU and

  1. Ugi and Passerini reactions of biocatalytically derived chiral aldehydes: application to the synthesis of bicyclic pyrrolidines and of antiviral agent telaprevir.

    PubMed

    Moni, Lisa; Banfi, Luca; Basso, Andrea; Carcone, Luca; Rasparini, Marcello; Riva, Renata

    2015-04-01

    Lipase mediated desymmetrization of a meso-diol (1,2-cyclopentanedimethanol) allows the synthesis of both enantiomers of some chiral aldehydes, whose behavior in Passerini and Ugi reactions has been explored. Exploiting these two complementary multicomponent reactions and coupling them with a subsequent cyclization process, we observed that 6 out of all 8 possible stereoisomers of peptidomimetic pyrrolidines can be obtained in good yields. The potential of these protocols has been proved by the development of a new efficient synthesis of antiviral drug telaprevir. PMID:25801330

  2. Optical reaction cell and light source for ›18F! fluoride radiotracer synthesis

    DOEpatents

    Ferrieri, Richard A. (Patchogue, NY); Schlyer, David (Bellport, NY); Becker, Richard J. (Islip, NY)

    1998-09-15

    Apparatus for performing organic synthetic reactions, particularly no-carrier-added nucleophilic radiofluorination reactions for PET radiotracer production. The apparatus includes an optical reaction cell and a source of broadband infrared radiant energy, which permits direct coupling of the emitted radiant energy with the reaction medium to heat the reaction medium. Preferably, the apparatus includes means for focusing the emitted radiant energy into the reaction cell, and the reaction cell itself is preferably configured to reflect transmitted radiant energy back into the reaction medium to further improve the efficiency of the apparatus. The apparatus is well suited to the production of high-yield syntheses of 2-›.sup.18 F!fluoro-2-deoxy-D-glucose. Also provided is a method for performing organic synthetic reactions, including the manufacture of ›.sup.18 F!-labeled compounds useful as PET radiotracers, and particularly for the preparation of 2-›.sup.18 F!fluoro-2-deoxy-D-glucose in higher yields than previously possible.

  3. Optical reaction cell and light source for [18F] fluoride radiotracer synthesis

    DOEpatents

    Ferrieri, R.A.; Schlyer, D.; Becker, R.J.

    1998-09-15

    An apparatus is disclosed for performing organic synthetic reactions, particularly no-carrier-added nucleophilic radiofluorination reactions for PET radiotracer production. The apparatus includes an optical reaction cell and a source of broadband infrared radiant energy, which permits direct coupling of the emitted radiant energy with the reaction medium to heat the reaction medium. Preferably, the apparatus includes means for focusing the emitted radiant energy into the reaction cell, and the reaction cell itself is preferably configured to reflect transmitted radiant energy back into the reaction medium to further improve the efficiency of the apparatus. The apparatus is well suited to the production of high-yield syntheses of 2-[{sup 18}F]fluoro-2-deoxy-Dglucose. Also provided is a method for performing organic synthetic reactions, including the manufacture of [{sup 18}F]-labeled compounds useful as PET radiotracers, and particularly for the preparation of 2-[{sup 18}F]fluoro-2-deoxy-D-glucose in higher yields than previously possible. 4 figs.

  4. Effects of aluminum additions to gas atomized reaction synthesis produced oxide dispersion strengthened alloys

    NASA Astrophysics Data System (ADS)

    Spicher, Alexander Lee

    The production of an aluminum containing ferritic oxide dispersion strengthened (ODS) alloy was investigated. The production method used in this study was gas atomization reaction synthesis (GARS). GARS was chosen over the previously commercial method of mechanical alloying (MA) process due to complications from this process. The alloy compositions was determined from three main components; corrosion resistance, dispersoid formation, and additional elements. A combination of Cr and Al were necessary in order to create a protective oxide in the steam atmosphere that the boiler tubing in the next generation of coal-fired power plants would be exposed to. Hf and Y were chosen as dispersoid forming elements due to their increased thermal stability and potential to avoid decreased strength caused by additions of Al to traditional ODS materials. W was used as an additive due to benefits as a strengthener as well as its benefits for creep rupture time. The final composition chosen for the alloy was Fe-16Cr-12Al-0.9W-0.25Hf-0.2Y at%. The aforementioned alloy, GA-1-198, was created through gas atomization with atomization gas of Ar-300ppm O2. The actual composition created was found to be Fe-15Cr-12.3Al-0.9W-0.24Hf-0.19Y at%. An additional alloy that was nominally the same without the inclusion of aluminum was created as a comparison for the effects on mechanical and corrosion properties. The actual composition of the comparison alloy, GA-1-204, was Fe-16Cr-0Al-0.9W-0.25Hf-0.24Y at%. An investigation on the processing parameters for these alloys was conducted on the GA-1-198 alloy. In order to predict the necessary amount of time for heat treatment, a diffusion study was used to find the diffusion rate of oxygen in cast alloys with similar composition. The diffusion rate was found to be similar to that of other GARS compositions that have been created without the inclusion of aluminum. The effect of heat treatment time was investigated with temperatures of 950°C, 1000°C, 1100°C, and 1200°C. A large precipitate phase, FeHf2 ht, was found in the 950°C and 1000°C samples through SEM. This was confirmed through XRD analysis where it was found that the 1100°C sample may have had clusters. These clusters could act as a location for the origination of cracks during future rolling operations. For this reason, an attempt to look at the hold time and ramp rates on the formation this phase. It was found that a 1200°C hold for 5 hours was able to homogenize the sample to prevent precipitation of the FeHf2 ht phase during a subsequent hold at 1000°C, the rolling temperature used in this study. For this reason a heat treatment at 1200°C for 5 hours was used in both alloys. Both alloys were rolled to 70% reduction in thickness and evaluated through microhardness, tensile testing, and corrosion testing. Microhardness showed high strength for the aluminum containing GA-1-198 and significantly more isotropic properties than mechanically alloyed ODS materials. Tensile testing showed GA-1-198 strength between MA956 and PM2000 for temperatures below 600°C and slightly lower strengths than MA856 at 800°C. GA-1-204 was not protective in either atmosphere; air at 1200°C and air with 10 vol% H2O at 1100°C. GA-1-198 showed increased mass gains due to sub-optimal oxygen content in the alloy. GA-1-198 had spallation in the air at 1200°C atmosphere, but remained protective up to 1000 hr in the water containing atmosphere.

  5. The production of ammonia by multiheme cytochromes C.

    PubMed

    Simon, Jörg; Kroneck, Peter M H

    2014-01-01

    The global biogeochemical nitrogen cycle is essential for life on Earth. Many of the underlying biotic reactions are catalyzed by a multitude of prokaryotic and eukaryotic life forms whereas others are exclusively carried out by microorganisms. The last century has seen the rise of a dramatic imbalance in the global nitrogen cycle due to human behavior that was mainly caused by the invention of the Haber-Bosch process. Its main product, ammonia, is a chemically reactive and biotically favorable form of bound nitrogen. The anthropogenic supply of reduced nitrogen to the biosphere in the form of ammonia, for example during environmental fertilization, livestock farming, and industrial processes, is mandatory in feeding an increasing world population. In this chapter, environmental ammonia pollution is linked to the activity of microbial metalloenzymes involved in respiratory energy metabolism and bioenergetics. Ammonia-producing multiheme cytochromes c are discussed as paradigm enzymes. PMID:25416396

  6. AMMONIA CONCENTRATION IN SALTSTONE HEADSPACE SUMMARY REPORT

    SciTech Connect

    Zamecnik, J; Alex Cozzi, A

    2008-09-26

    The Saltstone Facility Documented Safety Analysis (DSA) is under revision to accommodate changes in the Composite Lower Flammability Limit (CLFL) from the introduction of Isopar into Tank 50. Saltstone samples were prepared with an 'MCU' type salt solution spiked with ammonia. The ammonia released from the saltstone was captured and analyzed. The ammonia concentration found in the headspace of samples maintained at 95 C and 1 atm was, to 95% confidence, less than or equal to 3.9 mg/L. Tank 50 is fed by several influent streams. The salt solution from Tank 50 is pumped to the salt feed tank (SFT) in the Saltstone Production Facility (SPF). The premix materials cement, slag and fly ash are blended together prior to transfer to the grout mixer. The premix is fed to the grout mixer in the SPF and the salt solution is incorporated into the premix in the grout mixer, yielding saltstone slurry. The saltstone slurry drops into a hopper and then is pumped to the vault. The Saltstone Facility Documented Safety Analysis (DSA) is under revision to accommodate changes in the Composite Lower Flammability Limit (CLFL) from the introduction of Isopar{reg_sign} L into Tank 50. Waste Solidification-Engineering requested that the Savannah River National Laboratory (SRNL) perform testing to characterize the release of ammonia in curing saltstone at 95 C. The test temperature represents the maximum allowable temperature in the Saltstone Disposal Facility (SDF). Ammonia may be present in the salt solution and premix materials, or may be produced by chemical reactions when the premix and salt solution are combined. A final report (SRNS-STI-2008-00120, Rev. 0) will be issued that will cover in more depth the information presented in this report.

  7. A combined intramolecular Diels-Alder/intramolecular Schmidt reaction: Formal synthesis of (+/-)-stenine

    E-print Network

    Golden, Jennifer E.; Aubé , Jeffrey

    2002-01-01

    Information. Experimental procedures and characterization data for new compounds. REFERENCES [1] For reviews of domino processes in organic synthesis, see: a) L. F. Tietze, U. Beifuss, Angew. Chem., Int. Ed. Engl. 1993, 32, 131-163; b) R. A. Bunce..., Tetrahedron 1995, 51, 13103-13159; c) K. Neuschuetz, J. Velker, R. Neier, Synthesis 1998, 227-255; d) P. J. Parsons, C. S. Penkett, A. Shell, J. Chem. Rev; Washington, D. C.) 1996, 96, 195-206; e) H. Waldmann, Org. Synth. Highlights II 1995, 193-202; f) L...

  8. Nitrogen and Hydrogen on a Palladium-covered proton conductor: a first principle study of Ammonia catalysis

    Microsoft Academic Search

    Lorenzo Paulatto; Stefano de Gironcoli

    2009-01-01

    Being liquid at ambient conditions Ammonia would be an ideal Hydrogen vector. However, the industrial Haber process for Ammonia synthesis involves high pressures ( 100 bar) and temperatures (450-500 ^oC), making the process very expensive. Recently, ambient pressure Ammonia production, in the 570-750 ^oC temperature range, has been reported at the Palladium cathode of a proton conducting cell-reactor [1]. The

  9. SIRT5 regulation of ammonia-induced autophagy and mitophagy.

    PubMed

    Polletta, Lucia; Vernucci, Enza; Carnevale, Ilaria; Arcangeli, Tania; Rotili, Dante; Palmerio, Silvia; Steegborn, Clemens; Nowak, Theresa; Schutkowski, Mike; Pellegrini, Laura; Sansone, Luigi; Villanova, Lidia; Runci, Alessandra; Pucci, Bruna; Morgante, Emanuela; Fini, Massimo; Mai, Antonello; Russo, Matteo A; Tafani, Marco

    2015-01-01

    In liver the mitochondrial sirtuin, SIRT5, controls ammonia detoxification by regulating CPS1, the first enzyme of the urea cycle. However, while SIRT5 is ubiquitously expressed, urea cycle and CPS1 are only present in the liver and, to a minor extent, in the kidney. To address the possibility that SIRT5 is involved in ammonia production also in nonliver cells, clones of human breast cancer cell lines MDA-MB-231 and mouse myoblast C2C12, overexpressing or silenced for SIRT5 were produced. Our results show that ammonia production increased in SIRT5-silenced and decreased in SIRT5-overexpressing cells. We also obtained the same ammonia increase when using a new specific inhibitor of SIRT5 called MC3482. SIRT5 regulates ammonia production by controlling glutamine metabolism. In fact, in the mitochondria, glutamine is transformed in glutamate by the enzyme glutaminase, a reaction producing ammonia. We found that SIRT5 and glutaminase coimmunoprecipitated and that SIRT5 inhibition resulted in an increased succinylation of glutaminase. We next determined that autophagy and mitophagy were increased by ammonia by measuring autophagic proteolysis of long-lived proteins, increase of autophagy markers MAP1LC3B, GABARAP, and GABARAPL2, mitophagy markers BNIP3 and the PINK1-PARK2 system as well as mitochondrial morphology and dynamics. We observed that autophagy and mitophagy increased in SIRT5-silenced cells and in WT cells treated with MC3482 and decreased in SIRT5-overexpressing cells. Moreover, glutaminase inhibition or glutamine withdrawal completely prevented autophagy. In conclusion we propose that the role of SIRT5 in nonliver cells is to regulate ammonia production and ammonia-induced autophagy by regulating glutamine metabolism. PMID:25700560

  10. Microwave-Assisted Synthesis of 5-Phenyl-2-Hydroxyacetophenone Derivatives by a Green Suzuki Coupling Reaction

    ERIC Educational Resources Information Center

    Soares, Pedro; Fernandes, Carlos; Chavarria, Daniel; Borges, Fernanda

    2015-01-01

    In recent years, the use of boron-containing reagents in palladium-assisted C-C coupling reactions (the Suzuki reaction) has gained prominence due to the vast array of reagents commercially available. Consequently, the generation of carbon-carbon bonds, namely of functionalized biphenyl systems, is at present considered the backbone of organic…

  11. Oceanic emissions of ammonia

    NASA Astrophysics Data System (ADS)

    Paulot, F.; Jacob, D. J.; Johnson, M.; Bell, T. G.; Stock, C. A.; Doney, S. C.

    2013-12-01

    Half of natural ammonia (NH3) emissions is thought to originate from the oceans. Such large emissions have implications for the global budget of N and the acidity of marine aerosols. We develop two new inventories of oceanic NH3 emissions based on simulated monthly NH3 seawater concentrations from the GFDL-COBALT and the CESM-BEC ocean models. These new inventories explicitly account for the effect of temperature on the water-atmosphere exchange of NH3. We evaluate these inventory using cruise observations of gas-phase ammonia (AMT cruises) and ammonium (NOAA cruises) as well as seawater measurement of NHx. Implications of atmospheric NHx observations for the exchange of N between ocean and land and ocean N/P limitations are discussed.

  12. Synthesis of saturated 1,4-benzodiazepines via Pd-catalyzed carboamination reactions.

    PubMed

    Neukom, Joshua D; Aquino, Alvin S; Wolfe, John P

    2011-05-01

    A new synthesis of 1,4-benzodiazepines and 1,4-benzodiazepin-5-ones is reported. The Pd-catalyzed coupling of N-allyl-2-aminobenzylamine derivatives with aryl bromides affords the heterocyclic products in good yield, and substrates bearing allylic methyl groups are transformed to cis-2,3-disubstituted products with >20:1 dr. PMID:21446677

  13. Synthesis of Saturated 1,4-Benzodiazepines via Pd-Catalyzed Carboamination Reactions

    PubMed Central

    Neukom, Joshua D.; Aquino, Alvin S.; Wolfe, John P.

    2011-01-01

    A new synthesis of 1,4-benzodiazepines and 1,4-benzodiazepin-5-ones is reported. The Pd-catalyzed coupling ofN-allyl-2-aminobenzylamine derivatives with aryl bromides affords the heterocyclic products in good yield, and substrates bearing allylic methyl groups are transformed toc is-2,3-disubstituted products with >20:1 dr. PMID:21446677

  14. Fusion by diffusion. II. Synthesis of transfermium elements in cold fusion reactions

    Microsoft Academic Search

    W. J. Swiatecki; K. Siwek-Wilczynska; J. Wilczynski

    2005-01-01

    We describe a method of estimating cross sections for the synthesis of very heavy nuclei by the fusion of two lighter ones. The cross section is considered to be the product of three factors: the cross section for the projectile to overcome the Coulomb barrier, the probability that the resulting composite nucleus reaches the compound nucleus configuration by a shape

  15. Fischer-Tropsch synthesis in supercritical reaction media. Progress report, October 1, 1992--December 31, 1992

    SciTech Connect

    Subramaniam, B.; Bochniak, D.; Snavely, K.

    1993-01-01

    Our goals for this quarter were to complete construction of the reactor and analytical units for carrying out Fischer-Tropsch (F-T) synthesis in liquid (n-hexadecane) and in supercritical n-hexane phases. Progress during this quarter was slower than expected.

  16. A study of combustion synthesis reaction in the Ti + C\\/Ti + Al system

    Microsoft Academic Search

    Chyi-Ching Hwang; Shyan-Lung Chung

    2004-01-01

    Combustion synthesis (SHS) of the Ti + C\\/Ti + Al system was investigated by using titanium, graphite and aluminum powders as reactants. These powders were thoroughly mixed and pressed into cylindrical compacts, and heated in an argon atmosphere. The effects of the reactant composition and the heating rate were studied. The phase identification and morphology observation of the products were

  17. Ester coupling reactions - an enduring challenge in the chemical synthesis of bioactive natural products.

    PubMed

    Tsakos, Michail; Schaffert, Eva S; Clement, Lise L; Villadsen, Nikolaj L; Poulsen, Thomas B

    2015-03-25

    Covering: up to 2014In this review we investigate the use of complex ester fragment couplings within natural product total synthesis campaigns. We first outline the different biosynthetic and chemical strategies for performing complex ester couplings and on this mechanistic background we then present and discuss a collection of successful examples from the literature. PMID:25572105

  18. Toward the Total Synthesis of Norzoanthamine: The Development of a Transannular Michael Reaction Cascade 

    E-print Network

    Xue, Haoran

    2013-03-06

    of the synthesis of angular 6-6-6 tricyclic ring system, a mimic of the ABC core structure of norzoanthamine. Using 1,7-bis-enones in the form of 14-membered macrocyclic lactone as model substrates, we demonstrated that both E,Z- and E,E-macrocycles underwent...

  19. Synthesis of Spirocyclic Indolines by Interruption of the Bischler–Napieralski Reaction

    PubMed Central

    Medley, Jonathan William; Movassaghi, Mohammad

    2013-01-01

    The development of a versatile method for the synthesis of spirocyclic pyrrolidinoindolines is discussed. Treatment of N-acyltryptamines with trifluoromethanesulfonic anhydride–2-chloropyridine reagent combination affords highly persistent spiroindoleninium ions which are subject to intra- and intermolecular addition at C2 by nucleophiles. PMID:23829389

  20. Sugar-Driven Prebiotic Synthesis of 3,5(6)-Dimethylpyrazin-2-one: A Possible Nucleobase of a Primitive Replication Process

    NASA Astrophysics Data System (ADS)

    Weber, Arthur L.

    2008-08-01

    Reaction of glyceraldehyde with alanine amide (or ammonia) under anaerobic aqueous conditions yielded 3,5(6)-dimethylpyrazin-2-one that is considered a possible complementary residue of a primitive replicating molecule that preceded RNA. Synthesis of the dimethylpyrazin-2-one isomers under mild aqueous conditions (65°C, pH 5.5) from 100 mM glyceraldehyde and alanine amide (or ammonia) was complete in about 5 days. This synthesis using 25 mM glyceraldehyde and alanine amide gave a total pyrazinone yield of 9.3% consisting of 42% of the 3,5-dimethylprazin-2-one isomer and 58% of the 3,6-dimethylpyrazin-2-one isomer. The related synthesis of the dimethylpyrazin-2-one isomers from glyceraldehyde and ammonia was about 200-fold less efficient than the alanine amide reaction. This synthetic process is considered a reasonable model of origin-of-life chemistry because it uses plausible prebiotic substrates, and resembles modern biosynthesis by employing the energized carbon groups of sugars to drive the synthesis of small organic molecules. Possible sugar-driven pathways for the prebiotic synthesis of polymerizable 2-pyrazinone monomers are discussed.

  1. Facile synthesis of magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals via a cation-exchange reaction

    NASA Astrophysics Data System (ADS)

    Ning, Jiajia; Xiao, Guanjun; Wang, Li; Zou, Bo; Liu, Bingbing; Zou, Guangtian

    2011-02-01

    Magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals with small size and uniform size distribution are synthesized via a cation-exchange reaction. Two experimental stages are included in the synthesis of metal oxides nanocrystals. Firstly, Cu(OH)2 decomposes to CuO nanocrystals, induced by free metal cations. Compared to CuO nanocrystals produced without any free metal cation, the free metal cation has an important influence on the shape and size of CuO. Secondly, free metal cations exchange with the Cu2+ cation in the CuO nanocrystals to get Mn3O4, Fe2O3, CoO and NiO nanocrystals by cation-exchange reactions. The magnetic properties of these metal oxides nanocrystals have been investigated, all the nanocrystals are superparamagnetic at room temperature.Magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals with small size and uniform size distribution are synthesized via a cation-exchange reaction. Two experimental stages are included in the synthesis of metal oxides nanocrystals. Firstly, Cu(OH)2 decomposes to CuO nanocrystals, induced by free metal cations. Compared to CuO nanocrystals produced without any free metal cation, the free metal cation has an important influence on the shape and size of CuO. Secondly, free metal cations exchange with the Cu2+ cation in the CuO nanocrystals to get Mn3O4, Fe2O3, CoO and NiO nanocrystals by cation-exchange reactions. The magnetic properties of these metal oxides nanocrystals have been investigated, all the nanocrystals are superparamagnetic at room temperature. Electronic supplementary information (ESI) available: XPS of Fe2O3 nanoparticles, TEM images of Fe2O3 and Mn3O4 nanocrystals produced with different molar ratios of precursors, TEM images and XRD patterns of CuO nanocrystals produced without any free cations and XRD patterns of the transformation from Cu(OH)2 to metal oxide nanocrystals, photographs of color change when reaction solution was exposed to air. See DOI: 10.1039/c0nr00684j

  2. Sorption of Ammonia, Methylamine and Methanol by the P3 Polymorph of Gossypol. Synthesis of Unsymmetrical Monoamine Derivatives of Gossypol by a Solid-state Reaction

    Microsoft Academic Search

    S. A. Talipov; A. Manakov; B. T. Ibragimov; J. Lipkowski; Z. G. Tiljakov

    1997-01-01

    The P3 polymorph of gossypol has wide, empty channels andstrongly absorbs linear amines. One of the two gossypol aldehydegroups is located near the channel wall. This situation allowsreaction of the amines with half of a gossypol molecule,yielding unsymmetric monoaminoderivatives of gossypol in highyield and by a simple, solid-state method.

  3. The Synthesis and Characterization of Mesoporous High-Surface Area Ceria Prepared Using a Hybrid Organic\\/Inorganic Route

    Microsoft Academic Search

    Daniela Terribile; Alessandro Trovarelli; Jordi Llorca; Carla de Leitenburg; Giuliano Dolcetti

    1998-01-01

    The synthesis, characterization, and proposed formation mechanism of mesoporous high surface area ceria is described. It is shown that the reaction of cerium salts under basic conditions with ammonia in the presence of a cationic surfactant results in the precipitation of a gelatinous hydrous cerium oxide\\/surfactant mixture, which after drying and calcination gives pure, high surface area, fluorite-structured CeO2. Although

  4. Determination of ammonia in beers by pervaporation flow injection analysis and spectrophotometric detection

    Microsoft Academic Search

    Lijuan Wang; Terence J. Cardwell; Robert W. Cattrall; Maria D. Luque de Castro; Spas D. Kolev

    2003-01-01

    A pervaporation flow injection (PFI) method is described for the determination of ammonia in beers. After injecting the sample into a NaOH donor solution, ammonia and other volatiles are transferred in the pervaporation unit from the donor stream to an acceptor stream containing sodium salicylate and nitroprusside, which subsequently mixes with alkaline sodium dichloroisocyanurate to allow the classical Berthelot reaction

  5. Sodium Hydride Mediated Cascade Reaction towards the Synthesis of 1,5-Disubstituted Uracil from Cyanamides Derived from Baylis-Hillman Adducts

    Microsoft Academic Search

    S. Nag; G. P. Yadav; P. R. Maulik; S. Batraa

    2007-01-01

    The substituted cyanamide generated from the Baylis- Hillman adduct afford 1,5-disubstituted uracil via sodium hydride induced cascade reaction which involes a sequential intramolecu- lar attack of the hydroxyl group on the nitrile group, cyclization of resulting ureide with the ester moiety and rearrangement of the exocyclic double bond. The Baylis-Hillman reaction has been widely exploited for heterocyclic synthesis.2 In our

  6. In situ synthesis of ZrC particles and its formation mechanism by self-propagating reaction from Al–Zr–C elemental powders

    Microsoft Academic Search

    M. S. Song; B. Huang; M. X. Zhang; J. G. Li

    2009-01-01

    ZrC particles were fabricated via self-propagating high-temperature synthesis (SHS) from 0 to 40 mass% Al–Zr–C elemental powder mixtures. The typical layered structures of the reaction products were observed due to the non-steady-state oscillatory motion of the combustion wave. With the Al content increasing, the reaction temperature decreased and the ZrC particle sizes evidently reduced from ~ 8 µm in Al free to

  7. Synthesis of Tetrazolo-Fused Benzodiazepines and Benzodiazepinones by a Two-Step Protocol Using an Ugi-Azide Reaction for Initial Diversity Generation.

    PubMed

    Gunawan, Steven; Ayaz, Muhammad; De Moliner, Fabio; Frett, Brendan; Kaiser, Christine; Patrick, Nina; Xu, Zhigang; Hulme, Christopher

    2012-07-01

    A two-step strategy for the synthesis of arrays of tricyclic tetrazolo-fused benzodiazepines and benzodiazepinones has been investigated. The protocol uses ortho-N-Boc phenylisocyanides and phenylglyoxaldehydes or ethyl glyoxylate in the 4-component Ugi-Azide reaction to afford MCR (Multi Component Reactions) derived adducts equipped with the desired diversity inputs. A subsequent acidic treatment (TFA/DCE) allows a simultaneous deprotection-cyclization leading to the final products. PMID:22923851

  8. Synthesis of Tetrazolo-Fused Benzodiazepines and Benzodiazepinones by a Two-Step Protocol Using an Ugi-Azide Reaction for Initial Diversity Generation

    PubMed Central

    Gunawan, Steven; Ayaz, Muhammad; De Moliner, Fabio; Frett, Brendan; Kaiser, Christine; Patrick, Nina; Xu, Zhigang; Hulme, Christopher

    2012-01-01

    A two-step strategy for the synthesis of arrays of tricyclic tetrazolo-fused benzodiazepines and benzodiazepinones has been investigated. The protocol uses ortho-N-Boc phenylisocyanides and phenylglyoxaldehydes or ethyl glyoxylate in the 4-component Ugi-Azide reaction to afford MCR (Multi Component Reactions) derived adducts equipped with the desired diversity inputs. A subsequent acidic treatment (TFA/DCE) allows a simultaneous deprotection-cyclization leading to the final products. PMID:22923851

  9. Wittig Reaction: The Synthesis of trans-9-(2-Phenylethenyl)anthracene Revisited

    NASA Astrophysics Data System (ADS)

    Jaworek, Christine; Iacobucci, Sarah

    2002-01-01

    The revisit to this experimental procedure resulted in making a good undergraduate laboratory procedure even better. In this Wittig reaction, readily available starting materials are used; only the trans isomer is produced; the clear and characteristic 1H NMR spectrum of the product is ideal for a lesson in coupling constants to determine stereochemistry; and the product can be readily used in additional brilliant chemiluminescence laboratory experiments. The problematic step of generating tough emulsions during extractions with halogenated solvents has been eliminated by using N,N-dimethylformamide as the reaction solvent and readily precipitating the product from the reaction mixture using 1-propanol and water.

  10. System and method for determining an ammonia generation rate in a three-way catalyst

    DOEpatents

    Sun, Min; Perry, Kevin L; Kim, Chang H

    2014-12-30

    A system according to the principles of the present disclosure includes a rate determination module, a storage level determination module, and an air/fuel ratio control module. The rate determination module determines an ammonia generation rate in a three-way catalyst based on a reaction efficiency and a reactant level. The storage level determination module determines an ammonia storage level in a selective catalytic reduction (SCR) catalyst positioned downstream from the three-way catalyst based on the ammonia generation rate. The air/fuel ratio control module controls an air/fuel ratio of an engine based on the ammonia storage level.

  11. Synthesis of vinyl boronates from aldehydes by a practical boron-Wittig reaction.

    PubMed

    Coombs, John R; Zhang, Liang; Morken, James P

    2015-04-01

    A highly stereoselective boron-Wittig reaction between stable and readily accessible 1,1-bis(pinacolboronates) and aldehydes furnishes a variety of synthetically useful di- and trisubstituted vinyl boronate esters. PMID:25799147

  12. Clean synthesis in water. Part 2: Uncatalysed condensation reaction of Meldrum's acid and aldehydes

    Microsoft Academic Search

    Franca Bigi; Silvia Carloni; Leonetto Ferrari; Raimondo Maggi; Alessandro Mazzacani; Giovanni Sartori

    2001-01-01

    The environment-friendly condensation of Meldrum's acid and aromatic, heteroaromatic and hindered aliphatic aldehydes is performed carrying out the reaction in water at 75°C for 2 h, avoiding the addition of any catalyst.

  13. Highly-efficient synthesis of covalent porphyrinic cages via DABCO-templated imine condensation reactions.

    PubMed

    Ding, Huimin; Meng, Xiangshi; Cui, Xu; Yang, Yihui; Zhou, Tailin; Wang, Caixing; Zeller, Matthias; Wang, Cheng

    2014-10-01

    We report a new approach to construct covalent porphyrinic cages with different spacer lengths, in which the cage compounds have been conveniently synthesized in quantitative yields, via DABCO-templated imine condensation reactions. PMID:25111246

  14. Synthesis of (-)-?9-trans-Tetrahydrocannabinol - Stereocontrol via Mo-catalyzed Asymmetric Allylic Alkylation Reaction

    PubMed Central

    Trost, Barry M.; Dogra, Kalindi

    2008-01-01

    ?9-THC is synthesized in enantiomericaly pure form, where all of the stereochemistry is derived from the molybdenum catalyzed asymmetric alkylation reaction of the extremely sterically congested bis-ortho substituted cinnamyl carbonate in high regio- and enantioselectivity. PMID:17266321

  15. Highly convergent synthesis of chiral bicyclophosphinates by domino hydrophosphinylation/Michael/Michael reaction.

    PubMed

    Fourgeaud, Pierre; Daydé, Bénédicte; Volle, Jean-Noël; Vors, Jean-Pierre; Van der Lee, Arie; Pirat, Jean-Luc; Virieux, David

    2011-10-01

    Diastereoselective domino reactions of iminoalcohols and allenyl H-phosphinates produce chiral phosphorus bicycles in a regio- and stereoselective fashion. A predictive model for diastereoselection is used for these new chiral phosphinic esters. PMID:21888337

  16. Development of odd-Z-projectile reactions for transactinide element synthesis

    SciTech Connect

    Folden III, Charles Marvin

    2004-11-04

    The development of new odd-Z-projectile reactions leading to the production of transactinide elements is described. The cross section of the even-Z-projectile 208Pb(64Ni, n)271Ds reaction was measured at two new energies using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. In total, seven decay chains attributable to 271Ds were observed. These data, combined with previous results, establish an excitation function for the production of 271Ds. The maximum cross section was 20 +15 -11 pb at a center-of-target energy of 311.5 MeV in the laboratory frame.The data from the 271Ds experiments were used to estimate the optimum beam energy for the new odd-Z-projectile 208Pb(65Cu, n)272-111 reaction using the Fusion by Diffusion theory proposed by Swiatecki, Siwek-Wilczynska, and Wilczynski. A cross section for this reaction was measured for the first time, at a center-of-target energy of 321.1 MeV in the laboratory frame. The excitation energy f or compound nuclei formed at the target center was 13.2 MeV. One decay chain was observed, resulting in a measured cross section of 1.7 +3.9 -1.4 pb. This decay chain is in good agreement with previously published data on the decay of 272-111.The new odd-Z-projectile 208Pb(55Mn, n)262Bh reaction was studied at three different projectile energies, and 33 decay chains of 262Bh were observed. The existence of a previously reported alpha-decaying isomeric state in this nuclide was confirmed. Production of the ground state was preferred at all three beam energies. The maximum cross section was 540 +180 -150 pb at a projectile center-of-target energy of 264.0 MeV. This cross section is much larger than that previously reported for the even-Z-projectile 209Bi(54Cr, n)262Bh reaction, which may be because the 54Cr projectile energies in the latter reaction were too high for optimum production of the 1n product. At the highest projectile energy of 268.0 MeV in the target center, two decay chains from 261Bh were observed as a result of the 208Pb(55Mn, 2n) reaction. In summary, this work shows that odd-Z-projectile reactions can have cross sections comparable to analogous even-Z-projectile reactions, and that the energy of the maximum cross section for 1n reactions can be estimated simply.

  17. Expedient Synthesis of Norbenzomorphan Library via Multicomponent Assembly Process Coupled with Ring-Closing Reactions

    PubMed Central

    Sahn, James J.; Martin, Stephen F.

    2012-01-01

    A 124 member norbenzomorphan library has been prepared utilizing a novel multicomponent assembly process (MCAP) followed by a variety of ring-closing reactions to generate norbenzomorphan scaffolds that were readily derivatized via a series of aryl halide cross-coupling and nitrogen functionalization reactions. Biological screening has revealed some novel activities that have not been previously associated with this class of compounds. PMID:22857149

  18. Synthesis of Substituted Tetrahydroindoloisoquinoline Derivatives via Intramolecular Pd-Catalyzed Alkene Carboamination Reactions

    PubMed Central

    2015-01-01

    Intramolecular Pd-catalyzed alkene carboamination reactions of substituted 2-allyl-N-(2-bromobenzyl)anilines are described. The substrates for these reactions are generated in two steps from readily available 2-allylanilines and 2-bromobenzaldehyde derivatives. The transformations afford substituted tetrahydroindoloisoquinolines, an uncommon class of fused bicyclic heterocycles, in good yield. The mechanism of these transformations is described, and a model that accounts for the observed product stereochemistry is proposed. PMID:24724560

  19. Organo-niobate Ionic Liquids: Synthesis, Characterization and Application as Acid Catalyst in Pechmann Reactions

    PubMed Central

    Soares, Valerio C. D.; Alves, Melquizedeque B.; Souza, Ernesto R.; Pinto, Ivana O.; Rubim, Joel C.; Andrade, Carlos Kleber Z.; Suarez, Paulo A. Z.

    2007-01-01

    The combinations of 1-butyl-3-methylimidazolium chloride with NbCl5 yielded ionic mixtures with different melting point temperatures and acidity depending on the niobium molar fraction. The mixtures were characterized by thermal (DSC) and spectroscopic (FT-IR and 1H NMR) analysis. The Pechmann reactions of different phenols with ethylacetoacetate, producing coumarins, was used as model to evaluate the catalytic behavior of these mixtures as acid Lewis catalyst. These reactions were carried out using acidic mixtures of 60 mol%.

  20. First Synthesis of DL2-C-Hydroxymethyl-3-Pentulose in the Formose Reaction

    Microsoft Academic Search

    Yoshihiro Shigemasa; Takaaki Ueda; Hiroyuki Saimoto

    1989-01-01

    The formose reactions in N,N-dimethylformamide (DMF) catalyzed by 2-(dimethylamino)ethanol and thiamine hydrochloride, have been found to give rise to dihydroxyacetone and DL-glycero-tetrulose selectively at 1.1 M and 3.0 M of formaldehyde concentration, respectively. In our consecutive study on the formose reaction in DMF, it has been fortunately found that the distribution of products is able to be controlled by the

  1. Efficient Synthesis of Octahydrophenanthrene Derivatives with Mild Cascade Reactions of Isochromenylium Tetrafluoroborates and Bifunctional Styrenes.

    PubMed

    Mo, Lei; Wu, Lin-Lin; Wang, Shaozhong; Yao, Zhu-Jun

    2015-07-01

    A highly efficient catalyst-free cascade reaction of air-stable isochromenylium tetrafluoroborates and bifunctional styrenes containing a 1,3-diketone moiety has been developed, affording the corresponding single diastereomeric ocatahydrophenanthrene derivatives (21 examples, up to 86% yield). A cascade process of [4 + 2]-cyclization and subsequent intramolecular nucleophilic addition is proposed to generate the three new C-C bonds diastereoselectively in the reactions. PMID:26098712

  2. Efficient synthesis of carbazolespirooxindole skeletons via asymmetric Diels-Alder reaction of 3-vinylindoles and methyleneindolinones.

    PubMed

    Zheng, Haifeng; He, Peng; Liu, Yangbin; Zhang, Yulong; Liu, Xiaohua; Lin, Lili; Feng, Xiaoming

    2014-08-14

    A highly efficient catalytic asymmetric Diels-Alder reaction between 3-vinylindoles and methyleneindolinones has been achieved using chiral N,N'-dioxide-Ni(II) complexes as the catalysts. A wide variety of substrates were readily tolerated, generating exclusively the corresponding exo-carbazolespirooxindole derivatives in excellent yields with high enantiomeric excesses (up to 98% yield, >99?:?1 d.r., and 98% ee) under mild reaction conditions. PMID:24967917

  3. Ultrasound assisted lipase catalyzed synthesis of cinnamyl acetate via transesterification reaction in a solvent free medium.

    PubMed

    Tomke, Prerana D; Rathod, Virendra K

    2015-11-01

    Cinnamyl acetate is known for its use as flavor and fragrance material in different industries such as food, pharmaceutical, cosmetic etc. This work focuses on ultrasound assisted lipase (Novozym 435) catalyzed synthesis of cinnamyl acetate via transesterification of cinnamyl alcohol and vinyl acetate in non-aqueous, solvent free system. Optimization of various parameters shows that a higher yield of 99.99% can be obtained at cinnamyl alcohol to vinyl acetate ratio of 1:2 with 0.2% of catalyst, at 40°C and 150rpm, with lower ultrasound power input of 50W (Ultrasound intensity 0.81W/cm(2)), at 25kHz frequency, 50% duty cycle. Further, the time required for the maximum conversion is reduced to 20min as compared to 60min of conventional process. Similarly, the enzyme can be successfully reused seven times without loss of enzyme activity. Thus, ultrasound helps to enhance the enzyme catalyzed synthesis of flavors. PMID:26186841

  4. Asymmetric Synthesis of Functionalized Dihydro- and Tetrahydropyrans via an Organocatalytic Domino Michael–Hemiacetalization Reaction

    PubMed Central

    Urbanietz, Gregor; Atodiresei, Iuliana; Enders, Dieter

    2014-01-01

    Starting from ?-hydroxymethyl nitroalkenes and various 1,3-dicarbonyl compounds, a one-pot organocatalyzed diastereo- and enantioselective synthesis of polyfunctionalized dihydro- and tetrahydropyran derivatives via a domino Michael-hemiacetalization sequence is reported. The title compounds bearing a variety of functional groups can be synthesized in this way in good yields (59–91%) and with moderate to excellent diastereoselectivities (26–98% de) and enantioselectivities (71–99% ee). PMID:25284900

  5. Deep eutectic solvents and glycerol: a simple, environmentally benign and efficient catalyst\\/reaction media for synthesis of N-aryl phthalimide derivatives

    Microsoft Academic Search

    Hyacintha Rennet Lobo; Balvant Shyam Singh; Ganapati Subray Shankarling

    2012-01-01

    Deep eutectic solvents (DES) and glycerol have been successfully employed as efficient catalysts\\/reaction media in the synthesis of N-aryl phthalimide derivatives from phthalic anhydride and primary aromatic amines. The DES prepared from choline chloride and malonic acid proved to be an efficient catalyst whereas glycerol and the DES of choline chloride and urea played a dual role of catalyst and

  6. Parallel synthesis of dihydropyrimidinones using Yb(III)-resin and polymer-supported scavengers under solvent-free conditions. A green chemistry approach to the Biginelli reaction

    Microsoft Academic Search

    Alessandro Dondoni; Alessandro Massi

    2001-01-01

    An efficient synthesis of an array of 3,4-dihydropyrimidin-2-(1H)-ones using solid-supported ytterbium(III) reagent from aldehydes, 1,3-dicarbonyl compounds and urea (Biginelli reaction) under solvent-free conditions is described. Purification of each member of the library was carried out using a cocktail of acid and basic polymer-supported scavengers

  7. Synthesis, Properties, and Reactions of Trinuclear Macrocyclic Nickel(II) and Nickel(I) Complexes: Electrocatalytic Reduction of CO2 by Nickel(II) Complex

    E-print Network

    Paik Suh, Myunghyun

    FULL PAPER Synthesis, Properties, and Reactions of Trinuclear Macrocyclic Nickel(II) and Nickel(I) Complexes: Electrocatalytic Reduction of CO2 by Nickel(II) Complex Eun Young Lee,[a] Daewon Hong,[a] Han Woong Park,[a] and Myunghyun Paik Suh*[a] Keywords: Nickel / Macrocyclic compounds / Carbon dioxide

  8. Designed synthesis of size-tunable Ag2S nanoclusters via distinguishable C-S bond cleavage reaction of alkyl- and aryl-thiolates.

    PubMed

    Chen, Hang-Qing; He, Xin; Guo, Hui; Fu, Nan-Yan; Zhao, Liang

    2015-03-01

    We report herein the synthesis of two different silver clusters of aryl- and alkyl-thiolates. These two cluster complexes exhibited biased C-S bond cleavage reaction rates upon removing protective hexamethylazacalix[6]pyridine (Py[6]) ligands, which was applied in the fabrication of silver sulfide nanoclusters with variable and controllable sizes. PMID:25652650

  9. Synthesis of interstellar 1,3,5-heptatriynylidyne, C7H,,X 2 the neutral-neutral reaction of ground state carbon atom, C,,3

    E-print Network

    Kaiser, Ralf I.

    Langevin model for estimating capturing cross sections. The isomerization and dissociation channelsSynthesis of interstellar 1,3,5-heptatriynylidyne, C7H,,X 2 ..., via the neutral-neutral reaction molecules represent a significant fraction of those 150 detected molecules in the interstellar medium

  10. Synthesis of 2Amino5(6)-(4-aminophenyl)benzimidazole Derivatives: II. Reaction of 2Nitro4-thiocyanatoaniline with 4-Nitrochlorobenzene

    Microsoft Academic Search

    V. S. Pilyugin; Yu. E. Sapozhnikov; G. P. Shitov

    2003-01-01

    The reaction of 2-nitro-4-thiocyanatoaniline with 4-nitrochlorobenzene in aqueous alkaline medium in the presence of phase-transfer catalyst at 95-100°C was studied with a view to obtain 4-amino-3,4'-dinitrodiphenyl sulfide. Optimal conditions for the synthesis and isolation of the product were found.

  11. SOLID-LIQUID PHASE TRANSFER CATALYZED SYNTHESIS OF CINNAMYL ACETATE-KINETICS AND ANALYSIS OF FACTORS AFFECTING THE REACTION IN A BATCH REACTOR

    EPA Science Inventory

    The use of solid-liquid phase transfer catalysis has an advantage of carrying out reaction between two immiscible substrates, one in solid phase and the other in liquid phase, with high selectivity and at relatively low temperatures. In this study we investigated the synthesis ci...

  12. Production of Organometallic Polymers by the Interfacial Technique. XXXII. Reaction Variables in the Synthesis of Oligomeric Tin Poly(cobalticinium Esters) and Thermal Properties of the Products

    Microsoft Academic Search

    Charles E. Carraher Jr; George F. Peterson; John E. Sheats; Ted Kirsch

    1974-01-01

    The synthesis of oligomeric tin poly(cobalticinium esters) is presented as a function of the particular reaction variables stirring rate, pH and amount of added base, mole ratio of reactants, concentration of reactants, and volume of organic phase. Factors which decrease the solubility of the stannane apparently act to increase the yield of polyester. The thermal characterization of I was carried

  13. CATALYST-FREE REACTIONS UNDER SOLVENT-FEE CONDITIONS: MICROWAVE-ASSISTED SYNTHESIS OF HETEROCYCLIC HYDRAZONES BELOW THE MELTING POINT OF NEAT REACTANTS: JOURNAL ARTICLE

    EPA Science Inventory

    NRMRL-CIN-1437 Jeselnik, M., Varma*, R.S., Polanc, S., and Kocevar, M. Catalyst-free Reactions under Solvent-fee Conditions: Microwave-assisted Synthesis of Heterocyclic Hydrazones below the Melting Point of Neat Reactants. Published in: Chemical Communications 18:1716-1717 (200...

  14. One-pot sequential synthesis of isocyanates and urea derivatives via a microwave-assisted Staudinger–aza-Wittig reaction

    PubMed Central

    Carnaroglio, Diego; Martina, Katia; Palmisano, Giovanni; Penoni, Andrea; Domini, Claudia

    2013-01-01

    Summary A fast and efficient protocol for the synthesis of N,N'-disubstituted urea derivatives from alkyl halides and primary or secondary amines has been developed. The synthetic pathway combines nucleophilic substitutions and a Staudinger–aza-Wittig reaction in the presence of polymer-bound diphenylphosphine under 14 bar of CO2 pressure and has been performed in a one-pot two-step process. The protocol has been optimized under microwave irradiation and the scale-up experiment has been conducted under conventional conditions in a Parr reactor. The final compounds were isolated after simple filtration in almost quantitative overall yields which makes this procedure facile and rapid to execute. PMID:24367403

  15. One-pot sequential synthesis of isocyanates and urea derivatives via a microwave-assisted Staudinger-aza-Wittig reaction.

    PubMed

    Carnaroglio, Diego; Martina, Katia; Palmisano, Giovanni; Penoni, Andrea; Domini, Claudia; Cravotto, Giancarlo

    2013-01-01

    A fast and efficient protocol for the synthesis of N,N'-disubstituted urea derivatives from alkyl halides and primary or secondary amines has been developed. The synthetic pathway combines nucleophilic substitutions and a Staudinger-aza-Wittig reaction in the presence of polymer-bound diphenylphosphine under 14 bar of CO2 pressure and has been performed in a one-pot two-step process. The protocol has been optimized under microwave irradiation and the scale-up experiment has been conducted under conventional conditions in a Parr reactor. The final compounds were isolated after simple filtration in almost quantitative overall yields which makes this procedure facile and rapid to execute. PMID:24367403

  16. Effect of BN/Ti Ratio on the Reaction Synthesis of TiB2-TiNx Ceramics

    NASA Astrophysics Data System (ADS)

    Zhan, Lei; Shen, Ping; Jiang, Qi Chuan

    The effects of BN/Ti molar ratio on the self-propagating high-temperature synthesis (SHS) reaction behaviors and final products in the Ti-BN system were experimentally investigated. With an increase in the BN/Ti ratio, the combustion temperature and wave velocity first increase and then decrease with the maximum values displaying at BN/Ti=0.67. A substoichiometric TiN1-x was obtained for BN/Ti<0.67, and a stoichiometric one was produced for BN/Ti=0.67. Moreover, the microstructure photographs of the products reveal that with the increase of the BN/Ti ratio, the grains of the ceramic phases tend to be finer.

  17. Synthesis and characterization of palladium and palladium-cobalt nanoparticles on Vulcan XC-72R for the oxygen reduction reaction.

    PubMed

    Arroyo-Ramírez, Lisandra; Montano-Serrano, Rubenier; Luna-Pineda, Tatiana; Román, Félix R; Raptis, Raphael G; Cabrera, Carlos R

    2013-11-27

    A single-source approach was used to synthesize bimetallic nanoparticles on a high-surface-area carbon-support surface. The synthesis of palladium and palladium-cobalt nanoparticles on carbon black (Vulcan XC-72R) by chemical and thermal reduction using organometallic complexes as precursors is described. The electrocatalysts studied were Pd/C, Pd2Co/C, and PdCo2/C. The nanoparticles composition and morphology were characterized using inductively coupled plasma mass spectrophotometer (ICP-MS), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray fluorescence spectroscopy (EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. Electrocatalytic activity towards the oxygen reduction reaction (ORR) and methanol tolerance in oxygen-saturated acid solution were determined. The bimetallic catalyst on carbon support synthetized by thermal reduction of the Pd2Co precursor has ORR electrocatalytic activity and a higher methanol tolerance than a Pt/C catalyst. PMID:24102312

  18. Solid state displacement reaction synthesis of interpenetrating-phase Ni-Al/Al[sub 2]O[sub 3] composites

    SciTech Connect

    Henager, C.H. Jr.; Brimhall, J.L. (Pacific Northwest Lab., Richland, WA (United States))

    1993-12-15

    Interpenetrating-phase composites have certain advantages compared to discontinuous-phase composites. Among these are stability against microstructural coarsening and enhanced fracture resistance. However, it is difficult to fabricate IPCs in a controllable manner. Infiltration of porous performs, chemical vapor infiltration, directed metal oxidation, colloidal methods, and analogs to spinodal decomposition are all methods that have been used. Of particular interest are methods, such as the one presented here, that produce IPCs in situ without expensive lay-up processing. For the work presented here, synthesis of two composites, NiAl/Al[sub 2]O[sub 3] and NiAl+Ni[sub 3]Al+[gamma]-Ni/Al[sub 2]O[sub 3], exhibiting an interconnected cellular-phase structure by means of displacement reactions in situ is demonstrated.

  19. Ammonia-rich high-temperature superconducting intercalates of iron selenide revealed through time-resolved in situ X-ray and neutron diffraction.

    PubMed

    Sedlmaier, Stefan J; Cassidy, Simon J; Morris, Richard G; Drakopoulos, Michael; Reinhard, Christina; Moorhouse, Saul J; O'Hare, Dermot; Manuel, Pascal; Khalyavin, Dmitry; Clarke, Simon J

    2014-01-15

    The development of a technique for following in situ the reactions of solids with alkali metal/ammonia solutions, using time-resolved X-ray diffraction methods, reveals high-temperature superconducting ammonia-rich intercalates of iron selenide which reversibly absorb and desorb ammonia around ambient temperatures. PMID:24354523

  20. [Model of regularity of ammonia transformation along marine biological aerated filter].

    PubMed

    Luo, Rong-Qiang; Hou, Sha-Sha; Shen, Jia-Zheng; Chen, Zhu; Liu, Ying

    2012-09-01

    This study investigates the biological aerated filter (BAF) of a marine recirculating aquaculture system, which is important to remove harmful ammonia and organics. A model, characterizing the ammonia transformation along the BAF, was established on the basis of the principle of adsorption and the first order reaction bio-film. Experiments were performed and verified the effectiveness of the proposed model. The target BAF was packed with bamboo ring for 70 cm high. Study under the conditions [pH 7.1-7.6, DO 5-7 mg x L(-1), gas water ratio about 20 : 1, organic load about 4 g x (m3 x h)(-1)] shows that ammonia is removed significantly under the 10 cm height of medium, while less ammonia is removed between 10-70 cm. Experimental results confirm that the model predicts the ammonia concentration along the BAF accurately with a low influent ammonia concentration, but the predicted value is slightly lower than the true value with a high influent ammonia concentration. Study on ammonia concentration along the BAF reveals that the effluent ammonia concentration increases along with either the increment of the influent ammonia concentration or the reduction of the hydraulic retention time. PMID:23243879

  1. Changes in the community structure of ammonia-oxidizing bacteria during secondary succession of calcareous grasslands.

    PubMed

    Kowalchuk, G A; Stienstra, A W; Heilig, G H; Stephen, J R; Woldendorp, J W

    2000-02-01

    The community structure of beta-subclass Proteobacteria ammonia-oxidizing bacteria was determined in semi-natural chalk grassland soils at different stages of secondary succession. Both culture-mediated (most probable number; MPN) and direct nucleic acid-based approaches targeting genes encoding 16S rRNA and the AmoA subunit of ammonia monooxygenase were used. Similar shifts were detected in the composition of the ammonia oxidizer communities by both culture-dependent and independent approaches. A predominance of Nitrosospira sequence cluster 3 in early successional fields was replaced by Nitrosospira sequence cluster 4 in late successional fields. The rate of this shift differed between the two areas examined. This shift occurred in a background of relative stability in the dominant bacterial populations in the soil, as determined by domain-level polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Molecular analysis of enrichment cultures obtained using different ammonia concentrations revealed biases towards Nitrosospira sequence cluster 3 or Nitrosospira sequence cluster 4 under high- or low-ammonia conditions respectively. High-ammonia MPNs suggested a decease in ammonia oxidizer numbers with succession, but low-ammonia MPNs and competitive PCR targeting amoA failed to support such a trend. Ammonia turnover rate, not specific changes in plant diversity and species composition, is implicated as the major determinant of ammonia oxidizer community structure in successional chalk grassland soils. PMID:11243267

  2. QUANTIFIED DETRIMENT OF AMMONIA TO BROILERS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ammonia levels in broiler houses can reduce bird performance, increase susceptibility to disease and increase subsequent mortality. House management, season, humidity, stocking density, and litter properties influence ammonia concentrations. Though it is widely known that ammonia is detrimental to p...

  3. The ammonia transport, retention and futile cycling problem in cyanobacteria.

    PubMed

    Ritchie, Raymond J

    2013-01-01

    Ammonia is the preferred nitrogen source for many algae including the cyanobacterium Synechococcus elongatis (Synechococcus R-2; PCC 7942). Modelling ammonia uptake by cells is not straightforward because it exists in solution as NH(3) and NH (4) (+) . NH(3) is readily diffusible not only via the lipid bilayer but also through aquaporins and other more specific porins. On the other hand, NH (4) (+) requires cationic transporters to cross a membrane. Significant intracellular ammonia pools (?1-10 mol?m(-3)) are essential for the synthesis of amino acids from ammonia. The most common model envisaged for how cells take up ammonia and use it as a nitrogen source is the "pump-leak model" where uptake occurs through a simple diffusion of NH(3) or through an energy-driven NH (4) (+) pump balancing a leak of NH(3) out of the cell. The flaw in such models is that cells maintain intracellular pools of ammonia much higher than predicted by such models. With caution, [(14)C]-methylamine can be used as an analogue tracer for ammonia and has been used to test various models of ammonia transport and metabolism. In this study, simple "proton trapping" accumulation by the diffusion of uncharged CH(3)NH(2) has been compared to systems where CH(3)NH (3) (+) is taken up through channels, driven by the membrane potential (?U (i,o)) or the electrochemical potential for Na(+) (??Na (i,o) (+) ). No model can be reconciled with experimental data unless the permeability of CH(3)NH(2) across the cell membrane is asymmetric: permeability into the cell is very high through gated porins, whereas permeability out of the cell is very low (?40 nm?s(-1)) and independent of the extracellular pH. The best model is a Na (in) (+) /CH(3)NH (3) (+) (in) co-porter driven by ??Na (i,o) (+) balancing synthesis of methylglutamine and a slow leak governed by Ficks law, and so there is significant futile cycling of methylamine across the cell membrane to maintain intracellular methylamine pools high enough for fixation by glutamine synthetase. The modified pump-leak model with asymmetric permeability of the uncharged form is a viable model for understanding ammonia uptake and retention in plants, free-living microbes and organisms in symbiotic relationships. PMID:22940733

  4. Copolymers containing meta-pyridylvinylene and para-arylenevinylene fragments: synthesis, quaternization reaction, and photophysical properties

    NASA Astrophysics Data System (ADS)

    Barashkov, Nikolay N.; Olivos, Hernando J.; Ferraris, John P.

    1997-12-01

    We report the Wittig reaction of the diphosphonium salt of 2,6-bis(chloromethyl)pyridine with terephthaldehyde, 2.5- dioctyloxyterephthaldehyde, or 9,10-anthracenedicarbaldehyde to form conjugated copolymers with fragments of 2,6 - pyridylene and para-arylenevinylene. The protonation reaction of poly(para-arylenevinylene)-co-(meta- pyridylvinylene) with hydrochloric acid and the quaternization reaction of poly(2,5-dioctyloxy-1,4- phenylenevinylene)-co-(2,6-pyridylvinylene) with methyl triflate have been investigated by spectrophotometric and fluorescent methods. The absorption, excitation and fluorescence spectra of these copolymers as well as their corresponding model compounds were studied and compared. The photophysical properties of the investigated polymers suggest that these materials could be good candidates for the fabrication of efficient blue and green light-emitting diodes.

  5. Synthesis of TiO2 nanocoral structures in ever-changing aqueous reaction systems.

    PubMed

    Soejima, Tetsuro; Jin, Ren-Hua; Terayama, Yuki; Takahara, Atsushi; Shiraishi, Takamasa; Ito, Seishiro; Kimizuka, Nobuo

    2012-02-01

    A far-from-equilibrium strategy is developed to synthesize coral-like nanostructures of TiO(2) on a variety of surfaces. TiO(2) nanocoral structures consist of anatase base film and rutile nanowire layers, and they are continuously formed on substrates immersed in aqueous TiOSO(4)-H(2)O(2). The sequential deposition of TiO(2) starts with hydrolysis and condensation reactions of titanium peroxocomplexes in the aqueous phase, resulting in deposition of amorphous film. The film serves as adhesive interface on which succeeding growth of rutile nanowires to occur. This initial deposition reaction is accompanied by shift in pH of the reaction media, which is favorable condition for the growth of rutile nanocrystals. During the growth of rutile nanocoral layers, the amorphous base films are transformed to anatase phase. These sequential deposition reactions occur at temperatures as low as 80 °C, and the mild synthetic condition allows the use of a wide range of substrates such as ITO (indium tin oxide), glass, and even organic polymer films. The thickness of nanocoral layer is controllable by repeating the growth reaction of rutile nanocorals. TiO(2) nanocorals show photocatalytic activity as demonstrated by site-specific reduction of Ag(I) ions, which proceeds preferentially on the rutile nanowire layer. The rutile nanowire layer also shows photocatalytic decomposition of acetaldehyde, which is promoted upon increase of the thickness of the nanowire layer. The use of temporally transforming reaction media allows the formation of biphasic TiO(2) nanocoral structures, and the concept of nonequilibrium synthetic approach would be widely applicable to developing structurally graded inorganic nanointerfaces. PMID:22214471

  6. Nitridation of chromium powder in ammonia atmosphere

    NASA Astrophysics Data System (ADS)

    Li, Ling; Zhen, Qiang; Li, Rong

    2015-03-01

    CrN powder was synthesized by nitriding Cr metal in ammonia gas flow, and its chemical reaction mechanism and nitridation process were studied. Through thermodynamic calculations, the Cr-N-O predominance diagrams were constructed for different temperatures. Chromium nitride formed at 7002-1200°C under relatively higher nitrogen and lower oxygen partial pressures. Phases in the products were then investigated using X-ray diffraction (XRD), and the Cr2N content varied with reaction temperature and holding time. The results indicate that the Cr metal powder nitridation process can be explained by a diffusion model. Further, Cr2N formed as an intermediate product because of an incomplete reaction, which was observed by high-resolution transmission electron microscopy (HRTEM). After nitriding at 1000°C for 20 h, CrN powder with an average grain size of 63 nm was obtained, and the obtained sample was analyzed by using a scanning electron microscope (SEM).

  7. Synthesis of antitumor-active betulinic acid-derived hydroxypropargylamines by copper-catalyzend mannich reactions.

    PubMed

    Csuk, René; Nitsche, Christoph; Sczepek, Ronny; Schwarz, Stefan; Siewert, Bianka

    2013-03-01

    Several novel betulin derivates were prepared using Mannich reactions as a key step. Starting from 3-ethynyl-3-hydroxy-lup-20(29)-ene derivatives, copper-catalyzed Mannich reactions yielded hydroxypropargyl ammonium hydrochlorides or their corresponding methiodides. All compounds were screened in a sulforhodamine B assay for their antitumor activity using a panel of 9 human cancer cell lines. Some of these compounds showed significant cytotoxicity; they act by triggering apoptotic cell death as shown by additional acridine orange/propidium iodide assays, Trypan blue tests, DNA laddering experiments, and investigations of the cell cycle. PMID:23404652

  8. Stereoselective Synthesis of Saturated Heterocycles via Pd-Catalyzed Alkene Carboetherification and Carboamination Reactions

    PubMed Central

    Wolfe, John P.

    2009-01-01

    The development of Pd-catalyzed carboetherification and carboamination reactions between aryl/alkenyl halides and alkenes bearing pendant heteroatoms is described. These transformations effect the stereoselective construction of useful heterocycles such as tetrahydrofurans, pyrrolidines, imidazolidin-2-ones, isoxazolidines, and piperazines. The scope, limitations, and applications of these reactions are presented, and current stereochemical models are described. The mechanism of product formation, which involves an unusual intramolecular syn-insertion of an alkene into a Pd-Heteroatom bond is also discussed in detail. PMID:19183704

  9. Highly Stereoselective Synthesis of Natural-Product-Like Hybrids by an Organocatalytic/Multicomponent Reaction Sequence.

    PubMed

    Echemendía, Radell; de La Torre, Alexander F; Monteiro, Julia L; Pila, Michel; Corrêa, Arlene G; Westermann, Bernhard; Rivera, Daniel G; Paixão, Márcio W

    2015-06-22

    In an endeavor to provide an efficient route to natural product hybrids, described herein is an efficient, highly stereoselective, one-pot process comprising an organocatalytic conjugate addition of 1,3-dicarbonyls to ?,?-unsaturated aldehydes followed by an intramolecular isocyanide-based multicomponent reaction. This approach enables the rapid assembly of complex natural product hybrids including up to four different molecular fragments, such as hydroquinolinone, chromene, piperidine, peptide, lipid, and glycoside moieties. The strategy combines the stereocontrol of organocatalysis with the diversity-generating character of multicomponent reactions, thus leading to structurally unique peptidomimetics integrating heterocyclic, lipidic, and sugar moieties. PMID:25967546

  10. Formation of Al{sub 2}O{sub 3}-TIB{sub 2} composites using a high temperature synthesis reaction

    SciTech Connect

    Tefft, P.; Moore, J.J.; Readey, D.W. [Colorado School of Mines, Golden, CO (United States)

    1994-12-31

    Porous Al{sub 2}O{sub 3} + TiB{sub 2} ceramics can be prepared by self-propagating high temperature synthesis (SHS). This process, also known as combustion synthesis, uses the inherent exothermicity of the reaction: 3TiO{sub 2} + 3B{sub 2}O{sub 3} + 10Al = 5Al{sub 2}O{sub 3} + 3TiB{sub 2} to form the products without additional heating after ignition. The SHS reaction generates a combustion temperature in excess of 2000{degrees}C which results in volatilization of the B{sub 2}O{sub 3} and a high Al vapor pressure. Reaction kinetics are enhanced by the formation of liquid and gaseous phases. Decreasing the combustion temperature below the melting point of Al{sub 2}O{sub 3} by adding a diluent alters the morphology of the final product.

  11. A chemical synthesis of 11-methoxy mitragynine pseudoindoxyl featuring the interrupted Ugi reaction.

    PubMed

    Kim, Jimin; Schneekloth, John S; Sorensen, Erik J

    2012-09-01

    A synthesis of 11-methoxy mitragynine pseudoindoxyl, a new member of the mitragynine class of opioid agonists, from a derivative of the Geissman-Waiss lactone is described. An internal attack of an electron-rich aromatic ring on an electrophilic nitrilium ion and a late-stage construction of the functionalized piperidine ring by the method of reductive cyclization are the pivotal transformations; both ring annulations proceed in a highly diastereoselective fashion. The construction of substituted indoxyl frameworks by the interrupted Ugi method offers an attractive alternative to the strategy of oxidatively rearranging indoles. PMID:23878716

  12. A chemical synthesis of 11-methoxy mitragynine pseudoindoxyl featuring the interrupted Ugi reaction

    PubMed Central

    Kim, Jimin; Schneekloth, John S.

    2013-01-01

    A synthesis of 11-methoxy mitragynine pseudoindoxyl, a new member of the mitragynine class of opioid agonists, from a derivative of the Geissman-Waiss lactone is described. An internal attack of an electron-rich aromatic ring on an electrophilic nitrilium ion and a late-stage construction of the functionalized piperidine ring by the method of reductive cyclization are the pivotal transformations; both ring annulations proceed in a highly diastereoselective fashion. The construction of substituted indoxyl frameworks by the interrupted Ugi method offers an attractive alternative to the strategy of oxidatively rearranging indoles. PMID:23878716

  13. Ammonia Emissions from Dairy Production Systems in Wisconsin

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ammonia (NH3) gas is reactive and is the major basic gas that neutralizes atmospheric acid gases produced from combustion of fossil fuels. This reaction produces an aerosol that is a component of atmospheric haze and is implicated in nitrogen (N) deposition and as a potential human health hazard. T...

  14. New pathways for ammonia conversion in soil and aquatic systems

    Microsoft Academic Search

    Mike S. M. Jetten

    2001-01-01

    Ammonia conversion processes are essential for most soil and aquatic systems. Under natural conditions, the many possible reactions are difficult to analyze. For example, nitrification and denitrification have long been regarded as separate phenomena performed by different groups of bacteria in segregated areas of soils, sediments or aquatic systems sequentially in time. It has now been established that strict segregation

  15. Production of Ni3Ti-TiC x intermetallic-ceramic composites employing combustion synthesis reactions

    NASA Astrophysics Data System (ADS)

    Burkes, Douglas E.; Gottoli, Guglielmo; Moore, John J.; Yi, Hu Chun

    2006-03-01

    Combustion synthesis (CS) of nickel, titanium, and carbon (graphite) reactant particles can result in NiTi-TiC (stoichiometric) or Ni3Ti-TiC x (nonstoichiometric) composites. Since NiTi exhibits both superelasticity and shape memory properties while Ni3Ti does not, it is important to understand the SHS reaction conditions under which each of these composite systems may be synthesized. The stoichiometry of TiC x , for which 0.3? x?0.5, has an important controlling effect on the formation of either Ni3Ti or NiTi; i.e., formation of TiC0.7 results in a depletion of titanium and formation of Ni3Ti. This deficiency should be considered when developing the SHS reaction. This article examines the SHS conditions under which Ni3Ti-TiC x composites are produced. Ignition, combustion and microstructure characteristics of nickel, titanium, and carbon (graphite) particles were investigated as a function of initial relative density and thermophysical properties of the reactant mixture. Combination of the thermophysical properties and burning velocities controlled TiC x particle size, yielding a dependence of particle size on cooling rate. Theoretical calculations were performed and are in good agreement with the experimental data presented.

  16. Synthesis of Polycyclic Nitrogen Heterocycles via Cascade Pd-Catalyzed Alkene Carboamination/Diels-Alder Reactions.

    PubMed

    White, Derick R; Wolfe, John P

    2015-05-15

    Cascade Pd-catalyzed alkene carboamination/Diels-Alder reactions between bromodienes and amines bearing two pendant alkenes are described. These transformations generate 4 bonds, 3 rings, and 3-5 stereocenters to afford polycyclic nitrogen heterocycles with high diastereoselectivity. PMID:25946563

  17. Diastereoselective synthesis of ?-lactones through reaction of enediolates with ?,?-unsaturated sulfoxonium salts.

    PubMed

    Peraino, Nicholas J; Wheeler, Kraig A; Kerrigan, Nessan J

    2015-04-01

    Studies of the reaction of lithium enediolates with ?,?-unsaturated sulfoxonium salts are described. ?-Lactones were formed in very good to excellent yields (82% ? 99% for 11 examples) and with very good to excellent diastereoselectivity (dr >90:10 for 10 examples), favoring the trans-diastereomer. PMID:25783172

  18. Synthesis of naphthalene amino esters by the Blaise reaction of o-alkynylarenenitriles.

    PubMed

    Sakthivel, Karuppusamy; Srinivasan, Kannupal

    2014-04-01

    The action of a Reformatsky reagent on o-alkynylarenenitriles provides a convenient access to naphthalene amino esters via tandem 6-endo-dig carbannulation of in situ generated Blaise reaction intermediates. The products are formed in moderate to good yields with high chemo- and regioselectivity. PMID:24605780

  19. Microwave-Assisted Organic Synthesis and Transformations using Benign Reaction Media

    EPA Science Inventory

    The nonclassical heating technique using microwaves, termed as 'Bunsen burner of the 21st century, is rapidly becoming popular and is dramatically reducing the reaction times. The significant outcomes of microwave (MW)-assisted green chemistry endeavors are summarized that have r...

  20. Synthesis of biaryls via AlCl3 catalyzed domino reaction involving cyclization, dehydration, and oxidation.

    PubMed

    Narender, Tadigoppula; Sarkar, Satinath; Rajendar, Kandikonda; Tiwari, Sriniwas

    2011-12-01

    A new chemical access has been developed to synthesize biaryls from substituted acetophenones, phenylacetones, dihydrochalcone, and 2-acetylnaphthalene in reasonably good yields at room temperature via a domino reaction sequence of AlCl(3) catalyzed cyclization, dehydration, and then oxidation. PMID:22040063