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1

Ammonia synthesis  

Microsoft Academic Search

In a process for producing ammonia in a synthesis loop in which fresh synthesis gas containing hydrogen, nitrogen and, lesser amounts of argon and methane is combined with a hydrogen enriched recycle gas to provide combined synthesis gas, the combined synthesis is introduced to and reacted over ammonia synthesis catalyst under synthesis conditions to provide converted gas containing ammonia, hydrogen,

B. G. Mandelik; J. R. Cassata; P. J. S. Katy; C. P. Van Dijk

1986-01-01

2

Supplemental ammonia synthesis  

Microsoft Academic Search

In a process for producing ammonia in a synthesis loop fresh ammonia synthesis gas containing hydrogen, nitrogen, and lesser amounts of argon and methane is combined with a recycle gas to provide a combined synthesis gas. A portion of the combined synthesis gas is reacted over ammonia synthesis catalyst containing iron to provide a first converted gas having an ammonia

G. S. B. Katy; J. R. LeBlanc; J. M. Lee; H. P. Leftin; P. J. S. Katy; C. P. Van Dijk

1986-01-01

3

Reversibility of the Tryptophanase Reaction: Synthesis of Tryptophan from Indole, Pyruvate, and Ammonia  

PubMed Central

Degradation of tryptophan to indole, pyruvate, and ammonia by tryptophanase (EC 4....) from Escherichia coli, previously thought to be an irreversible reaction, is readily reversible at high concentrations of pyruvate and ammonia. Tryptophan and certain of its analogues, e.g., 5-hydroxytryptophan, can be synthesized by this reaction from pyruvate, ammonia, and indole or an appropriate derivative at maximum velocities approaching those of the degradative reactions. Concentrations of ammonia required for the synthetic reactions produce specific changes in the spectrum of tryptophanase that differ from those produced by K+ and indicate that ammonia interacts with bound pyridoxal 5?-phosphate to form an imine. Kinetic results indicate that pyruvate is the second substrate bound, hence indole must be the third. These results favor a modified mechanism for the multitude of tryptophanase-catalyzed reactions in which ?-aminoacrylate, which functions as a common enzyme-bound intermediate in both synthetic and degradative reactions, is not released into the medium during the latter reactions, but is degraded to pyruvate and ammonia by sequential reversible steps via enzyme-bound intermediates. PMID:4556453

Watanabe, Takehiko; Snell, Esmond E.

1972-01-01

4

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

E-print Network

reforming ........................................................................................ 12 2.1.5 Water gas shift reaction .............................................................................. 13 2.2 Plasma physics... and thus lower the required reaction temperatures and avoid unwanted by-product formation.[9] 2.2 Plasma physics Plasma is described as the fourth state of matter. Unlike solid, liquid and gas, plasma usually character with high energy, chemical...

Ming, Pingjia

2014-06-05

5

The Ammonia Synthesis Reaction: An Exception to the Le Chatelier Principle and Effects of Nonideality  

ERIC Educational Resources Information Center

Le Chatelier's principle states that the further addition of a particular component will cause the reaction to shift in the direction that reduces the total number of moles of the system. However, the addition of one reactant [N[subscript 2

Uline, Mark J.; Corti, David S.

2006-01-01

6

Energetic analysis of ammonia synthesis unit  

Microsoft Academic Search

In order to identify possible reserves in the ammonia synthesis, an exergetic analysis was made of the stages of nitrogen-hydrogen compression, ammonia synthesis and separation at an operating plant. The analysis showed that the unit has a relatively low degree of thermodynamic completeness: the target exergetic efficiency of the stages studied is 0.26. The margins for improvement are not great.

G. A. Britina; I. L. Leites; S. A. Mikhailova; M. B. Aizenbud

1977-01-01

7

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

Microsoft Academic Search

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

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

1982-01-01

8

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

NASA Technical Reports Server (NTRS)

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.

Weber, Arthur L.

2006-01-01

9

Passivation of iron catalysts for ammonia synthesis  

SciTech Connect

At the present time, the practical interest in passivation of iron ammonia synthesis catalyst results from production of catalyst in reduced form and also from the need for passivation of catalysts during temporary shutdowns of synthesis columns in order to maintain the activity of the catalyst. The spent catalyst also must be passivated prior to offloading, in order to avoid combustion upon contact with air. In all of these cases, the need for passivation of reduced ammonia synthesis catalysts is connected with the pyrophoric character of the iron. It has been established that the pyrophoric character is eliminated after an oxide layer of a specific thickness has been applied to the surface of the iron - i.e., after passivation. To resolve the problems of recovering spent catalyst with controllable depth of oxidation, tests were carried out on low-temperature oxidation of catalysts in the 50-200/sup 0/C temperature interval. This article presents the results of a study of the oxidation of iron on a sample of reduced magnetite and on samples of various industrial ammonia synthesis catalysts (types SA-1, SA-1V and SAMV-5) at 50, 100, 150 and 200/sup 0/C with oxygen from mixtures of oxygen and helium (oxygen concentrations 0.1, 1.0 and 3.0 vol%) under dynamic conditions. 9 references, 3 figures, 4 tables.

Chesnokova, R.V.; Minaev, D.M.; Vasilevich, A.A.; Kuznetsov, L.D.; Alekseev, A.M.; Mishchenko, Sh.Sh.

1984-11-01

10

Cryogenic production of ammonia synthesis gas  

Microsoft Academic Search

An improved cryogenic separation process is provided for forming a substantially CO-free and lower hydrocarbon-free hydrogen-rich gas, suitable for use in producing an ammonia synthesis gas, from a hydrogen-containing gas stream also containing carbon monoxide and lower hydrocarbon impurities, wherein the hydrogen containing gas is subject to a two-stage autorefrigerated cryogenic flash treatment to remove concentrated methane-containing and carbon monoxide-containing

Traficante

1985-01-01

11

Ammonia synthesis enhancement through heat-mass-exchange  

Microsoft Academic Search

The HME Ammonia Synthesis Enhancement is a simple process modification enhancing synthesis productivity by reducing energy consumption and\\/or increasing plant capacity as compared to conventional alternatives. In this paper, it is presented as an attractive alternative to low temperature ammonia separation in low pressure plants. Some HME performance sensitivities and their implications on the design of a unit are studied.

Lavie

1986-01-01

12

Ammonia synthesis enhancement through heat-mass-exchange  

Microsoft Academic Search

The HME Ammonia Synthesis Enhancement is a simple process modification enhancing synthesis productivity by reducing energy consumption and\\/or increasing plant capacity as compared to conventional alternatives. In this paper, it is presented as an attractive alternative to low temperature ammonia separation in low pressure plants. Some HME performance sensitivities and their implications on the design of a unit are studied.

Ram Lavie

1987-01-01

13

Large-scale and facile preparation of pure ammonia borane through displacement reactions.  

PubMed

Ammonia borane (AB) is the most widely studied hydride for hydrogen storage in addition to being a useful reducing agent. Attempts to synthesize pure AB through simple displacement reactions date back to the 1960s; but have been thwarted by the formation of the diammoniate of diborane (DADB), an ionic byproduct. Based on our recent characterization of the formation mechanism of DADB, we have developed a large-scale synthesis of pure AB by both increasing the basicity of the Lewis base of the borane carrier and using a nonpolar solvent to limit the formation of an intermediate, the ammonia diborane (AaDB). Conditions were optimized for the preparation of pure AB by two displacement reactions, either ammonia with dimethylsulfide borane or ammonia with dimethylaniline borane in toluene at room temperature. These procedures are also suitable for preparation of other amine boranes which had the same problem of forming ionic byproducts during displacement reactions. PMID:22886928

Chen, Xuenian; Bao, Xiaoguang; Billet, Beau; Shore, Sheldon G; Zhao, Ji-Cheng

2012-09-17

14

Process for treating gases in the ammonia synthesis. [separation and dehydration of gases leaving synthesis reactor  

Microsoft Academic Search

In the synthesis of ammonia, a process is disclosed for treating the gases flowing from the synthesis reactor wherein those gases flow through a film absorber countercurrent to a cooled aqueous film to extract ammonia which is withdrawn as a strong solution from the absorber and scrubbed gases are combined for recycle with a stream of fresh feed which is

Guadalupi

1977-01-01

15

Process for synthesis of ammonia borane for bulk hydrogen storage  

SciTech Connect

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.

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

16

Recovery of hydrogen from ammonia synthesis purge gas  

Microsoft Academic Search

In a process for the recovery of hydrogen from compressed purge gas withdrawn from a recyling gas stream of an ammonia synthesis wherein the hydrogen is separated from the purge gas by partial condensation at cryogenic temperatures, refrigeration is provided by expanding and evaporating the condensate so formed, and the partial pressure of the expanded condensate is lowered by withdrawing

A. A. Haslam; W. H. Isalski; T. R. Tomlinson

1983-01-01

17

Production of ammonia synthesis gas from solid carbonaceous fuels  

Microsoft Academic Search

This is a continuous process for producing ammonia synthesis gas and includes the partial oxidation of particles of solid carboniferous fuels entrained in nitrogen. In the process, air is separated into high pressure nitrogen and substantially pure oxygen. A first stream of said nitrogen is used as a safe pneumatic vehicle in a grinding and transport operation which introduces ground,

F. E. Guptill; J. R. Muenger

1980-01-01

18

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

NASA Technical Reports Server (NTRS)

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.

Summers, D. P.

1999-01-01

19

Distribution of ammonia\\/aflatoxin reaction products in corn following exposure to ammonia decontamination procedure  

Microsoft Academic Search

The distribution of aflatoxin decontamination reaction products in corn following ammonia decontamination treatment was determined. The parameters of the ammoniation procedure used to decontaminate aflatoxin contaminated corn were 2% NH3, 16% moisture, 55 psi, 40–45°C, and 60 min duration. Uniformly ring?labelled C?afiatoxin B1was added to corn (1.0 ?Ci\\/kg) containing 7500 ?g naturally?incurred aflatoxin B1(AFB1)\\/kg. Aflatoxin levels were reduced by ca

Amaury J. Martinez; Cong Ying Weng; Douglas L. Park

1994-01-01

20

Synthesis of nanostructured materials in supercritical ammonia: nitrides, metals and oxides Desmoulins-Krawiec S., Aymonier C., Loppinet-Serani A., Weill F., Grosse S., Etourneau J., Cansell F.  

E-print Network

Synthesis of nanostructured materials in supercritical ammonia: nitrides, metals and oxides3N), metal (Cu) and oxides (Al2O3, TiO2, Ga2O3) by using supercritical ammonia in the reaction in a supercritical ammonia­methanol mixture at a range of temperatures between 170 and 290 °C at about 16 MPa

Boyer, Edmond

21

Theoretical investigation of the reaction between carbonyl oxides and ammonia.  

PubMed

The gas-phase reaction between carbonyl oxides and ammonia is investigated by quantum mechanical calculations. The density functional method B3LYP with the basis set 6-311++G(2d,2p) was employed for the geometry and energy optimization of the stationary points along the reaction path. The energies have been refined by CCSD(T) with various basis sets and Gaussian-3 level of theory. The reaction mechanisms are studied for three different carbonyl oxides, H2COO (methyl carbonyl oxide), CH3HCOO (ethyl carbonyl oxide), and (CH3)2COO (acetone carbonyl oxide). First, a prereactive complex is formed, where a hydrogen bond is formed between ammonia and the terminal oxygen atom in the COO moiety. Next, a structural rearrangement occurs, leading to the formation of a chemical bond between the nitrogen atom and the carbon in the COO moiety as well as a transfer of the hydrogen atom from nitrogen atom to the terminal oxygen atom in the COO moiety. The newly formed molecule is a hydroperoxide amine. All the studied reactions are exothermic. The estimated reaction rates range from 1.8 x 10(-13) to 6.9 x 10(-14) and to 5.1 x 10(-18) cm3 molecule(-1) s(-1) for H2COO, CH3HCOO, and (CH3)2COO, respectively. This shows that the investigated process are important in locations with intensive farming. PMID:19711931

Jørgensen, Solvejg; Gross, Allan

2009-09-24

22

Phenylalanine ammonia lyase catalyzed synthesis of amino acids by an MIO-cofactor independent pathway.  

PubMed

Phenylalanine ammonia lyases (PALs) belong to a family of 4-methylideneimidazole-5-one (MIO) cofactor dependent enzymes which are responsible for the conversion of L-phenylalanine into trans-cinnamic acid in eukaryotic and prokaryotic organisms. Under conditions of high ammonia concentration, this deamination reaction is reversible and hence there is considerable interest in the development of PALs as biocatalysts for the enantioselective synthesis of non-natural amino acids. Herein the discovery of a previously unobserved competing MIO-independent reaction pathway, which proceeds in a non-stereoselective manner and results in the generation of both L- and D-phenylalanine derivatives, is described. The mechanism of the MIO-independent pathway is explored through isotopic-labeling studies and mutagenesis of key active-site residues. The results obtained are consistent with amino acid deamination occurring by a stepwise E1 cB elimination mechanism. PMID:24692092

Lovelock, Sarah L; Lloyd, Richard C; Turner, Nicholas J

2014-04-25

23

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

E-print Network

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

Sadoway, Donald Robert

24

Modification of active carbon and zeolite as ammonia separation materials for a new de-NO x process with ammonia on-site synthesis  

Microsoft Academic Search

Ammonia adsorption and desorption behavior of surface treated active carbon (AC) and ion-exchanged Y zeolite, as ammonia separation and storage materials for a new de-NOx process with ammonia on-site synthesis, were studied. Surface oxidized AC adsorbed more ammonia than non-treated AC due to ammonium ion formation. These materials were found to increase weak adsorption of ammonia and to be useful

Chun Yi Liu; Ken-Ichi Aika

2002-01-01

25

Synthesis of ammonia directly from air and water at ambient temperature and pressure  

PubMed Central

The N?N bond (225?kcal mol?1) in dinitrogen is one of the strongest bonds in chemistry therefore artificial synthesis of ammonia under mild conditions is a significant challenge. Based on current knowledge, only bacteria and some plants can synthesise ammonia from air and water at ambient temperature and pressure. Here, for the first time, we report artificial ammonia synthesis bypassing N2 separation and H2 production stages. A maximum ammonia production rate of 1.14 × 10?5?mol m?2 s?1 has been achieved when a voltage of 1.6?V was applied. Potentially this can provide an alternative route for the mass production of the basic chemical ammonia under mild conditions. Considering climate change and the depletion of fossil fuels used for synthesis of ammonia by conventional methods, this is a renewable and sustainable chemical synthesis process for future. PMID:23362454

Lan, Rong; Irvine, John T. S.; Tao, Shanwen

2013-01-01

26

Synthesis of ammonia directly from air and water at ambient temperature and pressure  

NASA Astrophysics Data System (ADS)

The N?N bond (225 kcal mol-1) in dinitrogen is one of the strongest bonds in chemistry therefore artificial synthesis of ammonia under mild conditions is a significant challenge. Based on current knowledge, only bacteria and some plants can synthesise ammonia from air and water at ambient temperature and pressure. Here, for the first time, we report artificial ammonia synthesis bypassing N2 separation and H2 production stages. A maximum ammonia production rate of 1.14 × 10-5 mol m-2 s-1 has been achieved when a voltage of 1.6 V was applied. Potentially this can provide an alternative route for the mass production of the basic chemical ammonia under mild conditions. Considering climate change and the depletion of fossil fuels used for synthesis of ammonia by conventional methods, this is a renewable and sustainable chemical synthesis process for future.

Lan, Rong; Irvine, John T. S.; Tao, Shanwen

2013-01-01

27

Theoretical study of the ammonia-hypochlorous acid reaction mechanism.  

PubMed

A mechanism for the oxidation of ammonia by hypochlorous acid to form nitrogen gas has been developed at the B3LYP/6-31G(d,p) level of theory using the Gaussian 03 software package. The formation of NH(2)Cl, NHCl(2), and NCl(3) was studied in the gas phase, with explicit water molecules included to examine the transition state energy in aqueous solution. The inclusion of explicit water molecules in the transition state dramatically reduced the reaction barrier in reactions involving transfer of a hydrogen atom between molecules, effects that were not taken into account through use of a solvation model alone. Three mechanisms were identified for the decomposition of chloramine species to form N(2), involving the combination of two chloramine species to form hydrazine, dichlorohydrazine and tetrachlorohydrazine intermediates. The highest barrier in each pathway was found to be the formation of the hydrazine derivative. PMID:20112901

Rayson, Mark S; Altarawneh, Mohammednoor; Mackie, John C; Kennedy, Eric M; Dlugogorski, Bogdan Z

2010-02-25

28

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...

29

Reaction synthesis of intermetallics  

SciTech Connect

Exothermicity associated with the synthesis of aluminides was utilized to obtain nickel, iron, and cobalt aluminides. Combustion synthesis, extrusion, and hot pressing were utilized to obtain intermetallics and their composites. Extrusion conditions, reduction ratios, and hot-pressing conditions of the intermetallics and their composites are discussed.

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

1994-12-31

30

Experimental study of separation of ammonia synthesis vent gas by hydrate formation  

Microsoft Academic Search

Termodynamic data on methane hydrate formation in the presence of ammonia are very important for upgrading of ammonia synthesis\\u000a vent gas using hydrate formation. This paper is focused on the formation conditions of methane hydrate in the presence of\\u000a ammonia and the effects of gas-liquid ratio and temperature on the separation of vent gas by hydrate formation. Equilibrium\\u000a data for

Taibin Dong; Leiyan Wang; Aixian Liu; Xuqiang Guo; Qinglan Ma; Guowen Li; Qiang Sun

2009-01-01

31

Reactions of diborane with ammonia and ammonia borane: catalytic effects for multiple pathways for hydrogen release.  

PubMed

High-level electronic structure calculations have been used to construct portions of the potential energy surfaces related to the reaction of diborane with ammonia and ammonia borane (B2H6 + NH3 and B2H6 + BH3NH3)to probe the molecular mechanism of H2 release. Geometries of stationary points were optimized at the MP2/aug-cc-pVTZ level. Total energies were computed at the coupled-cluster CCSD(T) theory level with the correlation-consistent basis sets. The results show a wide range of reaction pathways for H2 elimination. The initial interaction of B2H6 + NH3 leads to a weak preassociation complex, from which a B-H-B bridge bond is broken giving rise to a more stable H3BHBH2NH3 adduct. This intermediate, which is also formed from BH3NH3 + BH3, is connected with at least six transition states for H2 release with energies 18-93 kal/mol above the separated reactants. The lowest-lying transition state is a six-member cycle, in which BH3exerts a bifunctional catalytic effect accelerating H2 generation within a B-H-H-N framework. Diborane also induces a catalytic effect for H2 elimination from BH3NH3 via a three-step pathway with cyclic transition states. Following conformational changes, the rate-determining transition state for H2 release is approximately 27 kcal/mol above the B2H6 + BH3NH3 reactants, as compared with an energy barrier of approximately 37 kcal/mol for H2 release from BH3NH3. The behavior of two separated BH3 molecules is more complex and involves multiple reaction pathways. Channels from diborane or borane initially converge to a complex comprising the H3BHBH2NH3adduct plus BH3. The interaction of free BH3 with the BH3 moiety of BH3NH3 via a six-member transition state with diborane type of bonding leads to a lower-energy transition state. The corresponding energy barrier is approximately 8 kcal/mol, relative to the reference point H3BHBH2NH3 adduct + BH3. These transition states are 27-36 kcal/mol above BH3NH3 + B2H6, but 1-9 kcal/mol below the separated reactants BH3NH3 + 2 BH3. Upon chemical activation of B2H6 by forming 2 BH3, there should be sufficient internal energy to undergo spontaneous H2 release. Proceeding in the opposite direction, the H2 regeneration of the products of the B2H6 + BH3NH3reaction should be a feasible process under mild thermal conditions. PMID:18767778

Nguyen, Vinh Son; Matus, Myrna H; Nguyen, Minh Tho; Dixon, David A

2008-10-01

32

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

Microsoft Academic Search

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

M. R. Rahimpour; A. Asgari

2008-01-01

33

Nitropyridines: Synthesis and reactions  

Microsoft Academic Search

Reaction of pyridine and substituted pyridines with N2O5 in an organic solvent gives the N-nitropyridinium ion. When this is reacted with SO2\\/HSO3 - in water, 3-nitropyri- dine is obtained (77 % yield). With substituted pyridines, the method gives good yields for 4-substituted and moderate yields for 3-substituted pyridines. The reaction mechanism is not an electrophilic aromatic substitution, but one in

Jan M. Bakke

2003-01-01

34

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

DOEpatents

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.

Davis, Benjamin L; Rekken, Brian D

2014-04-01

35

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

SciTech Connect

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.

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

1984-07-01

36

Photoinduced catalytic synthesis of biologically important metabolites from formaldehyde and ammonia under plausible "prebiotic" conditions  

NASA Astrophysics Data System (ADS)

The article analyzes new and previously reported data on several catalytic and photochemical processes yielding biologically important molecules. UV-irradiation of formaldehyde aqueous solution yields acetaldehyde, glyoxal, glycolaldehyde and glyceraldehyde, which can serve as precursors of more complex biochemically relevant compounds. Photolysis of aqueous solution of acetaldehyde and ammonium nitrate results in formation of alanine and pyruvic acid. Dehydration of glyceraldehyde catalyzed by zeolite HZSM-5-17 yields pyruvaldehyde. Monosaccharides are formed in the course of the phosphate-catalyzed aldol condensation reactions of glycolaldehyde, glyceraldehyde and formaldehyde. The possibility of the direct synthesis of tetroses, keto- and aldo-pentoses from pure formaldehyde due to the combination of the photochemical production of glycolahyde and phosphate-catalyzed carbohydrate chain growth is demonstrated. Erythrulose and 3-pentulose are the main products of such combined synthesis with selectivity up to 10%. Biologically relevant aldotetroses, aldo- and ketopentoses are more resistant to the photochemical destruction owing to the stabilization in hemiacetal cyclic forms. They are formed as products of isomerization of erythrulose and 3-pentulose. The conjugation of the concerned reactions results in a plausible route to the formation of sugars, amino and organic acids from formaldehyde and ammonia under presumed 'prebiotic' conditions.

Delidovich, I. V.; Taran, O. P.; Simonov, A. N.; Matvienko, L. G.; Parmon, V. N.

2011-08-01

37

Control of Nitrogen Dioxide in Stack Emission by Reaction with Ammonia  

NASA Technical Reports Server (NTRS)

The development of an acid base gas-phase reaction system which utilizes anhydrous ammonia as the reactant to remove nitrogen dioxide from hydrazine-nitrogen tetroxide rocket combustion exhaust is reported. This reaction reduced NO2 levels in exhaust emissions so that the resulting stack emission is completely white instead of the earlier observed typical reddish-brown coloration. Preliminary analyses indicate the importance of reaction time and ammonia concentration on removal efficiency and elimination of the health hazard to individuals with respiratory problems.

Metzler, A. J.; Stevenson, E. F.

1970-01-01

38

Reaction synthesis of heat-resistant materials  

SciTech Connect

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.

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

1995-12-31

39

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

PubMed

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

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

2014-08-01

40

Ammonia purge gas conversion  

Microsoft Academic Search

In a process for producing ammonia in a first synthesis loop wherein fresh ammonia synthesis gas containing hydrogen, nitrogen, and lesser amounts of argon and methane is combined with a first recycle gas to provide a first combined synthesis gas, a portion of the first combined synthesis gas is reacted over ammonia synthesis catalyst containing iron to provide a first

C. P. Van Dijk; A. Solbakken; B. G. Mandelik

1986-01-01

41

Ammonia Inhibits Long-term Potentiation via Neurosteroid Synthesis in Hippocampal Pyramidal Neurons  

PubMed Central

Neurosteroids are a class of endogenous steroids synthesized in the brain that are believed to be involved in the pathogenesis of neuropsychiatric disorders and memory impairment. Ammonia impairs long-term potentiation (LTP), a synaptic model of learning, in the hippocampus, a brain region involved in memory acquisition. Although mechanisms underlying ammonia-mediated LTP inhibition are not fully understood, we previously found that activation of N-methyl-D-aspartate receptors (NMDARs) is important. Based on this, we hypothesize that metabolic stressors, including hyperammonemia, promote untimely NMDAR activation and result in neural adaptations that include the synthesis of allopregnanolone (alloP) and other ?-aminobutyric acid (GABA)-potentiating neurosteroids that dampen neuronal activity and impair LTP and memory formation. Using an antibody against 5?-reduced neurosteroids, we found that 100 ?M ammonia acutely enhanced neurosteroid immunostaining in pyramidal neurons in the CA1 region of rat hippocampal slices. The enhanced staining was blocked by finasteride, a selective inhibitor of 5?-reductase, a key enzyme required for alloP synthesis. Finasteride also overcame LTP inhibition by 100 ?M ammonia, as did picrotoxin, an inhibitor of GABA-A receptors. These results indicate that GABA enhancing neurosteroids, synthesized locally within pyramidal neurons, contribute significantly to ammonia-mediated synaptic dysfunction. These results suggest that manipulation of neurosteroid synthesis could provide a strategy to improve cognitive function in individuals with hyperammonemia. PMID:23276672

Izumi, Yukitoshi; Svrakic, Neda; O’Dell, Kazuko; Zorumski, Charles F.

2013-01-01

42

Carboxymethylguargum-silver nanocomposite: green synthesis, characterization and an optical sensor for ammonia detection  

NASA Astrophysics Data System (ADS)

This work describes the preparation of new carboxymethyl guar gum-silver nanocomposite (CMGG/Ag NC) by green synthesis method. For this carboxymethyl guar gum was used as a reducing agent as well as stabilizer. The silver nanoparticles obtained were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV–vis spectroscopy, Fourier transform infrared (FTIR) and energy dispersive x-ray analysis (EDX). The average size of the silver nanoparticles was found of ?6 nm. Thus, the obtained CMGG/AgNPs NC was examined for optical sensing property for detection of ammonia in aqueous medium. The response time and the detection limit of ammonia in aqueous solution were detected at room temperature. It was concluded that in the future, at this room temperature optical ammonia sensor may be used for medical diagnosis and clinically for detecting low ammonia level (up to 1 ppm) in biological samples for various biomedical applications.

Pal Gupta, Anek; Verma, Devendra Kumar

2014-09-01

43

Studies on the use of supercritical ammonia for ceramic nitride synthesis and fabrication  

NASA Technical Reports Server (NTRS)

The extractability of ammonia halides (including ammonium thiocyanate) formed as byproducts from the synthesis of Si(NH)2 via ammonolysis of the corresponding silicon tetrahalides using supercritical NH3 as the extraction medium was investigated. It was found that the NH4SCN byproduct of ammonolysis of Si(SCN)4 can be almost completely extracted from the insoluble Si(NH)2 forming a promising system for the synthesis of pure Si(NH)2, one of the best precursors for Si3N4. In addition it was found that Si3N4, AlN, BN, and Si(NH)2 are insoluble in SC ammonia. Also discussed are design considerations for a supercritical ammonia extraction unit.

Cornell, Linda; Lin, Y. C.; Philipp, Warren H.

1990-01-01

44

Kinetic resolution and stereoselective synthesis of 3-substituted aspartic acids by using engineered methylaspartate ammonia lyases.  

PubMed

Enzymatic amino acid synthesis: Kinetic resolution and asymmetric synthesis of various valuable 3-substituted aspartic acids, which were obtained in fair to good yields with diastereomeric ratio values of up to >98:2 and enantiomeric excess values of up to >99?%, by using engineered methylaspartate ammonia lyases are described. These biocatalytic methodologies for the selective preparation of aspartic acid derivatives appear to be attractive alternatives for existing chemical methods. PMID:23852946

Raj, Hans; Szymanski, Wiktor; de Villiers, Jandré; Puthan Veetil, Vinod; Quax, Wim J; Shimamoto, Keiko; Janssen, Dick B; Feringa, Ben L; Poelarends, Gerrit J

2013-08-19

45

Production of Hydrogen and Ammonia Synthesis Gas by Pressure Swing Adsorption  

Microsoft Academic Search

Two new pressure swing adsorption processes for the simultaneous production of hydrogen or ammonia synthesis gas and carbon dioxide from a reformer off-gas feed are described. Both products are produced at high purity and recovery. Performance data for these processes are reported.

Shivaji Sircar

1990-01-01

46

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

ERIC Educational Resources Information Center

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.

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

2007-01-01

47

Plasmon-induced ammonia synthesis through nitrogen photofixation with visible light irradiation.  

PubMed

We have successfully developed a plasmon-induced technique for ammonia synthesis that responds to visible light through a strontium titanate (SrTiO3) photoelectrode loaded with gold (Au) nanoparticles. The photoelectrochemical reaction cell was divided into two chambers to separate the oxidized (anodic side) and reduced (cathodic side) products. To promote NH3 formation, a chemical bias was applied by regulating the pH?value of these compartments, and ethanol was added to the anodic chamber as a sacrificial donor. The quantity of NH3 formed at the ruthenium surface, which was used as a co-catalyst for SrTiO3, increases linearly as a function of time under irradiation with visible light at wavelengths longer than 550?nm. The NH3 formation action spectrum approximately corresponds to the plasmon resonance spectrum. We deduced that plasmon-induced charge separation at the Au/SrTiO3 interface promotes oxidation at the anodic chamber and subsequent nitrogen reduction on the cathodic side. PMID:25045027

Oshikiri, Tomoya; Ueno, Kosei; Misawa, Hiroaki

2014-09-01

48

Failure analysis of the brittle fracture of a thick-walled 20 steel pipe in an ammonia synthesis unit  

Microsoft Academic Search

In this paper, the analysis of a brittle fracture explosion accident of a thick-walled 20 steel pipe, which connects the outlet of an ammonia separator and the inlet of a cold exchanger in an ammonia synthesis unit of a chemical fertilizer plant, is presented in detail. The causes and mechanism of the material degradation are investigated by analyzing chemical compositions

Haoxuan Cui; Weiqiang Wang; Aiju Li; Mengli Li; Shugen Xu; Huadong Liu

2010-01-01

49

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

SciTech Connect

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.

Bartram, Michael E.; Creighton, J. Randall

1999-05-26

50

Comparison of internal nitridation reactions in ammonia and in nitrogen  

SciTech Connect

Nine commercial high-temperature alloys were reacted with NH{sub 3} and with N{sub 2}-5% H{sub 2} at temperatures of 1000-1200{degrees}C. In all cases extensive internal nitridation developed according to parabolic kinetics. Reaction with N{sub 2} produced precipitates of Cr{sub 2}N plus, at 1000{degrees}C, some external CrN, in accordance with thermodynamic prediction. However, NH{sub 3} produced an external scale of CrN and a near-surface zone of internal CrN as well as a deeper zone of Cr{sub 2}N at 1100 and 1200{degrees}C. The CrN phase is metastable, and results from catalytic dissociation of NH{sub 3}, which produces a high effective nitrogen activity. This high activity also leads to faster internal-precipitation reactions, whereas reaction rates in nitrogen are in reasonable agreement with Wagner`s model of rate control by inwardly diffusing nitrogen at its equilibrium solubility. Precipitate morphologies are complex, reflecting the importance of the energy barrier to homogeneous nucleation.

Tjokro, K.; Young, D.J. [Univ. of New South Wales, Sydney (Australia)

1995-10-01

51

The reaction of monochloramine and hydroxylamine: implications for ammonia?oxidizing bacteria in chloraminated drinking water  

EPA Science Inventory

Drinking water chloramine use may promote ammonia?oxidizing bacteria (AOB) growth because of naturally occurring ammonia, residual ammonia remaining from chloramine formation, and ammonia released from chloramine decay and demand. A rapid chloramine residual loss is often associa...

52

Process for the production of ammonia and the corresponding synthesis gas  

Microsoft Academic Search

A process to produce ammonia from a hydrocarbon feedstock involves basically the following steps: dividing the feedstock into two fractions, subjecting the first fraction to a primary steam reforming reaction at high pressure and moderate temperature, combining the effluent from the primary reforming with the second fraction of the feedstock, and subjecting the mixture thereof to a secondary adiabatic reforming

Banquy

1981-01-01

53

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

E-print Network

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

Zare, Richard N.

54

Synthesis and application of a new fluorous-tagged ammonia equivalent.  

PubMed

A novel fluorous-tagged ammonia equivalent has been developed. It is based on a nitrogen-oxygen bond, which can be cleaved in a traceless manner by a molybdenum complex or samarium diiodide. The application in the synthesis of ureas, amides, sulfonamides, and carbamates is described. The scope of the fluorous N-O linker is exemplified by the synthesis of itopride, a drug used for the treatment of functional dyspepsia. Itopride was synthesized with the aid of fluorous purification methods and the product was isolated in good overall yield, with high purity. PMID:20333716

Nielsen, Simon D; Smith, Garrick; Begtrup, Mikael; Kristensen, Jesper L

2010-04-19

55

Liquid ammonia as a dipolar aprotic solvent for aliphatic nucleophilic substitution reactions.  

PubMed

The rate constants for the reactions of a variety of nucleophiles reacting with substituted benzyl chlorides in liquid ammonia (LNH(3)) have been determined. To fully interpret the associated linear free-energy relationships, the ionization constants of phenols ions in liquid ammonia were obtained using UV spectra. These equilibrium constants are the product of those for ion-pair formation and dissociation to the free ions, which can be separated by evaluating the effect of added ammonium ions. There is a linear relationship between the pK(a) of phenols in liquid ammonia and those in water of slope 1.68. Aminium ions exist in their unprotonated free base form in liquid ammonia and their ionization constants could not be determined by NMR. The rates of solvolysis of substituted benzyl chlorides in liquid ammonia at 25 °C show a Hammett ? of zero, having little or no dependence upon ring substituents, which is in stark contrast with the hydrolysis rates of substituted benzyl halides in water, which vary 10(7) fold. The rate of substitution of benzyl chloride by substituted phenoxide ions is first order in the concentration of the nucleophile indicative of a S(N)2 process, and the dependence of the rate constants on the pK(a) of the phenol in liquid ammonia generates a Brønsted ?(nuc) = 0.40. Contrary to the solvolysis reaction, the reaction of phenoxide ion with 4-substituted benzyl chlorides gives a Hammett ? = 1.1, excluding the 4-methoxy derivative, which shows the normal positive deviation. The second order rate constants for the substitution of benzyl chlorides by neutral and anionic amines show a single Brønsted ?(nuc) = 0.21 (based on the aqueous pK(a) of amine), but their dependence on the substituent in substituted benzyl chlorides varies with a Hammett ? of 0 for neutral amines, similar to that seen for solvolysis, whereas that for amine anions is 0.93, similar to that seen for phenoxide ion. PMID:21348532

Ji, Pengju; Atherton, John; Page, Michael I

2011-03-01

56

Surface science and catalysis. studies on the mechanism of ammonia synthesis the P. H. Emmett Award Address  

SciTech Connect

A review of recent studies on the mechanism of ammonia synthesis on iron catalyst includes ESCA and Auger spectroscopic studies of the catalyst surface and of surface species on clean single crystal and on commercial catalyst surfaces, and adsorption studies. Results show that the dissociation of adsorbed nitrogen is the rate-determining step above 300/sup 0/C, that the reaction of adsorbed atomic hydrogen and adsorbed nitrogen may become rate-limiting at lower temperatures, and that the potassium promoter transfers valence electrons to the iron, which increases the adsorption energy of molecular nitrogen, decreases the effective dissociation energy to zero, and increases the initial rate of formation of adsorbed nitrogen atoms by more than two orders of magnitude at 160/sup 0/C.

Ertl, G.

1980-01-01

57

Deuterium enrichment of ammonia produced by surface N+H/D addition reactions at low temperature  

NASA Astrophysics Data System (ADS)

The surface formation of NH3 and its deuterated isotopologues - NH2D, NHD2, and ND3 - is investigated at low temperatures through the simultaneous addition of hydrogen and deuterium atoms to nitrogen atoms in CO-rich interstellar ice analogues. The formation of all four ammonia isotopologues is only observed up to 15 K, and drops below the detection limit for higher temperatures. Differences between hydrogenation and deuteration yields result in a clear deviation from a statistical distribution in favour of deuterium enriched species. The data analysis suggests that this is due to a higher sticking probability of D atoms to the cold surface, a property that may generally apply to molecules that are formed in low temperature surface reactions. The results found here are used to interpret ammonia-deuterium fractionation as observed in pre-protostellar cores.

Fedoseev, G.; Ioppolo, S.; Linnartz, H.

2015-01-01

58

Long-term real-time monitoring catalytic synthesis of ammonia in a microreactor by VUV-lamp-based charge-transfer ionization time-of-flight mass spectrometry.  

PubMed

With respect to massive consumption of ammonia and rigorous industrial synthesis conditions, many studies have been devoted to investigating more environmentally benign catalysts for ammonia synthesis under moderate conditions. However, traditional methods for analysis of synthesized ammonia (e.g., off-line ion chromatography (IC) and chemical titration) suffer from poor sensitivity, low time resolution, and sample manipulations. In this work, charge-transfer ionization (CTI) with O2(+) as the reagent ion based on a vacuum ultraviolet (VUV) lamp in a time-of-flight mass spectrometer (CTI-TOFMS) has been applied for real-time monitoring of the ammonia synthesis in a microreactor. For the necessity of long-term stable monitoring, a self-adjustment algorithm for stabilizing O2(+) ion intensity was developed to automatically compensate the attenuation of the O2(+) ion yield in the ion source as a result of the oxidation of the photoelectric electrode and contamination on the MgF2 window of the VUV lamp. A wide linear calibration curve in the concentration range of 0.2-1000 ppmv with a correlation coefficient (R(2)) of 0.9986 was achieved, and the limit of quantification (LOQ) for NH3 was in ppbv. Microcatalytic synthesis of ammonia with three catalysts prepared by transition-metal/carbon nanotubes was tested, and the rapid changes of NH3 conversion rates with the reaction temperatures were quantitatively measured with a time resolution of 30 s. The high-time-resolution CTI-TOFMS could not only achieve the equilibrium conversion rates of NH3 rapidly but also monitor the activity variations with respect to investigated catalysts during ammonia synthesis reactions. PMID:24968116

Xie, Yuanyuan; Hua, Lei; Hou, Keyong; Chen, Ping; Zhao, Wuduo; Chen, Wendong; Ju, Bangyu; Li, Haiyang

2014-08-01

59

Process for the production of ammonia  

Microsoft Academic Search

A process for the production of ammonia, comprising the steps of: gasifying a feedstock containing carbon and a source of hydrogen with air as the only source of free oxygen, to produce a raw synthesis gas comprising nitrogen, hydrogen, carbon oxides, and methane; subjecting the raw synthesis gas to a shift conversion reaction; removing the carbon oxides from the shift

Banquy

1985-01-01

60

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

DOEpatents

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.

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

1982-01-01

61

Pericyclic reactions in organic synthesis  

E-print Network

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 ...

Robinson-Surry, Julia M. (Julia Mae)

2011-01-01

62

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

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

Zare, Richard N.

63

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

PubMed

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

Yoshikawa, Eishi; Sasaki, Atsushi; Endo, Masatoshi

2012-10-30

64

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

NASA Astrophysics Data System (ADS)

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

Flores, J. R.; Redondo, P.

65

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

PubMed

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

Montazer, Majid; Shamei, Ali; Alimohammadi, Farbod

2014-05-01

66

Novel Haloperoxidase Reaction: Synthesis of Dihalogenated Products  

PubMed Central

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

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

1983-01-01

67

Synthesis and Evaluation of Cu-SAPO-34 Catalysts for Ammonia Selective Catalytic Reduction. 1. Aqueous Solution Ion Exchange  

SciTech Connect

SAPO-34 molecular sieves are synthesized using various structure directing agents (SDAs). Cu-SAPO-34 catalysts are prepared via aqueous solution ion exchange. Catalysts are characterized with surface area/pore volume measurements, temperature programmed reduction (TPR), electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopies. Catalytic properties are examined using standard ammonia selective catalytic reduction (NH3-SCR) and ammonia oxidation reactions. During solution ion exchange, different SAPO-34 samples undergo different extent of structural damage via irreversible hydrolysis. Si content within the samples (i.e., Al-O-Si bond density) and framework stress are key factors that affect irreversible hydrolysis. Even using very dilute Cu acetate solutions, it is not possible to generate Cu-SAPO-34 samples with only isolated Cu2+ ions. Small amounts of CuOx species always coexist with isolated Cu2+ ions. Highly active and selective Cu-SAPO-34 catalysts for NH3-SCR are readily generated using this synthesis protocol, even for SAPO-34 samples that degrade substantially during solution ion exchange. High-temperature aging is found to improve the catalytic performance. This is likely due to reduction of intracrystalline mass-transfer limitations via formation of additional porosity in the highly defective SAPO-34 particles formed after ion exchange. The authors gratefully acknowledge the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Office of Vehicle Technologies for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle Memorial Institute under contract number DE-AC05-76RL01830.

Gao, Feng; Walter, Eric D.; Washton, Nancy M.; Szanyi, Janos; Peden, Charles HF

2013-09-06

68

Thermodynamics of formation reaction and hydrometallurgical application of metal-ammonia complexes in aqueous solutions  

NASA Astrophysics Data System (ADS)

Critically selected activity coefficients of individual ions stepwise stability constants, and enthalpy and entropy changes during formation of metal-ammonia complexes in aqueous salt solutions are summarised and analysed. Special attention is paid to the specifics of ammonia complexation in solutions with high ammonia concentrations (>=1 mol dm-3), which are of interest in hydrometallurgy. Certain problems and prospects for use of metal-ammonia complexation in hydrometallurgy are discussed. The bibliography includes 154 references.

Mironov, V. E.; Pashkov, G. L.; Stupko, T. V.

1992-09-01

69

Synthesis of starch-g-lactic acid copolymer with high grafting degree catalyzed by ammonia water.  

PubMed

The study of starch-g-lactic acid copolymer has gained much attention for its completely degradable property, but its intricate synthetic procedure and low graft degree inhibited its further application. In this work, the synthesis of starch-g-lactic acid copolymer was attempted via the catalysis of ammonia water by one-step process, and the structure of starch-g-lactic acid copolymer was characterized by means of IR, (13)C NMR and HMBC. The synthetic conditions were optimized as follows, the starch was activated for 2h at 80°C at first, starch and lactic acid with weight ratios of 1:4 reacted for 4h at 90°C in vacuum. The starch-g-lactic acid copolymer can be finally obtained with graft degree of starch 58.9%. PMID:25542110

Hu, Yingmo; Tang, Mingru

2015-03-15

70

Process for the recovery of hydrogen from ammonia purge gases  

Microsoft Academic Search

Ammonia synthesis processes are disclosed which provide enhanced conversion of hydrogen values to ammonia. In the processes, a purge stream from an ammonia synthesis loop is treated to reduce its ammonia content to less than about 0.5 volume percent. The purge stream is then contacted at a pressure of at least substantially the superatmospheric synthesis pressure of the ammonia synthesis

1979-01-01

71

Glutamine inhibits ammonia-induced accumulation of cGMP in rat striatum limiting arginine supply for NO synthesis.  

PubMed

Brain L-glutamine (Gln) accumulation and increased activity of the NO/cGMP pathway are immediate consequences of acute exposure to ammonia. This study tested whether excess Gln may influence NO and/or cGMP synthesis. Intrastriatal administration of the glutaminase inhibitor 6-diazo-5-oxo-L-norleucine or the system A-specific Gln uptake inhibitor methylaminoisobutyrate increased microdialysate Gln concentration and reduced basal and ammonia-induced NO and cGMP accumulation. Gln applied in vivo (via microdialysis) or in vitro (to rat brain cortical slices) reduced NO and cGMP accumulation in the presence and/or absence of ammonia, but not cGMP synthesis induced by the NO donor sodium nitroprusside. Attenuation of cGMP synthesis by Gln was prevented by administration of L-arginine (Arg). The L-arginine co-substrates of y(+)LAT2 transport system, L-leucine and cyclo-leucine, mimicked the effect of exogenous Gln, suggesting that Gln limits Arg supply for NO synthesis by interfering with y+LAT2-mediated Arg uptake across the cell membrane. PMID:19379813

Hilgier, Wojciech; Fre?ko, Inez; Klemenska, Emilia; Beresewicz, Andrzej; Oja, Simo S; Saransaari, Pirjo; Albrecht, Jan; Zieli?ska, Magdalena

2009-07-01

72

Synthesis and photocatalytic performances of BiVO{sub 4} by ammonia co-precipitation process  

SciTech Connect

This paper reports the preparation and photocatalytic performance of Bismuth vanadate (BiVO{sub 4}) by a facile and inexpensive approach. An amorphous BiVO{sub 4} was first prepared by a co-precipitation process from aqueous solutions of Bi(NO{sub 3}){sub 3} and NH{sub 4}VO{sub 3} using ammonia. Followed by heating treatment at various temperatures, the amorphous phase converted to crystalline BiVO{sub 4} with a structure between monoclinic and tetragonal scheelite. The crystallization of BiVO{sub 4} occurred at about 523 K, while the nanocrystalline BiVO{sub 4} were formed with a heat-treatment of lower than 673 K. However, when the heat-treatment was carried out at 773 K, the accumulation of nanocrystals to bulk particles was observed. The photocatalytic performances of the materials were investigated by O{sub 2} evolution under visible-light, and MB decomposition under solar simulator. The results demonstrated that the crystalline structure is still the vital factor for the activities of both reactions. However, the crystallinity of BiVO{sub 4} gives a major influence on the activity of O{sub 2} evolution, whereas the surface area, plays an important role for photocatalytic MB decomposition. - Abstract: BiVO{sub 4} was prepared by a co-precipitation process using aqueous ammonia solution, followed by heating treatment at various temperatures. The crystalline structure and crystallization process, and their influences on photocatalytic O{sub 2} evolution and organic pollutants degradation were investigated. It demonstrated that the crystalline structure is still the vital factor for the activities of both reactions. However, the crystallinity of BiVO{sub 4} gives a major influence on the activity of O{sub 2} evolution, whereas the surface area, plays an important role for photocatalytic MB decomposition. Display Omitted.

Yu Jianqiang [Laboratory of Fiber Materials and Modern Textile, Institute of Multifunctional Materials, Qingdao University, No. 308 Ningxia Road, Qingdao 266071 (China); School of Chemistry, Chemical Engineering and Environment, Qingdao University, No. 308 Ningxia Road, Qingdao 266071 (China)], E-mail: jianqyu@qdu.edu.cn; Zhang Yan [School of Chemistry, Chemical Engineering and Environment, Qingdao University, No. 308 Ningxia Road, Qingdao 266071 (China); Kudo, Akihiko [Department of Applied Chemistry, Faculty of Science, Tokyo University of Sciences, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan); Core Research for Evolutional Science and Technology, Japan Science and Technology Agency (CREST, JST), 4-1-8 Honcho, Kawaguchi-shi, Saitama 332-0012 (Japan)], E-mail: a-kudo@rs.kagu.tus.ac.jp

2009-02-15

73

Eddy covariance flux measurements of ammonia by electron transfer reaction-mass spectrometry  

NASA Astrophysics Data System (ADS)

A system for fast ammonia (NH3) measurements based on a commercial Proton Transfer Reaction-Mass Spectrometer is presented. It uses electron transfer reaction (eTR) as ionisation pathway and features a drift tube of polyetheretherketone (PEEK) and silica-coated steel. Heating the instrumental inlet and the drift tube to 180° C enabled an effective time resolution of ~1 s and made it possible to apply the eTR-MS for eddy covariance (EC) measurements. EC fluxes of NH3 were measured over two agricultural fields in Oensingen, Switzerland, following fertilisations with cattle slurry. Air was aspirated close to a sonic anemometer at a flow of 100 STP L min-1 and was directed through a 23 m long 1/2" PFA tube heated to 150°C to an air-conditioned trailer where the eTR-MS sub-sampled from the large bypass stream. This setup minimised damping of fast NH3 concentration changes between the sampling point and the actual measurement. High-frequency attenuation loss of the NH3 fluxes of 20 to 40% was quantified and corrected for using an empirical ogive method. The instrumental NH3 background signal showed a minor interference with H2O which was characterised in the laboratory. The resulting correction of the NH3 flux after slurry spreading was less than 1‰. The flux detection limit of the EC system was about 5 ng m-2 s-1 while the accuracy of individual flux measurements was estimated 16% for the high-flux regime during these experiments. The NH3 emissions after broad spreading of the slurry showed an initial maximum of 150 ?g m2 s-1 with a fast decline in the following hours.

Sintermann, J.; Spirig, C.; Jordan, A.; Kuhn, U.; Ammann, C.; Neftel, A.

2010-11-01

74

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

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

Zare, Richard N.

75

Superheavy Elements -- Synthesis, Structure and Reaction Mechanism  

SciTech Connect

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.

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

2006-08-14

76

Hydrogen generation from ammonia borane and water through the combustion reactions with mechanically alloyed Al/Mg powder  

NASA Astrophysics Data System (ADS)

Finding and developing a safe and effective method for hydrogen storage is integral to its use as an alternative source of energy. The goal of the studies described in this thesis was to investigate the feasibility of developing combustible hydrogen-generating compositions based on ammonia borane and novel energetic materials such as nanocomposite and mechanically alloyed reactive materials, recently obtained by Prof. Edward Dreizin's team at the New Jersey Institute of Technology (NJIT). Such compositions could be stored for long time and release hydrogen on demand, upon ignition. The first phase of the research included thermodynamic calculations for combustion of ammonia borane with various reactive materials obtained at NJIT. The second phase involved experiments with compositions that appeared to be promising based on thermodynamic calculations. An experimental setup with laser ignition of mixtures was developed for these experiments. As a result of these tests, further work was focused on mixtures of ammonia borane, gelled water, and mechanically alloyed Al/Mg powder. The last part of the research revealed the reaction mechanisms during combustion of these mixtures. For this purpose, isotopic tests, involving use of heavy water and mass-spectroscopy of gaseous combustion products, were conducted. The results of the present work indicate that combustible mixtures of ammonia borane, water, and mechanically alloyed Al/Mg powder are promising for the development of hydrogen generators that release large amounts of hydrogen upon ignition.

Rodriguez, Daniel

77

Effects of Light and of Fusarium solani on Synthesis and Activity of Phenylalanine Ammonia-Lyase in Peas 1  

PubMed Central

Phenylalanine ammonia-lyase was purified from peas, and a specific antiserum against the enzyme was produced in rabbits. The antiserum was used to study the first 8 hours of the phenylalanine ammonia-lyase activity response in two different organs of the pea from different developmental stages and in response to two different stimuli. Etiolated seedlings were pulse-labeled with l-[35S]methionine after either no light exposure or after specific periods of irradiation with blue light. Immature pods were pulse labeled with mixed l-[3H]amino acids after specific time periods following inoculation of the pod endocarp surfaces with macroconidia of Fusarium solani. Immunoprecipitates isolated from extracts of each group were analyzed with sodium dodecyl sulfate disc gel electrophoresis and were found to contain a radioactive protein with an electrophoretic mobility identical to that of the phenylalanine ammonia-lyase subunit (Mr 81,000). The radioactivity contained in the subunit band was interpreted as being due to de novo synthesis of the enzyme. The net rate of phenylalanine ammonia-lyase labeling, found to be initially low in both tissue types, rose dramatically, peaking at approximately a six- to ten-fold greater level at 4 hours after the beginning of the stimulus. Thereafter, the rate of labeling declined slowly. Inoculation with F. solani f. sp. pisi, a true pathogen of peas, caused a fifty per cent greater rate of peak labeling than did inoculation with a nonpathogen, F. solani f. sp. phaseoli. The time profile of the changing rate of labeling correlates with the changing activity level of the enzyme which peaks at 12 hours after the onset of the stimulus. The data presented favor a model which explains the changing activity of phenylalanine ammonia-lyase as being due to a changing rate of synthesis or degradation (or both) of the enzyme rather than due to the activation of a preformed zymogen. PMID:16661979

Loschke, David C.; Hadwiger, Lee A.; Schröder, Joachim; Hahlbrock, Klaus

1981-01-01

78

Reaction mechanism of combustion synthesis of NiAl  

Microsoft Academic Search

Based on precise temperature measurements during combustion and microstructural analysis of quenched samples, the evolution of reaction of the NiAl combustion synthesis has been studied. The combustion reaction of a multilayer Ni\\/Al system takes place in a thermal explosion mode under near adiabatic conditions. The experimental results clearly show that the combustion reaction starts right after the melting of Al.

Ping Zhu; J. C. M Li; C. T Liu

2002-01-01

79

Poly (2-(acetoacetoxy) ethyl methacrylate) : environmentally friendly synthesis, fluorescent properties and optical sensing for ammonia.  

E-print Network

??An environmentally friendly fabrication technology to synthesize ?-dicarbonyl polymers is developed with tailored properties of fluorescence and ammonia sensing. It is achieved by utilizing the… (more)

He, Jing

2012-01-01

80

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...

81

?-Telluroacroleins and tellurovinyl ketones: synthesis, reactions and structures  

NASA Astrophysics Data System (ADS)

The published data on the synthesis, reactions and structures of novel organotellurium synthones, viz., ?-tellurovinylcarbonyl compounds, are systematised and generalised. Special attention is given to the use of these compounds in the synthesis of tellurium-containing heterocycles. The bibliography includes 57 references.

Sadekov, Igor D.

2002-11-01

82

Synthesis of hexagonal gold nanoparticles using a microfluidic reaction system  

Microsoft Academic Search

A new microfluidic reaction system capable of mixing, transporting and reacting is developed for the synthesis of gold nanoparticles. It allows for a rapid and a cost-effective approach to accelerate the synthesis of gold nanoparticles. The microfluidic reaction chip is made from micro-electro-mechanical-system technologies which integrate a micro-mixer, micro-pumps, a micro-valve, micro-heaters and a micro temperature sensor on a single

Chen-Hsun Weng; Chih-Chia Huang; Chen-Sheng Yeh; Huan-Yao Lei; Gwo-Bin Lee

2008-01-01

83

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)

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.

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

2011-11-01

84

SOURCE ASSESSMENT: SYNTHETIC AMMONIA PRODUCTION  

EPA Science Inventory

The report describes a study of air emissions from the production of synthetic ammonia. In 1976, 90 synthetic ammonia plants in 30 states produced 15.2 million metric tons of anhydrous ammonia. Ammonia is synthesized by the reaction of nitrogen and hydrogen. Most plants produce h...

85

Process for hydrogen recovery from ammonia purge gases  

Microsoft Academic Search

Ammonia synthesis processes are disclosed which provide enhanced conversion of hydrogen values to ammonia. In the processes, a purge stream from an ammonia synthesis loop, which purge stream contains ammonia, is contacted at a superatmospheric pressure with the feed side of a separation membrane which exhibits selective permeation of each of hydrogen and ammonia as compared to the permeation of

H. R. Null; E. Perry

1979-01-01

86

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

PubMed

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

Ringer, Joachim M

2013-01-01

87

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

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.

Ferguson, Michael James

2005-12-15

88

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)

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.

Bosco, S. R.

1982-01-01

89

Process for hydrogen recovery from ammonia purge gases  

Microsoft Academic Search

Ammonia synthesis processes are disclosed which provide enhanced recovery of hydrogen from ammonia synthesis purge streams by selective permeation. The enhanced recovery of hydrogen can provide increased conversion of hydrogen values to ammonia. In the processes, a purge stream from an ammonia synthesis loop at a superatmospheric pressure is passed to at least two permeator stages in series. Each permeator

T. E. Graham; D. L. MacLean

1979-01-01

90

Transannular Claisen rearrangement reactions for the synthesis of vinylcyclobutanes: formal synthesis of (±)-grandisol.  

PubMed

Unsaturated eight-membered lactones undergo decarboxylative and non-decarboxylative transannular Ireland-Claisen rearrangement reactions, to give substituted vinylcyclobutanes. A formal synthesis of (±)-grandisol is described. PMID:22011731

Craig, Donald; Funai, Kiyohiko; Gore, Sophie J; Kang, Albert; Mayweg, Alexander V W

2011-12-01

91

The Chemistry of Liquid Ammonia.  

ERIC Educational Resources Information Center

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)

Lagowski, J. J.

1978-01-01

92

Temperature dependences of the effective diffusion coefficients of the components of three-component gas systems, used in the synthesis of ammonia  

NASA Astrophysics Data System (ADS)

The temperature dependences of the effective diffusion coefficients of the components of three-component gas systems, used in the synthesis of ammonia, were calculated in the temperature range 298-800 K. The results obtained can be used as reference data.

Zhavrin, Yu. I.; Kosov, V. N.; Poyarkov, I. V.; Asembaeva, M. K.; Fedorenko, O. V.; Nysanbaeva, A. T.

2013-05-01

93

Shock-induced reaction synthesis (SRS) of nickel aluminides  

SciTech Connect

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.

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

94

Synthesis and characterization of polyaniline–carboxylated PVC composites: Application in development of ammonia sensor  

Microsoft Academic Search

Polyaniline (PAni) and carboxylated polyvinyl chloride (PVC) composites were synthesized and studied for their structural, electrical and electrochemical properties and used as a novel material for development of an ammonia gas sensor. Processible conducting composites were prepared by introducing carboxylated PVC in the PAni matrix under vigorous stirring and sonication conditions. Self-standing films of these electroactive and homogeneous composites were

Vandana Singh; Swati Mohan; G. Singh; P. C. Pandey; Rajiv Prakash

2008-01-01

95

Tests of Mechanism for Ammonia Synthesis by a Molybdenum Catalyst at Very Low Pressure  

Microsoft Academic Search

Ammonia has long been synthesized commercially on supported iron catalysts, of complex nature not well understood. Authors usually imply that catalysis occurs on the surface and involves four distinct steps: (1) gaseous N2 and H2 adsorb as atoms; (2) one or both species scurry over the surface as a two-dimensional gas; (3) atomic collisions in this phase form the radicals

George E. Moore; F. C. Unterwald

1968-01-01

96

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

PubMed Central

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

Wellmann, Eckard; Schopfer, Peter

1975-01-01

97

Achieving Chemical Equilibrium: The Role of Imposed Conditions in the Ammonia Formation Reaction  

ERIC Educational Resources Information Center

Under conditions of constant temperature T and pressure P, chemical equilibrium occurs in a closed system (fixed mass) when the Gibbs free energy G of the reaction mixture is minimized. However, when chemical reactions occur under other conditions, other thermodynamic functions are minimized or maximized. For processes at constant T and volume V,…

Tellinghuisen, Joel

2006-01-01

98

Crossed beam studies of ion-molecule reactions in methane and ammonia  

NASA Technical Reports Server (NTRS)

A crossed-beam apparatus is used to measure the product ion velocity and angular distributions for the following ion-molecule reactions in the relative energy range from 2 to 9 eV: CH4(+) + NH3 yields NH4(+) + CH3; CH4(+) + NH3 yields CNH5(+) + H2; NH2(+) + CH4 yields CNH4(+) + H2 (or 2H); and CH3(+) + NH3 yields CNH4(+) + H2 (or 2H). These reactions are also studied by means of deuterium labeling as a further probe of the detailed reaction dynamics. Probability contour plots for the four reactions are constructed in Cartesian velocity space, and product peaks in the plots are discussed. Relative cross sections and Q values are computed for two of the reactions as well as for the corresponding deuterium-labelled reactions. The results show that the present ion-neutral condensation reactions are highly exothermic with a deep well for the internal complex, that little hydrogen scrambling occurs, and that the energy of the reactions is released mainly as internal energy, even to the extent of producing two hydrogen atoms in some cases rather than one hydrogen atom or molecule.

Smith, G. P. K.; Saunders, M.; Cross, R. J., Jr.

1976-01-01

99

Synthesis imaging of the DR 21 (OH) cluster. II - Thermal ammonia and water maser emission  

NASA Astrophysics Data System (ADS)

Results of high-sensitivity, 4-arcsec-resolution imaging of the thermal ammonia and water maser emission of the DR 21 (OH) molecular cloud are presented. Images of the NH3(1, 1) and 2, 2) transitions show four primary emission regions embedded in a generally clumpy emission distribution. A total of 18 ammonia cores are identified in these images. An analysis of the physical properties of these cores shows that they are massive (15-1000 solar masses) and warm (about 20 to greater than 80 K) with a range of sizes (0.06-0.28 pc). One of these cores is a hot (greater than 80 K), compact (about 0.07 pc) region associated with shell-type H2O maser emission. The 3D distribution of these cores suggests a strong interaction between young massive stars and their maternal environs. Two source concepts are formulated to explain this distribution.

Mangum, Jeffrey G.; Wootten, Alwyn; Mundy, Lee G.

1992-04-01

100

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

PubMed

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

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

2014-08-13

101

Formaldehyde Reactions with Amines and Ammonia: Particle Formation and Product Identification  

NASA Astrophysics Data System (ADS)

Aqueous phase reactions between carbonyls and amines or ammonium salts have recently been implicated in secondary organic aerosol and brown carbon formation processes. Formaldehyde is ubiquitous in the atmosphere, and is present in both the gas and aqueous phases. However, the reactions of formaldehyde in the aqueous phase have not been completely characterized. This study aims to determine the interactions between formaldehyde and amines or ammonium salts present in atmospheric droplets. Bulk phase reactions of formaldehyde with these reactive nitrogen-containing compounds were monitored with ESI-MS and NMR to determine reaction kinetics and for product characterization, while UV-Vis spectroscopy was used to monitor changes in light absorption over time. Hexamethylenetetramine was found to be a major product of the formaldehyde/ammonium sulfate reaction, appearing within minutes of mixing. No products were formed that absorbed light beyond 225 nm. Mono-disperse particles containing mixtures of formaldehyde and ammonium sulfate or an amine were dried and analyzed via SMPS to determine the non-volatile fraction of the reaction products. Similarly, aqueous droplets were dried in a humid atmosphere to determine residual aerosol sizes over time as a function of formaldehyde concentration. This work indicates that formaldehyde plays a key role in aqueous-phase organic processing, as it has been observed to contribute to both an increase and reduction in the diameter and volume of residual aerosol particles.

Galloway, M. M.; Millage, K. D.; Rodriguez, A.; Sedehi, N.; Powelson, M. H.; De Haan, D. O.

2012-12-01

102

Measurement and estimation of ammonia emissions from lagoon-atmosphere interface using a coupled mass transfer and chemical reactions model, and an equilibrium model  

NASA Astrophysics Data System (ADS)

Ammonia has recently gained importance for its increasing atmospheric concentrations and its role in the formation of aerosols. The anaerobic lagoon and spray method, commonly used for waste storage and disposal in confined animal feeding operations (CAFO), is a significant source of ammonia emissions. An accurate emission model for ammonia from aqueous surfaces can help in the development of emission factors. Data collected from field measurements made at hog waste lagoons in south eastern North Carolina, using the flow through dynamic chamber technique, were used to evaluate the Coupled mass transfer and Chemical reactions model and Equilibrium model developed by Aneja et al. [2001a. Measurement and modeling of ammonia emissions at waste treatment lagoon-Atmospheric Interface. Water, Air and Soil pollution: Focus 1, 177-188]. Sensitivity analysis shows that ammonia flux increases exponentially with lagoon temperature and pH, but a linear increase was observed with an increase in total ammoniacal nitrogen (TAN). Ammonia flux also shows a nonlinear increase with increasing wind speed. Observed ammonia fluxes were generally lower in the cold season than in the warm season when lagoon temperatures are higher. About 41% of the equilibrium model predictions and 43% of the Coupled model predictions are found to be within a factor of two of the observed fluxes. Several model performance statistics were used to evaluate the performance of the two models against the observed flux data. These indicate that the simpler Equilibrium model does as well as the Coupled model. The possible effects of the "artificial" environment within the chamber, which is different from that in the ambient atmospheric conditions above the open lagoon surface, on the measured fluxes are also recognized.

Bajwa, Kanwardeep S.; Aneja, Viney P.; Pal Arya, S.

103

Formation of brown carbon via reactions of ammonia with secondary organic aerosols from biogenic and anthropogenic precursors  

NASA Astrophysics Data System (ADS)

Filter samples of secondary organic aerosols (SOA) generated from the ozone (O3)- and hydroxyl radical (OH)-initiated oxidation of various biogenic (isoprene, ?-pinene, limonene, ?-cedrene, ?-humulene, farnesene, pine leaf essential oils, cedar leaf essential oils) and anthropogenic (tetradecane, 1,3,5-trimethylbenzene, naphthalene) precursors were exposed to humid air containing approximately 100 ppb of gaseous ammonia (NH3). Reactions of SOA compounds with NH3 resulted in production of light-absorbing "brown carbon" compounds, with the extent of browning ranging from no observable change (isoprene SOA) to visible change in color (limonene SOA). The aqueous phase reactions with dissolved ammonium (NH4+) salts, such as ammonium sulfate, were equally efficient in producing brown carbon. Wavelength-dependent mass absorption coefficients (MAC) of the aged SOA were quantified by extracting known amounts of SOA material in methanol and recording its UV/Vis absorption spectra. For a given precursor, the OH-generated SOA had systematically lower MAC compared to the O3-generated SOA. The highest MAC values, for brown carbon from SOA resulting from O3 oxidation of limonene and sesquiterpenes, were comparable to MAC values for biomass burning particles but considerably smaller than MAC values for black carbon aerosols. The NH3/NH4+ + SOA brown carbon aerosol may contribute to aerosol optical density in regions with elevated concentrations of NH3 or ammonium sulfate and high photochemical activity.

Updyke, Katelyn M.; Nguyen, Tran B.; Nizkorodov, Sergey A.

2012-12-01

104

Synthesis and Reactions of Some New Thienopyrimidines  

Microsoft Academic Search

4-Methyl-6-mercapto-2-phenylpyrimidine-5-carbonitrile ( 1 ) was reacted with different halo compounds, namely ethylchloroacetate, chloroacetone, bromoacetanilide, p-chlorobromoacetanilide, and p -methoxy chloroacetanilide in ethanol in the presence of sodium acetate yielded the corresponding S-alkylated derivatives ( 2a-e ). The latter compounds underwent cyclization into thienopyrimidines ( 4a-e ) upon treatment with sodium ethoxide in ethanol. The reaction of ( 4a ) with hydrazine

Maisa I. Abdel Moneam; Ahmed A. Geies; Galal M. El-Naggar; Suliman M. Mussa

2003-01-01

105

Ammonia Test  

MedlinePLUS

... of this website will be limited. Search Help? Ammonia Share this page: Was this page helpful? Also ... to normal, can it rise again? 1. Is ammonia testing used to detect or monitor ammonia poisoning? ...

106

Photoionization-induced intracluster reactions of chlorobenzene/ammonia mixed complexes  

SciTech Connect

Complexes of chlorobenzene and ammonia, C[sub 6]H[sub 5]Cl-NH[sub 3], C[sub 6]H[sub 5]Cl(NH[sub 3])[sub 2], and C[sub 6]H[sub 5]Cl(NH[sub 3])[sub 3], were studied by single-photon ionization. The ionization potentials of these three complexes were measured to be 8.744 [+-] 0.022, 8.652 [+-] 0.013, and 8.555 [+-] 0.012 eV, respectively. The appearance potential of C[sub 6]H[sub 5]NH[sub 3][sup +] from C[sub 6]H[sub 5]Cl[center dot]NH[sub 3] was found at 8.935 [+-] 0.004 eV, which, with the known heat of formation of anilinium ion, gives the dissociation energy D(C[sub 6]H[sub 5]Cl[center dot]NH[sub 3]) = 2.9 [+-] 0.5 kcal mol[sup [minus]1] (12.0 [+-] 2.2 kJ mol[sup [minus]1]). Then, from its onset energy from C[sub 6]H[sub 5]Cl[center dot]NH[sub 3], the dissociation energy of (C[sub 6]H[sub 5]Cl[center dot]NH[sub 3])[sup +] is calculated to be D[(C[sub 6]H[sub 5]Cl[center dot]NH[sub 3])[sup +

Grover, J.R. (Brookhaven National Lab., Upton, NY (United States)); Cheng, B.M. (Synchrotron Radiation Research Center (Taiwan, Province of China) Brookhaven National Lab., Upton, NY (United States)); Herron, W.J.; Coolbaugh, M.T.; Peifer, W.R.; Garvey, J.F. (State Univ. of New York, Buffalo, NY (United States))

1994-08-04

107

Recovery of hydrogen and ammonia from purge gas  

Microsoft Academic Search

Ammonia and hydrogen values are recovered from the purge gas from an ammonia synthesis recycle stream by removing the ammonia from the purge gas by adsorption in an ammonia adsorber, thereafter separating the hydrogen by cryogenic partial condensation, the refrigeration for which is provided by expanding and evaporating the condensate, and recovering the ammonia from the adsorber by heating a

Isalski

1981-01-01

108

Regioselective Reactions for Programmable Resveratrol Oligomer Synthesis  

PubMed Central

Although much attention has been devoted to resveratrol, a unique polyphenol produced by plants throughout the world and credited as potentially being responsible for the so-called “French paradox” given its broad spectrum activity, the hundreds of oligomeric materials derived from it have been largely ignored despite their similarly high biochemical potential. Challenges in achieving their isolation in quantity from natural sources, coupled with an inability to rationally prepare them in the laboratory, are the main culprits. Here we show that a programmable, controlled, and potentially scaleable synthesis of the resveratrol family is possible through a unique three-stage design. These efforts required novel tactics coupled with strategy- and reagent-guided functionalizations to differentiate two distinct cores possessing multiple sites with the same and/or similar reactivity, ultimately leading to five higher-order natural products. We anticipate that this work 1) demonstrates that challenging, positionally-selective functionalizations of complex materials are possible where biosynthetic studies have indicated otherwise, 2) provides materials and tools to finally unlock the full biochemical potential of the family, particularly from the standpoint of activity and drug-property optimization, and 3) affords an intellectual framework to potentially access other oligomeric families controllably. PMID:21697944

Snyder, Scott A.; Gollner, Andreas; Chiriac, Maria I.

2011-01-01

109

Synthesis of size tuneable cadmium sulphide nanoparticles from a single source precursor using ammonia as the solvent  

SciTech Connect

Graphical abstract: UV-vis absorption spectra for CdS prepared by decomposing cadmium xanthates (Cd(ROCS{sub 2}){sub 2}) exhibit a marked blue-shift with increasing the alkyl chain length (where R denotes: (a) -C{sub 2}H{sub 5}, (b) -C{sub 4}H{sub 9}, (c) -C{sub 8}H{sub 17}, and (d) -C{sub 12}H{sub 25}, respectively), indicating the progressive size reduction of formed CdS nanoparticles. Highlights: Black-Right-Pointing-Pointer Synthesis of CdS nanoparticles using a single source precursor. Black-Right-Pointing-Pointer Tailoring the nanocrystal sizes using cadmium alkyl xanthate with different carbonyl length. Black-Right-Pointing-Pointer Preparation in an environment-friendly solvent. -- Abstract: Size tuneable cadmium sulphide nanoparticles of a few nanometres in size were prepared by thermolysis of a single source precursor of cadmium xanthates with variable carbon chain length (Cd(ROCS{sub 2}){sub 2}, where R denotes -C{sub 2}H{sub 5}, -C{sub 4}H{sub 9}, -C{sub 8}H{sub 17} and -C{sub 12}H{sub 25}, respectively) in an ammonia solution. The particle size, morphology and crystallinity of these nanoparticles were characterized using X-ray powder diffractometry, transmission electron microscopy, and nitrogen adsorption/desorption techniques. The results show that hexagonal CdS nanoparticles can be produced by thermolysis of cadmium alkyl xanthate in an ammonia solution at a temperature as low as 100 Degree-Sign C. The size of CdS particles (between 5.60 nm and 3.71 nm) decreases with increasing length of carbon chain in the precursor, as further confirmed by UV-visible and fluorescence spectrophotometric measurements. The size tuning mechanism of CdS from cadmium alkyl xanthate is also discussed.

Zhang, Wei-Min [School of Chemistry and Chemical Engineering, University of Jinan, 250022 Jinan, Shandong (China)] [School of Chemistry and Chemical Engineering, University of Jinan, 250022 Jinan, Shandong (China); Sun, Zhong-Xi, E-mail: sunzx@ujn.edu.cn [School of Chemistry and Chemical Engineering, University of Jinan, 250022 Jinan, Shandong (China)] [School of Chemistry and Chemical Engineering, University of Jinan, 250022 Jinan, Shandong (China); Hao, Wei; Su, Da-Wei [School of Chemistry and Chemical Engineering, University of Jinan, 250022 Jinan, Shandong (China)] [School of Chemistry and Chemical Engineering, University of Jinan, 250022 Jinan, Shandong (China); Vaughan, David J. [Williamson Research Centre for Molecular Environmental Science, and School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL (United Kingdom)] [Williamson Research Centre for Molecular Environmental Science, and School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL (United Kingdom)

2011-12-15

110

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)

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.

Chen, Lina; Woon, David E.

2011-01-01

111

The reaction conditions influence on hydrothermal synthesis of boehmite nanorods  

Microsoft Academic Search

Synthesis of boehmite (?-AlOOH) nanorods were performed by using aluminum nitrate and sodium hydroxide as starting materials\\u000a in conditions of controlled pH value of reaction mixture, temperature and holding time. X-ray diffraction, transmission electron\\u000a microscope, high resolution transmission electron microscope, selected area electron diffraction and N2 adsorption-desorption analysis were used to characterize morphology and structure feathers of the obtained products.

Qi Yang

2010-01-01

112

Formation of ammonia in the reactions of a tungsten dinitrogen with ruthenium dihydrogen complexes under mild reaction conditions.  

PubMed

Treatment of cis-[W(N2)2(PMe2Ph)4] (5) with an equilibrium mixture of trans-[RuCl(eta 2-H2)(dppp)2]X (3) with pKa = 4.4 and [RuCl(dppp)2]X (4) [X = PF6, BF4, or OTf; dppp = 1,3-bis(diphenylphosphino)propane] containing 10 equiv of the Ru atom based on tungsten in benzene-dichloroethane at 55 degrees C for 24 h under 1 atm of H2 gave NH3 in 45-55% total yields based on tungsten, together with the formation of trans-[RuHCl(dppp)2] (6). Free NH3 in 9-16% yields was observed in the reaction mixture, and further NH3 in 36-45% yields was released after base distillation. Detailed studies on the reaction of 5 with numerous Ru(eta 2-H2) complexes showed that the yield of NH3 produced critically depended upon the pKa value of the employed Ru(eta 2-H2) complexes. When 5 was treated with 10 equiv of trans-[RuCl(eta 2-H2)(dppe)2]X (8) with pKa = 6.0 [X = PF6, BF4, or OTf; dppe = 1,2-bis(diphenylphosphino)ethane] under 1 atm of H2, NH3 was formed in higher yields (up to 79% total yield) compared with the reaction with an equilibrium mixture of 3 and 4. If the pKa value of a Ru(eta 2-H2) complex was increased up to about 10, the yield of NH3 was remarkably decreased. In these reactions, heterolytic cleavage of H2 seems to occur at the Ru center via nucleophilic attack of the coordinated N2 on the coordinated H2 where a proton (H+) is used for the protonation of the coordinated N2 and a hydride (H-) remains at the Ru atom. Treatment of 5, trans-[W(N2)2(PMePh2)4] (14), or trans-[M(N2)2(dppe)2] [M = Mo (1), W (2)] with Ru(eta 2-H2) complexes at room temperature led to isolation of intermediate hydrazido(2-) complexes such as trans-[W(OTf)(NNH2)(PMe2Ph)4]OTf (19), trans-[W(OTf)(NNH2)(PMePh2)4]OTf (20), and trans-[WX(NNH2)(dppe)2]+ [X = OTf (15), F (16)]. The molecular structure of 19 was determined by X-ray analysis. Further ruthenium-assisted protonation of hydrazido(2-) intermediates such as 19 with H2 at 55 degrees C was considered to result in the formation of NH3, concurrent with the generation of W(VI) species. All of the electrons required for the reduction of N2 are provided by the zerovalent tungsten. PMID:11151496

Nishibayashi, Y; Takemoto, S; Iwai, S; Hidai, M

2000-12-25

113

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

USGS Publications Warehouse

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.

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

2007-01-01

114

Interorgan ammonia metabolism in liver failure.  

PubMed

In the post-absorptive state, ammonia is produced in equal amounts in the small and large bowel. Small intestinal synthesis of ammonia is related to amino acid breakdown, whereas large bowel ammonia production is caused by bacterial breakdown of amino acids and urea. The contribution of the gut to the hyperammonemic state observed during liver failure is mainly due to portacaval shunting and not the result of changes in the metabolism of ammonia in the gut. Patients with liver disease have reduced urea synthesis capacity and reduced peri-venous glutamine synthesis capacity, resulting in reduced capacity to detoxify ammonia in the liver. The kidneys produce ammonia but adapt to liver failure in experimental portacaval shunting by reducing ammonia release into the systemic circulation. The kidneys have the ability to switch from net ammonia production to net ammonia excretion, which is beneficial for the hyperammonemic patient. Data in experimental animals suggest that the kidneys could have a major role in post-feeding and post-haemorrhagic hyperammonemia.During hyperammonemia, muscle takes up ammonia and plays a major role in (temporarily) detoxifying ammonia to glutamine. Net uptake of ammonia by the brain occurs in patients and experimental animals with acute and chronic liver failure. Concomitant release of glutamine has been demonstrated in experimental animals, together with large increases of the cerebral cortex ammonia and glutamine concentrations. In this review we will discuss interorgan trafficking of ammonia during acute and chronic liver failure. Interorgan glutamine metabolism is also briefly discussed, since glutamine synthesis from glutamate and ammonia is an important alternative pathway of ammonia detoxification. The main ammonia producing organs are the intestines and the kidneys, whereas the major ammonia consuming organs are the liver and the muscle. PMID:12020618

Olde Damink, Steven W M; Deutz, Nicolaas E P; Dejong, Cornelis H C; Soeters, Peter B; Jalan, Rajiv

2002-01-01

115

Ruthenium supported on zeolite A: preparation and characterisation of a stable catalyst for ammonia synthesis  

Microsoft Academic Search

Reaction of Ru(NH3)6Cl3 with Na-A and K-A zeolites yielded oligomeric amino-oxo-complexes supported on the zeolite. Controlled thermal activation under hydrogen converted the precursor in a two-step reaction into an active catalyst with good long-term stability and resistance against small doses of oxygen poison. Several nanometers sized Ru metal particles are chemically bonded to the zeolite surface which provides in the

J. Wellenbüscher; M. Muhler; W. Mahdi; U. Sauerlandt; J. Schütze; G. Ertl; R. Schlögl

1994-01-01

116

Synthesis of 2-Aminoquinoline-3-carboamides and Pyrimido[4,5-b]quinolin-4-ones through Copper-Catalyzed One-pot Multicomponent Reactions.  

PubMed

Pyrimido[4,5-b]quinolinones have attracted considerable interest from both chemical and medicinal scientists as these compounds display remarkable antimicrobial, anti-inflammatory, antitumor, antiallergy, analgesic, and antioxidant activities. The importance of pyrimido[4,5-b]quinolinones has stimulated enormous efforts to develop efficient methodologies for their synthesis. Herein, we disclose a novel synthetic protocol toward pyrimido[4,5-b]quinolin-4-ones through Cu(OAc)2 -catalyzed one-pot four-component reactions of 2-bromobenzaldehydes, aqueous ammonia, cyanoacetamides and aldehydes. The synthetic procedure combines amination/condensation/cyclization/dehydrogenation reactions in one pot, allowing synthesis of complex compounds in a simple and practical manner. Compared with literature procedures, the synthetic strategies developed herein showed advantages such as readily available and economically sustainable starting materials, structural diversity of products, good functional group tolerance, and a remarkably simple operation process. PMID:25318983

Zhang, Xin-Ying; Guo, Xiao-Jie; Fan, Xue-Sen

2015-01-01

117

Reaction kinetics of hydrothermal depolymerization of poly(ethylene naphthalate), poly(ethylene terephthalate), and polycarbonate with aqueous ammonia solution  

Microsoft Academic Search

Poly(ethylene naphthalate) (PEN), poly(ethylene terephthalate) (PET) and poly(carbonate) (PC) were depolymerized in a semi-batch reactor with a 0.6M aqueous ammonia solution under hydrothermal conditions, at 433–553K and 10MPa, compared with aqueous alkaline (NaOH and KOH) solutions and water alone. The polymers studied were almost completely converted into monomers in an aqueous ammonia solution as well as aqueous NaOH and KOH

Risa Arai; Kentaro Zenda; Kohei Hatakeyama; Kazuko Yui; Toshitaka Funazukuri

2010-01-01

118

Pressure-reaction synthesis of titanium composite materials  

DOEpatents

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.

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

1993-01-01

119

Iminium Ion Cascade Reactions: Stereoselective Synthesis of Quinolizidines and Indolizidines  

PubMed Central

A novel iminium ion cascade reaction has been developed that allows for the stereoselective synthesis of a variety of substituted aza-fused bicycles. The combination of amino allylsilanes and aldehydes (or ketones) was used to synthesize a number of quinolizidines and indolizidines in an one-pot reaction sequence. This technology has been used to effect the facile syntheses of several indolizidine and quinolizidine natural products including, (±)-epilupinine, (±)-tashiromine, and (?)-epimyrtine. Substrate scope has been examined varying the type of amino allylsilanes (primary, secondary and conjugated) and carbonyl compounds (aldehydes and ketones) to give a variety of fused ring structures. Varying the components chosen allows for the inclusion of synthetically useful functional groups at different positions on the core structure. The methodology has been used to construct the tricyclic core structures present in the cylindricine family and halichlorine. PMID:20890382

Amorde, Shawn M.; Jewett, Ivan T.; Martin, Stephen F.

2009-01-01

120

Ammonia-free method for synthesis of CdS nanocrystalline thin films through chemical bath deposition technique  

Microsoft Academic Search

The preparation of thin films of CdS by chemical bath deposition is mostly based on the utilisation of ammonia as a complexing agent for cadmium ions. Here we report on a technique based on sodium citrate dihydrate that eliminates the problems of ammonia volatility and toxicity. The crystallites with a size range of 10–20 nm in diameter with zinc blend

M. Karimi; M. Rabiee; F. Moztarzadeh; M. Bodaghi; M. Tahriri

2009-01-01

121

The Development of the First Catalyzed Reaction of Ketenes and Imines: Catalytic, Asymmetric Synthesis of -Lactams  

E-print Network

The Development of the First Catalyzed Reaction of Ketenes and Imines: Catalytic, Asymmetric for the catalytic, asymmetric synthesis of -lactams resulting from the development of a catalyzed reaction resistance pressures,1 recently -lactams (especially nonnatural ones) have achieved many important

Lectka, Thomas

122

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

SciTech Connect

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)

Weydert, M.

1993-04-01

123

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

SciTech Connect

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)

Weydert, M.

1993-04-01

124

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

PubMed

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

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

2014-03-01

125

Solid-state synthesis reaction between Al and Cu powders during ball milling  

Microsoft Academic Search

The solid-state synthesis reaction between Al and Cu during high energy ball milling has been studied. The most important effect of ball milling is that the grain size of the constituents decreased to the nanometer range and the constituents dissolved at the nanograin boundaries. This provides feasible conditions for the solid state synthesis reactions. The milling conditions have a sensitive

Shengqi Xi; Jingen Zhou; Dongwen Zhang; Xiaotian Wang

1996-01-01

126

Catalytic synthesis of biologically important metabolites from formaldehyde and ammonia as a putative way of their prebiotic emergence  

NASA Astrophysics Data System (ADS)

The modern `RNA-world' theory considering the primary life as a system of self-replicating informational and catalytic oligomers is the most widespread hypothesis of life's origin. At the same time an alternative major theory antithetic to the genetic one exists. It is based on the primary formation of important metabolites and building blocks of biopolymers and appearance of the primordial autocatalytic cycles in geochemical environment. [1]. Encouraged by this theory, we suggest the putative emergence pathways to biologically relevant metabolites from simple precursors: formaldehyde (FA) and ammonia, which are known to be present in the interstellar space [2]. Based on our earlier [3, 4] and novel findings as well as on the literature data [5, 6] the scheme of conjugate autocatalytic processes including photochemical condensation of FA yielding C-C bond and catalytic formation of pyruvaldehyde, pyruvic acid, sugars, aminoacids catalyzed by minerals (aluminum silicate, phoshates) and by aminoacids themselves is proposed. Acetaldehyde, glyoxal, glycol-and glyceraldehydes (GA and GCA) were identified in this work as products of photolysis of FA aqueous solution with summary selectivity up to 20% and can serve as substrates for the synthesis of more complex organic compounds. In turn, alanine and pyruvic acid are formed during UV-irradiation of aqueous solution of acetaldehyde and ammonium nitrate [6]. Pyruvaldehyde formation from GCA and FA in presence of amino acids was observed by A. Weber [5]. Finally, we revealed the catalytic activity of zeolite HZSM-5-17 in acid form towards formation of pyruvaldehyde from GA and GCA in presence of alanine with the yield about 5%. This observation indicates that the assumption of catalytic activity of silica-alumina towards the synthesis of metabolites could be realistic. Prebiotic synthesis of sugars from lower monosacharides, as we showed earlier, could take place over phosphate catalysts [4]. The substrates and the products of the proposed scheme were detected in the interstellar space and meteorites [7, 8], evidencing of the possibility of its realization either on the Protoeath or in the protoplanet disk supplying the initial compounds for contemporary metabolism. Acknowledgements. The financial support of Program RAS, IP SB RAS N 10 is gratefully acknowledged. References 1. A. Eschenmoser, in "Origin of life. Chemical approach", Eds. P. Herdewijn, M.V. Kisakurek, Wiley-VCH, placeCityZurich, 2008 and refs therein. 2. D.A. Williams, J. Phys. Conf. 6, 1-17, 2005. 3. Pestunova, O., Simonov, A., Snytnikov, V., et al., Adv. Space Res. 36/2, 214-219, 2005. 4. Simonov, A., Pestunova, O., Matvienko, L., et al., Adv. Space Res. 40, 1634-1640, 2007. 5. A.L. Weber, Orig. Life Evol. Biosph. 31, 71-86, 2001. 6. T.A. Telegina, et. al., Journ. Evol. Biochim. i Fiziol. (Rus). 4/8, 429-434, 1977. 7. Hollis, J., Jewell, P., Lovas, F., et al., The Astrophysical Journal 613, L45-L48, 2004 8. Cooper, G., Kimmich, N., Belisle, W., et al., Nature 414(6866), 879, 2001.

Delidovich, Irina; Taran, Oxana; Simonov, Alexander; Parmon, Valentin

127

Analysis of Instability in an Industrial Ammonia Reactor  

E-print Network

Analysis of Instability in an Industrial Ammonia Reactor John C. Morud and Sigurd Skogestad Dept point for this study was an incident in an industrial plant, where the ammonia synthesis reactor became of this work was an incident in an indus- trial ammonia fixed-bed synthesis reactor in Germany in 1989. After

Skogestad, Sigurd

128

Asymmetric synthesis of tetrahydroisoquinolines by enzymatic Pictet-Spengler reaction.  

PubMed

Norcoclaurine synthase (NCS) catalyzes the stereoselective Pictet-Spengler reaction between dopamine and 4-hydroxyphenylacetaldehyde as the first step of benzylisoquinoline alkaloid synthesis in plants. Recent studies suggested that NCS shows relatively relaxed substrate specificity toward aldehydes, and thus, the enzyme can serve as a tool to synthesize unnatural, optically active tetrahydroisoquinolines. In this study, using an N-terminally truncated NCS from Coptis japonica expressed in Escherichia coli, we examined the aldehyde substrate specificity of the enzyme. Herein, we demonstrate the versatility of the enzyme by synthesizing 6,7-dihydroxy-1-phenethyl-1,2,3,4-tetrahydroisoquinoline and 6,7-dihydroxy-1-propyl-1,2,3,4-tetrahydroisoquinoline in molar yields of 86.0 and 99.6% and in enantiomer excess of 95.3 and 98.0%, respectively. The results revealed the enzyme is a promising catalyst that functions to stereoselectively produce various 1-substituted-1,2,3,4-tetrahydroisoquinolines. PMID:25036970

Nishihachijo, Masakatsu; Hirai, Yoshinori; Kawano, Shigeru; Nishiyama, Akira; Minami, Hiromichi; Katayama, Takane; Yasohara, Yoshihiko; Sato, Fumihiko; Kumagai, Hidehiko

2014-01-01

129

Ammonia Monitor  

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

130

Method for polymer synthesis in a reaction well  

DOEpatents

A method of synthesis is described 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 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 includes at least one orifice extending into the well, and is of a size and dimension to form a capillary liquid seal to retain the reagent solution in the well to enable polymer chain growth on the solid support. The method further includes the step of (B) expelling the reagent solution from the well, 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 of the orifice exceeds a predetermined amount sufficient to overcome the capillary liquid seal and expel the reagent solution from the well through the orifice exit. 9 figs.

Brennan, T.M.

1998-09-29

131

Method for polymer synthesis in a reaction well  

DOEpatents

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).

Brennan, Thomas M. (San Francisco, CA)

1998-01-01

132

Reaction synthesis of Ni-Al based particle composite coatings  

SciTech Connect

Electrodeposited metal matrix/metal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles. By optimizing the process parameters, coatings were deposited with 20 volume percent aluminum particles. Coating morphology and composition were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on coating phase formation was studied in the temperature range 415 to 1,000 C. Long-time exposure at low temperature results in the formation of several intermetallic phases at the Ni matrix/Al particle interfaces and concentrically around the original Al particles. Upon heating to the 500--600 C range, the aluminum particles react with the nickel matrix to form NiAl islands within the Ni matrix. When exposed to higher temperatures (600--1,000 C), diffusional reaction between NiAl and nickel produces ({gamma})Ni{sub 3}Al. The final equilibrium microstructure consists of blocks of ({gamma}{prime})Ni{sub 3}Al in a {gamma}(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during intermetallic phase formation and microstructural development is discussed with reference to reaction synthesis of bulk nickel aluminides.

SUSAN,DONALD F.; MISIOLEK,WOICECK Z.; MARDER,ARNOLD R.

2000-02-11

133

Reaction of lithium enediolates with perfluoroketene dithioacetals. Synthesis of ?-trifluoromethyl ?-dicarboxylic acid derivatives  

Microsoft Academic Search

The reaction of perfluoroketene dithioacetals with dianions of carboxylic acids proceeds through the substitution of the vinylic fluoride. The preparative value of this reaction depends strongly on the reaction and work-up conditions, the optimisation of which led to use LDA as a base and multiple extraction techniques. The overall process may be considered as a formal synthesis of ?-trifluoromethyl ?-dicarboxylic

Enrique Sotoca; Jean-Philippe Bouillon; Salvador Gil; Margarita Parra; Charles Portella

2004-01-01

134

Stereoselective synthesis of new chiral N-tertiary tetrasubstituted beta-enamino ester piperidines through an ammonia-catalyzed process.  

PubMed

We report here two approaches for the preparation of new N-substituted beta-enamino ester piperidines featuring an exocyclic tetrasubstituted double bond, based either on the direct alkylation of piperidine beta-enamino esters bearing an exocyclic trisubstituted double bond or on the intramolecular cyclization of linear amino beta-keto esters. The target compounds were obtained as unusual (Z)-stereoisomers in high yields. The key role of ammonia as reagent, acting both as a nucleophile and a base, was underlined. The diastereoselective formation of the products was rationalized on the basis of an ammonia addition-syn elimination catalytic process. PMID:16496995

Calvet-Vitale, Sandrine; Vanucci-Bacqué, Corinne; Fargeau-Bellassoued, Marie-Claude; Lhommet, Gérard

2006-03-01

135

Photodissociation of pyrrole-ammonia clusters by velocity map imaging: mechanism for the H-atom transfer reaction.  

PubMed

The photodissociation dynamics of pyrrole-ammonia clusters (PyH·(NH(3))(n), n = 2-6) has been studied using a combination of velocity map imaging and non-resonant detection of the NH(4)(NH(3))(n-1) products. The excited state hydrogen-atom transfer mechanism (ESHT) is evidenced through delayed ionization and presents a threshold around 236.6 nm, in agreement with previous reports. A high resolution determination of the kinetic energy distributions (KEDs) of the products reveals slow (?0.15 eV) and structured distributions for all the ammonia cluster masses studied. The low values of the measured kinetic energy rule out the existence of a long-lived intermediate state, as it has been proposed previously. Instead, a direct N-H bond rupture, in the fashion of the photodissociation of bare pyrrole, is proposed. This assumption is supported by a careful analysis of the structure of the measured KEDs in terms of a discrete vibrational activity of the pyrrolyl co-fragment. PMID:21076731

Rubio-Lago, L; Amaral, G A; Oldani, A N; Rodríguez, J D; González, M G; Pino, G A; Bañares, L

2011-01-21

136

Ammonia (GCMP)  

NSDL National Science Digital Library

Ammonia fountain: this is a resource in the collection "General Chemistry Multimedia Problems". In an ammonia fountain, a flask is filled with ammonia gas. A tube from the flask extends into a pan of water that contains phenolphthalein. When a rubber bulb full of water is squeezed, the water squirts into the flask. Water from the pan then is pushed into the flask and the indicator changes color. General Chemistry Multimedia Problems ask students questions about experiments they see presented using videos and images. The questions asked apply concepts from different parts of an introductory course, encouraging students to decompartmentalize the material.

137

Transannular Diels-Alder reaction on macrocycles. A general strategy for the synthesis of polycyclic compounds  

Microsoft Academic Search

Various aspects of the transannular Diels-Alder reaction are examined in order to eventually develop a general method for the synthesis of a large variety of polycyclic compounds related to the diterpenes, mterpenes and steroids. Emphasis is made on the control of the relative and absolute configuration of the polycyclic products. Preliminary work towards the synthesis of some specific target natural

Pierre Deslongchamps

1992-01-01

138

Synthesis of Non-racemic ?-Hydroxy Phosphonates via Asymmetric Phospho-Aldol Reaction.  

PubMed

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

Spilling, Christopher D; Malla, Raj K

2014-12-01

139

Green synthesis of silver nanoparticles in xylan solution via Tollens reaction and their detection for Hg2+  

NASA Astrophysics Data System (ADS)

This work reported a facile and green method to prepare highly stable and uniformly distributed Ag nanoparticles (AgNPs), in which a biopolymer xylan was used as the stabilizing and reducing agent via the Tollens reaction under microwave irradiation. Different variables were evaluated to optimize the reaction conditions. Complete characterization was performed using UV-Vis, XRD, TEM, size distribution analysis and XPS. The results revealed that AgNPs were well dispersed with diameters of 20-35 nm due to the packing of xylan. The optimal conditions were as follows: microwave irradiation temperature was 60-70 °C, microwave power was 800 W, microwave time was 30 min, the ratio of xylan to AgNO3 was 50 mg: 0.13 mmol, and ammonia concentration was 2%. In addition, the AgNPs were collected via high-speed centrifugal separation, and the supernatant was tested by HPAEC, GPC, FT-IR, and NMR. By comparing the structure of xylan before and after the reaction, the reaction mechanism was discussed. It was noted that the xylan-AgNPs composites showed high selectivity and sensitivity for Hg2+ detection. The other 15 metal ions used had no obvious effect on the detection of Hg2+, and the limit of detection (LOD) was 4.6 nM, which is lower than the allowed maximum level of 30 nM for drinking water by WHO. In addition, the xylan-AgNPs composites can be applied for Hg2+ detection in real water samples. This study provides a novel way for the high-value utilization of a rich biomass resource, and a green method for the synthesis of AgNPs for the selective and sensitive detection of harmful heavy metals.This work reported a facile and green method to prepare highly stable and uniformly distributed Ag nanoparticles (AgNPs), in which a biopolymer xylan was used as the stabilizing and reducing agent via the Tollens reaction under microwave irradiation. Different variables were evaluated to optimize the reaction conditions. Complete characterization was performed using UV-Vis, XRD, TEM, size distribution analysis and XPS. The results revealed that AgNPs were well dispersed with diameters of 20-35 nm due to the packing of xylan. The optimal conditions were as follows: microwave irradiation temperature was 60-70 °C, microwave power was 800 W, microwave time was 30 min, the ratio of xylan to AgNO3 was 50 mg: 0.13 mmol, and ammonia concentration was 2%. In addition, the AgNPs were collected via high-speed centrifugal separation, and the supernatant was tested by HPAEC, GPC, FT-IR, and NMR. By comparing the structure of xylan before and after the reaction, the reaction mechanism was discussed. It was noted that the xylan-AgNPs composites showed high selectivity and sensitivity for Hg2+ detection. The other 15 metal ions used had no obvious effect on the detection of Hg2+, and the limit of detection (LOD) was 4.6 nM, which is lower than the allowed maximum level of 30 nM for drinking water by WHO. In addition, the xylan-AgNPs composites can be applied for Hg2+ detection in real water samples. This study provides a novel way for the high-value utilization of a rich biomass resource, and a green method for the synthesis of AgNPs for the selective and sensitive detection of harmful heavy metals. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05999a

Luo, Yuqiong; Shen, Suqin; Luo, Jiwen; Wang, Xiaoying; Sun, Runcang

2014-12-01

140

Green synthesis of silver nanoparticles in xylan solution via Tollens reaction and their detection for Hg(2+).  

PubMed

This work reported a facile and green method to prepare highly stable and uniformly distributed Ag nanoparticles (AgNPs), in which a biopolymer xylan was used as the stabilizing and reducing agent via the Tollens reaction under microwave irradiation. Different variables were evaluated to optimize the reaction conditions. Complete characterization was performed using UV-Vis, XRD, TEM, size distribution analysis and XPS. The results revealed that AgNPs were well dispersed with diameters of 20-35 nm due to the packing of xylan. The optimal conditions were as follows: microwave irradiation temperature was 60-70 °C, microwave power was 800 W, microwave time was 30 min, the ratio of xylan to AgNO3 was 50 mg: 0.13 mmol, and ammonia concentration was 2%. In addition, the AgNPs were collected via high-speed centrifugal separation, and the supernatant was tested by HPAEC, GPC, FT-IR, and NMR. By comparing the structure of xylan before and after the reaction, the reaction mechanism was discussed. It was noted that the xylan-AgNPs composites showed high selectivity and sensitivity for Hg(2+) detection. The other 15 metal ions used had no obvious effect on the detection of Hg(2+), and the limit of detection (LOD) was 4.6 nM, which is lower than the allowed maximum level of 30 nM for drinking water by WHO. In addition, the xylan-AgNPs composites can be applied for Hg(2+) detection in real water samples. This study provides a novel way for the high-value utilization of a rich biomass resource, and a green method for the synthesis of AgNPs for the selective and sensitive detection of harmful heavy metals. PMID:25429650

Luo, Yuqiong; Shen, Suqin; Luo, Jiwen; Wang, Xiaoying; Sun, Runcang

2014-12-11

141

Reactions of aromatic hydrocarbons with nucleophilic reagents in liquid ammonia. VII. Direction of hydroxylation of 3-substituted (Cl, Br, I, NO/sub 2/) nitrobenzenes with potassium hydroxide  

SciTech Connect

The reaction of 3-chloro-, 3-bromo-, and 3-iodonitrobenzenes with potassium hydroxide and oxygen in liquid ammonia (-33/sup 0/C) leads to the formation of nitrohalogenophenols, corresponding to substitution of the hydrogen atom at the ortho and para positions of the ring in relation to the nitro group by a hydroxy group. In the case of the last two substrates it also leads to the corresponding 2-halo-geno-3',4'-dinitrodiphenylamines. In view of the fact that substituted diphenylamines are formed under the same conditions as a result of the reaction of 3-nitro-aniline with 3-halogenonitrobenzenes it is suggested that 3-bromo- and 3-iodonitrobenzenes are partly converted into 3-nitroaniline through the intermediate formation of 3-nitrodehydrobenzene. During dehydroxylation in the absence of oxygen the proportion of the phenols corresponding to substitution of the hydrogen atom at the para position to the nitro group by the hydroxy group increases, and the degree of transformation of the initial compounds decreases. 2,4-dinitrophenol is formed with a low yield during the reaction of 1,3-nitrobenzene and potassium hydroxide in the presence of oxygen or in an atmosphere of argon.

Malykhin, E.V.; Kolesnichenko, G.A.; Shteingarts, V.D.

1986-09-20

142

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

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

143

Microwave-assisted organic synthesis and transformations using benign reaction media.  

PubMed

A nonclassical heating technique using microwaves, termed "Bunsen burner of the 21st century", is rapidly becoming popular and is dramatically reducing reaction times. The significant outcomes of microwave (MW)-assisted green chemistry endeavors, which have resulted in the development of synthetic protocols for drugs and fine chemicals synthesis that are relatively more sustainable, are summarized. The use of emerging microwave-assisted chemistry techniques in conjunction with greener reaction media is dramatically reducing chemical waste and reaction times in several organic syntheses and chemical transformations. A brief historic account of our own experiences in developing MW-assisted organic transformations, which involve various benign alternatives, such as solid-supported reagents, and greener reaction media, namely, aqueous, ionic liquid, and solvent-free, for the synthesis of various heterocycles, coupling reactions, oxidation-reduction reactions, and some name reactions are described. Synthesis of Heterocycles. The synthetic chemistry community has been under increased pressure to produce, in an environmentally benign fashion, the myriad of heterocyclic systems required by society in a short span of time, and one of the best options to accelerate these synthetic processes is to use MW technology. The efficient use of the MW heating approach for the synthesis of various heterocyclic compounds in aqueous and solvent-free medium is discussed. Organic Named Reactions. The application of MW chemistry for various named reaction such as the Prins reaction, the Suzuki reaction, the Heck reaction, the Aza-Michael reaction, Trost's gamma-addition, and the Cannizzaro reaction are summarized. Synthesis and Application of Ionic Liquids. Ionic liquids (ILs), being polar and ionic, in character couple with MW irradiation very efficiently and are, therefore, ideal MW-absorbing candidates for expediting chemical reactions. MW-assisted solvent-free synthesis and application of ILs are discussed. Oxidation-Reduction Reactions. MW protocols using mineral oxides such as alumina, silica, and clay to immobilize reagents on such solid supports have been extensively explored under "dry" media conditions. Various solvent-free examples of oxidation reactions are discussed that involve mixing of neat substrates with clay-supported iron(III) nitrate (clayfen) or iodobenzene diacetate (IBD) as an oxidant; some interesting MW reduction protocols using borohydrides are also discussed. Protection-Deprotection Reactions. The protection and deprotection of alcohols and amines are common events in multistep organic syntheses. Various protection and deprotection protocols under MW irradiation are discussed, including tetrahydropyranylation and (benzyloxycarbonyl) (Cbz)-protection, which are the most frequently employed methods. PMID:18419142

Polshettiwar, Vivek; Varma, Rajender S

2008-05-01

144

Single Polypyrrole Nanowire Ammonia Gas Sensor Sandra C. Hernandez, Debangshu Chaudhuri, Wilfred Chen, Nosang V. Myung,* Ashok Mulchandani*  

E-print Network

Full Paper Single Polypyrrole Nanowire Ammonia Gas Sensor Sandra C. Hernandez, Debangshu Chaudhuri report the synthesis, electrical characterization and ammonia gas sensing with single nanowire nanowire exhibited good sensitivity towards ammonia, and provided a reliable detection at concentration

Chen, Wilfred

145

Equation of state of ammonia  

NASA Astrophysics Data System (ADS)

Ammonia and water are critical components of extraterrestrial bodies, determining the density and physical properties of the Outer Planets, their moons, and of extrasolar planets. Ammonia is unusual in having a high heat capacity relative to other molecular species. Equations of state (EOS) are presented for ammonia and for mixtures of ammonia and water. Their properties are discussed in terms of chemical compositions that evolve as pressure and temperature are varied. The NH4OH hydrate of ammonia is known to exist as a separate molecular species at pressures above about 5 GPa, and an effort was made to include reaction between NH3 and H2O in the mixture EOS. The EOS are suitable for calculating structures of icy planets and exoplanets, and of impacts. mass-radius relations which bound the possible interpretations of composition and structure for extraterrestrial bodies of unknown composition, such as exoplanets.

Mulford, R.; Swift, D. C.; Hamel, S.

2014-05-01

146

The reductive supercritical hydrothermal process, a novel synthesis method for cobalt nanoparticles: synthesis and investigation on the reaction mechanism.  

PubMed

Highly crystalline cobalt nanoparticles with low surface oxidation were synthesized by the reductive supercritical hydrothermal process in the temperature range from 340 to 420 °C. Under these reaction conditions, hydrogen generated from formic acid decomposition is maximally soluble in water, enabling the effective reduction of cobalt ions and cobalt oxide. The reaction mechanism was investigated by kinetic analysis on the formation of cobalt nanoparticles. This analysis assumed the first order irreversible reaction and two different types of shrinking core models (chemical reaction and inter-diffusion dominated). According to the proposed reaction mechanism, cobalt monoxide is probably formed at the early reaction stage, where insufficient H2 is available, or under high temperature conditions. Moreover, cobalt monoxide influences the entire reaction rate. Thus, suppressing the formation and growth of cobalt monoxide is of primary importance in the optimal synthesis of cobalt nanoparticles by the reductive supercritical hydrothermal process. PMID:24878608

Seong, Gimyeong; Adschiri, Tadafumi

2014-07-28

147

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

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

Bandarian, V; Reed, G H

2000-10-01

148

Chemical synthesis of proanthocyanidins in vitro and their reactions in aging wines.  

PubMed

Proanthocyanidins are present in many fruits and plant products like grapes and wine, and contribute to their taste and health benefits. In the past decades of years, substantial progresses has been achieved in the identification of composition and structure of proanthocyanidins, but the debate concerning the existence of an enzymatic or nonenzymatic mechanism for proanthocyanidin condensation still goes on. Substantial attention has been paid to elucidating the potential mechanism of formation by means of biomimetic and chemical synthesis in vitro. The present paper aims at summarizing the research status on chemical synthesis of proanthocyanidins, including non-enzymatic synthesis of proanthocyanidin precursors, chemical synthesis of proanthocyanidins with direct condensation of flavanols and stereoselective synthesis of proanthocyanidins. Proanthocyanidin-involved reactions in aging wines are also reviewed such as direct and indirect reactions among proanthocyanidins, flavanols and anthocyanins. Topics for future research in this field are also put forward in this paper. PMID:19052525

He, Fei; Pan, Qiu-Hong; Shi, Ying; Duan, Chang-Qing

2008-01-01

149

Synthesis of the Bicyclic Welwitindolinone Core via an Alkylation/Cyclization Cascade Reaction  

PubMed Central

Synthesis of an advanced welwitindolinone intermediate via an alkylation/cyclization reaction is reported. The key step involves a one pot Lewis acid mediated alkylation of a silylketene aminal with a furan alcohol followed by an intramolecular cyclization. The reaction is stereoselective and takes place at low temperature. The cycloadduct is highly functionalized and contains the welwitindolinone core structure. PMID:19860385

Brailsford, John A.; Lauchli, Ryan; Shea, Kenneth J.

2009-01-01

150

Synthesis of Triarylmethane and Xanthene Dyes Using Electrophilic Aromatic Substitution Reactions  

ERIC Educational Resources Information Center

The synthesis of dyes has long been a popular topic in organic chemistry laboratory experiments because it allows students to see first hand that reactions learned in class can be used to make compounds with useful applications. In this experiment electrophilic aromatic substitution reactions are used to synthesize several triarylmethane and…

McCullagh, James V.; Daggett, Kelly A.

2007-01-01

151

Advances in understanding the mechanism and improved stability of the synthesis of ammonia from air and water in hydroxide suspensions of nanoscale Fe?O?.  

PubMed

We report a mechanism of electrochemical ammonia (NH3) production via an iron intermediate in which H2 and NH3 are cogenerated by different electron-transfer pathways. Solar thermal can contribute to the energy to drive this synthesis, resulting in a STEP, solar thermal electrochemical process, for NH3. Enhancements are presented to this carbon dioxide (CO2)-free synthesis, which uses suspensions of nano-Fe2O3 in high-temperature hydroxide electrolytes at nickel and Monel electrodes. In a 200 °C molten eutectic Na(0.5)K(0.5)OH electrolyte, the 3 Faraday efficiency per mole of synthesized NH3, ?(NH3), increases with decreasing current density, and at j(electrolysis) = 200, 25, 2, and 0.7 mA cm(-2), ?(NH3) = 1%, 7%, 37%, and 71%, respectively. At 200 mA cm(-2), over 90% of applied current drives H2, rather than NH3, formation. Lower temperature supports greater electrolyte hydration. At 105 °C in the hydrated Na(0.5)K(0.5)OH electrolyte, ?(NH3) increases and then is observed to be highly stable at ?(NH3) = 24(+2)%. PMID:25247873

Li, Fang-Fang; Licht, Stuart

2014-10-01

152

Samarium Diiodide-Mediated Reactions in Total Synthesis  

PubMed Central

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

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

2009-01-01

153

The synthesis and benzannulation reactions of (trialkylsilyl)vinylketenes  

E-print Network

(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 ...

Austin, Wesley F

2008-01-01

154

Stereoselective synthesis of 2,6-trans-tetrahydropyran via primary diamine-catalyzed oxa-conjugate addition reaction of ?,?-unsaturated ketone: total synthesis of psymberin.  

PubMed

The total synthesis of psymberin was achieved employing a readily available chiral epoxide to prepare two of the three subunits in the natural product. The key reaction was a highly stereoselective organocatalytic oxa-conjugate addition reaction of ?,?-unsaturated ketone catalyzed by primary diamine for the synthesis of the 2,6-trans-tetrahydropyran embedded in psymberin. PMID:21988493

Byeon, Seong Rim; Park, Heekwang; Kim, Hyoungsu; Hong, Jiyong

2011-11-01

155

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

PubMed Central

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

Bhanushali, Mayur; Zhao, Cong-Gui

2011-01-01

156

Diffusion of ammonia gas in PDMS characterized by ATR spectroscopy  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

157

Dynamics of ammonia exchange with cut grassland: synthesis of results and conclusions of the GRAMINAE Integrated Experiment  

NASA Astrophysics Data System (ADS)

Improved data on biosphere-atmosphere exchange are fundamental to understanding the production and fate of ammonia (NH3) in the atmosphere. The GRAMINAE Integrated Experiment combined novel measurement and modelling approaches to provide the most comprehensive analysis of the interactions to date. Major inter-comparisons of micrometeorological parameters and NH3 flux measurements using the aerodynamic gradient method and relaxed eddy accumulation (REA) were conducted. These showed close agreement, though the REA systems proved insufficiently precise to investigate vertical flux divergence. Grassland management had a large effect on fluxes: emissions increased after grass cutting (-50 to 700 ng m-2 s-1 NH3) and after N-fertilization (0 to 3800 ng m-2 s-1) compared with before the cut (-60 to 40 ng m-2 s-1). Effects of advection and air chemistry were investigated using horizontal NH3 profiles, acid gas and particle flux measurements. Inverse modelling of NH3 emission from an experimental farm agreed closely with inventory estimates, while advection errors were used to correct measured grassland fluxes. Advection effects were caused both by the farm and by emissions from the field, with an inverse dispersion-deposition model providing a reliable new approach to estimate net NH3 fluxes. Effects of aerosol chemistry on net NH3 fluxes were small, while the measurements allowed NH3-induced particle growth rates to be calculated and aerosol fluxes to be corrected. Bioassays estimated the emission potential ? = [NH4+]/[H+] for different plant pools, with the apoplast having the smallest values (30-1000). The main within-canopy sources of NH3 emission appeared to be leaf litter and the soil surface, with ? up to 3 million and 300 000, respectively. Cuvette and within-canopy analyses confirmed the role of leaf litter NH3 emission, which, prior to cutting, was mostly recaptured within the canopy. Measured ammonia fluxes were compared with three models: an ecosystem model (PaSim), a soil vegetation atmosphere transfer model (SURFATM-NH3) and a dynamic leaf chemistry model (DCC model). The different models each reproduced the main temporal dynamics in the flux, highlighting the importance of canopy temperature dynamics (Surfatm-NH3), interactions with ecosystem nitrogen cycling (PaSim) and the role of leaf surface chemistry (DCC model). Overall, net above-canopy fluxes were mostly determined by stomatal and cuticular uptake (before the cut), leaf litter emissions (after the cut) and fertilizer and litter emissions (after fertilization). The dynamics of ammonia emission from leaf litter are identified as a priority for future research.

Sutton, M. A.; Nemitz, E.; Milford, C.; Campbell, C.; Erisman, J. W.; Hensen, A.; Cellier, P.; David, M.; Loubet, B.; Personne, E.; Schjoerring, J. K.; Mattsson, M.; Dorsey, J. R.; Gallagher, M. W.; Horvath, L.; Weidinger, T.; Meszaros, R.; Dämmgen, U.; Neftel, A.; Herrmann, B.; Lehman, B. E.; Flechard, C.; Burkhardt, J.

2009-12-01

158

The effects of processing variables on reaction synthesis of Fe-Al alloys  

SciTech Connect

The effects of alloy composition and reaction atmosphere on reaction synthesis of binary FeAl alloys were studied. Reactions were observed in an open (air) furnace, under static vacuum (in an evacuated quartz tube) and in a dynamic vacuum furnace. High-speed videotapes of reaction syntheses of compacts formed from 45-{mu}m Fe and 10-{mu}m Al powders reacted in air and under static vacuum revealed that an unusual ``two-stage`` reaction exists in this system under these conditions. The first stage of the two-stage reaction lasts several seconds and starts at around 650 C. The second stage begins at about 900 C, reaching temperatures between 1,250 and 1,350 C. The progress of the reaction to the second stage is sensitive to the alloy composition and reaction environment. The reaction behavior is explained in terms of thermodynamics and heat transfer, which control the delicate balance between beat accumulation and heat loss during reaction synthesis.

Joslin, D.L.; Easton, D.S.; Liu, C.T.; David, S.A. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1994-12-31

159

Enhanced Chemical Synthesis at Soft Interfaces: A Universal Reaction-Adsorption Mechanism in Microcompartments  

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

160

Enabling electrochemical reduction of nitrogen to ammonia at ambient conditions through rational catalyst design.  

PubMed

Commercial design of a sustainable route for on-site production of ammonia represents a potential economic and environmental breakthrough. In an analogous process to the naturally occurring enzymatic mechanism, synthesis of ammonia could be achieved in an electrochemical cell, in which electricity would be used to reduce atmospheric nitrogen and water into ammonia at ambient conditions. To date, such a process has not been realized due to slow kinetics and low faradaic efficiencies. Although progress has been made in this regard, at present there exists no device that can produce ammonia efficiently from air and water at room temperature and ambient pressure. In this work, a scheme is presented in which electronic structure calculations are used to screen for catalysts that are stable, active and selective towards N2 electro-reduction to ammonia, while at the same time suppressing the competing H2 evolution reaction. The scheme is applied to transition metal nitride catalysts. The most promising candidates are the (100) facets of the rocksalt structures of VN and ZrN, which show promise of producing ammonia in high yield at low onset potentials. PMID:25446373

Abghoui, Younes; Garden, Anna L; Hlynsson, Valtýr Freyr; Björgvinsdóttir, Snædís; Olafsdóttir, Hrefna; Skúlason, Egill

2014-12-01

161

Synthesis and Minisci Reactions of Organotrifluoroborato Building Blocks  

PubMed Central

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

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

2013-01-01

162

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

E-print Network

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

Wang, Zhong L.

163

Organocatalytic asymmetric cascade reactions of 7-vinylindoles: diastereo- and enantioselective synthesis of c7-functionalized indoles.  

PubMed

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

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

2015-02-16

164

Low-temperature synthesis of LiBH4 by gas-solid reaction.  

PubMed

The solvent-free synthesis of LiBH(4) from LiH in a borane atmosphere at 120 degrees C and ambient pressures is demonstrated. The source of borane is a milled LiBH(4)/ZnCl(2) mixture, in which Zn(BH(4))(2) is generated by a metathesis reaction. The yield of the reaction of about 74 % LiBH(4) shows that a bulk reaction is taking place upon borane absorption by LiH. This indicates that the formation of B-H bonds is the limiting step for the formation of LiBH(4) from the elements. Therefore, the use of diborane as a starting reactant allows one to circumvent the reaction barrier for the B-B bond dissociation and explains the rather moderate synthesis conditions. PMID:19373797

Friedrichs, Oliver; Borgschulte, Andreas; Kato, Shunsuke; Buchter, Florian; Gremaud, Robin; Remhof, Arndt; Züttel, Andreas

2009-01-01

165

Quinones as dienophiles in the Diels-Alder reaction: history and applications in total synthesis.  

PubMed

In the canon of reactions available to the organic chemist engaged in total synthesis, the Diels-Alder reaction is among the most powerful and well understood. Its ability to rapidly generate molecular complexity through the simultaneous formation of two carbon-carbon bonds is almost unrivalled, and this is reflected in the great number of reported applications of this reaction. Historically, the use of quinones as dienophiles is highly significant, being the very first example investigated by Diels and Alder. Herein, we review the application of the Diels-Alder reaction of quinones in the total synthesis of natural products. The highlighted examples span some 60?years from the landmark syntheses of morphine (1952) and reserpine (1956) by Gates and Woodward, respectively, through to the present day examples, such as the tetracyclines. PMID:24446164

Nawrat, Christopher C; Moody, Christopher J

2014-02-17

166

Reaction synthesis of TiB 2–TiC composites with enhanced toughness  

Microsoft Academic Search

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

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

2001-01-01

167

Dynamics of ammonia exchange with cut grassland: synthesis of results and conclusions of the GRAMINAE Integrated Experiment  

NASA Astrophysics Data System (ADS)

Improved data on biosphere-atmosphere exchange are fundamental to understanding the production and fate of ammonia (NH3) in the atmosphere. The GRAMINAE Integrated Experiment combined novel measurement and modelling approaches to provide the most comprehensive analysis of the interactions to date. Major inter-comparisons of micrometeorological parameters and NH3 flux measurements using the aerodynamic gradient method and relaxed eddy accumulation (REA) were conducted. These showed close agreement, though the REA systems proved insufficiently precise to investigate vertical flux divergence. Grassland management had a large effect on fluxes: Emissions increased after grass cutting (-50 to 700 ng m-2 s-1 NH3) and after N-fertilization (0 to 3800 ng m-2 sammonia emission from leaf litter are identified as a priority for future research.

Sutton, M. A.; Nemitz, E.; Milford, C.; Campbell, C.; Erisman, J. W.; Hensen, A.; Cellier, P.; David, M.; Loubet, B.; Personne, E.; Schjoerring, J. K.; Mattsson, M.; Dorsey, J. R.; Gallagher, M. W.; Horvath, L.; Weidinger, T.; Meszaros, R.; Dämmgen, U.; Neftel, A.; Herrmann, B.; Lehman, B. E.; Flechard, C.; Burkhardt, J.

2009-01-01

168

Efficient synthesis and reactions of 1,2-dipyrrolylethynes  

PubMed Central

Various dipyrroles possess important motifs for construction of pyrrole-containing pigments. A series of 1,2-dipyrrolylethynes (4a–d) has been efficiently synthesized using an improved one-pot double Sonagashira coupling from trimethylsilylethyne and various 2-iodopyrroles. The resulting 1,2-dipyrrolylethynes were further transformed into novel indolyl-, ethenyl- and carboranyl-dipyrroles (5–7) using the Larock indole synthesis, stereoselective catalytic hydrogenation, or B10H14. Indolyl-dipyrroles were found to selectively bind fluoride ions using one pyrrolic and the indolyl NHs, whereas the carboranyl- and ethenyl-dipyrroles are potentially valuable precursors for the synthesis of porphyrin isomers and expanded pigments. PMID:21822371

Tanui, Hillary K.; Hao, Erhong; Ihachi, Moses I.; Fronczek, Frank R.; Smith, Kevin M.; Vicente, M. Graça H.

2011-01-01

169

METHOD FOR PRODUCING DEUTERIUM WHEN SYNTHESIZING AMMONIA  

Microsoft Academic Search

Deuterium can be produced by means of hydrogen exchange reactions ; between the hydrogen molecules and ammonia in the presence of a catalyst or by ; means of distillation. The method described is for producing a base material for ; this process which is already enriched in deuterium. It comprises the steps of ; separating ammonia, nitrogen, and inert gases

G. Schaurer; A. Heinzel

1963-01-01

170

Regeneration of ammonia borane from polyborazylene  

DOEpatents

Method of producing ammonia borane, comprising providing a reagent comprising a dehydrogenated material in a suitable solvent; and combining the reagent with a reducing agent comprising hydrazine, a hydrazine derivative, or combinations thereof, in a reaction which produces a mixture comprising ammonia borane.

Sutton, Andrew; Gordon, John C; Ott, Kevin C; Burrell, Anthony K

2013-02-05

171

Parallel DNA polymerase chain reaction: Synthesis of two different PCR products from a DNA template  

PubMed Central

Conventionally, in a polymerase chain reaction (PCR), oligonucleotide primers bind to the template DNA in an antiparallel complementary way and the template DNA is amplified as it is. Here we describe an approach in which the first primer binds in a parallel complementary orientation to the single-stranded DNA, leading to synthesis in a parallel direction. Further reactions happened in a conventional way leading to the synthesis of PCR product having polarity opposite to the template used. This is the first study showing that synthesis of DNA can happen also in a parallel direction. We report that from a single-stranded DNA template, two different but related PCR products can be synthesized.

Bhardwaj, Vikash; Sharma, Kulbhushan

2014-01-01

172

Facile synthesis of palladium nanoclusters and their catalytic activity in Sonogashira coupling reactions  

Microsoft Academic Search

This work reports a facile synthesis of palladium nanoclusters (PdNCs) in MeCN\\/MeOH mixture without any stabilizer. The PdNCs were found to be effective catalysts for copper-free, amine-free and ligand-free Songashira coupling reactions under ambient conditions.

J. Athilakshmi; S. Ramanathan; Dillip Kumar Chand

2008-01-01

173

Toward the ideal synthesis. New transition metal-catalyzed reactions inspired by novel medicinal leads  

Microsoft Academic Search

Studies in our laboratory are directed at the advancement of synthesis, biology, and medicine. This lecture will focus on new transition metal-catalyzed reactions that have been inspired by biologically potent targets such as phorbol and Taxol ® and by the more general interest in producing syntheses that are concise, efficient, cost- and resource-effective, envi- ronmentally benign, quick, and simple to

Paul A. Wender; F. Christopher Bi; Gabriel G. Gamber; Francis Gosselin; Robert D. Hubbard; Marc J. C. Scanio; Robert Sun; Travis J. Williams; Lei Zhang

2002-01-01

174

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

PubMed

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

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

2014-11-01

175

Synthesis and Reactions of Tungsten Alkylidene Complexes That Contain the 2,6-Dichlorophenylimido Ligand  

E-print Network

Synthesis and Reactions of Tungsten Alkylidene Complexes That Contain the 2,6-Dichlorophenylimido Institute of Technology, Cambridge, Massachusetts 02139 ReceiVed October 30, 2006 Tungsten alkylidene alkylidene bisalkoxide complexes of molybdenum or tungsten of the type M(NR)(CHR)(OR)2 are now established

Müller, Peter

176

Carbon Nanotube Synthesis via the Catalytic CVD Method: A Review on the Effect of Reaction Parameters  

Microsoft Academic Search

This review covers the results obtained in carbon nanotube synthesis by chemical vapor deposition. Parameters such as catalysts, supports, carbon precursors, reaction time, temperature and gas flow rates that are used in the production of carbon nanotubes are discussed throughout the text. Purification of the synthesized carbon nanotubes and methods utilized for cost reduction were also explored.

Ç?nar Öncel; Yuda Yürüm

2006-01-01

177

A novel three-component reaction for the synthesis of 1,3-benzoxazines in water.  

PubMed

A simple and proficient method for the synthesis of 1,3-benzoxazine derivatives via three-component reaction of isocyanide and isoquinoline with 1-(6-hydroxy-2-isopropenyl-1-benzofuran-yl)-1-ethanone or 4-hydroxycumarine in water in the presence of piperidine at 70°C is reported. PMID:23782038

Rostami-Charati, Faramarz

2013-12-01

178

The Influence of Ignition Manner on Micropyretic Synthesis of Low Exothermic Reaction with Ni+Al  

Microsoft Academic Search

The influence of ignition manner on micropyretic synthesis of low exothermic reaction with Ni+Al is numerically investigated in this study. The different ignition powers and ignition regions are chosen to illustrate the influences on the length of pre-heating zone and propagation velocity of the specimens. The numerical results indicate that a lower ignition power or igniting in the center region

H. P. Li

2005-01-01

179

Reaction synthesis of dynamically densified titanium-based intermetallic and ceramic-forming powders  

NASA Astrophysics Data System (ADS)

The mechanism(s) and kinetics of the reaction synthesis of dynamically-densified Ti-based intermetallic and ceramic forming powder mixtures were investigated in this study. Dynamic densification employing shock-compression produces a dense-packed and highly-activated state of powder mixture constituents resulting in significantly increased mass transport rates and enhanced chemical reactivity. Green density compacts (˜85--95% TMD) of Ti-Si, Ti-B, and Ti-Al powder mixtures, obtained using shock-densification under different loading conditions, were heat treated in an inert atmosphere, at their respective eutectic temperatures. Microstructural observation showed evidence of reaction initiating in the solid state, but eventually being taken over by a self sustained combustion type reaction mechanism. Activation energies determined using differential thermal analysis were used to correlate the reaction behavior in Ti-Si (as the model system), based on Carter's kinetic model for solid-state reactions and the Johnson-Mehl-Avrami kinetics for the combustion-type reaction, with experimental measurements of fraction of Ti5Si3 formed as a function of time and temperature. It was confirmed that in Ti-Si dynamically-densified powder compacts the reaction occurs in the solid-state up to temperatures <1000°C, but with further increase in temperature the reaction is taken over by a combustion-type reaction. The Ti-Si compacts thus produced are 92--95% dense and show a fully reacted Ti5Si3 microstructure, with ~6 mum grain size and ˜800 kg/mm2 microhardness. A predictive model was developed, incorporating a balance between rate of heat generation (due to reaction) and heat dissipation, to determine optimum synthesis conditions under which the reaction occurs in the solid state without being taken over by the combustion mode. The model considered synthesis temperature, compact porosity, and activation energy as the variables, to determine the fraction reacted as a function of time under various conditions, based on which the dominant reaction mechanism can be inferred in any given shock-densified powder mixture (including Ti-Si, Ti-Al, and Ti-B). Functionally graded Ti5Si3-TiAl and TiB2-TiAl3 composite systems were also synthesized, showing the potential of the combined dynamic-densification and reaction synthesis technique for the fabrication of such materials.

Namjoshi, Shantanu Ashok

180

Synthesis of rhenabenzenes from the reactions of rhenacyclobutadienes with ethoxyethyne.  

PubMed

Treatment of Na[Re(CO)5 ] with RC?CCO2 Et (R=phenyl, naphthalen-1-yl, phenanthren-9-yl and pyren-1-yl) followed by reaction with acetyl chloride and ethanol afforded the rhenacyclobutadienes Re{-C(R)?C(CO2 Et)C(OEt)?}(CO)4 . Reactions of these rhenacyclobutadienes with HC?COEt produced rhenabenzenes Re{-C(R)?C(CO2 Et)C(OEt)?CHC(OEt)?}(CO)4 . Except for R=Ph, new rhenacyclobutadienes with pendant alkenyl substituents Re{-C(R)?C(C(OEt)?CH(CO2 Et))C(OEt)?}(CO)4 were also isolated from these reactions. The NMR spectroscopic and X-ray structural data, as well as the aromatic stabilization energy (ASE) values suggest that the rhenabenzenes are aromatic, with extensive delocalized ? character. PMID:25220667

Lin, Ran; Lee, Ka-Ho; Poon, Ka Chun; Sung, Herman H Y; Williams, Ian D; Lin, Zhenyang; Jia, Guochen

2014-11-01

181

Triple ring closing metathesis reaction: synthesis of adjacent cyclic ethers.  

PubMed

[reaction: see text] Adjacent tris(cyclic ethers) and enol ethers have been synthesized in good yields for the first time via a triple olefin metathesis reaction using Grubbs' catalyst RuCl(2)(=C(H)Ph)(PCy(3))(2) (Cy = cyclohexyl), and the 1,3-dimesitylimidazol-2-ylidene ruthenium benzylidene catalyst RuCl(2)(=C(H)Ph)(PCy(3))(IMes) ((IMes) = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene). The latter proved to be the most efficient catalyst in these transformations. PMID:11418031

Heck, M P; Baylon, C; Nolan, S P; Mioskowski, C

2001-06-28

182

Ammonia metabolism in Aedes aegypti.  

PubMed

We investigated the mechanisms by which Aedes aegypti mosquitoes are able to metabolize ammonia. When females were given access to solutions containing NH(4)Cl or to a blood meal, hemolymph glutamine and proline concentrations increased markedly, indicating that ammonium/ammonia can be removed from the body through the synthesis of these two amino acids. The importance of glutamine synthetase was shown when an inhibitor of the enzyme was added to the meal causing the glutamine concentration in hemolymph to decrease significantly, while the proline concentration increased dramatically. Unexpectedly, we found an important role for glutamate synthase. When mosquitoes were fed azaserine, an inhibitor of glutamate synthase, the glutamine concentration increased and the proline concentration decreased significantly. This confirms the presence of glutamate synthase in mosquitoes and suggests that this enzyme contributes to the production of glutamate for proline synthesis. Several key enzymes related to ammonium/ammonia metabolism showed activity in homogenates of mosquito fat body and midgut. The mosquito genes encoding glutamate dehydrogenase, glutamine synthetase, glutamate synthase, pyrroline-5-carboxylate synthase were cloned and sequenced. The mRNA expression patterns of these genes were examined by a real-time RT-PCR in fat body and midgut. The results show that female mosquitoes have evolved efficient mechanisms to detoxify large loads of ammonium/ammonia. PMID:15804581

Scaraffia, Patricia Y; Isoe, Jun; Murillo, Adrian; Wells, Michael A

2005-05-01

183

Synthesis of arbutin by two-step reaction from glucose  

Microsoft Academic Search

Arbutin was synthesized from glucose by two-step reaction below: (a) 2,3,4,6-tetra-O-acetyl-?-D-glucosyl chloride or bromide was prepared by glucose and acetyl halide (chloride or bromide). (b) 2,3,4,6-tetra-O-ace- tyl-?-D-glucosyl halide (Cl, Br) reacted with hydroquinone, methanol as solvent at pH=9.5~10.0.

HUANG Shen-lin; ZHU Yu-lin; PAN Yuan-jiang; WU Shi-hua

184

Synthesis, structure and a nucleophilic coordination reaction of Germanetellurones.  

PubMed

?-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

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

2014-08-21

185

C-C bond fragmentation by Grob/Eschenmoser reactions, applications in dendrimer synthesis.  

PubMed

C-C bond fragmentation of structurally diverse carbocycles has been applied to the divergent synthesis of dendrimers. The fragmentation has been paired to deprotection or thio-Michael reaction, allowing the preparation of a fourth generation dendrimer of narrow molecular weight distribution. Methodologies to increase water solubility have been examined using appended carboxylic acid or oligoether moieties. In addition, incorporation of chiral prolinol derivatives has resulted in the synthesis of dendrimers that have been shown to catalyse the ?-amination of aldehydes in good yield and modest enantioselectivity. PMID:23925375

Hierold, Judith; Lupton, David W

2013-09-28

186

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

PubMed Central

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

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

2014-01-01

187

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)

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.

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

2014-12-01

188

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

PubMed

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

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

2014-01-01

189

Synthesis of new cellulose ethers using Suzuki-Miyaura reactions.  

PubMed

Cellulose ethers are functionalized biopolymers that are industrially produced through drastic conditions employing gaseous reactants with a high risk of industrial accident. The cellulose ethers that are commercially available generally bear short carbon-chains. In this work, an alternative method using non-gaseous chemicals is proposed. It relies on the use of the Suzuki-Miyaura reaction employing mild, moisture- and air-stable conditions. Relatively innocuous reagents are used for this step, which allows the formation of a wide range of cellulose ethers bearing various functional groups with different chain-length. PMID:25458272

Goncalves, Cédric; Favre, Camille; Feuardant, Pierre; Klein, Sarah; Vaca-Garcia, Carlos; Cecutti, Christine; Thiébaud-Roux, Sophie; Vedrenne, Emeline

2015-02-13

190

Process for manufacture of ammonia  

Microsoft Academic Search

An improved process is described for making synthetic ammonia wherein a make-up synthesis gas is added to recycled unreacted gas from the catalytic conversion loop including the steps of introducing a volatile anti-icing compound into the hot make-up gas to vaporize the compound, cooling the gas and vaporized anti-icing compound to condense part of the anti-icing compound, separating the condensed

Parrish

1986-01-01

191

Reaction synthesis and processing of nickel and iron aluminides  

SciTech Connect

Composites of Ni and Fe aluminides were obtained by hot pressing and hot extrusion of a blended mixture of Ni and Al or Fe and Al with ceramic phases such as TiC, ZrO{sub 2}, and Al{sub 2}O{sub 3}. Aluminides were analyzed by XRD to determine the phase structures, and optical and scanning electron microscopies were used to determine the grain sizes of the aluminides and dispersion of ceramics. Tensile properties (0.2% YS, UTS, total elong., RIA) were measured on buttonhead and sheet specimens of Ni and Fe aluminides and their composites at room and high temperatures in air at a strain rate of 1. 2x10{sup -3}/s. Tensile properties of Fe-8 wt% Al from partial mechanical alloying and then combustion synthesis compare very well with oxide-dispersed alloys of Fe. Fe aluminides of FeAl and their composites, based on Fe-24 wt% Al from hot pressing of Fe and Al powders with or without ceramic phases, exhibited full densities and uniform grain sizes. Tensile properties of FeAl and composites (hot pressing of elemental powders) were excellent compared to those of FeAl alloys from hot extrusion of water-atomized powders. Fe aluminides were also obtained by hot extrusion of Fe and Al powders at 950, 1000, and 1100 C.

Deevi, S.C. [Philip Morris U.S.A., Richmond, VA (United States). Research Center; Sikka, V.K. [Oak Ridge National Lab., TN (United States)

1996-12-31

192

Porous silicon ammonia gas sensor  

NASA Astrophysics Data System (ADS)

A planar optical waveguide is manufactured by the functionnalisation of oxidised mesoporous silicon with Bromothymol Blue to achieve a sensitive ammonia sensor suitable for low gas concentrations. The propagated light intensity is measured at the output of the waveguide. The sensitivity at low concentrations and the short time of reaction of the sensor are enhanced by a confinement effect of the gas molecules inside the pores. The dependence of the output signal with gas concentration is demonstrated. When the ammonia flow is stopped, the reversibility of the initial characteristics of the propagated light is naturally obtained with the disappearance of the gas molecules.

Chaillou, A.; Charrier, J.; Lorrain, N.; Sarret, M.; Haji, L.

2006-04-01

193

Template-Based Synthesis: Polymerase Chain Reaction (PCR)  

NSDL National Science Digital Library

In this activity, by the Concord Consortium's Molecular Literacy project, students learn that "it is difficult, if not practically impossible, for organisms to create a polymer without some guiding template molecule. DNA is then discussed as an example and the basics of DNA replication are explored." Upon completion of this activity students should be able to demonstrate how using a template is an efficient way to create a molecule of specific sequence; discuss the basic mechanism of how DNA replicates; and apply their knowledge of DNA replication to the Polymerase Chain Reaction procedure. The activity itself is a java-based interactive resource built upon the free, open source Molecular Workbench software. In the activity, students are allowed to explore at their own pace in a digital environment full of demonstrations, illustrations, and models they can manipulate. In addition to the activity, visitors will find an overview of the activity, a test and rubric, central concepts, and their correlation to AAAS standards.

194

Synthesis, reactions and biological activities of furochromones: A review.  

PubMed

Furochromone derivatives are important synthetic targets which showed a myriad of interesting biological activities. Ammi visnaga (Umbelliferae) is the most famous source of these derivatives, which has been used in folk medicine for millennia targeting different ailments. Since the isolation of furochromone derivatives, different synthetic methodologies were developed for their preparation. Despite the recent interesting findings on this class of compounds, the chemical literatures lack a comprehensive summary on the synthetic methodologies and biological activities of furochromone derivatives. This review highlights recent advances in furochromones chemistry by discussing different synthetic procedures developed for the preparation of naturally occurring derivatives as well as other unique derivatives which showed promising biological activities. It also sheds light on the most common reactions of furochromone derivatives and the utilization of these derivatives as the blocks for many biologically active compounds. PMID:25499986

Abu-Hashem, Ameen A; El-Shazly, Mohamed

2015-01-27

195

Synthesis of most polyene natural product motifs using just twelve building blocks and one coupling reaction  

PubMed Central

The inherent modularity of polypeptides, oligonucleotides, and oligosaccharides has been harnessed to achieve generalized building block-based 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 the synthesis of a wide range of polyene frameworks covering all of this natural product chemical space, and 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 for making small molecules in the laboratory. PMID:24848233

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

2014-01-01

196

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

197

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

SciTech Connect

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.

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

198

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

SciTech Connect

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.

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

199

Enantioselective Synthesis of Tetrahydroquinolines, Tetrahydroquinoxalines, and Tetrahydroisoquinolines via Pd-Catalyzed Alkene Carboamination Reactions.  

PubMed

A catalyst composed of Pd2(dba)3 and (S)-Siphos-PE provides excellent results in Pd-catalyzed alkene carboamination reactions between aniline derivatives bearing pendant alkenes and aryl or alkenyl halides. These transformations generate tetrahydroquinolines and tetrahydroquinoxalines that contain quaternary carbon stereocenters with high levels of asymmetric induction. In addition this catalyst also effects the asymmetric synthesis of tetrahydroisoquinolines via related transformations of 2-allylbenzylamines. In contrast to most other approaches to the asymmetric synthesis of these compounds, which frequently involve functional group interconversion or a single C-C or C-N bond-forming event, the carboamination reactions generate both a C-N bond, a C-C bond, and a stereocenter. PMID:25431650

Hopkins, B A; Wolfe, J P

2014-12-01

200

Synthesis of the zoanthamine ABC ring system: some surprises from intramolecular Diels-Alder reactions.  

PubMed

[reaction: see text] In connection with the total synthesis of the marine alkaloids zoanthamine and norzoanthamine, an elaborate model study was conducted starting from (-)-carvone. In nine steps alkenyl iodides corresponding to the C11-C24 fragment of zoanthamine were obtained. The alkenyl iodides were coupled to various stannanes (C6-C10 fragment) via the Corey modification of the Stille reaction, affording a variety of Diels-Alder precursors. An interesting and highly unexpected cascade reaction sequence was observed during the screening of an intramolecular Diels-Alder reaction, generating a novel tetracyclic framework. A slight modification in the Diels-Alder precursor allowed the desired cycloaddition to take place, giving the cycloadduct in 87% yield. PMID:16388646

Juhl, Martin; Nielsen, Thomas E; Le Quement, Sebastian; Tanner, David

2006-01-01

201

Synthesis of ?,?'-trans-oxepanes through an organocatalytic oxa-conjugate addition reaction.  

PubMed

Oxepanes are found in a wide range of natural products; however, they are challenging synthetic targets due to enthalpic and entropic barriers. Organocatalytic oxa-conjugate addition reactions promoted by the gem-disubstituent (Thorpe-Ingold) effect stereoselectively provided ?,?'-trans-oxepanes. In addition, the potential of an organocatalytic tandem oxa-conjugate addition/?-oxidation was demonstrated in a rapid generation of molecular complexity. These organocatalytic oxa-conjugate addition reactions would provide powerful tools for the synthesis of natural products that contain highly functionalized oxepanes. PMID:24724535

Lanier, Megan L; Kasper, Amanda C; Kim, Hyoungsu; Hong, Jiyong

2014-05-01

202

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

PubMed Central

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

Lam, Tin Yiu; Wang, Yu-Pu

2013-01-01

203

Low-Temperature Synthesis of Actinide Tetraborides by Solid-State Metathesis Reactions  

SciTech Connect

The synthesis of actinide tetraborides including uranium tetraboride (UB,), plutonium tetraboride (PUB,) and thorium tetraboride (ThB{sub 4}) by a solid-state metathesis reaction are demonstrated. The present method significantly lowers the temperature required to {approx_equal}850 C. As an example, when UCl{sub 4}, is reacted with an excess of MgB{sub 2}, at 850 C, crystalline UB, 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, product is purified by washing water and drying.

Lupinetti, Anthony J.; Garcia, Eduardo; Abney, Kent D.

2004-12-14

204

Stereoselective synthesis of caffeic acid amides via enzyme-catalyzed asymmetric aminolysis reaction.  

PubMed

In this study, a new method was developed to prepare enantiopure caffeic acid amides by enzyme-catalyzed asymmetric aminolysis reaction. Methoxymethyl chloride (MOMCl) was first introduced as a protective and esterified reagent to obtain the MOM-protected caffeic acid MOM ester 1d. Aminolysis reaction occurred between 1d and (R, S)-?-phenylethylamine in the presence of an immobilized lipase (Novozym 435) from Candida antarctica. Compared with the methyl-protected caffeic acid methyl ester 1c, 1d as substrate improved the lipase-catalyzed reaction rate by 5.5-fold. After Novozym 435-catalyzed aminolysis reaction was established, we evaluated the effects of synthesis parameters on the catalytic activity and enantioselectivity of Novozym 435. A reaction conversion rate of 25.5% and an E value of >100 were achieved under the following optimum conditions: reaction solvent, anhydrous isooctane; reaction temperature, 70°C; reaction time, 24h; ester-to-amine substrate molar ratio, 1:40; and enzyme additive amount, 40 mg. Kinetic and thermodynamic analyses were conducted to determine the main factors affecting enantiomeric discrimination. Novozym 435 still showed 80% of its initial activity after recycling five times. Highly optically pure caffeic acid amides with an enantiomeric excess of 98.5% were finally obtained by HCl deprotection. The established enzyme-catalyzed asymmetric aminolysis method in this study might be used to prepare other caffeic acid amides. PMID:24056082

Xiao, Peiliang; Zhang, Suoqin; Ma, Huayu; Zhang, Aijun; Lv, Xiaoli; Zheng, Liangyu

2013-12-01

205

Reaction synthesis of dynamically densified titanium-based intermetallic and ceramic-forming powders  

Microsoft Academic Search

The mechanism(s) and kinetics of the reaction synthesis of dynamically-densified Ti-based intermetallic and ceramic forming powder mixtures were investigated in this study. Dynamic densification employing shock-compression produces a dense-packed and highly-activated state of powder mixture constituents resulting in significantly increased mass transport rates and enhanced chemical reactivity. Green density compacts (˜85--95% TMD) of Ti-Si, Ti-B, and Ti-Al powder mixtures, obtained

Shantanu Ashok Namjoshi

1999-01-01

206

Enzymatic Synthesis of Biodiesel from Transesterification Reactions of Vegetable Oils and Short Chain Alcohols  

Microsoft Academic Search

Biodiesel synthesis by alcoholysis of three vegetable oils (soybean, sunflower and rice bran) catalyzed by three commercial\\u000a lipases (Novozym 435, Lipozyme TL-IM and Lipozyme RM-IM), and the optimization of the enzymes stability over repeated batches\\u000a is described. The effects of the molar ratio of alcohol to oil and the reaction temperature with methanol, ethanol, propanol\\u000a and butanol were also studied.

Rafael Costa Rodrigues; Giandra Volpato; Keiko Wada; Marco Antônio Záchia Ayub

2008-01-01

207

Synthesis and processing of AgInO 2 delafossite compounds by cation exchange reactions  

Microsoft Academic Search

In recent years, ternary noble metal oxide compounds based on the delafossite structure have attracted great interest because of their potential use as transparent conductors. In this work, the experimental conditions which affect the synthesis and properties of Ag-based compounds by the cation exchange technique was explored. The reaction between AgNO3 and NaInO2 was performed at temperatures ranging from 200

Jane E Clayton; David P Cann; Nathan Ashmore

2002-01-01

208

Synthesis and Isolation of Stable 1,2-Siloxetanes from Reaction of Transient Silenes with Acetone  

E-print Network

Synthesis and Isolation of Stable 1,2-Siloxetanes from Reaction of Transient Silenes with Acetone,2,2-triphenyldisilanes (R3Si-SiPh3; SiR3 ) SiMe3, SiEt3, SiMe2 tBu) in hydrocarbon solution in the presence of acetone,2,2-triphenyldisilane yields an intractable mixture upon photolysis in the presence of acetone under the above

Leigh, William J.

209

Iron-catalyzed cross-coupling reactions. A scalable synthesis of the immunosuppressive agent FTY720.  

PubMed

A chemo- and regioselective cross-coupling reaction of the functionalized aryl triflate 5 with octylmagnesium bromide catalyzed by cheap, nontoxic, and environmentally benign Fe(acac)(3) sets the basis for a practical and scaleable synthesis of the octylbenzene derivative 6, which serves as a key building block for the preparation of FTY720 (1). This 2-amino-1,3-propanediol derivative shows highly promising immunosuppressive properties and is currently in human clinical phase III trials. PMID:15153030

Seidel, Günter; Laurich, Daniel; Fürstner, Alois

2004-05-28

210

Asymmetric Synthesis of Fully Substituted Cyclopentane-Oxindoles through an Organocatalytic Triple Michael Domino Reaction.  

PubMed

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

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

2015-01-12

211

Enantioselective synthesis of beta-trifluoromethyl-beta-lactones via NHC-catalyzed ketene-ketone cycloaddition reactions.  

PubMed

The highly diastereo- and enantioselective synthesis of beta-trifluoromethyl-beta-lactones bearing two contiguous stereocenters was realized by chiral N-heterocyclic carbene-catalyzed formal cycloaddition reaction of alkyl(aryl)ketenes and trifluoromethyl ketones. PMID:19681591

Wang, Xiao-Na; Shao, Pan-Lin; Lv, Hui; Ye, Song

2009-09-17

212

A Review of Study on Thermal Energy Transport System by Synthesis and Decomposition Reactions of Methanol  

NASA Astrophysics Data System (ADS)

The study on thermal energy transport system by synthesis and decomposition reactions of methanol was reviewed. To promote energy conservation and global environment protection, a two-step liquid-phase methanol synthesis process, which starts with carbonylation of methanol to methyl formate, then followed by the hydrogenolysis of the formate, was studied to recover wasted or unused discharged heat from industrial sources for the thermal energy demands of residential and commercial areas by chemical reactions. The research and development of the system were focused on the following three points. (1) Development of low-temperature decomposition and synthetic catalysts, (2) Development of liquid phase reactor (heat exchanger accompanying chemical reaction), (3) Simulation of the energy transport efficiency of entire system which contains heat recovery and supply sections. As the result of the development of catalyst, promising catalysts which agree with the development purposes for the methyl formate decomposition reaction and the synthetic reaction are being developed though some studies remain for the methanol decomposition and synthetic reactions. In the fundamental development of liquid phase reactor, the solubilities of CO and H2 gases in methanol and methyl formate were measured by the method of total pressure decrease due to absorption under pressures up to 1500kPa and temperatures up to 140°C. The diffusivity of CO gas in methanol was determined by measuring the diameter and solution time of single CO bubbles in methanol. The chemical reaction rate of methanol synthesis by hydrogenolysis of methyl formate was measured using a plate-type of Raney copper catalyst in a reactor with rectangular channel and in an autoclave reactor. The reaction characteristics were investigated by carrying out the experiments at various temperatures, flow rates and at various catalyst development conditions. We focused on the effect of Raney copper catalyst thickness on the liquid-phase chemical reaction by varying the development time of the catalyst. Investigation results of the catalyst such as surface area, pore radius, lattice size, and photographs of scanning electron microscope (SEM) were also given. In the simulation of energy transport efficiency of this system, by simulating the energy transfer system using two-step liquid phase methanol decomposition and synthetic reactions, and comparing with the technology so far, it can be expected that an innovative energy transfer system is possible to realize.

Liu, Qiusheng; Yabe, Akira; Kajiyama, Shiro; Fukuda, Katsuya

213

Influence of particle size distribution of precursor oxides on the synthesis of cordierite by solid-state reaction  

Microsoft Academic Search

The influence of the particle size distribution of the precursor oxides on the synthesis of cordierite by solid-state reaction has been investigated. Expectedly, it is found that reducing the particle size of the raw materials results in a decrease in the temperature at which the synthesis process starts. Likewise, small particle sizes promote the sintering when subjecting the monoliths to

J. R. González-Velasco; R. Ferret; R. López-Fonseca; M. A. Gutiérrez-Ortiz

2005-01-01

214

Formal synthesis of kingianin A based upon a novel electrochemically-induced radical cation Diels-Alder reaction.  

PubMed

The application of electrochemical reactions in natural product synthesis has burgeoned in recent years. We herein report a formal synthesis of the complex and dimeric natural product kingianin A, which employs an electrochemically-mediated radical cation Diels-Alder cycloaddition as the key step. PMID:25196219

Moore, Jonathan C; Davies, E Stephen; Walsh, Darren A; Sharma, Pallavi; Moses, John E

2014-10-25

215

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

ERIC Educational Resources Information Center

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…

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

2004-01-01

216

Copper-catalyzed intramolecular tandem reaction of (2-halogenphenyl)(3-phenyloxiran-2-yl)methanones: synthesis of (Z)-aurones.  

PubMed

A convenient and efficient method for the copper-catalyzed synthesis of (Z)-aurones via intramolecular tandem reaction of (2-halogenphenyl)(3-phenyloxiran-2-yl)methanones is reported. Moreover, a plausible mechanism for the formation of (Z)-aurones is proposed. This is the first report on the synthesis of (Z)-aurones through copper-catalyzed Ullmann coupling reaction employing epoxides as substrates. PMID:24735197

Weng, Yiyi; Chen, Qixu; Su, Weike

2014-05-01

217

A new Heck reaction modification using ketone Mannich bases as enone precursors: parallel synthesis of anti-leishmanial chalcones.  

PubMed

A new Heck-type reaction for the synthesis of chalcones has been established using Mannich bases as enone precursors. The novel reaction proceeds rapidly in air atmosphere under ligandless conditions and can be adapted for library synthesis in a parallel reactor station. Screening of the synthesized chalcones revealed N-{4-[(1E)-3-oxo-3-(3-pyridinyl)-1-propenyl]phenyl}benzamide (3f) to be a potent anti-leishmanial agent. PMID:18276134

Reichwald, Christina; Shimony, Orly; Sacerdoti-Sierra, Nina; Jaffe, Charles L; Kunick, Conrad

2008-03-15

218

Synthesis of nanocrystals of gadolinium carbonate by reaction crystallization.  

PubMed

The formation of nano-sized crystals of gadolinium carbonate via reaction crystallization was studied in a semi-batch crystallizer using gadolinium chloride and ammonium hydrogen carbonate as the reactants. The gadolinium carbonate crystals were formed by the aggregation of primary particles sized about 5 nm. Thereby, the crystallization parameters acting directly on the aggregation of the primary particles, such as the reactant concentrations, non-stoichiometry of the reactants, solution pH, acoustic energy, and agitation speed, were mechanistically investigated. As such, increasing the reactant concentrations enhanced the crystal size due to higher nucleation of the primary particles for the aggregation. Non-stoichiometric reactant concentrations resulted in a significant reduction of the crystal size, due to the adsorption of the excess species on the primary particles. Similarly, the surface charge of the primary particles depended on the solution pH. Thus, the crystal size was reduced when the pH deviated from the neutral point. The acoustic cavitation of the ultrasound was much more effective than the turbulent fluid motion of the agitation in inhibiting the primary particle aggregation. Thus, the crystal size was remarkably reduced, even at a low acoustic energy of 6 watts. PMID:22755060

He, Xin-Kuai; Shin, Dongmin; Kim, Woo-Sik

2012-03-01

219

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

SciTech Connect

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.

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

220

Synthesis of three kinds of GaN nanowires through Ga 2O 3 films’ reaction with ammonia  

NASA Astrophysics Data System (ADS)

A new method was employed to obtain GaN nanowires (NWs). In this method, SiC films were deposited with radio frequency (r.f.) magnetron sputtering onto silicon substrates and annealed at high temperature, and then Ga 2O 3 films were deposited on top of the SiC intermediate layers and annealed in NH 3 atmosphere. SiC layer was used to reduce thermal and lattice mismatch between GaN and Si, and improve NWs’ quality. After Ga 2O 3 films reacted with NH 3, a great quantity of GaN NWs with the shape of birch trunks and stalactites were found by transmission electron microscopy (TEM). At the same time, a few very even and uniform pillarlike NWs were observed. The electron diffraction patterns (EDP) show that birch trunk-shaped and pillarlike NWs are all single-crystalline structures. These NWs were also analyzed with the assistance of X-ray diffraction (XRD), Fourier transformed infrared spectra (FTIR) and high-resolution transmission electron microscopy (HRTEM) to show their properties.

Dong, Zhihua; Xue, Chengshan; Zhuang, Huizhao; Wang, Shuyun; Gao, Haiyong; Tian, Deheng; Wu, Yuxin; He, Jianting; Liu, Yi'an

2005-03-01

221

Synthesis of chemically-modified single-walled carbon nanotubes by counter-current ammonia gas injection into the induction thermal plasma process  

NASA Astrophysics Data System (ADS)

Pristine single-walled carbon nanotubes (SWCNTs) are poorly dispersible and insoluble in many solvents and need to be chemically modified prior to their use in many applications. This work is focused on the investigation of the synthesis of chemically modified SWCNTs material through an in situ approach. The main objectives of the presented research are: 1) to explore the in situ chemical process during the synthesis of SWCNT and 2) to closely examine the effect of a reactive environment on SWCNTs. Effects of the catalyst type and content on the SWCNTs final product, synthesized by induction thermal plasma (ITP), were studied to replace toxic cobalt (Co) in the feedstock. In this regard, three different catalyst mixtures (i.e. Ni-Y2O3, Ni-Co-Y2O3, and Ni-Mo-Y2O3) were used. Experimental results showed that the catalyst type affects the quality of the SWCNT final product. Similar quality SWCNTs can be produced when the same amount of Co was replaced by Ni. Moreover, the results observed in this experimental work were further explained by thermodynamic calculation results. Thermogravimetry (TG) was used throughout the work to characterize the SWCNTs product. TG was firstly standardized by studying the effects of three main instrumental parameters (temperature ramp, TR, initial mass of the sample, IM, and gas flow rate, FR) on the Tonset and full-width half maximum (FWHM) obtained from TG and derivative TG graphs of carbon black, respectively. Therefore, a two-level factorial statistical design was performed. The statistical analysis showed that the effect of TR, IM, and to a lower extent, FR, is significant on FWHM and insignificant on Tonset. A methodology was then developed based upon the SWCNTs synthesis using the ITP system, through an in situ chemistry approach. Ammonia (NH3) was selected and counter-currently injected into the ITP reactor at three different flow rates and by four different nozzle designs. Numerical simulation indicated a better mixing of NH3 in the ITP reactor when a certain nozzle was used. The experimental results showed the increase of D-band intensity in the Raman spectra of SWCNT samples upon the NH3 injection. NH3 could increase the nitrogen content of the SWCNTs final product up to 10 times. The SWCNTs sample treated with 15 vol% NH3 showed an enhanced dispersibility in Dimethylformamide and Isopropanol. Onion-like and planar carbon nanostructures were also observed. Complementary characterization on the SWCNT samples treated by 15 vol% NH3 indicated the surface modification of nanotubes. Metallic tubes showed a higher reactivity with NH3 than semiconducting ones. The model including the reactor thermo-flow field and NH3 thermal decomposition kinetics suggested a two-step SWCNT surface modification in which nanotubes firstly react with H and NH2 intermediates and later, NH3 chemisorbs on the nanotubes. The model also suggested that the intermediate species, like NNH and N2H2, play a role primarily in driving the NH3 decomposition rather than the chemical modification of SWCNTs. Keywords: Single-walled carbon nanotube, Induction thermal plasma, Thermogravimetry, Kinetic, Computational fluid dynamic, Thermodynamic, modification, Functionalization

Shahverdi, Ali

222

Formation of hydantoins in gasifier condensate water. [5,5-dimethyl hydantoin synthesis by reaction of acetone cyanohydrin with excess ammonium carbonate  

SciTech Connect

A number of 5,5-diakyl and 5-alkylhydantoins have been detected in the condensate water from the gasification of Indian Head (ND) lignite in the University of North Dakota Energy Research Center (UNDERC) slagging fixed bed gasifier. These compounds do not form directly in the gasifier. They were shown to be either absent or present in low concentrations in water samples which were collected from a side stream sampler on the UNDERC gasifier and quickly frozen. When this side stream condensed water was heated in a constant temperature bath at 40/sup 0/C, hydantoin concentrations increased in an approximately second-order manner. The formation is believed to proceed by the Bucherer-Berg reaction, the same reaction used in commercial hydantoin synthesis, from ammonia, carbonate, hydrogen cyanide and various ketones and aldehydes at a pH of 8.5. A kinetic study was undertaken to obtain useful rate data for this reaction. Reliable and reproducible concentration data for acetone and cyanide were impossible to obtain for the raw gasifier condensate water because of the presence of reversible addition products of cyanide such as acetone cyanohydrin and 2-amino-2-methylpropanonitrile as well as large amounts of sulfide. Thus a model system was investigated where acetone cyanohydrin was reacted with excess ammonium carbonate at concentrations approaching those obtained in the condensate water, 0.020M and 0.25M, respectively. The reaction was studied at 50/sup 0/, 70/sup 0/, and 90/sup 0/C using a capillary GC (0V351 phase) for the analysis of 5.5-dimethylhydantoin (DMH) using 4-methoxyphenol as the internal standard. Results are discussed. 8 references, 2 tables.

Olson, E.S.; Worman, J.J.; Diehl, J.W.

1984-12-01

223

Development of a Quantitative Real-Time Polymerase Chain Reaction Assay to Target a Novel Group of Ammonia-Producing Bacteria Found in Poultry Litter  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ammonia production in poultry houses has serious implications for flock health and performance, nutrient value of poultry litter, and energy costs for running poultry operations. The urease enzyme is responsible for the final step in the conversion of organic N (specifically uric acid and urea) to ...

224

Integrated process for the production of methanol and ammonia  

Microsoft Academic Search

Disclosed is an integrated process for the production of methanol and ammonia which comprises the steps of subjecting a gaseous hydrocarbon feed to primary reforming with steam to produce a methanol synthesis gas containing H2 and CO, synthesizing methanol from this methanol synthesis gas, subjecting the purge gas resulting from the methanol synthesis step to secondary reforming with steam and

K. Miyashita; S. Nozawa

1982-01-01

225

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

PubMed

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

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

2015-02-16

226

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

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.

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

227

Methanol synthesis on ZnO(000overline{1}). IV. Reaction mechanisms and electronic structure  

NASA Astrophysics Data System (ADS)

Methanol synthesis from CO and H2 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(000overline{1}) 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 H2 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.

Frenzel, Johannes; Marx, Dominik

2014-09-01

228

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

PubMed

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

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

229

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

Microsoft Academic Search

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

Shuhei Inoue; Shigeo Maruyama

2008-01-01

230

Lipid synthesis under hydrothermal conditions by Fischer-Tropsch-type reactions  

NASA Technical Reports Server (NTRS)

Ever since their discovery in the late 1970's, mid-ocean-ridge hydrothermal systems have received a great deal of attention as a possible site for the origin of life on Earth (and environments analogous to mid-ocean-ridge hydrothermal systems are postulated to have been sites where life could have originated or Mars and elsewhere as well). Because no modern-day terrestrial hydrothermal systems are free from the influence of organic compounds derived from biologic processes, laboratory experiments provide the best opportunity for confirmation of the potential for organic synthesis in hydrothermal systems. Here we report on the formation of lipid compounds during Fischer-Tropsch-type synthesis from aqueous solutions of formic acid or oxalic acid. Optimum synthesis occurs in stainless steel vessels by heating at 175 degrees C for 2-3 days and produces lipid compounds ranging from C2 to > C35 which consist of n-alkanols, n-alkanoic acids, n-alkenes, n-alkanes and alkanones. The precursor carbon sources used are either formic acid or oxalic acid, which disproportionate to H2, CO2 and probably CO. Both carbon sources yield the same lipid classes with essentially the same ranges of compounds. The synthesis reactions were confirmed by using 13C labeled precursor acids.

McCollom, T. M.; Ritter, G.; Simoneit, B. R.

1999-01-01

231

Pyranoside-into-furanoside rearrangement: new reaction in carbohydrate chemistry and its application in oligosaccharide synthesis.  

PubMed

Great interest in natural furanoside-containing compounds has challenged the development of preparative methods for their synthesis. Herein a novel reaction in carbohydrate chemistry, namely a pyranoside-into-furanoside (PIF) rearrangement permitting the transformation of selectively O-substituted pyranosides into the corresponding furanosides is reported. The discovered process includes acid-promoted sulfation accompanied by rearrangement of the pyranoside ring into a furanoside ring followed by solvolytic O-desulfation. This process, which has no analogy in organic chemistry, was shown to be a very useful tool for the synthesis of furanoside-containing complex oligosaccharides, which was demonstrated by synthesizing disaccharide derivatives ?-D-Galp-(1?3)-?-D-Galf-OPr, 3-O-s-lactyl-?-D-Galf-(1?3)-?-D-Glcp-OPr, and ?-L-Fucf-(1?4)-?-D-GlcpA-OPr related to polysaccharides from the bacteria Klebsiella pneumoniae and Enterococcus faecalis and the brown seaweed Chordaria flagelliformis. PMID:25319316

Krylov, Vadim B; Argunov, Dmitry A; Vinnitskiy, Dmitry Z; Verkhnyatskaya, Stella A; Gerbst, Alexey G; Ustyuzhanina, Nadezhda E; Dmitrenok, Andrey S; Huebner, Johannes; Holst, Otto; Siebert, Hans-Christian; Nifantiev, Nikolay E

2014-12-01

232

Synthesis of 2,5-asymmetrically substituted 3,4-diaminothieno[2,3-b]thiophenes by domino reaction.  

PubMed

A convenient one pot synthesis of 2,5-asymmetrically substituted thieno[2,3-b]thiophenes is developed. The method is based on consecutive domino reactions (SN2 reaction ? Thorpe-Ziegler reaction) using malononitrile and carbon disulfide as starting materials with the generation of potassium 2,2-dicyanoethene-1,1-bis(thiolate) in a solution. The high yield of the target thienothiophenes was achieved using the Ziegler dilution effect. PMID:24028177

Zubarev, Andrey A; Larionova, Natalia A; Rodinovskaya, Lyudmila A; Mortikov, Valery Yu; Shestopalov, Anatoliy M

2013-10-14

233

Mechanistic investigations of the reaction network in chemo-bio catalyzed synthesis of R -1-phenylethyl acetate  

Microsoft Academic Search

The kinetics and reaction network of the one-pot synthesis of R-1-phenylethyl acetate was investigated at 70°C in toluene over a combination of three different catalysts: PdZn\\/Al2O3 as a catalyst for acetophenone hydrogenation, lipase as an enzymatic catalyst for R-1-phenylethanol acylation with ethyl acetate and Ru\\/Al2O3 as a racemization catalyst for S-1-phenylethanol. In addition to the desired reactions, other reactions, namely

A. Kirilin; S. Sahin; A. Tokarev; P. Mäki-Arvela; K. Kordas; A.-R. Leino; A. Shchukarev; J.-P. Mikkola; L. M. Kustov; T. Salmi; D. Yu. Murzin

2010-01-01

234

Radical Coupling Reactions in Lignin Synthesis: A Density Functional Theory Study  

SciTech Connect

Lignin is a complex, heterogeneous polymer in plant cell walls that provides mechanical strength to the plant stem and confers resistance to degrading microbes, enzymes, and chemicals. Lignin synthesis initiates through oxidative radical-radical coupling of monolignols, the most common of which are p-coumaryl, coniferyl, and sinapyl alcohols. Here, we use density functional theory to characterize radical-radical coupling reactions involved in monolignol dimerization. We compute reaction enthalpies for the initial self- and cross-coupling reactions of these monolignol radicals to form dimeric intermediates via six major linkages observed in natural lignin. The 8-O-4, 8-8, and 8-5 coupling are computed to be the most favorable, whereas the 5-O-4, 5-5, and 8-1 linkages are less favorable. Overall, p-coumaryl self- and cross-coupling reactions are calculated to be the most favorable. For cross-coupling reactions, in which each radical can couple via either of the two sites involved in dimer formation, the more reactive of the two radicals is found to undergo coupling at its site with the highest spin density.

Sangha, A. K.; Parks, J. M.; Standaert, R. F.; Ziebell, A.; Davis, M.; Smith, J. C.

2012-04-26

235

Fusion reactions and experimental approaches to the synthesis of superheavy nuclei  

SciTech Connect

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.

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

236

Optimization of reaction conditions for enzymatic synthesis of palm fatty hydrazides using response surface methodology.  

PubMed

Optimization of the enzymatic synthesis of palm fatty hydrazide by the response surface methodology (RSM) was conducted using the Design-Expert 6 software. The palm fatty hydrazide was synthesized from refined, bleached and deodorized palm olein (RBDPOo) and neutralized hydrazine monohydrate in the presence of Rhizomucor miehei lipase, Lipozyme RMIM, an immobilized lipase in n-hexane. The reaction conditions such as the percentage of enzyme, reaction temperature, stirring speed and reaction time were selected as independent variables or studied factors, while the amount of crude palm fatty hydrazide obtained was selected as a dependent variable or response. The study was conducted using a central composite design (CCD) at five coded levels and the experimental data were analyzed using a quadratic model. The analysis of variance (ANOVA) indicates that the model was significant at 95% confidence level with Prob>F of 0.0033, where the regression coefficient value, R² was 0.8415 and lack-of-fit of 0.0984. A percentage of enzyme of 6%, a reaction temperature of 40°C, a stirring speed of 350 rpm and a reaction time of 18 h were found to be the optimum conditions for the conversion of RBDPOo into palm fatty hydrazide. PMID:22531058

Tuan Noor Maznee, T I; Hazimah, A H; Wan Zin, W Y

2012-01-01

237

Synthesis of the clathrate-I phase Ba(8-x)Si46 via redox reactions.  

PubMed

The clathrate-I phase Ba(8-x)Si(46) (space group Pm3?n) was synthesized by oxidation of Ba(4)Li(2)Si(6) with gaseous HCl. Microcrystalline powders of the clathrate phase were obtained within a few minutes. The reaction temperature and the pressure of HCl were optimized to achieve good-quality crystalline products with a composition range of 1.3 < x < 1.9. The new preparation route presented here provides an alternative to the high-pressure synthesis applied so far. PMID:21486020

Liang, Ying; Böhme, Bodo; Reibold, Marianne; Schnelle, Walter; Schwarz, Ulrich; Baitinger, Michael; Lichte, Hannes; Grin, Yuri

2011-05-16

238

Study on reaction rates for methanol synthesis from carbon monoxide, carbon dioxide, and hydrogen  

Microsoft Academic Search

The reaction rates for methanol synthesis from carbon monoxide, carbon dioxide, and hydrogen over a copper-zinc-based catalyst were measured under the following conditions: temperature, 210-300°C; pressure, 4-10 MPa, feed gas composition Hâ\\/CO 2.7-720, Hâ\\/COâ, 4.3-120, COâ\\/CO, 0.05-180 (in moles). It was concluded that direct methanol production from COâ takes place under the above conditions in addition to the two well-known

M. Takagawa; M. Ohsugi

1987-01-01

239

Synthesis, characterisation and reactions of phosphine-substituted alkynylboronates and alkynyltrifluoroborate salts.  

PubMed

The synthesis and structural characterisation of phosphine-substituted alkynylboronates is reported. A P(III)-centred alkynylboronate (2) was prepared that showed little evidence for the conjugation of the P-lone pair to the boron via the alkyne ?-system, as judged by X-ray crystallography studies of 2 and a related P(V) compound, 3. In addition, corresponding alkynyltrifluoroborate salts were prepared that showed improved stability by comparison to their boronic ester counterparts. These salts undergo Pd-catalysed cross-coupling reactions with aryl halides. PMID:25529019

Vivat, Jérôme F; Bachollet, Sylvestre P J T; Adams, Harry; Harrity, Joseph P A

2014-01-01

240

Ammonia utilization process  

Microsoft Academic Search

This patent describes a process for gasification of organic carbonaceous materials in a hydrogen forming gasifier. The improvement consists of: separating ammonia from product gas of the gasifier by dissolving in an aqueous liquid forming sour water; separating the sour water from the gasifier product gas; separating gaseous ammonia from the sour water; and recycling the gaseous ammonia to the

1987-01-01

241

A convenient synthesis and a NMR study of the diammoniate of diborane.  

PubMed

DADB synthesis: The diammoniate of diborane (DADB) was synthesized in a new metathesis reaction between the diammoniate of monochloroborane and potassium borohydride in liquid ammonia. (1)H and (11)B?NMR spectra of DADB are reported. The stability in THF was examined by variable-temperature (11)B?NMR spectroscopy. PMID:22359312

Lingam, Hima K; Chen, Xuenian; Zhao, Ji-Cheng; Shore, Sheldon G

2012-03-19

242

Synthesis of Shape-Anisotropic Nanomaterials using Spontaneous Galvanic Displacement Reactions  

SciTech Connect

The direct synthesis of nanostructures using wet chemical reduction methods has had a major impact on catalysis and materials design. However, no mechanism has yet been reported that explicitly provides growth parameters for shapes and sizes as a function of desired metals, making it difficult to directly synthesize shaped particles from specific metals. There have been reports in the literature using this method to obtain core-shell, porous cage-like and irregular structures, however only one report proposing a mechanism of the displacement process exists, which does not explain surface and bulk morphology changes as a function of reaction condition. Here, we demonstrate the use of small angle x-ray scattering (SAXS), and microscopy to study the Ag-to-Pt displacement process of nanoparticles, nanowires and nanoplates at known intervals throughout the reaction. Obtaining a fundamental understanding of the displacement process will allow us to tune composition, morphology, and thus electronic properties of novel materials.

Leong, G. J.; Strand, M.; Schulze, M.; Maloney, D.; Larson, D.; Alia, S.; Perry, K.; Neyerlin, K. C.; Pivovar, B.; Wise, A. M.; Toney, M.; Richards, R. M.

2013-01-01

243

Facile synthesis of ultrathin magnetic iron oxide nanoplates by Schikorr reaction  

PubMed Central

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

2013-01-01

244

The design and synthesis of artificial photosynthetic antennas, reaction centres and membranes.  

PubMed Central

Artificial antenna systems and reaction centres synthesized in our laboratory are used to illustrate that structural and thermodynamic factors controlling energy and electron transfer in these constructs can be modified to optimize performance. Artificial reaction centres have been incorporated into liposomal membranes where they convert light energy to vectorial redox potential. This redox potential drives a Mitchellian, quinone-based, proton-transporting redox loop that generates a Deltamu H(+) of ca. 4.4 kcal mol(-1) comprising DeltapH ca. 2.1 and Deltapsi ca. 70 mV. In liposomes containing CF(0)F(1)-ATP synthase, this system drives ATP synthesis against an ATP chemical potential similar to that observed in natural systems. PMID:12437888

Moore, T A; Moore, A L; Gust, D

2002-01-01

245

Alkaline earth metallocenes coordinated with ester pendants: synthesis, structural characterization, and application in metathesis reactions.  

PubMed

A variety of ester-substituted cyclopentadiene derivatives have been synthesized by one-pot reactions of 1,4-dilithio-1,3-butadienes, CO, and acid chlorides. Direct deprotonation of the ester-substituted cyclopentadienes with Ae[N(SiMe3 )2 ]2 (Ae=Ca, Sr, Ba) efficiently generated members of a new class of heavier alkaline earth (Ca, Sr, Ba) metallocenes in good to excellent yields. Single-crystal X-ray structural analysis demonstrated that these heavier alkaline earth metallocenes incorporated two intramolecularly coordinated ester pendants and multiply-substituted cyclopentadienyl ligands. The corresponding transition metal metallocenes, such as ferrocene derivatives and half-sandwich cyclopentadienyl tricarbonylrhenium complexes, could be generated highly efficiently by metathesis reactions. The multiply-substituted cyclopentadiene ligands bearing an ester pendant, and the corresponding heavier alkaline earth and transition-metal metallocenes, may have further applications in coordination chemistry, organometallic chemistry, and organic synthesis. PMID:23934787

Li, Heng; Zhang, Wen-Xiong; Xi, Zhenfeng

2013-09-16

246

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

DOEpatents

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.

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

2004-12-14

247

The densities and reaction heat of methanol synthesis System from cornstalk syngas  

NASA Astrophysics Data System (ADS)

Methanol can be used as possibole replacement for conventional gasoline and Diesel fuel. In order to produce methanol, it is necessary to decompose biomass, including cornstalks, which is a raw material from agricultural residues. A promising route for processing cornstals is made cornstalks gasficated with thermochemical method to prepare the syngas, which has been conducted under a down-flow fixed bed gasifier. While the low-heat-value cornstalk gas produced in the down-flow fixed bed gasifier needs purified and a variety of technical procedures such as deoxygenation, desulfurization, catalytic cracking of tar and hydrogenation. In this paper, the catalytic experiments of methanol synthesis with cornstalk syngas were carried out in a tubular-flow integral and isothermal reactor. The effect of reaction temperature, pressure, catalyst types, catalyst particle size, syngas flow at entering end and composition of syngas was determind. The experimental results indicated that the proper catalyst of the synthetic reaction was C301 and the optimum catalyst size (?) was 0.833 mm×0.351 mm. The optimal operating temperature and pressure were found to be 235° C and 5 MPa, respectively. The suitable syngas flow 0.9-1.10 mol/h at entering end was selected and the suitable composition of syngas were CO 10.49%, CO28.8%, N237.32%, CnHm0.95% and H240.49%. The methanol yield is 0.418 g/g cornstalk. Moreover, the densities, state equation parameters and the total reaction heat ?HT,P, of methanol reacting system was calculated by SHBWR state equation under givern reaction pressure. The calculation results provided basic data for the design of the industrial equipments in which catalyzed synthesis of methanol from cornstalk gases is operated.

Zhu, Ling-feng; Zhao, Qing-ling; Chen, Jing; Zhang, Le; Zhang, Run-tao; Liu, Li-li; Zhang, Zhao-yue

2010-11-01

248

Low-temperature synthesis of Mn-based mixed metal oxides with novel fluffy structures as efficient catalysts for selective reduction of nitrogen oxides by ammonia.  

PubMed

A series of Mn-based mixed metal oxide catalysts (Co-Mn-O, Fe-Mn-O, Ni-Mn-O) with high surface areas were prepared via low temperature crystal splitting and exhibited extremely high catalytic activity for the low-temperature selective catalytic reduction of nitrogen oxides with ammonia. PMID:25188714

Meng, Bo; Zhao, Zongbin; Chen, Yongsheng; Wang, Xuzhen; Li, Yong; Qiu, Jieshan

2014-10-21

249

Proline catalyzed ?-aminoxylation reaction in the synthesis of biologically active compounds.  

PubMed

The search for new and efficient ways to synthesize optically pure compounds is an active area of research in organic synthesis. Asymmetric catalysis provides a practical, cost-effective, and efficient method to create a variety of complex natural products containing multiple stereocenters. In recent years, chemists have become more interested in using small organic molecules to catalyze organic reactions. As a result, organocatalysis has emerged both as a promising strategy and as an alternative to catalysis with expensive proteins or toxic metals. One of the most successful and widely studied secondary amine-based organocatalysts is proline. This small molecule can catalyze numerous reactions such as the aldol, Mannich, Michael addition, Robinson annulation, Diels-Alder, ?-functionalization, ?-amination, and ?-aminoxylation reactions. Catalytic and enantioselective ?-oxygenation of carbonyl compounds is an important reaction to access a variety of useful building blocks for bioactive molecules. Proline catalyzed ?-aminoxylation using nitrosobenzene as oxygen source, followed by in situ reduction, gives enantiomerically pure 1,2-diol. This molecule can then undergo a variety of organic reactions. In addition, proline organocatalysis provides access to an assortment of biologically active natural products including mevinoline (a cholesterol lowering drug), tetrahydrolipstatin (an antiobesity drug), R(+)-?-lipoic acid, and bovidic acid. In this Account, we present an iterative organocatalytic approach to synthesize both syn- and anti-1,3-polyols, both enantio- and stereoselectively. This method is primarily based on proline-catalyzed sequential ?-aminoxylation and Horner-Wadsworth-Emmons (HWE) olefination of aldehyde to give a ?-hydroxy ester. In addition, we briefly illustrate the broad application of our recently developed strategy for 1,3-polyols, which serve as valuable, enantiopure building blocks for polyketides and other structurally diverse and complex natural products. Other research groups have also applied similar strategies to prepare such bioactive molecules as littoralisone, brasoside and (+)-cytotrienin A. Among the various synthetic approaches reported for 1,3-polyols, our organocatalytic iterative approach appears to be very promising and robust. This method combines the merit of organocatalytic reaction with an easy access to both enantiomerically pure forms of proline, mild reaction conditions, and tolerance to both air and moisture. In this Account, we present the latest applications of organocatalysis and how organic chemists can use this new tool for the total synthesis of complex natural products. PMID:23148510

Kumar, Pradeep; Dwivedi, Namrata

2013-02-19

250

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

PubMed

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

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

2014-07-01

251

Journey on greener pathways: from the use of alternate energy inputs and benign reaction media to sustainable applications of nano-catalysts in synthesis and environmental remediation  

EPA Science Inventory

Sustainable synthetic processes developed during the past two decades involving the use of alternate energy inputs and greener reaction media are summarized. These processes include examples of coupling reactions, the synthesis of heterocyclic compounds, and a variety of reactio...

252

Synthesis of cyclobakuchiols A, B, and C by using conformation-controlled stereoselective reactions.  

PubMed

Cyclohexanone with the pMeOC6H4 and CH2=C(Me) substituents at the C3 and C4-positions was prepared from (+)-?-pinene and converted to the allylic picolinate by a Masamune-Wittig reaction followed by reduction and esterification. Allylic substitution of this picolinate with Me2CuMgBr·MgBr2 in the presence of ZnI2 proceeded with ? regio- and stereoselectively to afford the quaternary carbon center on the cyclohexane ring with the CH2=CH and Me groups in axial and equatorial positions, respectively. This product was converted to cyclobakuchiol A by demethylation and to cyclobakuchiol C by epoxidation of the CH2=C(Me) group. For the synthesis of cyclobakuchiol B, the enantiomer of the above cyclohexanone derived from (-)-?-pinene was converted to the cyclohexane-carboxylate, and the derived enolate was subjected to the reaction with CH2=CHSOPh followed by sulfoxide elimination to afford the intermediate with the quaternary carbon center with MeOC(=O) and CH2=CH groups in axial and equatorial positions. The MeOC(=O) group was transformed to the Me group to complete the synthesis of cyclobakuchiol B. PMID:24273103

Kawashima, Hidehisa; Kaneko, Yuki; Sakai, Masahiro; Kobayashi, Yuichi

2014-01-01

253

Synthesis of nanocrystalline yttrium iron garnet by low temperature solid state reaction  

SciTech Connect

In this work, nanocrystalline yttrium iron garnet powders were produced by low temperature solid state reaction. The phase evolution during the procedure was determined from the thermogravimetric and differential thermal analysis, and the x-ray diffraction patterns. The results of transmission electron microscopy indicated that the prepared powders exhibited grain size at the nano-level of 20 {approx} 40 nm. Dense ceramics with a theoretical density of around 98% were obtained from the prepared powders after sintering at 1280 deg. C, a relative low sintering temperature compared with conventional ceramic processes, and the saturation magnetizations of sintered samples were also determined. - Research Highlights: {yields}No sol or gel form during the synthesis processing using nitrates and citric acid as raw materials. {yields}The synthesis method needs a low heating temperature (700 deg. C) compared with conventional solid state reaction. {yields}The product is a single phase with homogeneous size distribution and nano grains (20 {approx} 40 nm) confirmed by TEM. {yields}Dense YIG ceramic can be sintered at a low temperature (1280 deg. C) compared with that in conventional processing.

Yu Hongtao, E-mail: yuhongtao@swust.edu.cn; Zeng Liwen; Lu Chao; Zhang Wenbo; Xu Guangliang

2011-04-15

254

The Synthesis of "N"-Benzyl-2-Azanorbornene via Aqueous Hetero Diels-Alder Reaction: An Undergraduate Project in Organic Synthesis and Structural Analysis  

ERIC Educational Resources Information Center

The synthesis of "N"-benzyl-2-azanorbornene via aqueous hetero Diels-Alder reaction of cyclopentadiene and benzyliminium chloride formed in situ from benzylamine hydrochloride and formaldehyde is described. Characterization of the product was achieved by IR and NMR spectroscopies. The spectral data acquired are thoroughly discussed. Numerous…

Sauvage, Xavier; Delaude, Lionel

2008-01-01

255

Biochemistry of Ammonia Monoxygenase from Nitrosomonas  

SciTech Connect

Major results. 1. CytochromecM552, a protein in the electron transfer chain to ammonia monooxygenase. Purification, modeling of protein structure based on primary structure, characterization of 4 hemes by magnetic spectroscopy, potentiometry, ligand binding and turnover. Kim, H. J., ,Zatsman, et al. 2008). 2. Characterization of proteins which thought to be involved in the AMO reaction or to protect AMO from toxic nitrogenous intermediates such as NO. Nitrosocyanin is a protein present only in bacteria which catalyze the ammonia monoxygenase reaction (1). Cytochrome c P460 beta and cytochrome c’ beta.

Alan Hooper

2009-07-15

256

Efficient synthesis of ?- and ?-carbolines by sequential Pd-catalyzed site-selective C-C and twofold C-N coupling reactions.  

PubMed

Two concise and efficient approaches were developed for the synthesis of ?- and ?-carboline derivatives. The success of the synthesis relies on site-selective Suzuki-Miyaura reactions of 1-chloro-2-bromopyridine or 2,3-dibromopyridine with 2-bromophenylboronic acid and subsequent cyclization with amines which proceeds by twofold Pd-catalyzed C-N coupling reactions. PMID:25464277

Hung, Tran Quang; Dang, Tuan Thanh; Janke, Julia; Villinger, Alexander; Langer, Peter

2015-01-21

257

The Influence of Mixing on Staged Flame Processes (Synthesis of Hydrogen Cyanide or Acetylene and Ethylene by Light Hydrocarbons in a Flame Reaction)  

Microsoft Academic Search

The formation of hydrogen cyanide by propane and ammonia and the formation of acetylene and ethylene by propane in flame-reactions was investigated in a special burner using pure oxygen as oxidant. It was possible to perform the reactions in a one-stage or a two-stage process under turbulent flow conditionsIn the case of hydrogen cyanide formation in a one-stage process propane,

H. BOCKHORN; N. GALDO; H. A. KERBERTZ; F. FETTING

1971-01-01

258

Synthesis of chiral 3-substituted phthalides by a sequential organocatalytic enantioselective aldol-lactonization reaction. Three-step synthesis of (S)-(-)-3-butylphthalide.  

PubMed

The development of efficient methods for the facile construction of important molecular frameworks is an important goal in organic synthesis. Chiral 3-substituted phthalides are widely distributed in a large collection of natural products with broad, potent, and potentially path-pointing biological activities. In this investigation, we have uncovered an unprecedented organocatalytic asymmetric aldol-lactonization reaction of 2-formylbenzoic esters with ketones/aldehydes for convenient construction of the enantioenriched "privileged" scaffold. As a result of the sensitive nature of substrate structures of an organocatalytic enantioselective aldol reaction, after extensive optimization of reaction conditions, catalyst L-prolinamide alcohol IV is identified as the best promoter. Interestingly, it is found that in this reaction, addition of an acid additive PhCO(2)H can significantly enhance reaction efficiency with use of only as low as 2.5 mol % IV for the process. Moreover, due to the sensitivity of reaction conditions toward a sequential aldol-lactonization process without affecting enantioselectivity and racemization, it is essential to remove the catalyst for the subsequent facile lactonization reaction in the presence of K(2)CO(3). The aldol-lactonization processes serve as a powerful approach to the preparation of synthetically and biologically important 3-substituted phthalides with a high level of enantioselectivities. A 3-step catalytic asymmetric synthesis of the natural product of 3-butylphthalide is reported. PMID:20000698

Zhang, Haoyi; Zhang, Shilei; Liu, Lu; Luo, Guangshun; Duan, Wenhu; Wang, Wei

2010-01-15

259

One-pot quadruple/triple reaction sequence: a useful tool for the synthesis of natural products.  

PubMed

Multiple reactions in one pot has always been a useful technique for synthetic organic chemists, as it can minimizes solvent usage, time and the number of purification steps when compared to individual multi-step syntheses. In line with this, here in this perspective we discuss a one-pot quadruple/triple reaction sequence comprising an enyne ring-closing metathesis/cross-metathesis/Diels-Alder/aromatization for the synthesis of natural products setting. PMID:25407375

Kashinath, K; Srinivasa Reddy, D

2015-01-28

260

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

PubMed

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

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

2014-10-01

261

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

ERIC Educational Resources Information Center

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…

Graham, Richard C.; DePew, Steven

1983-01-01

262

Sources of atmospheric ammonia  

NASA Astrophysics Data System (ADS)

The information available on factors that influence emissions from the principal societal sources of ammonia to the atmosphere, namely combustion processes, volatilization of farm animal wastes, and volatilization of fertilizers, is reviewed. Emission factors are established for each major source of atmospheric ammonia. The factors are then multiplied by appropriate source characterization descriptors to obtain calculated fluxes of ammonia to the atmosphere on a state-by-state basis for the United States.

Harriss, R. C.; Michaels, J. T.

1982-05-01

263

Determination of the activity of diamine oxidases, urease and histidine ammonia-lyase by enzymatic assay of ammonia  

Microsoft Academic Search

The activities of diamine oxidases (DAO) from submaxillary glands, parotid glands and kidneys, from human serum during the pregnancy and from pig serum and of DAO from pea seedlings and the activities of urease and histidine ammonia-lyase have been determined by measuring NH4+ released from the corresponding substrates. Ammonia has been determined with the aid of glutamate dehydrogenase reaction in

W. Lorenz; J. Kusche; H. Hahn; E. Werle

1968-01-01

264

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

SciTech Connect

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.

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

1996-04-01

265

Palladium-catalyzed reactions in the synthesis of 3- and 4-substituted indoles. 4  

SciTech Connect

4-Bromo-1-tosylindole (1) was converted to tricyclic indole enone 11, a potential intermediate in the synthesis of tetracyclic ergot alkaloids, by a series of palladium-catalyzed processes. Attempts to construct the ergot D ring by the hetero-Diels-Alder reaction of enone 11 and 1-azabutadiene 12 produced not the expected (4 + 2) adduct 13 but the benz(cd)indoline derivative 14 resulting from attack of the aza diene at the indole 2-position. The thermodynamic stability of the naphthol nucleus makes enone 11 generally susceptible to attack at the indole 2-position, as evidenced by the attack of hydride and methyl cuprate nucleophiles at this portion forming indolines 16 and 17, respectively.

Hegedus, L.S.; Sestrick, M.R.; Michaelson, E.T.; Harrington, P.J. (Colorado State Univ., Fort Collins (USA))

1989-08-18

266

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

ERIC Educational Resources Information Center

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…

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

2007-01-01

267

Highly enantioselective synthesis of tetrahydrocarbolines via iridium-catalyzed intramolecular Friedel-Crafts type allylic alkylation reactions.  

PubMed

A highly enantioselective synthesis of substituted tetrahydrocarbolines via Ir-catalyzed Friedel-Crafts type intramolecular asymmetric allylic alkylation of 2-indolyl allyl carbonates has been developed. This strategy features excellent chemoselectivity and enantioselectivity, mild reaction conditions, and an easily accessed chiral ligand. PMID:24215126

Xu, Qing-Long; Zhuo, Chun-Xiang; Dai, Li-Xin; You, Shu-Li

2013-12-01

268

Discrete mechanics optimal control (DMOC) and model predictive control (MPC) synthesis for reaction-diffusion process system with  

E-print Network

Discrete mechanics optimal control (DMOC) and model predictive control (MPC) synthesis for reaction of optimal motion control as well as the optimal input injection policy of an actuator arm regulating proposed in this paper is aimed at solving this coupled problem. The actuator mechanics and its control

Kobilarov, Marin

269

Synthesis of BaZrO3 by a solid-state reaction technique using nitrate precursors  

E-print Network

Synthesis of BaZrO3 by a solid-state reaction technique using nitrate precursors Abdul-Majeed Azada of barium nitrate and zirconyl nitrate at 8008C up to 8 h. Simultaneous thermal analysis (TG-DTA) assisted

Azad, Abdul-Majeed

270

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

ERIC Educational Resources Information Center

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…

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

2010-01-01

271

Transition-metal/Lewis acid free synthesis of acyl benzothiophenes via C-C bond forming reaction.  

PubMed

A simple and single-step synthesis of 2- and 3-acyl substituted benzothiophenes has been described via environmentally benign acylation of benzothiophene with in situ generated acyl trifluoroacetates. Both aliphatic and aromatic carboxylic acids participated in trifluoroacetic anhydride/phosphoric acid mediated C-C bond forming reactions under solvent-free conditions affording acyl benzothiophenes in good overall yields. PMID:17961232

Pal, Sarbani; Khan, Mohammad Ashrafuddin; Bindu, P; Dubey, P K

2007-01-01

272

Transition-metal/Lewis acid free synthesis of acyl benzothiophenes via C-C bond forming reaction  

PubMed Central

A simple and single-step synthesis of 2- and 3-acyl substituted benzothiophenes has been described via environmentally benign acylation of benzothiophene with in situ generated acyl trifluoroacetates. Both aliphatic and aromatic carboxylic acids participated in trifluoroacetic anhydride/phosphoric acid mediated C-C bond forming reactions under solvent-free conditions affording acyl benzothiophenes in good overall yields. PMID:17961232

Pal, Sarbani; Khan, Mohammad Ashrafuddin; Bindu, P; Dubey, PK

2007-01-01

273

Nafion®-catalyzed microwave-assisted Ritter reaction: An atom-economic solvent-free synthesis of amides  

EPA Science Inventory

An atom-economic solvent-free synthesis of amides by the Ritter reaction of alcohols and nitriles under microwave irradiation is reported. This green protocol is catalyzed by solid supported Nafion®NR50 with improved efficiency and reduced waste production....

274

Synthesis of phenanthrenes and polycyclic heteroarenes by transition-metal catalyzed cycloisomerization reactions.  

PubMed

Readily available biphenyl derivatives containing an alkyne unit at one of their ortho-positions are converted into substituted phenanthrenes on exposure to catalytic amounts of either PtCl2, AuCl, AuCl3, GaCl3 or InCl3 in toluene. This 6-endo-dig cyclization likely proceeds through initial pi-complexation of the alkyne unit followed by interception of the resulting eta2-metal species by the adjacent arene ring. The reaction is inherently modular, allowing for substantial structural variations and for the incorporation of substituents at any site of the phenanthrene product. Moreover, it is readily extended to the heterocyclic series as exemplified by the preparation of benzoindoles, benzocarbazoles, naphthothiophenes, as well as bridgehead nitrogen heterocycles such as pyrrolo[1,2-a]quinolines. Depending on the chosen catalyst, biaryls bearing halo-alkyne units can either be converted into the corresponding 10-halo-phenanthrenes or into the isomeric 9-halo-phenanthrenes; in the latter case, the concomitant 1,2-halide shift is best explained by assuming a metal vinylidene species as the reactive intermediate. The scope of this novel method for the preparation of polycyclic arenes is illustrated by the total synthesis of a series of polyoxygenated phenanthrenes that are close relatives of the anticancer agent combretastatin A-4, as well as by the total synthesis of the aporphine alkaloid O-methyl-dehydroisopiline and its naturally occurring symmetrical dimer. PMID:15378635

Mamane, Victor; Hannen, Peter; Fürstner, Alois

2004-09-20

275

Sodium dodecyl benzene sulfonate-assisted synthesis through a hydrothermal reaction  

SciTech Connect

Graphical abstract: Reaction of a SeCl{sub 4} aqueous solution with a NiCl{sub 2}·6H{sub 2}O aqueous solution in presence of sodium dodecyl benzene sulfonate (SDBS) as capping agent and hydrazine (N{sub 2}H{sub 4}·H{sub 2}O) as reductant, produces nanosized nickel selenide through a hydrothermal method. The effect of temperature, reaction time and amounts of reductant on the morphology, particle sizes of NiSe nanostructures has been investigated. Highlights: ? NiSe nanostructures were synthesized by hydrothermal method. ? A novel Se source was used to synthesize NiSe. ? SDBS as capping agent plays a crucial role on the morphology of products. ? A mixture of Ni{sub 3}Se{sub 2} and NiSe was prepared in the presence of 2 ml hydrazine. ? A pure phase of NiSe was prepared in the presence of 4 or 6 ml hydrazine. -- Abstract: The effects of the anionic surfactant on the morphology, size and crystallization of NiSe precipitated from NiCl{sub 2}·6H{sub 2}O and SeCl{sub 4} in presence of hydrazine (N{sub 2}H{sub 4}·H{sub 2}O) as reductant were investigated. The products have been successfully synthesized in presence of sodium dodecyl benzene sulfonate (SDBS) as surfactant via an improved hydrothermal route. A variety of synthesis parameters, such as reaction time and temperature, capping agent and amount of reducing agent have a significant effect on the particle size, phase purity and morphology of the obtained products. The sample size became bigger with decreasing reaction temperature and increasing reaction time. In the presence of 2 ml hydrazine, the samples were found to be the mixture of Ni{sub 3}Se{sub 2} and NiSe. With increasing the reaction time and amount of hydrazine a pure phase of hexagonal NiSe was obtained. X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) images indicate phase, particle size and morphology of the products. Chemical composition and purity of the products were characterized by X-ray energy dispersive spectroscopy (EDS). Photoluminescence (PL) was used to study the optical properties of NiSe samples.

Sobhani, Azam [Department of Inorganic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, P.O. Box 87317–51167, Islamic Republic of Iran (Iran, Islamic Republic of)] [Department of Inorganic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, P.O. Box 87317–51167, Islamic Republic of Iran (Iran, Islamic Republic of); Salavati-Niasari, Masoud, E-mail: salavati@kashanu.ac.ir [Department of Inorganic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, P.O. Box 87317–51167, Islamic Republic of Iran (Iran, Islamic Republic of) [Department of Inorganic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, P.O. Box 87317–51167, Islamic Republic of Iran (Iran, Islamic Republic of); Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317–51167, Islamic Republic of Iran (Iran, Islamic Republic of)

2012-08-15

276

Effect of reaction conditions on the catalytic performance of Fe-Mn catalyst for Fischer-Tropsch synthesis  

Microsoft Academic Search

The effects of reaction conditions on the performance of an Fe-Mn catalyst for Fischer-Tropsch synthesis (FTS) have been investigated in a continuous spinning basket reactor. Experiments were carried out under a wide range of industrially relevant reaction conditions including reaction temperature of 533–573K, pressure of 0.93–2.96MPa, inlet H2\\/CO molar ratio of 0.80–2.50 and space velocity of (0.46–1.85)×10?3Nm3kgcat?1s?1. The selectivities to

Ying Liu; Bo-Tao Teng; Xiao-Hui Guo; Ying Li; Jie Chang; Lei Tian; Xu Hao; Yu Wang; Hong-Wei Xiang; Yuan-Yuan Xu; Yong-Wang Li

2007-01-01

277

Multicomponent versus domino reactions: One-pot free-radical synthesis of ?-amino-ethers and ?-amino-alcohols  

PubMed Central

Summary Following an optimized multicomponent procedure, an aryl amine, a ketone, and a cyclic ether or an alcohol molecule are assembled in a one-pot synthesis by nucleophilic radical addition of ketyl radicals to ketimines generated in situ. The reaction occurs under mild conditions by mediation of the TiCl4/Zn/t-BuOOH system, leading to the formation of quaternary ?-amino-ethers and -alcohols. The new reaction conditions guarantee good selectivity by preventing the formation of secondary products. The secondary products are possibly derived from a competitive domino reaction, which involves further oxidation of the ketyl radicals. PMID:25670994

Rossi, Bianca; Prosperini, Simona

2015-01-01

278

Synthesis of heterogeneous catalysts with well shaped platinum particles to control reaction selectivity  

PubMed Central

Colloidal and sol-gel procedures have been used to prepare heterogeneous catalysts consisting of platinum metal particles with narrow size distributions and well defined shapes dispersed on high-surface-area silica supports. The overall procedure was developed in three stages. First, tetrahedral and cubic colloidal metal particles were prepared in solution by using a procedure derived from that reported by El-Sayed and coworkers [Ahmadi TS, Wang ZL, Green TC, Henglein A, El-Sayed MA (1996) Science 272:1924–1926]. This method allowed size and shape to be controlled independently. Next, the colloidal particles were dispersed onto high-surface-area solids. Three approaches were attempted: (i) in situ reduction of the colloidal mixture in the presence of the support, (ii) in situ sol-gel synthesis of the support in the presence of the colloidal particles, and (iii) direct impregnation of the particles onto the support. Finally, the resulting catalysts were activated and tested for the promotion of carbon–carbon double-bond cis-trans isomerization reactions in olefins. Our results indicate that the selectivity of the reaction may be controlled by using supported catalysts with appropriate metal particle shapes. PMID:18832170

Lee, Ilkeun; Morales, Ricardo; Albiter, Manuel A.; Zaera, Francisco

2008-01-01

279

Synthesis and characterization of isomaltulose-derived oligosaccharides produced by transglucosylation reaction of Leuconostoc mesenteroides dextransucrase.  

PubMed

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

Barea-Alvarez, Montserrat; Benito, Maria Teresa; Olano, Agustín; Jimeno, Maria Luisa; Moreno, F Javier

2014-09-17

280

Assessing Ammonia Treatment Options  

EPA Science Inventory

This is the second of three articles to help water system operators understand ammonia and how to monitor and control its effects at the plant and in the distribution system. The first article (Opflow, April 2012) provided an overview of ammonia's chemistry, origins, and water sy...

281

Monodisperse metal nanoparticle catalysts on silica mesoporous supports: synthesis, characterizations, and catalytic reactions  

SciTech Connect

The design of high performance catalyst achieving near 100% product selectivity at maximum activity is one of the most important goals in the modern catalytic science research. To this end, the preparation of model catalysts whose catalytic performances can be predicted in a systematic and rational manner is of significant importance, which thereby allows understanding of the molecular ingredients affecting the catalytic performances. We have designed novel 3-dimensional (3D) high surface area model catalysts by the integration of colloidal metal nanoparticles and mesoporous silica supports. Monodisperse colloidal metal NPs with controllable size and shape were synthesized using dendrimers, polymers, or surfactants as the surface stabilizers. The size of Pt, and Rh nanoparticles can be varied from sub 1 nm to 15 nm, while the shape of Pt can be controlled to cube, cuboctahedron, and octahedron. The 3D model catalysts were generated by the incorporation of metal nanoparticles into the pores of mesoporous silica supports via two methods: capillary inclusion (CI) and nanoparticle encapsulation (NE). The former method relies on the sonication-induced inclusion of metal nanoparticles into the pores of mesoporous silica, whereas the latter is performed by the encapsulation of metal nanoparticles during the hydrothermal synthesis of mesoporous silica. The 3D model catalysts were comprehensively characterized by a variety of physical and chemical methods. These catalysts were found to show structure sensitivity in hydrocarbon conversion reactions. The Pt NPs supported on mesoporous SBA-15 silica (Pt/SBA-15) displayed significant particle size sensitivity in ethane hydrogenolysis over the size range of 1-7 nm. The Pt/SBA-15 catalysts also exhibited particle size dependent product selectivity in cyclohexene hydrogenation, crotonaldehyde hydrogenation, and pyrrole hydrogenation. The Rh loaded SBA-15 silica catalyst showed structure sensitivity in CO oxidation reaction. In addition, Pt-mesoporous silica core-shell structured NPs (Pt{at}mSiO{sub 2}) were prepared, where the individual Pt NP is encapsulated by the mesoporous silica layer. The Pt{at}mSiO{sub 2} catalysts showed promising catalytic activity in high temperature CO oxidation. The design of catalytic structures with tunable parameters by rational synthetic methods presents a major advance in the field of catalyst synthesis, which would lead to uncover the structure-function relationships in heterogeneous catalytic reactions.

Somorjai, G.A.

2009-09-14

282

Copper catalysed azide-alkyne cycloaddition (CuAAC) in liquid ammonia.  

PubMed

Copper(I) catalysed azide-alkyne cycloaddition reactions (CuAAC) occur smoothly in liquid ammonia (LNH(3)) at room temperature to give exclusively 1,4-substituted 1,2,3-triazoles with excellent yields (up to 99%). The CuAAC reactions in liquid ammonia require relatively small amounts of copper(I) catalyst (0.5 mole%) compared with that in conventional solvents. The product can be obtained conveniently by simply evaporation of ammonia, indicating its potential application in industry. The rate of the CuAAC reaction in liquid ammonia shows a second order dependence on the copper(I) concentration and the reaction occurs only with terminal alkynes. Deuterium exchange experiments with phenyl acetylene-d(1) show that the acidity of the alkyne is increased at least 1000-fold with catalytic amounts of copper(I) in liquid ammonia. The mechanism of the CuAAC reaction in liquid ammonia is discussed. PMID:22930181

Ji, Pengju; Atherton, John H; Page, Michael I

2012-10-21

283

Fate of ammonia in the atmosphere--a review for applicability to hazardous releases.  

PubMed

The physical and chemical mechanisms responsible for the removal of ammonia from the atmosphere have been reviewed. Capture by atmospheric moisture (clouds, rain, fog), surface water (rivers, lakes, seas), and deposition on vegetation and soil constitute the main pathways for ammonia removal from the troposphere. Ammonia catalyzes the atmospheric oxidation of sulfur dioxide to sulfur trioxide and reacts rapidly with acidic components of the atmosphere (sulfuric, nitric, and hydrochloric acids). The ammonium salts formed are the main components of smog aerosols and thus affect the opacity of the atmosphere and the earth radiation budget. Slow oxidation of ammonia in the atmosphere plays only a minor role in its removal. The data obtained for ammonia reactions under normal atmospheric conditions are generally applicable to model chemical reactions occurring during massive release of ammonia in the atmosphere, provided the impact of high ammonia concentration on the mass transfer processes that control some of these reactions, are taken into account. PMID:15081162

Renard, Jean J; Calidonna, Sheryl E; Henley, Michael V

2004-04-30

284

A photoisomerization-coupled asymmetric Stetter reaction: application to the total synthesis of three diastereomers of (?)-cephalimysin A  

PubMed Central

The total synthesis of 8-epi, 8,9-epi, and 9-epi-(?)-cephalimysin A is described. Our catalytic enantioselective synthesis takes advantage of a novel tandem photoisomerization/Stetter reaction. The approach provides rapid access to the desired spirofuranone lactam core in good yield and excellent enantioselectivity. A late stage oxidation strategy allows for flexible access to three of the four diastereomers of cephalimysin A. Access to the epimers provides further support for the correction of the initially proposed relative stereochemistry of cephalimysin A. PMID:24224080

Lathrop, Stephen P.

2013-01-01

285

Chemical pathways for the formation of ammonia in Hanford wastes  

SciTech Connect

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.

Stock, L.M.; Pederson, L.R.

1997-09-01

286

Application of the sila-Friedel-Crafts reaction to the synthesis of ?-extended silole derivatives and their properties.  

PubMed

The intramolecular sila-Friedel-Crafts reaction was developed as a new method for the construction of a dibenzosilole skeleton. This reaction proceeds under mild conditions to afford the target in relatively good yield, indicating its availability as a versatile synthetic method. This reaction can be applied to the synthesis of ?-extended silole derivatives such as ladder-type silafluorene 8 and spiro-type silabifluorene 9. Furthermore, the synthesis of two-dimensionally extended silole derivatives utilizing the sila-Friedel-Crafts reaction as the multiple intramolecular cyclization was achieved, including the first synthesis of trisilasumanene 18. The X-ray crystallographic analysis of trisilasumanene 18 demonstrated the planarity in the main ?-framework, in contrast to sumanene and its sulfur analogue, trithiasumanene, bearing the bowl-shaped structures. In the UV-vis absorption spectra, the absorption bands of triphenylenosiloles 18 and 19 were slightly red-shifted compared to that of hexabutoxytriphenylene 22. The weak absorption bands were also observed in the longer-wavelength region in 18 and 19, which is derived from ?*-?* conjugation of the silole skeletons. In addition, 18 and 19 showed the blue fluorescence in dichloromethane and in the solid state. PMID:20830392

Furukawa, Shunsuke; Kobayashi, Junji; Kawashima, Takayuki

2010-10-21

287

Ammonia Leak Locator Study  

NASA Technical Reports Server (NTRS)

The thermal control system of International Space Station Alpha will use liquid ammonia as the heat exchange fluid. It is expected that small leaks (of the order perhaps of one pound of ammonia per day) may develop in the lines transporting the ammonia to the various facilities as well as in the heat exchange equipment. Such leaks must be detected and located before the supply of ammonia becomes critically low. For that reason, NASA-JSC has a program underway to evaluate instruments that can detect and locate ultra-small concentrations of ammonia in a high vacuum environment. To be useful, the instrument must be portable and small enough that an astronaut can easily handle it during extravehicular activity. An additional complication in the design of the instrument is that the environment immediately surrounding ISSA will contain small concentrations of many other gases from venting of onboard experiments as well as from other kinds of leaks. These other vapors include water, cabin air, CO2, CO, argon, N2, and ethylene glycol. Altogether, this local environment might have a pressure of the order of 10(exp -7) to 10(exp -6) torr. Southwest Research Institute (SwRI) was contracted by NASA-JSC to provide support to NASA-JSC and its prime contractors in evaluating ammonia-location instruments and to make a preliminary trade study of the advantages and limitations of potential instruments. The present effort builds upon an earlier SwRI study to evaluate ammonia leak detection instruments [Jolly and Deffenbaugh]. The objectives of the present effort include: (1) Estimate the characteristics of representative ammonia leaks; (2) Evaluate the baseline instrument in the light of the estimated ammonia leak characteristics; (3) Propose alternative instrument concepts; and (4) Conduct a trade study of the proposed alternative concepts and recommend promising instruments. The baseline leak-location instrument selected by NASA-JSC was an ion gauge.

Dodge, Franklin T.; Wuest, Martin P.; Deffenbaugh, Danny M.

1995-01-01

288

Chemical pathways for the formation of ammonia in Hanford wastes  

SciTech Connect

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).

Stock, L.M.; Pederson, L.R.

1997-12-01

289

Synthesis of Unsymmetrical Diarylureas via Pd-Catalyzed C–N Cross-Coupling Reactions  

E-print Network

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 ...

Breitler, Simon

290

Absolute asymmetric synthesis in enantioselective autocatalytic reaction networks: theoretical games, speculations on chemical evolution and perhaps a synthetic option.  

PubMed

The Soai reaction and the Viedma deracemization of racemic conglomerate crystal mixtures are experimental pieces of evidence of the ability of enantioselective autocatalytic coupled networks to yield absolute asymmetric synthesis. Thermodynamically open systems or systems with non-uniform energy distributions may lead to chiral final states and, in systems able to come into thermodynamic equilibrium with their surroundings, to kinetically controlled absolute asymmetric synthesis. The understanding of network parameters and of the thermodynamic scenarios that may lead to spontaneous mirror symmetry breaking (SMSB) could assist in the development of new methods for asymmetric synthesis and enantioselective polymerizations (e.g., replicators), and to frame reasonable speculations on the origin of biological homochirality. PMID:25352056

Ribó, Josep M; Blanco, Celia; Crusats, Joaquim; El-Hachemi, Zoubir; Hochberg, David; Moyano, Albert

2014-12-22

291

Synthesis and crossover reaction of TEMPO containing block copolymer via ROMP  

PubMed Central

Summary We report on the block copolymerization of two structurally different norbornene monomers (±)-endo,exo-bicyclo[2.2.1]-hept-5-ene-2,3-dicarboxylic acid dimethylester (7), and (±)-endo,exo-bicyclo[2.2.1]-hept-5-ene-2,3-dicarboxylic acid bis(1-oxyl-2,2,6,6-tetramethyl-piperidin-4-yl) ester (9) using ruthenium based Grubbs’ type initiators [(PCy3)2Cl2Ru(benzylidene)] G1 (PCy3 = tricyclohexylphosphine), [(H2IMes)(PCy3)Cl2Ru(benzylidene)] G2 (H2IMes = 1,3-bis(mesityl)-2-imidazolidinylidene), [(H2IMes)(py)2Cl2Ru(benzylidene)] G3 (py = pyridine or 3-bromopyridine) and Umicore type initiators [(PCy3)2Cl2Ru(3-phenylinden-1-ylidene)] U1 (PCy3 = tricyclohexylphosphine), [(H2IMes)(PCy3)Cl2Ru(3-phenylinden-1-ylidene)] U2 (H2IMes = 1,3-bis(mesityl)-2-imidazolidinylidene), [(H2IMes)(py)Cl2Ru(3-phenylinden-1-ylidene)] U3 (py = pyridine or 3-bromopyridine) via ring opening polymerization (ROMP). The crossover reaction and the polymerization kinetics were investigated using matrix assisted laser desorption ionization mass spectroscopy (MALDI-TOF) and nuclear magnetic resonance (NMR), respectively. MALDI showed that there was a complete crossover reaction after the addition of 25 equivalents of the second monomer. NMR investigation showed that U3 gave a faster rate of polymerization in comparison to U1. The synthesis of block copolymers with molecular weights up to M n = 31 000 g/mol with low polydispersities (M w/M n = 1.2) is reported. PMID:20625541

Adekunle, Olubummo; Tanner, Susanne

2010-01-01

292

Synthesis and crossover reaction of TEMPO containing block copolymer via ROMP.  

PubMed

We report on the block copolymerization of two structurally different norbornene monomers (±)-endo,exo-bicyclo[2.2.1]-hept-5-ene-2,3-dicarboxylic acid dimethylester (7), and (±)-endo,exo-bicyclo[2.2.1]-hept-5-ene-2,3-dicarboxylic acid bis(1-oxyl-2,2,6,6-tetramethyl-piperidin-4-yl) ester (9) using ruthenium based Grubbs' type initiators [(PCy?)?Cl?Ru(benzylidene)] G1 (PCy? = tricyclohexylphosphine), [(H?IMes)(PCy?)Cl?Ru(benzylidene)] G2 (H?IMes = 1,3-bis(mesityl)-2-imidazolidinylidene), [(H?IMes)(py)?Cl?Ru(benzylidene)] G3 (py = pyridine or 3-bromopyridine) and Umicore type initiators [(PCy?)?Cl?Ru(3-phenylinden-1-ylidene)] U1 (PCy?= tricyclohexylphosphine), [(H?IMes)(PCy?)Cl?Ru(3-phenylinden-1-ylidene)] U2 (H?IMes = 1,3-bis(mesityl)-2-imidazolidinylidene), [(H?IMes)(py)Cl?Ru(3-phenylinden-1-ylidene)] U3 (py = pyridine or 3-bromopyridine) via ring opening polymerization (ROMP). The crossover reaction and the polymerization kinetics were investigated using matrix assisted laser desorption ionization mass spectroscopy (MALDI-TOF) and nuclear magnetic resonance (NMR), respectively. MALDI showed that there was a complete crossover reaction after the addition of 25 equivalents of the second monomer. NMR investigation showed that U3 gave a faster rate of polymerization in comparison to U1. The synthesis of block copolymers with molecular weights up to M(n) = 31 000 g/mol with low polydispersities (M(w)/M(n) = 1.2) is reported. PMID:20625541

Adekunle, Olubummo; Tanner, Susanne; Binder, Wolfgang H

2010-01-01

293

Rhenium 2-oxoalkyl (enolate) complexes: Synthesis and carbon-carbon bond-forming reactions with nitriles  

SciTech Connect

The (2-oxoalkyl)rhenium complexes (rhenium enolates) (CO){sub 5}ReCH{sub 2}COR{sup 1} (R{sup 1} = OEt, Me, Ph, 1-3) can be prepared on a multigram scale by alkylation of (CO){sub 5}ReNa with ClCH{sub 2}COR{sup 1}. The secondary enolate (CO){sub 5}ReCH(Me)CO{sub 2}Et (4) can also be prepared in a similar fashion with use of MsOCH(Me)CO{sub 2}Et (Ms = CH{sub 3}SO{sub 2}{sup {minus}}). The mono(phosphine) enolates cis-(Ph{sub 3}P)(CO){sub 4}ReCH{sub 2}R{sup 2}(R{sup 2} = CO{sub 2}Et, CO{sub 2}Bu{sup t}, CONEt{sub 2}, COMe, COPh, CN, 8-13) are prepared in high yield via alkylation of (Ph{sub 3}P)(CO){sub 4}ReNa with ClCH{sub 2}R{sup 2}. Synthesis of the secondary enolate cis-(Ph{sub 3}P)(CO){sub 4}ReCH(Me)CO{sub 2}Et (14) is accomplished in 75% yield by alkylation with TfOCH(Me)CO{sub 2}Et (Tf = CF{sub 3}SO{sub 2}{sup {minus}}). The chelating phosphine complex is substitutionally inert under forcing thermal and photochemical conditions. Kinetic studies of the nitrile insertion reaction revealed a weak linear dependence of the rate constant of the reaction on the concentration of added CH{sub 3}CN in benzene; we believe this to be a medium effect.

Stack, J.G.; Doney, J.J.; Bergman, R.G.; Heathcock, C.H. (Univ. of California, Berkeley (USA))

1990-02-01

294

Synthesis and reaction pathway investigation of chalcopyrite CuInSe2 nanoparticles for one-pot method  

NASA Astrophysics Data System (ADS)

Highly dispersed and near stoichiometric chalcopyrite CuInSe2 nanoparticles were successfully synthesized via a facile and rapid one-pot method. For understanding the reaction pathway, the solid intermediates obtained at different stages of CuInSe2 nanoparticles synthesis process were investigated in detail by powder X-ray diffraction (XRD), X-ray photoelectron spectrometer (XPS), energy dispersive spectroscopy (EDS) and Raman spectroscopy. The XRD patterns showed that the phase formation sequence was CuSe ? CuInSe2. The XPS results indicated that the valences of Cu and Se in CuSe were +1 and -1, respectively. The chemical composition of the solid intermediates revealed the presence of the solid-state In-Se secondary phases in the synthesis process. However, no XRD signals or Raman signals of the solid-state In-Se secondary phase were observed. Based on the experimental results, the possible reaction pathway was proposed.

Han, Zhaoxia; Zhang, Dawei; Zhang, Daohua; Hong, Ruijin; Chen, Qinmiao; Tao, Chunxian; Huang, Yuanshen; Ni, Zhengji; Zhuang, Songlin

2013-10-01

295

Lessons from the Total Synthesis of (±) Phalarine: Insights Into the Mechanism of the Pictet–Spengler Reaction  

PubMed Central

The furanobisindole alkaloid, phalarine, possesses a unique structural framework within the alkaloid family of natural products. Our laboratory recently disclosed the racemic total synthesis of phalarine, featuring an efficient azaspiroindolenine rearrangement; this achievement is revisited in detail. Upon completion of the first-generation total synthesis, we explored some interesting mechanism-level issues with regard to the key azaspiroindolenine rearrangement. These investigations provided valuable insights into the mechanism of racemization during the azaspiroindolenine rearrangement en route to synthetic phalarine. In addition, in the course of these studies, we demonstrated the Pictet–Spengler capture reaction for C2-aryl indoles, and successfully isolated the elusive azaspiroindolenine intermediate of the Pictet–Spengler reaction. Key insights into the remarkably subtle stereoelectronics that govern this rearrangement for C2-arylated indoles are discussed. PMID:20711493

Trzupek, John D.; Li, Chaomin; Chan, Collin; Crowley, Brendan M.; Heimann, Annekatrin C.; Danishefsky, Samuel J.

2010-01-01

296

The mimic of type II aldolases chemistry: asymmetric synthesis of beta-hydroxy ketones by direct aldol reaction.  

PubMed

An efficient direct aldol reaction has been developed for the synthesis of chiral beta-hydroxy ketone using a combination of C(1)-symmetric chiral prolinamides based on o-phenylenediamine and zinc triflate as catalyst. The reaction was convenient to carry out in aqueous media with up to 98% chemical yields and up to 94% ee values. The current strategy can be regarded as the analogue of aldolase type II, which suggests a new pathway for the designing of new organocatalysts. PMID:20572810

Lu, Zhijin; Mei, Haibo; Han, Jianlin; Pan, Yi

2010-08-01

297

Synthesis of 1,5-Benzodiazepine and Its Derivatives by Condensation Reaction Using H-MCM-22 as Catalyst  

PubMed Central

A simple and versatile method for the synthesis of 1,5-benzodiazepines is via condensation of o-phenylenediamines (OPDA) and ketones in the presence of catalytic amount of H-MCM-22 using acetonitrile as solvent at room temperature. In all the cases, the reactions are highly selective and are completed within 1–3?h. The method is applicable to both cyclic and acyclic ketones without significant differences. The reaction proceeds efficiently under ambient conditions with good-to-excellent yields. PMID:22570531

Majid, Sheikh Abdul; Khanday, Waheed Ahmad; Tomar, Radha

2012-01-01

298

Concise synthesis of multisubstituted isoquinolines from pyridines by regioselective Diels-Alder reactions of 2-silyl-3,4-pyridynes.  

PubMed

A four-step regioselective synthesis of multisubstituted isoquinoline derivatives from 3-bromopyridines was developed by the Diels-Alder (DA) reactions of 2-silyl-3,4-pyridynes with furans, followed by functional-group transformations. In particular, the silyl group at the C2-position of the 3,4-pyridynes played two important roles: firstly, it functioned as the directing group for the DA reaction, and secondly, it served to introduce diverse substituents at the C1-position of the isoquinolines by electrophilic ipso-substitution. PMID:25308533

Ikawa, Takashi; Urata, Hirohito; Fukumoto, Yutaka; Sumii, Yuta; Nishiyama, Tsuyoshi; Akai, Shuji

2014-12-01

299

One-pot synthesis of S-alkyl dithiocarbamates via the reaction of N-tosylhydrazones, carbon disulfide and amines.  

PubMed

A new, convenient and efficient transition metal-free synthesis of S-alkyl dithiocarbamates through one-pot reaction of N-tosylhydrazones, carbon disulfide and amines is reported. Tosylhydrazones derived from various aromatic and aliphatic ketones or aldehydes were tested and gave dithiocarbamates in good to excellent yields. The tosylhydrazones can be generated in situ without isolation, which provides a simpler one-pot method to synthesize dithiocarbamates via the reaction of carbonyl compounds, carbon disulfide and amines in the presence of 4-methylbenzenesulfonohydrazide. PMID:23863979

Sha, Qiang; Wei, Yun-Yang

2013-09-14

300

Methanol synthesis on ZnO(0001). II. Structure, energetics, and vibrational signature of reaction intermediates.  

PubMed

A rigorous characterization of a wealth of molecular species adsorbed at oxygen defects on ZnO(0001) is given. These defects represent the putative active sites in methanol synthesis from CO and H2. The oxidation state of the ZnO catalyst and thus the preferred charge state and the reactivity of the oxygen vacancies depend on the gas phase temperature and pressure conditions. Considering charge states of oxygen vacancies relevant at the reducing conditions of the industrial process, i.e., F(++)/H2, F(0), F(0)/H2, and F(--), as well as the F(++) center which is abundant at UHV conditions and therefore important to allow for comparison with surface science experiments, we have investigated the structure, energetics, and vibrational frequencies of an exhaustive catalog of reaction intermediates using electronic structure calculations. After having identified the characteristic adsorption modes of CO, formate, formic acid, hydroxymethylene, formyl, formaldehyde, dioxomethylene, hydroxymethyl, hydroxymethoxide, methoxide, as well as methanol itself, the thermodynamic stability of all species with respect to the charge state of the oxygen vacancy and their electronic stabilization is discussed in detail and summarized in an energy level diagram. PMID:23902001

Kiss, Janos; Frenzel, Johannes; Meyer, Bernd; Marx, Dominik

2013-07-28

301

Reactor for removing ammonia  

DOEpatents

Disclosed is a device for removing trace amounts of ammonia from a stream of gas, particularly hydrogen gas, prepared by a reformation apparatus. The apparatus is used to prevent PEM "poisoning" in a fuel cell receiving the incoming hydrogen stream.

Luo, Weifang (Livermore, CA); Stewart, Kenneth D. (Valley Springs, CA)

2009-11-17

302

Ammonia Release on ISS  

NASA Technical Reports Server (NTRS)

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

Macatangay, Ariel

2009-01-01

303

A modular approach to catalytic synthesis using a dual-functional linker for Click and Suzuki coupling reactions  

Microsoft Academic Search

The stable benzylazido-boronate ester 1 is presented as an example of a dual-functional linker that allows the synthetically valuable boronate motif to be clicked onto other molecules under mild conditions. The utility of the azido-boronate motif as a modular building block is demonstrated in the rapid synthesis of drug-like structures employing sequential catalytic azide–alkyne cycloaddition and Suzuki coupling reactions.

James R. White; Gareth J. Price; Stefanie Schiffers; Paul R. Raithby; Pawel K. Plucinski; Christopher G. Frost

2010-01-01

304

One-pot stereoselective synthesis of ?,?-differentiated diamino esters via the sequence of aminochlorination, aziridination and intermolecular SN2 reaction  

PubMed Central

Summary We report here an efficient one-pot method for the synthesis of ?,?-differentiated diamino esters directly from cinnamate esters using N,N-dichloro-p-toluenesulfonamide and benzylamine as nitrogen sources. The key transformations include a Cu-catalyzed aminohalogenation and aziridination, followed by an intermolecular SN2 nucleophilic ring opening by benzylamine. The reactions feature a wide scope of substrates and proceed with excellent stereo- and regioselectivity (anti:syn >99:1) . PMID:25161740

Xiong, Yiwen; Qian, Ping; Cao, Chenhui; Mei, Haibo; Li, Guigen

2014-01-01

305

Sequential decarboxylative azide–alkyne cycloaddition and dehydrogenative coupling reactions: one-pot synthesis of polycyclic fused triazoles  

PubMed Central

Summary Herein, we describe a one-pot protocol for the synthesis of a novel series of polycyclic triazole derivatives. Transition metal-catalyzed decarboxylative CuAAC and dehydrogenative cross coupling reactions are combined in a single flask and achieved good yields of the respective triazoles (up to 97% yield). This methodology is more convenient to produce the complex polycyclic molecules in a simple way. PMID:25670973

Bharathimohan, Kuppusamy; Ponpandian, Thanasekaran; Bhuvanesh, Nattamai

2014-01-01

306

Nanocomposite of a chromium Prussian blue with TiO2. Redox reactions and the synthesis of Prussian blue  

E-print Network

Nanocomposite of a chromium Prussian blue with TiO2. Redox reactions and the synthesis of Prussian is a nanocomposite of CrII [CrIII (CN)6]0.67 � xH2O and TiO2 in the ratio of 1­1.6. These results suggest that Ti; Hexacyanometalate; Magnetic; Hydrolysis; Redox; Nanocomposite 1. Introduction In the 1990s, an entirely new class

Girolami, Gregory S.

307

Characterization of a silicon carbide thin layer prepared by a self-propagating high temperature synthesis reaction  

Microsoft Academic Search

Silicon carbide was deposited by a self-propagating high temperature synthesis reaction between graphite and silicon layers on an oxide substrate. Chemical analyses by Auger electron microscopy and X-ray diffractometry revealed that the final product was beta-SiC without an inter-diffusional layer at the interface between the carbide and graphite layers. Transmission electron microscope observation showed that the silicon carbide layer has

Bong G. Kim; Yong Choi; Jung W. Lee; Young W. Lee; Gil M. Kim

2000-01-01

308

Highly enantioselective Friedel-Crafts alkylation reaction catalyzed by rosin-derived tertiary amine-thiourea: synthesis of modified chromanes with anticancer potency.  

PubMed

We present herein for the first time the synthesis and preliminary biological evaluation of various modified chromanes via a rosin-derived tertiary amine-thiourea-catalyzed highly enantioselective Friedel-Crafts alkylation reaction. PMID:22080190

Jiang, Xianxing; Wu, Lipeng; Xing, Yanhong; Wang, Long; Wang, Shoulei; Chen, Zongyao; Wang, Rui

2012-01-11

309

Enantioselective nickel-catalyzed reductive coupling reactions of alkynes and aldehydes. Synthesis of amphidinolides T1 and T4 via catalytic, stereoselective macrocyclizations  

E-print Network

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 ...

Colby Davie, Elizabeth A. (Elizabeth Anne)

2005-01-01

310

Ammonia Clouds on Jupiter  

NASA Technical Reports Server (NTRS)

[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.

2007-01-01

311

Ion chemistry at high temperatures. 1. Thermochemistry of the ammonium ion from variable-temperature equilibrium measurements. Proton transfer, association, and decomposition reactions in ammonia, isobutene, and tert-butylamine  

SciTech Connect

At 580-680 K, the proton-transfer reaction t-C{sub 4}H{sub 9}{sup +} + NH{sub 3} {leftrightarrow} NH{sub 4}{sup +} + i-C{sub 4}H{sub 8} is in equilibrium in mixtures containing ammonia and isobutene. In the same mixtures, t-C{sub 4}H{sub 9}NH{sub 3}{sup +} is also formed reversibly, and kinetic experiments identify the addition/thermal decomposition equilibrium NH{sub 4}{sup +} + i-C{sub 4}H{sub 8} + M {leftrightarrow} t-C{sub 4}H{sub 9}NH{sub 3}{sup +} + M. The decomposition of t-C{sub 4}H{sub 9}NH{sub 3}{sup +} is at the low-pressure limit, with rate constants of (1-14) {times} 10{sup {minus}14} cm{sup 3}/s, and E{sub a} = 29.1 kcal/mol. The thermally activated addition of NH{sub 4}{sup +} to i-C{sub 4}H{sub 8} shows third-order kinetics with k = (2-6) {times} 10{sup {minus}29} cm{sup 6}/s and a negative temperature coefficient of k = AT{sup {minus}10.8}. Equilibrium studies of the proton-transfer reaction yield {Delta}H{degree} = {minus}12.5 kcal/mol and {Delta}S{degree} = {minus}6.1 cal/(mol K). Referred to PA(i-C{sub 4}H{sub 8}) = 195.9 kcal/mol, these results yield PA(NH{sub 3}) = 208.4 kcal/mol, at the high end of published values ranging from 202 to 210 kcal/mol (PA = proton affinity).

Meot-Ner Mautner, M.; Sieck, L.W. (National Institute of Standards and Technology, Gaithersburg, MD (USA))

1990-09-20

312

Ammonia in comet P/Halley  

NASA Technical Reports Server (NTRS)

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.

Meier, R.; Eberhardt, P.; Krankowsky, D.; Hodges, R. R.

1994-01-01

313

Argon recovery from hydrogen depleted ammonia plant purge gas using a HARP Plant  

Microsoft Academic Search

A number of ammonia plants employ membranes or cryogenic hydrogen recovery units to separate hydrogen contained in the purge gas for recycle to the ammonia synthesis loop. The resulting hydrogen depleted purge gas, which is usually used for fuel, is an attractive source of argon. This paper presents the novel features of a process which employs a combination of pressure

R. Krishnamurthy; S. L. Lerner; D. L. Maclean

1987-01-01

314

Simultaneous synthesis of gold nanoparticle/graphene nanocomposite for enhanced oxygen reduction reaction  

NASA Astrophysics Data System (ADS)

We report here on a novel and facile technique for the simultaneous synthesis of a highly active and stable gold (Au) nanoparticle/reduced graphene oxide (rGO) sheet nanocomposite as an efficient electrocatalyst to facilitate the oxygen reduction reaction (ORR). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray (EDX) spectroscopy and electrochemical methods were employed to characterize the Au and rGO nanocomposites formed on the electrode surface. The major advantage of the simultaneous synthetic method is the integration of the superb properties of both Au nanoparticles and graphene in a single-step with a 100% usage of the precursors. The Au/rGO nanocomposites exhibited pronounced electrocatalytic performance towards ORR with approximately three times higher than that of Au nanoparticles. The nanocomposites show the ORR onset peak potentials at 0.12 and -0.03 V (vs Ag/AgCl), with reduction peaks at -0.06 and -0.16 V (vs Ag/AgCl) in 0.1 M H2SO4 and KOH media, which is ?120-190 mV more positive than that of Au nanoparticles and a commercial Pt/C catalyst. Moreover, the nanocomposites exhibit excellent methanol tolerance and high durability in comparison with the commercial Pt/C. The new method demonstrated in this study provides an efficient route for the generation of ultrafine and highly dense Au nanoparticles that are homogeneously dispersed on rGO sheets for ORR.

Govindhan, Maduraiveeran; Chen, Aicheng

2015-01-01

315

Cross-metathesis reactions as an efficient tool in the synthesis of fluorinated cyclic beta-amino acids.  

PubMed

The synthesis of enantiomerically pure, cyclic, gamma,gamma-difluorinated beta-amino acids with various ring sizes has been carried out with a cross-metathesis (CM) reaction being one of the key steps, followed by a Dieckmann-type condensation to bring about the cyclization. Subsequent catalytic hydrogenation under microwave irradiation with (-)-8-phenylmenthol as a chiral auxiliary led to the successful chemo- and diastereoselective chemical reduction of the resulting cyclic beta-enamino esters. The efficiency and scope of the CM reaction with different types of fluorinated imidoyl chlorides and unsaturated esters has also been studied in order to determine the optimal reaction conditions with regard to selectivity and reactivity. PMID:19348493

Fustero, Santos; Sánchez-Roselló, María; Aceña, José Luis; Fernández, Begoña; Asensio, Amparo; Sanz-Cervera, Juan F; del Pozo, Carlos

2009-05-01

316

Synthesis, characterization, and ceramic conversion reactions of borazine-modified hydridopolysilazanes: New polymeric precursors to SiNCB ceramic composites  

SciTech Connect

The high-yield synthesis of borazine-substituted hydridopolysilazanes has been achieved by the reaction of liquid borazine with hydridopolysilazane (HPZ) at temperatures between 60 and 90 [degrees]C. The spectroscopic data for the polymers and a model study of the reaction of hexamethyldisilazane with borazine indicate that the new polymers have retained their hydridopolysilazane backbones but are substituted with pendant borazines by means of a borazine-boron to polymer-nitrogen linkage. Such linkages may have been formed by either hydrogen or trimethylsilane elimination reactions. Molecular weight and distribution studies suggest an inhomogeneous distribution of borazine throughout the molecular weight distribution. A decrease in molecular weight with increasing borazine content was observed that apparently results from chain scission reactions of Si-N bonds in the polymer backbone. Studies of the thermolytic reactions of the polymers demonstrated that they are converted in high ceramic and chemical yields to SiNCB ceramic composites. The ceramic yield is increased over that observed for the unmodified hydridopolysilazane due to both the retention of borazine-boron and-nitrogen in the ceramic and a borazine cross-linking reaction which retards the loss of polymer backbone components. Significant differences in the onset, phases and extent of crystallization in the ceramic products obtained from HPZ and the modified polymers were observed. In contrast to the ceramic materials obtained from HPZ, the borazine-modified polymers yield ceramics that are amorphous to 1400[degrees]C. 21 refs., 15 figs., 3 tabs.

Su, Kai; Sneddon, L.G. (Univ. of Pennsylvania, Philadelphia (United States)); Remsen, E.E. (Monsanto Corp. Research, St. Louis, MO (United States)); Zank, G.A. (Dow Corning Corp., Midland, MI (United States))

1993-04-01

317

A facile one-pot synthesis of functionalized 1,3-oxathiolan-2-yliden derivatives: multicomponent reaction of oxiranes in water.  

PubMed

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

Rostami-Charati, Faramarz; Hosseini-Tabatabaei, Mohammad R; Shahraki, Mehdi

2014-01-01

318

Bismuth Subnitrate Catalyzed Efficient Synthesis of 3,4?Dihydropyrimidin?2(1H)?Ones: An Improved Protocol for the Biginelli Reaction  

Microsoft Academic Search

An efficient synthesis of 3,4?dihydropyrimidinones (DHPMs) using bismuth subnitrate as the catalyst for the first time from an aldehyde, ??ketoester, and urea in acetonitrile is described. This new method consistently has the advantage of excellent yields (88–96%) and short reaction times (1.5–4 h) than do classical Biginelli reaction conditions.

Y. Thirupathi Reddy; B. Rajitha; P. Narsimha Reddy; B. Sunil Kumar; V. P. Rao G

2004-01-01

319

Synthesis of 1,2-dihydroisoquinolin-1-ylphosphonates via three-component reactions of 2-(2-formylphenyl)ethanone, amine, and diethyl phosphite  

Microsoft Academic Search

Synthesis of 1,2-dihydroisoquinolin-1-ylphosphonates via CuI-catalyzed three-component tandem reactions of 2-(2-formylphenyl)ethanone, amine, and diethyl phosphite is described. The reactions proceed smoothly under mild conditions leading to the desired products in good yields.

Shengqing Ye; Haibo Zhou; Jie Wu

2009-01-01

320

Synthesis of intermetallic NiAl by SHS reaction using coarse-grained nickel and ultrafine-grained aluminum produced by wire electrical explosion  

Microsoft Academic Search

Nickel aluminide NiAl was synthesized by using aluminum nanoparticles via the thermal explosion mode of the self-propagating high temperature synthesis (SHS). Differential scanning calorimetry (DSC) was used to investigate the reaction process and mechanism. It was found that the mode and mechanism of reaction strongly depended on the charateristics of aluminum nanoparticles that have small grain size, high surface areas,

Shushan Dong; Ping Hou; Haibin Yang; Guangtian Zou

2002-01-01

321

Synthesis of a ketone analog of biotin via the intramolecular Pauson-Khand reaction  

PubMed Central

We report an improved synthesis of 5-(5-oxohexahydrocyclopenta[c]thiophen-1-yl)pentanoic acid (ketone biotin, 1) based on the intramolecular Pauson-Khand cyclization. The synthesis proceeds in 8 steps and in 2.7% overall yield from cyclohexene. PMID:16986958

McNeill, Eric; Chen, Irwin; Ting, Alice Y.

2008-01-01

322

Synthesis of a ketone analogue of biotin via the intramolecular Pauson-Khand reaction.  

PubMed

We report an improved synthesis of 5-(5-oxohexahydrocyclopenta[c]thiophen-1-yl)pentanoic acid (ketone biotin, 1) based on the intramolecular Pauson-Khand cyclization. The synthesis proceeds in eight steps and in 2.7% overall yield from cyclohexene. PMID:16986958

McNeill, Eric; Chen, Irwin; Ting, Alice Y

2006-09-28

323

TfOH-catalyzed synthesis of 3-aryl isoindolinones via a tandem reaction.  

PubMed

A convenient metal-free method for the synthesis of 3-aryl isoindolinones via TfOH catalyzed aromatic C-H functionalization of electron-rich arenes with 2-formylbenzonitriles is developed. This process provided a new efficient strategy for the synthesis of isoindolinone derivatives in good to high yields and regioselectivities by forming two bonds. PMID:25370938

Hu, Jiaxing; Qin, Hua-Li; Xu, Wengang; Li, Junli; Zhang, Fanglin; Zheng, Hua

2014-12-25

324

The synthesis of methanol and the reverse water-gas shift reaction over Zn-deposited Cu(100) and Cu(110) surfaces: comparison with Zn/Cu(111)  

NASA Astrophysics Data System (ADS)

The catalytic activity of Zn vapor-deposited Cu(100) and Cu(110) surfaces for methanol synthesis by the hydrogenation of CO 2 and the reverse water-gas shift reaction were studied using an XPS apparatus combined with a high-pressure flow reactor (18 atm). At a reaction temperature of 523 K, no promotional effect of Zn was observed for the methanol synthesis on both Zn/Cu(100) and Zn/Cu(110). The results were quite different from those for Zn/Cu(111), on which a significant promotion of methanol synthesis activity appeared to be due to the deposition of Zn, indicating that the promotional effect of Zn was sensitive to the surface structure of Cu. However, hysteresis was observed in the catalytic activity for methanol synthesis over the Zn/Cu(110) surface upon heating above 543 K in the reaction mixture. The activity became twice that measured before heating, which was close to the methanol synthesis activity of Zn/Cu(111) at the same Zn coverage. On the other hand, no such hysteresis was observed for the reverse water-gas shift reaction on Zn/Cu(110), indicating that the active site for methanol synthesis was not identical to that for the reverse water-gas shift reaction. In the post-reaction surface analysis, formate species was detected on both Zn/Cu(100) and Zn/Cu(110), whose coverage increased with increasing Zn coverage at 0< ?Zn<0.2. No correlation between the formate coverage and the methanol synthesis activity was obtained, which was in contrast to the results for Zn/Cu(111). Thus, the structure sensitivity observed in the catalytic activity of methanol synthesis over Zn-deposited Cu surfaces is ascribed to the significant difference in the reactivity of the formate intermediate.

Nakamura, I.; Fujitani, T.; Uchijima, T.; Nakamura, J.

1998-03-01

325

Design and synthesis of chiral Zn2+ complexes mimicking natural aldolases for catalytic C-C bond forming reactions in aqueous solution.  

PubMed

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

Itoh, Susumu; Sonoike, Shotaro; Kitamura, Masanori; Aoki, Shin

2014-01-01

326

Design and Synthesis of Chiral Zn2+ Complexes Mimicking Natural Aldolases for Catalytic C–C Bond Forming Reactions in Aqueous Solution  

PubMed Central

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

Itoh, Susumu; Sonoike, Shotaro; Kitamura, Masanori; Aoki, Shin

2014-01-01

327

The Ammonia-Soda Process.  

ERIC Educational Resources Information Center

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)

Tingle, M.

1979-01-01

328

Liberation of ammonia by cyanobacteria  

SciTech Connect

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.

Newton, J.W.

1986-04-01

329

Synthesis of complex benzenoids via the intermediate generation of o-benzynes through the hexadehydro-Diels–Alder reaction  

PubMed Central

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

Baire, Beeraiah; Niu, Dawen; Willoughby, Patrick H.; Woods, Brian P.; Hoye, Thomas R.

2014-01-01

330

Synthesis of Pyrroloquinones via a CAN Mediated Oxidative Free Radical Reaction of 1,3-Dicarbonyl Compounds with Aminoquinones  

PubMed Central

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%.

Nguyen, Thao; Nadkarni, Dwayaja; Dutta, Shilpa; Xu, Su; Kim, Sanghun; Murugesan, Srinivasan; Velu, Sadanandan

2015-01-01

331

California's ammonia emissions have been drastically underestimated  

NASA Astrophysics Data System (ADS)

In California, Los Angeles and the Central Valley often have atmospheric concentrations of particulate matter that exceed the U.S. Environmental Protection Agency's health guidelines. In the air, chemical reactions between ammonia, nitrogen oxides, and sulfur oxides can create inorganic aerosols like ammonium nitrate and ammonium sulfate. With their small particle sizes, these compounds can be dangerous to breathe, particularly for those with respiratory problems.

Schultz, Colin

2014-08-01

332

A comparison of the abilities of acetylsalicylic acid, flurbiprofen and indomethacin to inhibit the release reaction and prostaglandin synthesis in human blood platelets.  

PubMed Central

1 A quantitative comparison has been made of the abilities of acetylsalicylic acid, flurbiprofen and indomethacin to inhibit the adenosine diphosphate (ADP)-induced platelet release reaction and to inhibit the synthesis of prostaglandins from arachidonic acid. 2 Experiments were carried out on human platelets that had been incubated with the agents in vitro and on platelets obtained from volunteers who had ingested standard doses of the drugs. 3 The results obtained for acetylsalicylic acid show that there is a close relation between the release reaction and the synthesis of prostaglandins in platelets. 4 Flurbiprofen and indomethacin appear to inhibit the release reaction rather more effectively than they inhibit the synthesis of prostaglandins. It is possible that these agents inhibit the release reaction by another mechanism. PMID:115531

Cockbill, S. R.; Heptinstall, S.; Taylor, P. M.

1979-01-01

333

Cell-free protein synthesis in a microchamber revealed the presence of an optimum compartment volume for high-order reactions.  

PubMed

The application of microelectromechanical systems (MEMS) to chemistry and biochemistry allows various reactions to be performed in microscale compartments. Here, we aimed to use the glass microchamber to study the compartment size dependency of the protein synthesis, one of the most important reactions in the cell. By encapsulating the cell-free protein synthesis system with different reaction orders in femtoliter microchambers, chamber size dependency of the reaction initiated with a constant copy number of DNA was investigated. We were able to observe the properties specific to the high order reactions in microcompartments with high precision and found the presence of an optimum compartment volume for a high-order reaction using real biological molecules. PMID:23991849

Okano, Taiji; Matsuura, Tomoaki; Suzuki, Hiroaki; Yomo, Tetsuya

2014-06-20

334

M{prime}-RTaO{sub 4} synthesis: Activation of the precursor oxides by the reaction flux  

SciTech Connect

Studies of the M{prime}-RTaO{sub 4} (R = Gd, Y, Lu) phosphor synthesis reaction show that, contrary to previous views, the flux (e.g., Li{sub 2}SO{sub 4}, LiCl, Na{sub 2}SO{sub 4}) serves as in important reactant. Through a combination of techniques (DTA, TGA, XRPD, and mass balance), the authors find that close to its melting point, the flux reacts exothermically with the blended tantalum and yttrium oxides to give intermediate compounds. These reactive intermediates then combine to make M`-REaO{sub 4} and to regenerate the flux. Thus, the flux serves a dual purpose; it first activates the oxide reaction mixture and then serves as a classical flux in the growth of RTaO{sub 4} crystals. In light of this discovery, a more appropriate term for these flux compounds is catalyst or reactive flux because they facilitate the synthesis of RTaO{sub 4} through chemical reaction.

Hedden, D.B.; Zegarski, W. [DuPont Company, Towanda, PA (United States)] [DuPont Company, Towanda, PA (United States); Torardi, C.C. [DuPont Company, Wilmington, DE (United States)] [DuPont Company, Wilmington, DE (United States)

1995-09-01

335

Ammonia-activated mesoporous carbon membranes for gas separations  

Microsoft Academic Search

Porous carbon membranes, which generally show improved chemical and thermal stability compared to polymer membranes, have been used in gas separations for many years. In this work, we show that the post-synthesis ammonia treatment of porous carbon at elevated temperature can improve the permeance and selectivity of these membranes for the separation of carbon dioxide and hydrocarbons from permanent gases.

Shannon Mark Mahurin; Je Seung Lee; Xiqing Wang; Sheng Dai

2011-01-01

336

Synthesis of superheavy element 120 via {sup 50}Ti+{sup A}Cf hot fusion reactions  

SciTech Connect

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.

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

337

7, 383403, 2007 Ammonia aged  

E-print Network

ACPD 7, 383­403, 2007 Ammonia aged montmorillonite as ice nuclei A. Salam et al. Title Page Chemistry and Physics Discussions Ice nucleation of ammonia gas exposed montmorillonite mineral dust@mathstat.dal.ca) 383 #12;ACPD 7, 383­403, 2007 Ammonia aged montmorillonite as ice nuclei A. Salam et al. Title Page

Paris-Sud XI, Université de

338

5, 25052540, 2008 Modeling ammonia  

E-print Network

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

Paris-Sud XI, Université de

339

Atmospheric Ammonia From Undisturbed Land  

Microsoft Academic Search

Emissions of ammonia from the land areas of the world are calculated by using a simplified model. Soil ammonium concentrations are obtained from relative decomposition and nitrification rates; Henry's law gives the equilibrium concentration of ammonia gas in the soil, and a simplified diffusion equation yields the flux to the atmosphere. The model predicts negligible ammonia production in the polar

G. A. Dawson

1977-01-01

340

AMMONIA DISTILLATION FOR DEUTERIUM SEPARATION  

Microsoft Academic Search

The relative volatility or separation factor for deuterium enrichment in ; ammonia distillation was measured at several pressures and deuterium ; concentrations. The knowledge of this ingormation is very helpful in predicting ; costs of heawy water production by the ammonia distillation process. It hss been ; stated by others, that the ammonia distillation process of heawy water production ;

G. T. Petersen; M. Benedict

1960-01-01

341

Enantioselective synthesis of triarylmethanes by chiral imidodiphosphoric acids catalyzed Friedel-Crafts reactions.  

PubMed

The first enantioselective synthesis of pyrrolyl-substituted triarylmethanes has been accomplished using a novel imidodiphosphoric acid catalyst, which is derived from two (R)-BINOL frameworks with different 3,3'-substituents. This strategy was also expanded to the synthesis of bis(indolyl)-substituted triarylmethanes with high enantioselectivities, which could only be obtained with moderate ee values in previous reports. These two efficient Friedel-Crafts alkylation processes feature low catalyst loading, broad functional group compatibilities, and the potential to provide practical pathways for the synthesis of enantioenriched bioactive triarylmethanes. PMID:24490630

Zhuo, Ming-Hua; Jiang, Yi-Jun; Fan, Yan-Sen; Gao, Yang; Liu, Song; Zhang, Suoqin

2014-02-21

342

An enolate-mediated organocatalytic azide-ketone [3+2]-cycloaddition reaction: regioselective high-yielding synthesis of fully decorated 1,2,3-triazoles.  

PubMed

An enolate-mediated organocatalytic azide-ketone [3+2]-cycloaddition (OrgAKC) reaction of a variety of enolizable arylacetones and deoxybenzoins with aryl azides was developed for the synthesis of fully decorated 1,4-diaryl-5-methyl(alkyl)-1,2,3-triazoles in excellent yields with high regioselectivity at 25?°C for 0.5-6?h. This reaction has an excellent outcome with reference to reaction rate, yield, regioselectivity, operation simplicity, and availability of substrates and catalyst. This reaction has advantages over the previously known metal-mediated reactions. PMID:25367870

Shashank, Adluri B; Karthik, S; Madhavachary, R; Ramachary, Dhevalapally B

2014-12-15

343

N-halosuccinimide/AgNO3-efficient reagent systems for one-step synthesis of 2-haloglycals from glycals: application in the synthesis of 2C-branched sugars via Heck coupling reactions.  

PubMed

An expedient one-step synthesis of 2-iodoglycals and 2-bromoglycals from glycals using NIS/AgNO3 and NBS/AgNO3 as reagent systems has been developed. The utility of these 2-haloglycals has been demonstrated by converting them into 2C-branched glycals via the Heck coupling reaction. Ferrier reaction of tri-O-acetyl-2-iodoglycals followed by Heck coupling reaction with methyl acrylate leads to 2C-branched O-glycosides. PMID:24499471

Dharuman, Suresh; Vankar, Yashwant D

2014-02-21

344

Synthesis, reactions and biological activity of some new bis-heterocyclic ring compounds containing sulphur atom  

PubMed Central

Background The derivatives of thieno[2,3-b]thiophene belong to a significant category of heterocyclic compounds, which have shown a wide spectrum of medical and industrial application. Results A new building block with two electrophilic center of thieno[2,3-b]thiophene derivatives 2 has been reported by one-pot reaction of diketone derivative 1 with Br2/AcOH in excellent yield. A variety of heteroaromatics having bis(1H-imidazo[1,2a] benzimidazole), bis(1H-imidazo[1,2-b][1,2,4]triazole)-3-methyl-4-phenylthieno[2,3-b]thiophene derivatives, dioxazolo-, dithiazolo-, and 1H-imidazolo-3-methyl-4-phenylthieno[2,3-b]thiophene derivatives as well pyrrolo, thiazolo -3-methyl-4-phenylthieno[2,3-b]thiophene derivatives have been designed, synthesized, characterized, and evaluated for their biological activity. Compounds 3–9 showed good bioassay result. These new derivatives were evaluated for anti-cancer activity against PC-3 cell lines, in vitro antioxidant potential and ?-glucuronidase and ?-glucosidase inhibitory activities. Compound 3 (IC50?=?56.26?±?3.18??M) showed a potent DPPH radical scavenging antioxidant activity and found to be more active than standard N-acetylcystein (IC50?=?105.9?±?1.1??M). Compounds 8a (IC50?=?13.2?±?0.34??M) and 8b (IC50?=?14.1?±?0.28??M) found as potent inhibitor of ?-glucusidase several fold more active than the standard acarbose (IC50?=?841?±?1.73??M). Most promising results were obtained in ?-glucuronidase enzyme inhibition assay. Compounds 5 (IC50?=?0.13?±?0.019??M), 6 (IC50?=?19.9?±?0.285??M), 8a (IC50?=?1.2?±?0.0785??M) and 9 (IC50?=?0.003?±?0.09??M) showed a potent inhibition of ?-glucuronidase. Compound 9 was found to be several hundred fold more active than standard D-Saccharic acid 1,4-lactone (IC50?=?45.75?±?2.16??M). Conclusions Synthesis, characterization, and in vitro biological activity of a series of thieno[2,3-b]thiophene have been investigated. PMID:23829861

2013-01-01

345

Hydrothermal reactions: From the synthesis of ligand to new lanthanide 3D-coordination polymers  

SciTech Connect

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.

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

346

Sequential elimination-reduction reactions promoted by samarium diiodide: synthesis of 2,3-dideuterioesters or -amides.  

PubMed

A facile and general sequential elimination/reduction process promoted by samarium diiodide provides an efficient method for synthesizing saturated esters or amides 3 from readily available starting materials. The reaction involves a beta-elimination of the starting 2-halo-3-hydroxyesters or -amides 1 and subsequent 1,4-reduction of the obtained alpha,beta-unsaturated esters or amides in the presence of H2O. When D20 is used instead of H2O, 2,3-dideuterioesters or -amides 4 are isolated. A mechanism is proposed to account for this synthesis. PMID:11686607

Concellón, J M; Rodríguez-Solla, H

2001-10-01

347

[4 + 1] annulation reactions of (trialkylsilyl)ketenes : synthesis of substituted indanones and cyclopentenones  

E-print Network

(Trialkylsilyl)vinylketenes ("(TAS)vinylketenes") and (trialkylsilyl)arylketenes ("(TAS)- arylketenes") function as versatile four-carbon building blocks for the synthesis of carbocyclic and heterocyclic compounds. A new ...

Davie, Christopher P

2005-01-01

348

Synthesis of butyronitrile via ammonolysis of butylalcohol and dehydrogenation of butylamine over Mo[sub 2]N  

SciTech Connect

Investigations were carried out of the synthesis of butyronitrile via the ammonolysis of butylalcohol and the dehydrogenation of butylamine over Mo[sub 2]N. At 573 K butyronitrile is produced with virtually 100% yielded by both reactions. The ammonolysis of butylalcohol proceeds via dehydrogenation of the butylalcohol to form butyraldehyde, which then reacts with ammonia to produce butylimine. Butyronitrile is formed by butylimine dehydrogenation. The formation of butyronitrile from butylamine occurs via the stepwise dehydrogenation of the amine. The presence of ammonia in the gas phase suppresses the hydrogenolysis of either butylalcohol or butylamine. 11 refs., 8 figs., 2 tabs.

Abe, H.; Bell, A.T. (Lawrence Berkeley Lab., CA (United States) Univ. of California, Berkeley, CA (United States))

1993-08-01

349

Synthesis of (±)-cis-clavicipitic acid by a Rh(I)-catalyzed intramolecular imine reaction.  

PubMed

A new and short synthesis of racemic cis-clavicipitic acid was achieved by taking advantage of the double nucleophilic character of indole-4-pinacolboronic ester. Key to the success of the synthesis were an efficient and selective C-3 indole Friedel-Crafts alkylation and the development of an unprecedented intramolecular rhodium-catalyzed 1,2-addition of an aryl pinacolboronic ester to an unactivated imine. PMID:24605802

Bartoccini, Francesca; Casoli, Mariangela; Mari, Michele; Piersanti, Giovanni

2014-04-01

350

Atmospheric ammonia - Measurements and modeling  

NASA Technical Reports Server (NTRS)

Ammonia possesses a unique position in the terrestrial atmosphere in that it is the only gaseous basic constituent. Ammonia readily forms aerosols, and by virtue of its high solubility controls the pH of cloud droplets and precipitation. Over the past year a ground-based solar viewing Infrared Heterodyne Radiometer has been used at Langley Research Center to infer the vertical distribution of ammonia. Ground level in situ measurements of ammonia have also been obtained to supplement the profile data. The ammonia profiles have been analyzed and interpreted with a one-dimensional photochemical model of the troposphere to assess the sources and sinks of NH3.

Hoell, J. M., Jr.; Levine, J. S.; Augustsson, T. R.; Harward, C. N.

1981-01-01

351

Synthesis of acylphosphonates by a palladium-catalyzed phosphonocarbonylation reaction of aryl iodides with phosphites.  

PubMed

Acylphosphonates are conveniently synthesized from aryl iodides by a palladium-catalyzed reaction with dialkyl phosphites under an atmospheric pressure of carbon monoxide. The reaction demonstrates the first example of the use of phosphorus nucleophiles in related metal-catalyzed carbonylation reactions. PMID:25414042

Masuda, Yusuke; Ishida, Naoki; Murakami, Masahiro

2015-02-01

352

Microwave-Assisted Organic Synthesis in the Organic Teaching Lab: A Simple, Greener Wittig Reaction  

ERIC Educational Resources Information Center

A greener, microwave-assisted Wittig reaction has been developed for the second-semester organic teaching laboratory. Utilizing this microwave technique, a variety of styrene derivatives have been successfully synthesized from aromatic aldehydes in good yields (41-68%). The reaction not only occurs under neat reaction conditions, but also employs…

Martin, Eric; Kellen-Yuen, Cynthia

2007-01-01

353

One-pot synthesis of dihydropyrimidinones using facile and reusable polyoxometalate catalysts for the Biginelli reaction  

Microsoft Academic Search

The efficiency of various heteropoly compounds as well-known solid acids is investigated for the three-component condensation reaction of an aldehyde with ?-ketoester and urea in acetonitrile to afford the dihydropyrimidinones (DHPM). Compared to the classical Biginelli reaction conditions, this new method consistently has the advantage of excellent yields and short reaction times. Furthermore, the catalyst could be easily recovered after

Razieh Fazaeli; Shahram Tangestaninejad; Hamid Aliyan; Majid Moghadam

2006-01-01

354

Facile synthesis of functionalized tetrahydroquinolines via domino Povarov reactions of arylamines, methyl propiolate and aromatic aldehydes  

PubMed Central

Summary In the presence of p-toluenesulfonic acid as catalyst the domino reaction of arylamines, methyl propiolates and aromatic aldehydes in ethanol proceeded smoothly to give polysubstituted 1,2,3,4-tetrahydroquinolines in moderate yields. The reaction is believed to involve the Povarov reaction of in situ generated ?-enamino ester with the in situ formed aromatic imine. PMID:23209520

Sun, Jing; Gao, Hong; Wu, Qun

2012-01-01

355

A novel oxy-oxonia(azonia)-cope reaction: serendipitous discovery and its application to the synthesis of macrocyclic musks.  

PubMed

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

Zou, Yue; Zhou, Lijun; Ding, Changming; Wang, Quanrui; Kraft, Philip; Goeke, Andreas

2014-10-01

356

Synthesis of tunable diamine ligands with spiro indane-2,2?-pyrrolidine backbone and their applications in enantioselective Henry reaction.  

PubMed

Novel diamine ligands with spiro indane-2,2?-pyrrolidine scaffold were synthesized starting from Seebach’s oxazolidinone 6 and were subsequently employed in asymmetric Henry reaction. Following the initial experimental findings, further synthesis resulted in two types of spiro diamines, with varying substituents at both nitrogen atoms. Ligands of type A, containing a small substituent at N-1? atom, and a large group at N-1 atom gave predominantly the S-configured ?-nitroalcohol, while ligands of type B, with the reversed location of small and large substituents furnished the R-configured product. Both types of ligands turned out to be versatile catalysts for the Henry reaction between nitromethane and an assortment of aryl as well as alkyl aldehydes offering either S- (lig. A) or R-configured (lig. B) nitroalcohols in a good to high chemical yield and an excellent enantioselectivity up to 99% ee. PMID:24437641

?wiek, Rafa?; Niedziejko, Piotr; Ka?u?a, Zbigniew

2014-02-01

357

On the formation process of silicon carbide nanophases via hydrogenated thermally induced templated synthesis  

Microsoft Academic Search

A thermally induced templated synthesis for SiC nanotubes and nanofibers is presented using ammonia or N2 with vaporized Si is presented. The bundles of SWCNT act as both the carbon source and as a nanoframe from which SiC structures form. Depending on the duration of the thermally induced templated reaction, various SiC nanostructures are obtained for a fixed temperature, carrier

Mark. H. Rümmeli; Ewa Borowiak-Palen; Thomas Gemming; Martin Knupfer; Kati Biedermann; Ryszard J. Kalenczuk; Thomas Pichler

2005-01-01

358

Optimization of reaction parameters in hydrothermal synthesis: a strategy towards the formation of CuS hexagonal plates  

PubMed Central

Background For decades, copper sulphide has been renowned as the superior optical and semiconductor materials. Its potential applications can be ranged from solar cells, lithium-ion batteries, sensors, and catalyst systems. The synthesis methodologies of copper sulphide with different controlled morphology have been widely explored in the literature. Nevertheless, the understanding on the formation chemistry of CuS is still limited. The ultimate approach undertaking in this article is to investigate the formation of CuS hexagonal plates via the optimization of reaction parameters in hydrothermal reaction between copper (II) nitrate and sodium thiosulphate without appending any assistant agent. Results Covellite (CuS) hexagonal plates were formed at copper ion: thiosulphate ion (Cu2+:S2O32?) mole ratio of 1:2 under hydrothermal treatment of 155°C for 12 hours. For synthesis conducted at reaction temperature lower than 155°C, copper sulphate (CuSO4), krohnite (NaCu2(SO4)(H2O)2] and cyclooctasulphur (S8) were present as main impurities with covellite (CuS). When Cu2+:S2O32? mole ratio was varied to 1: 1 and 1: 1.5, phase pure plate-like natrochalcite [NaCu2(SO4)(H2O)] and digenite (Cu9S5) were produced respectively. Meanwhile, mixed phases of covellite (CuS) and cyclooctasulphur (S8) were both identified when Cu2+:S2O32? mole ratio was varied to 1: 2.5, 1: 3 and 1: 5 as well as when reaction time was shortened to 1 hour. Conclusions CuS hexagonal plates with a mean edge length of 1 ?m, thickness of 100 nm and average crystallite size of approximately (45?±?2) nm (Scherrer estimation) were successfully synthesized via assisting agent- free hydrothermal method. Under a suitable Cu2+:S2O32? mole ratio, we evidenced that the formation of covellite (CuS) is feasible regardless of the reaction temperature applied. However, a series of impurities were attested with CuS if reaction temperature was not elevated high enough for the additional crystallite phase decomposition. It was also identified that Cu2+:S2O32? mole ratio plays a vital role in controlling the amount of cyclooctasulphur (S8) in the final powder obtained. Finally, reaction time was recognized as an important parameter in impurity decomposition as well as increasing the crystallite size and crystallinity of the CuS hexagonal plates formed. PMID:23575312

2013-01-01

359

On-surface synthesis of single-layered two-dimensional covalent organic frameworks via solid-vapor interface reactions.  

PubMed

Surface covalent organic frameworks (SCOFs), featured by atomic thick sheet with covalently bonded organic building units, are promised to possess unique properties associated with reduced dimensionality, well-defined in-plane structure, and tunable functionality. Although a great deal of effort has been made to obtain SCOFs with different linkages and building blocks via both "top-down" exfoliation and "bottom-up" surface synthesis approaches, the obtained SCOFs generally suffer a low crystallinity, which impedes the understanding of intrinsic properties of the materials. Herein, we demonstrate a self-limiting solid-vapor interface reaction strategy to fabricate highly ordered SCOFs. The coupling reaction is tailored to take place at the solid-vapor interface by introducing one precursor via vaporization to the surface preloaded with the other precursor. Following this strategy, highly ordered honeycomb SCOFs with imine linkage are obtained. The controlled formation of SCOFs in our study shows the possibility of a rational design and synthesis of SCOFs with desired functionality. PMID:23786481

Liu, Xuan-He; Guan, Cui-Zhong; Ding, San-Yuan; Wang, Wei; Yan, Hui-Juan; Wang, Dong; Wan, Li-Jun

2013-07-17

360

Synthesis of pyrrolophenanthridine alkaloids based on C(sp³)-H and C(sp²)-H functionalization reactions.  

PubMed

Assoanine, pratosine, hippadine, and dehydroanhydrolycorine belong to the pyrrolophenanthridine family of alkaloids, which are isolated from plants of the Amaryllidaceae species. Structurally, these alkaloids are characterized by a tetracyclic skeleton that contains a biaryl moiety and an indole core, and compounds belonging to this class have received considerable interest from researchers in a number of fields because of their biological properties and the challenges associated with their synthesis. Herein, a strategy for the total synthesis of these alkaloids by using C-H activation chemistry is described. The tetracyclic skeleton was constructed in a stepwise manner by C(sp(3))-H functionalization followed by a Catellani reaction, including C(sp(2))-H functionalization. A one-pot reaction involving both C(sp(3))-H and C(sp(2))-H functionalization was also attempted. This newly developed strategy is suitable for the facile preparation of various analogues because it uses simple starting materials and does not require protecting groups. PMID:25044314

Tsukano, Chihiro; Muto, Nobusuke; Enkhtaivan, Iderbat; Takemoto, Yoshiji

2014-09-01

361

Interactive oxidation-reduction reaction for the in situ synthesis of graphene-phenol formaldehyde composites with enhanced properties.  

PubMed

We report a facile in situ synthesis of reduced graphene oxide (RGO)-phenol formaldehyde (PF) composites with an interactive oxidation-reduction reaction. In this interactive chemical reaction, graphene oxide (GO) was reduced to RGO by phenol, and simultaneously phenol was oxidized to benzoquinone. The noncovalently adsorbed phenol on the RGO surface can not only serve as an effective reductant but also participate in the in situ polymerization and guide the formation of PF on the RGO surface. RGO-PF composites with different RGO contents were prepared successfully and further characterized with fluorescent spectroscopy, scanning electron microscopy, and transmission electron microscopy. The mechanical strength, electrical conductivity, thermal conductivity, and thermal resistance of the created RGO-PF were investigated. The results indicated that the dispersity of RGO in the PF matrix and the interfacial interaction between RGO and PF were improved greatly because of formation of the RGO-PF hybrid in the in situ synthesis. The homogeneous dispersion and in situ polymerization of RGO sheets help to enhance the thermal conductivity of RGO-PF composites from 0.1477 to 0.3769 W m(-1) K(-1) and endow the composites with a good electrical conductivity. In addition, the well-dispersed RGO-PF composites are much more effective in improving their mechanical property and heat resistance. PMID:24588055

Zhao, Xiaojia; Li, Yang; Wang, Jinhui; Ouyang, Zhaofei; Li, Jingfeng; Wei, Gang; Su, Zhiqiang

2014-03-26

362

AMMONIA CONCENTRATION IN SALTSTONE HEADSPACE SUMMARY REPORT  

SciTech Connect

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.

Zamecnik, J; Alex Cozzi, A

2008-09-26

363

Computational Study of Field Initiated Surface Reactions for Synthesis of Diamond and Silicon  

NASA Technical Reports Server (NTRS)

This project involves using quantum chemistry to simulate surface chemical reactions in the presence of an electric field for nanofabrication of diamond and silicon. A field delivered by a scanning tunneling microscope (STM) to a nanometer scale region of a surface affects chemical reaction potential energy surfaces (PES) to direct atomic scale surface modification to fabricate sub-nanometer structures. Our original hypothesis is that the applied voltage polarizes the charge distribution of the valence electrons and that these distorted molecular orbitals can be manipulated with the STM so as to change the relative stabilities of the electronic configurations over the reaction coordinates and thus the topology of the PES and reaction kinetics. Our objective is to investigate the effect of applied bias on surface reactions and the extent to which STM delivered fields can be used to direct surface chemical reactions on an atomic scale on diamond and silicon. To analyze the fundamentals of field induced chemistry and to investigate the application of this technique for the fabrication of nanostructures, we have employed methods capable of accurately describing molecular electronic structure. The methods we employ are density functional theory (DFT) quantum chemical (QC) methods. To determine the effect of applied bias on surface reactions we have calculated the QC PESs in various applied external fields for various reaction steps for depositing or etching diamond and silicon. We have chosen reactions which are thought to play a role in etching and the chemical vapor deposition growth of Si and diamond. The PESs of the elementary reaction steps involved are then calculated under the applied fields, which we vary in magnitude and configuration. We pay special attention to the change in the reaction barriers, and transition state locations, and search for low energy reaction channels which were inaccessible without the applied bias.

Musgrave, Charles Bruce

1999-01-01

364

Synthesis and cross-coupling reaction of alkenyl[(2-hydroxymethyl)phenyl]dimethylsilanes  

Microsoft Academic Search

Highly stable alkenyl[2-(hydroxymethyl)phenyl]dimethylsilanes are prepared by stereo- and regioselective hydrosilylation of alkynes catalyzed either by a platinum or ruthenium catalyst using protected [2-(hydroxymethyl)phenyl]dimethylsilanes. Cyclic silyl ether, 1,1-dimethyl-2-oxa-1-silaindan, also serves as a starting material for the alkenylsilanes by the ring-opening reaction with alkenyl Grignard reagents. The resulting alkenylsilanes undergo cross-coupling reaction with various aryl and alkenyl iodides under reaction conditions employing

Yoshiaki Nakao; Hidekazu Imanaka; Jinshui Chen; Akira Yada; Tamejiro Hiyama

2007-01-01

365

Effects of aluminum additions to gas atomized reaction synthesis produced oxide dispersion strengthened alloys  

NASA Astrophysics Data System (ADS)

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.

Spicher, Alexander Lee

366

Oceanic emissions of ammonia  

NASA Astrophysics Data System (ADS)

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.

Paulot, F.; Jacob, D. J.; Johnson, M.; Bell, T. G.; Stock, C. A.; Doney, S. C.

2013-12-01

367

Optical reaction cell and light source for ›18F! fluoride radiotracer synthesis  

DOEpatents

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.

Ferrieri, Richard A. (Patchogue, NY); Schlyer, David (Bellport, NY); Becker, Richard J. (Islip, NY)

1998-09-15

368

Improving ammonia plant production  

Microsoft Academic Search

Investigates the effect of small variations in loop parameters on the production rate for an existing ammonia plant. A 73-psi (503-kPa) step in loop pressure or a 0.1% change in feed inerts or a roughly 7F (4C) step in condensation temperature do correspond to each other in terms of the effect on the production rate. Discusses hydrogen recovery from purge

N. Neth; W. Liebe; H. Puhl

1982-01-01

369

Improving ammonia plant production  

Microsoft Academic Search

In the reported experimental program, for an existing ammonia plant, the effect of small variations in loop parameters on the production rate was investigated. For the plant considered, a 73-psi (503-kPa) step in loop pressure or a 0.1% change in feed inerts or a roughly 7\\/degree\\/F (4\\/degree\\/C) step in condensation temperature do correspond to each other in terms of the

N. Neth; H. Puhl; W. Liebe

1982-01-01

370

Industrial ammonia gassing  

PubMed Central

Walton, M. (1972).British Journal of Industrial Medicine,30, 78-86. Industrial ammonia gassing. Seven cases of ammonia gassing are described with follow-up for five years of the six survivors and the post-mortem findings of the fatal case. All the survivors attributed continuing symptoms to the gassing. The study failed to demonstrate permanent ill effects in the one case of mild exposure. Of the more serious cases one has stopped smoking and taken up physical training teaching. He now has above average lung function. Two serious cases who continued to smoke have the lung function abnormalities expected from their smoking. In the other two seriously exposed cases, who also continued to smoke, there is a persistent reduction in ventilation and gas transfer which seems to be due to the ammonia gassing. The post-mortem findings in the fatal case showed acute congestion and oedema of the mucosa of the respiratory tract, the bronchial walls being stripped of their lining epithelium and the alveoli stuffed with red blood cells and oedema fluid. Images PMID:4685304

Walton, M.

1973-01-01

371

Atmospheric dispersion of ammonia: an ammonia fog model  

SciTech Connect

A simplification to the two-phase ammonia vapor-droplet fog problem has been implemented to study the dispersion of a spill of 40 tons of ammonia. We have circumvented the necessity of adding the partial differential equations for mass, momentum, and energy for the ammonia in the liquid phase by certain assumptions. It is assumed that the ammonia fog behaves as an ideal gas including the droplets. A temperature-dependent molecular weight was introduced to simulate the transition from a vapor-droplet cloud to a pure vapor cloud of ammonia. Likewise, the vaporization of ammonia was spread out over a temperature range. Mass, momentum, energy, and total ammonia is conserved rigorously. The observed features of the ammonia spill simulation have pointed out phenomena that could not be predicted in simpler calculations. Perhaps the most obvious feature is the cloud bifurcation due to the strength of the gravity current relative to the ambient wind. The gravity spreading of the denser ammonia fog significantly perturbs the unidirectional windfield in the vicinity of the spill, setting up complex eddy patterns in the cloud which are enhanced by ground heating and warm dry air entrainment. The lower concentrations appear to lift off by a buoyancy-induced flow. The ammonia cloud, rather than being cigar shaped as assumed in simpler models, ranges from pancake shaped to pear shaped, depending upon the ambient windfield. The fact that the ammonia cloud remains cold, very low, and wide is in qualitative agreement with some of the large-scale ammonia spill accidents. 14 figures.

Kansa, E.J.; Rodean, H.C.; Chan, S.T.; Ermak, D.L.

1983-01-01

372

Fungal and Plant Phenylalanine Ammonia-lyase  

PubMed Central

L-Phenylalanine is one of the essential amino acids that cannot be synthesized in mammals in adequate amounts to meet the requirements for protein synthesis. Fungi and plants are able to synthesize phenylalanine via the shikimic acid pathway. L-Phenylalanine, derived from the shikimic acid pathway, is used directly for protein synthesis in plants or metabolized through the phenylpropanoid pathway. This phenylpropanoid metabolism leads to the biosynthesis of a wide array of phenylpropanoid secondary products. The first step in this metabolic sequence involves the action of phenylalanine ammonia-lyase (PAL). The discovery of PAL enzyme in fungi and the detection of 14CO2 production from 14C-ring-labeled phenylalanine and cinnamic acid demonstrated that certain fungi can degrade phenylalanine by a pathway involving an initial deamination to cinnamic acid, as happens in plants. In this review, we provide background information on PAL and a recent update on the presence of PAL genes in fungi. PMID:22783113

Hyun, Min Woo; Yun, Yeo Hong; Kim, Jun Young

2011-01-01

373

The dynamics of ammonia metabolism in man. Effects of liver disease and hyperammonemia.  

PubMed Central

The cyclotron-produced radionuclide, 13N, was used to label ammonia and to study its metabolism in a group of 5 normal subjects and 17 patients with liver disease, including 5 with portacaval shunts and 11 with encephalopathy. Arterial ammonia levels were 52-264 micron. The rate of ammonia clearance from the vascular compartment (metabolism) was a linear function of its arterial concentration: mumol/min = 4.71 [NH3]a + 3.76, r = +0.85, P less than 0.005. Quantitative body scans showed that 7.4 +/- 0.3% of the isotope was metabolized by the brain. The brain ammonia utilization rate, calculated from brain and blood activities, was a function of the arterial ammonia concentration: mumol/min per whole brain = 0.375 [NH3]a - 3.6, r = +0.93, P less than 0.005. Assuming that cerebral blood flow and brain weights were normal, 47 +/- 3% of the ammonia was extracted from arterial blood during a single pass through the normal brains. Ammonia uptake was greatest in gray matter. The ammonia utilization reaction(s) appears to take place in a compartment, perhaps in astrocytes, that includes less than 20% of all brain ammonia. In the 11 nonencephalopathic subjects the [NH3]a was 100 +/- 8 micron and the brain ammonia utilization rate was 32 +/- 3 mumol/min per whole brain; in the 11 encephalopathic subjects these were respectively elevated to 149 +/- 18 micron (P less than 0.01), and 53 +/- 7 mumol/min per whole brain (P less than 0.01). In normal subjects, approximately equal to 50% of the arterial ammonia was metabolized by skeletal muscle. In patients with portal-systemic shunting, muscle may become the most important organ for ammonia detoxification. Muscle atrophy may thereby contribute to the development of hyperammonemic encephalopathy with an associated increase in the brain ammonia utilization rate. Images PMID:429564

Lockwood, A H; McDonald, J M; Reiman, R E; Gelbard, A S; Laughlin, J S; Duffy, T E; Plum, F

1979-01-01

374

THE IMPROVED SYNTHESIS OF CARBONATED SOYBEAN OIL USING SUPERCRITICAL CARBON DIOXIDE AT A REDUCED REACTION TIME  

Technology Transfer Automated Retrieval System (TEKTRAN)

We have demonstrated at improved synthesis of a cyclic carbonate of soybean oil (CSO) utilizing supercritical carbon dioxide (CO2) as the solvent. Because the mutual solubility of supercritical CO2 and oil is significantly higher than that of the gas, our method synthesizes the material in ~1/3 of ...

375

Toward the Total Synthesis of Norzoanthamine: The Development of a Transannular Michael Reaction Cascade  

E-print Network

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...

Xue, Haoran

2013-03-06

376

Modulating the Synthesis of Dextran with the Acceptor Reaction Using Native and Encapsulated Dextransucrases  

Microsoft Academic Search

Summary Dextransucrases are glucansucrases with broad applications in the food, cosmetics and pharmaceutical industries. Using sucrose as the glucosyl donor, they synthesize both high molecular weight (HMW) dextrans and potential prebiotic oligosaccharides. The pro- cess selectivity can be modulated by varying the reaction conditions. When no other mole- cule is present in the reaction, only dextrans are synthesized. In the

Arantza Gómez de Segura; Miguel Alcalde; Nieves López-Cortés; Francisco J. Plou; Antonio Ballesteros

377

Synthesis, hydrothermal stability and thermal reaction behavior of nepheline hydrate i (NH I)  

Microsoft Academic Search

Summary The field of formation of nepheline hydrate I (NH I) was investigated under mild hydrothermal conditions (473 K for 5 d) using low temperature reaction of kaolinite. Therefore alkaline transformation in 2-, 4-, and 6 molar NaOH solutions was performed to investigate the influence of sodium hydroxide on the phase formation process controlled by kinetics under mild reaction conditions.

Josef-Christian Buhl

2005-01-01

378

Synthesis of ?-Hydroxy-?-haloesters through Super Silyl Ester Directed SYN-Selective Aldol Reaction  

PubMed Central

Super silyl haloesters including chloro- and bromoacetate were synthesized and utilized for aldol reactions to give SYN-?-hydroxy-?-haloacetates in good yields with high diastereoselectivities. ?-Hydroxy-?-fluoroacetate was obtained by lithiation of super silyl bromofluoroacetate. Sequential Darzens reactions provided CIS-glycidic esters in moderate yields. PMID:24205937

Oda, Susumu

2013-01-01

379

Heteroatom-embedded Medium-Sized Cycloalkynes: Concise Synthesis, Structural Analysis, and Reactions.  

PubMed

A variety of medium-sized cycloalkynes were efficiently synthesized by the double Nicholas reaction of cobalt complex and bis(hetero)substituted acyclic compound. The alkyne moiety within the ring has a unique bent structure and high reactivity toward cycloaddition reactions. Furthermore, preparation of multifunctionalized alkynes was achieved by embedding the cycloalkyne within a peptide chain. PMID:25470001

Ni, Runyan; Mitsuda, Naoto; Kashiwagi, Takeru; Igawa, Kazunobu; Tomooka, Katsuhiko

2015-01-19

380

A facile solution phase combinatorial synthesis of tetrasubstituted pyridines using the Bohlmann-Rahtz heteroannulation reaction.  

PubMed

The solution phase combinatorial Bohlmann-Rahtz reaction gives highly functionalized pyridine libraries from enamino esters and alkynones in a single synthetic step. Good product ratios and library purities were obtained in reactions catalyzed by zinc(II) bromide, the acid-catalyzed heteroannulation procedure offering considerable improvements over traditional methodology. PMID:12523833

Bagley, Mark C; Dale, James W; Ohnesorge, Maren; Xiong, Xin; Bower, Justin

2003-01-01

381

The formation and removal characteristics of aerosols in ammonia-based wet flue gas desulfurization  

Microsoft Academic Search

The characteristics of aerosol generation were studied experimentally in an ammonia-based wet flue gas desulfurization process. Particle size distributions and concentrations, morphologies and compositions before and after desulfurization were measured using an electrical low pressure impactor and scanning electron microscopy, respectively. The results show that aerosols can be generated between ammonia and sulfur dioxide resulting in gas-phase reaction and the

Jinpei Yan; Jingjing Bao; Linjun Yang; Fengxian Fan; Xianglin Shen

2011-01-01

382

Process for co-production of higher alcohols, methanol and ammonia  

Microsoft Academic Search

This patent describes an integrated process for the production of higher alcohols, methanol and ammonia. It comprises: catalytically reforming at first methane-containing stream with steam and carbon dioxide to form first a hydrogen and carbon monoxide-containing synthesis gas; removing carbon dioxide from the first synthesis gas and recycling at least a portion of the carbon dioxide to the reformation; rejecting

N. M. Patel; S. I. Wang

1989-01-01

383

One-pot synthesis of cycloamyloses from sucrose by dual enzyme treatment: combined reaction of amylosucrase and 4-?-glucanotransferase.  

PubMed

Amylose-like ?-(1,4)-glucan known as the most favorable substrate for the enzymatic production of cycloamyloses (CAs) using 4-?-glucanotransferase has a solubility issue, which requires an additional solubilization process. In our study, two glucosyltransferases, Synechocystis 4-?-glucanotransferase and Neisseria amylosucrase, were adopted to develop an efficient biocatalytic production process of CAs directly from sucrose. From one-pot synthesis, the maximum CA yield (9.6%, w/w) with 0.3 M sucrose was achieved with 10 units/mL of amylosucrase and 0.1 unit/mL of 4-?-glucanotransferase at 40 °C for a 3 h reaction in a simultaneous dual enzyme reaction mode. The size of linear ?-(1,4)-glucan was positively related to the CA productivity by 4-?-glucanotransferase in a hyperbolic manner. Using our innovative bioprocess, there was no practical limitation on the initial sucrose concentration and no use of insoluble linear ?-(1,4)-glucan substrate. Consequently, the concomitant dual enzyme reaction converted sucrose directly to CAs via in situ transient linear ?-(1,4)-glucan as an soluble intermediate. PMID:21434692

Kim, Jung-Hwan; Wang, Ren; Lee, Wang-Hee; Park, Cheon-Seok; Lee, Suyong; Yoo, Sang-Ho

2011-05-11

384

Facile Synthesis of ?-Amino-?-ketoesters and Piperidinediones via a Vinylogous Mannich-Type Reaction of Brassard-Type Diene with Aldimines without Catalyst  

Microsoft Academic Search

The vinylogous Mannich reaction of N-tosyl-aldimines with Brassard diene proceeds at room temperature under catalyst-free conditions smoothly to give ?-amino-?-ketoesters (4b–l) in good to excellent yields, which are easily converted to piperidinediones at higher temperature. The two-step reactions could be combined in a one-pot process with toluene as a solvent and without the use of any catalyst for direct synthesis

Chun-Ling Gu; Li Liu; Dong Wang; Yong-Jun Chen

2009-01-01

385

A Novel Method for Synthesis of Sulfonated SBS Ionomers by Ring-Opening Reaction of Epoxidized SBS, Their Characterization, Properties, and Blends  

Microsoft Academic Search

A novel method for synthesis of sulfonated ionomer of (styrene-butadiene-styrene) triblock copolymer (SBS) is developed. SBS is first epoxidized by performic acid formed in situ, followed by ring-opening reaction with an aqueous solution of NaHSO3. The optimum conditions for ring-opening reaction of the epoxidized SBS with aqueous solution of NaHSO3 and some properties of the ionomer are studied. It has

Hong-Quan Xie; Wu-Gang Yu; Gui-Yin Liao; Wei Yang; Dong Xie

2007-01-01

386

One-pot synthesis of dihydropyrimidones using silica-supported heteropoly acid as an efficient and reusable catalyst: Improved protocol conditions for the Biginelli reaction  

Microsoft Academic Search

An efficient synthesis of 3,4-dihydropyrimidinones or thiones (DHPMs) is described, using silica-supported heteropoly acid H3PW12O40\\/SiO2 (PW\\/SiO2) for the first time as the catalyst from an aldehyde, ?-keto ester and urea or thiourea in acetonitrile. Compared to the classical Biginelli reaction conditions, this method consistently has the advantage of excellent yields, mild reaction conditions, ease of workup, survival of different functional

Ezzat Rafiee; Fomaida Shahbazi

2006-01-01

387

Solvent-free synthesis of 1-[3-alkyl-4-methyl-2-thioxo-2,3-dihydrothiazole-5-yl]-ethanones in a multicomponent reaction  

Microsoft Academic Search

A simple and efficient one-pot synthesis of 1-[3-alkyl-4-methyl-2-thioxo-2,3-dihydrothiazole-5-yl]-ethanones from the reaction of primary alkylamines and carbon disulfide in the presence of 3-chloro acetylacetone is described. This protocol has several advantages such as lack of need for a solvent and catalyst, high yields, mild conditions and short reaction times.

Nasir Iravani; Bahador Karami; Farideh Asadimoghaddam; Maryam Monfared; Nahid Karami

2012-01-01

388

System and method for determining an ammonia generation rate in a three-way catalyst  

DOEpatents

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.

Sun, Min; Perry, Kevin L; Kim, Chang H

2014-12-30

389

Synthesis of 3-indole derivatives by copper sulfonato Salen catalyzed three-component reactions in water.  

PubMed

An efficient three-component reaction of indole, aldehyde, and malononitrile in water catalyzed by a copper(II) sulfonato Salen complex afforded 3-indole derivatives in good to excellent yields up to 97%. PMID:21340052

Qu, Yanyang; Ke, Fang; Zhou, Li; Li, Zhengkai; Xiang, Haifeng; Wu, Di; Zhou, Xiangge

2011-04-01

390

Development of odd-Z-projectile reactions for transactinide element synthesis  

SciTech Connect

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.

Folden III, Charles Marvin

2004-11-04

391

Enantioselective total synthesis of isishippuric acid B via intramolecular Michael reaction.  

PubMed

The first enantioselective total synthesis of isishippuric acid B bearing a novel 4,5-seco-6-norquadrane skeleton was accomplished from (R)-citronellal with use of a Diels-Alder cycloaddition and an intramolecular Michael addition as the ring-forming steps. Comparison of the optical rotation of the synthetic material with that of the natural product confirmed the absolute configuration of isishippuric acid B to be 1R, 2R, 8R, and 11R. PMID:17539655

Torihata, Munefumi; Nakahata, Takashi; Kuwahara, Shigefumi

2007-06-21

392

Total Synthesis of Cyclosporine: Access to N-Methylated Peptides via Isonitrile Coupling Reactions  

PubMed Central

Recent developments in the use of isonitriles to furnish secondary and tertiary amide bond formations are applied to a novel total synthesis of the important cyclic polypeptide cyclosporine A. Specifically, the disclosed synthetic route demonstrates the utility of microwave-mediated carboxylic acid isonitrile couplings, thioacid isonitrile couplings at ambient temperature, and isonitrile-mediated couplings of carboxylic acids and thioacids with amines to form challenging amide bonds. PMID:20199071

Wu, Xiangyang; Stockdill, Jennifer L.; Wang, Ping; Danishefsky, Samuel J.

2010-01-01

393

Expedient Synthesis of Norbenzomorphan Library via Multicomponent Assembly Process Coupled with Ring-Closing Reactions  

PubMed Central

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

Sahn, James J.; Martin, Stephen F.

2012-01-01

394

Leuconostoc mesenteroides glucansucrase synthesis of flavonoid glucosides by acceptor reactions in aqueous-organic solvents  

Microsoft Academic Search

The enzymatic glucosylation of luteolin was attempted using two glucansucrases: the dextransucrase from Leuconostoc mesenteroides NRRL B-512F and the alternansucrase from L. mesenteroides NRRL B-23192. Reactions were carried out in aqueous-organic solvents to improve luteolin solubility. A molar conversion of 44% was achieved after 24h of reaction catalysed by dextransucrase from L. mesenteroides NRRL B-512F in a mixture of acetate

Anne Bertrand; Sandrine Morel; François Lefoulon; Yves Rolland; Pierre Monsan; Magali Remaud-Simeon

2006-01-01

395

Organo-niobate Ionic Liquids: Synthesis, Characterization and Application as Acid Catalyst in Pechmann Reactions  

PubMed Central

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%.

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

396

Solvothermal reactions: an original route for the synthesis of novel materials  

Microsoft Academic Search

Twenty years after the first development of solvothermal reactions, it appears important through the last research activities\\u000a to trace the future trends taking into account their potentialities and the different economical constraints. During these\\u000a last 20 years solvothermal reactions have been mainly used from preparing micro- or nanoparticles with different morphologies.\\u000a Due to the importance to dispose of new materials for

Gérard Demazeau

2008-01-01

397

Effects of solid-state reaction synthesis processing parameters on thermoelectric properties of Mg 2 Si  

Microsoft Academic Search

The Mg2 Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction. This paper studies the effects\\u000a of holding time and reaction temperature on the particle size and the properties of the material, and also studies effects\\u000a of doping elemental Sb, Te and their doping seqence on the properties of the material. The result shows that excessively high\\u000a temperature and

Hong-yi Jiang; Hai-shan Long; Lian-meng Zhang

2004-01-01

398

Stoichiometric Reactions of Acylnickel(II) Complexes with Electrophiles and the Catalytic Synthesis of Ketones.  

PubMed

Acylnickel(II) complexes feature prominently in cross-electrophile coupling (XEC) reactions that form ketones, yet their reactivity has not been systematically investigated. We present here our studies on the reactivity of acylnickel(II) complexes with a series of carbon electrophiles. Bromobenzene, ?-chloroethylbenzene, bromooctane, and iodooctane were reacted with (dtbbpy)Ni(II)(C(O)C5H11)(Br) (1b) and (dtbbpy)Ni(II)(C(O)tolyl)(Br) (1c) to form a variety of organic products. While reactions with bromobenzene formed complex mixtures of ketones, reactions with ?-chloroethylbenzene were highly selective for the cross-ketone product. Reactions with iodooctane and bromooctane also produced the cross-ketone product, but in intermediate yield and selectivity. In most cases the presence or absence of a chemical reductant (zinc) had only a small effect on the selectivity of the reaction. The coupling of 1c with iodooctane (60% yield) was translated into a catalytic reaction, the carbonylative coupling of bromoarenes with primary bromoalkanes (six examples, 60% average yield). PMID:25364092

Wotal, Alexander C; Ribson, Ryan D; Weix, Daniel J

2014-10-27

399

27 CFR 21.96 - Ammonia, aqueous.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Ammonia, aqueous. 21.96 Section 21...Specifications for Denaturants § 21.96 Ammonia, aqueous. (a) Alkalinity. Strongly alkaline to litmus. (b) Ammonia content. 27 to 30...

2010-04-01

400

27 CFR 21.96 - Ammonia, aqueous.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Ammonia, aqueous. 21.96 Section 21...Specifications for Denaturants § 21.96 Ammonia, aqueous. (a) Alkalinity. Strongly alkaline to litmus. (b) Ammonia content. 27 to 30...

2012-04-01

401

21 CFR 573.180 - Anhydrous ammonia.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Anhydrous ammonia. 573.180 Section 573.180 Food and...Additive Listing § 573.180 Anhydrous ammonia. (a) The food additive anhydrous ammonia is applied directly to corn plant...

2012-04-01

402

21 CFR 573.180 - Anhydrous ammonia.  

...2014-04-01 2014-04-01 false Anhydrous ammonia. 573.180 Section 573.180 Food and...Additive Listing § 573.180 Anhydrous ammonia. (a) The food additive anhydrous ammonia is applied directly to corn plant...

2014-04-01

403

21 CFR 573.180 - Anhydrous ammonia.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Anhydrous ammonia. 573.180 Section 573.180 Food and...Additive Listing § 573.180 Anhydrous ammonia. (a) The food additive anhydrous ammonia is applied directly to corn plant...

2013-04-01

404

21 CFR 573.180 - Anhydrous ammonia.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Anhydrous ammonia. 573.180 Section 573.180 Food and...Additive Listing § 573.180 Anhydrous ammonia. (a) The food additive anhydrous ammonia is applied directly to corn plant...

2011-04-01

405

27 CFR 21.96 - Ammonia, aqueous.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Ammonia, aqueous. 21.96 Section 21...Specifications for Denaturants § 21.96 Ammonia, aqueous. (a) Alkalinity. Strongly alkaline to litmus. (b) Ammonia content. 27 to 30...

2013-04-01

406

27 CFR 21.96 - Ammonia, aqueous.  

...2014-04-01 2014-04-01 false Ammonia, aqueous. 21.96 Section 21...Specifications for Denaturants § 21.96 Ammonia, aqueous. (a) Alkalinity. Strongly alkaline to litmus. (b) Ammonia content. 27 to 30...

2014-04-01

407

27 CFR 21.96 - Ammonia, aqueous.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Ammonia, aqueous. 21.96 Section 21...Specifications for Denaturants § 21.96 Ammonia, aqueous. (a) Alkalinity. Strongly alkaline to litmus. (b) Ammonia content. 27 to 30...

2011-04-01

408

21 CFR 573.180 - Anhydrous ammonia.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Anhydrous ammonia. 573.180 Section 573.180 Food and...Additive Listing § 573.180 Anhydrous ammonia. (a) The food additive anhydrous ammonia is applied directly to corn plant...

2010-04-01

409

Protease-catalyzed peptide synthesis using inverse substrates: the influence of reaction conditions on the trypsin acyl transfer efficiency.  

PubMed

Benzyloxycarbonyl-L-alanine p-guanidinophenyl ester behaves as a trypsin "inverse substrate," i.e., a cationic center is included in the leaving group instead of being in the acyl moiety. Using this substrate as an acyl donor, trypsin catalyzes the synthesis of peptide bonds that cannot be split by this enzyme. An optimal acyl transfer efficiency was achieved between pH 8 and 9 at 30 degrees C.The addition of as much as 50% cosolvent was shown to be of minor influence on the acyl transfer efficiency, whereas the reaction velocity decreases by more than one order of magnitude. The efficiency of H-Leu-NH(2) and H-Val-NH(2) in deacylation is almost the same for "inverse" and normal type substrates. PMID:18600704

Schellenberger, V; Jakubke, H D; Zapevalova, N P; Mitin, Y V

1991-06-01

410

Template-free synthesis of hollow nitrogen-doped carbon as efficient electrocatalysts for oxygen reduction reaction  

NASA Astrophysics Data System (ADS)

In this paper, we report a template-free method to fabricate hollow nitrogen-doped carbon (HNC) by pyrolysis of hollow polyaniline microspheres, which were synthesized by suspension polymerization method. The entire synthesis is simple, environmentally benign, and economic. The oxygen reduction reaction (ORR) activity of the as-prepared HNC catalyst is close to that of the commercial Pt/C catalyst in alkaline media with four electron pathway. Moreover, the HNC shows much better fuel crossover resistance and long-term durability than the commercial Pt/C in alkaline medium. All these features make HNC a potentially promising and suitable substitute for the expensive noble metal catalysts in the next generation alkaline fuel cells.

Wu, Rui; Chen, Siguo; Zhang, Yuanliang; Wang, Yao; Ding, Wei; Li, Li; Qi, Xueqiang; Shen, Xiu; Wei, Zidong

2015-01-01

411

Au-ZnO hybrid nanoflowers, nanomultipods and nanopyramids: one-pot reaction synthesis and photocatalytic properties  

NASA Astrophysics Data System (ADS)

The preparation of noble metal-semiconductor hybrid nanocrystals with controlled morphologies has received intensive interest in recent years. In this study, facile one-pot reactions have been developed for the synthesis of Au-ZnO hybrid nanocrystals with different interesting morphologies, including petal-like and urchin-like nanoflowers, nanomultipods and nanopyramids. In the synthesis strategy, oleylamine-containing solution serves as the reaction medium, and the in situ generated Au seeds play an important role in the subsequently induced growth of ZnO nanocrystals. With the aid of several surfactants, hybrid nanocrystals with different morphologies that have considerable influences on their optical and photocatalytic activities are readily achieved. Through high-resolution transmission electron microscopy measurements, an observed common orientation relationship between ZnO and Au is that ZnO nanocrystals prefer to grow with their polar {001} facets on the {111} facets of Au nanocrystals, and well-defined interfaces are evident. Surface plasmon resonance bands of Au with different positions are observed in the UV-vis spectra, and the UV and visible emissions of ZnO are found to be dramatically reduced. Finally, the as-prepared Au-ZnO nanocrystals exhibit excellent photocatalytic activity for the photodegradation of rhodamine B compared with pure ZnO nanocrystals. The Au-ZnO hybrid nanopyramids show the highest catalytic efficiency, which is correlated with the exposed crystal facets, crystallinity and the formation of hybrid nanostructures. The as-prepared Au-ZnO hybrid nanocrystals are expected to find diverse potential applications in the fields such as photocatalysis, solar energy conversion, sensing and biological detection.The preparation of noble metal-semiconductor hybrid nanocrystals with controlled morphologies has received intensive interest in recent years. In this study, facile one-pot reactions have been developed for the synthesis of Au-ZnO hybrid nanocrystals with different interesting morphologies, including petal-like and urchin-like nanoflowers, nanomultipods and nanopyramids. In the synthesis strategy, oleylamine-containing solution serves as the reaction medium, and the in situ generated Au seeds play an important role in the subsequently induced growth of ZnO nanocrystals. With the aid of several surfactants, hybrid nanocrystals with different morphologies that have considerable influences on their optical and photocatalytic activities are readily achieved. Through high-resolution transmission electron microscopy measurements, an observed common orientation relationship between ZnO and Au is that ZnO nanocrystals prefer to grow with their polar {001} facets on the {111} facets of Au nanocrystals, and well-defined interfaces are evident. Surface plasmon resonance bands of Au with different positions are observed in the UV-vis spectra, and the UV and visible emissions of ZnO are found to be dramatically reduced. Finally, the as-prepared Au-ZnO nanocrystals exhibit excellent photocatalytic activity for the photodegradation of rhodamine B compared with pure ZnO nanocrystals. The Au-ZnO hybrid nanopyramids show the highest catalytic efficiency, which is correlated with the exposed crystal facets, crystallinity and the formation of hybrid nanostructures. The as-prepared Au-ZnO hybrid nanocrystals are expected to find diverse potential applications in the fields such as photocatalysis, solar energy conversion, sensing and biological detection. Electronic supplementary information (ESI) available: EDS spectra, SEM images and TEM images of products synthesized under different conditions, and time-dependent UV-vis spectra recorded during the photocatalytic degradation of RhB by using different samples. See DOI: 10.1039/c3nr04558g

Chen, Yuanzhi; Zeng, Deqian; Zhang, Kun; Lu, Aolin; Wang, Laisen; Peng, Dong-Liang

2013-12-01

412

Synthesis of 3-heteryl substituted pyrrolidine-2,5-diones via catalytic Michael reaction and evaluation of their inhibitory activity against InhA and Mycobacterium tuberculosis.  

PubMed

In the present paper, we report the synthesis via catalytic Michael reaction and biological results of a series of 3-heteryl substituted pyrrolidine-2,5-dione derivatives as moderate inhibitors against Mycobacterium tuberculosis H37Rv growth. Some of them present also inhibition activities against InhA. PMID:24269516

Matviiuk, Tetiana; Mori, Giorgia; Lherbet, Christian; Rodriguez, Frédéric; Pasca, Maria Rosalia; Gorichko, Marian; Guidetti, Brigitte; Voitenko, Zoia; Baltas, Michel

2014-01-01

413

Deep eutectic solvents and glycerol: a simple, environmentally benign and efficient catalyst\\/reaction media for synthesis of N-aryl phthalimide derivatives  

Microsoft Academic Search

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

Hyacintha Rennet Lobo; Balvant Shyam Singh; Ganapati Subray Shankarling

2012-01-01

414

Synthesis of the ‘green apple ester’ ethyl valerate in organic solvents by Candida rugosa lipase immobilized in MBGs in organic solvents: Effects of immobilization and reaction parameters  

Microsoft Academic Search

Ethyl valerate, also known as the green apple flavor is well known for its wide applications in the areas of food, pharmaceuticals and cosmetics industries. Candida rugosa lipase was immobilized in microemulsion based organogels (MBGs) and used for ethyl valerate synthesis in organic solvents. Various immobilization and reaction parameters were scrutinized for enhancement of ester production. Among the immobilization parameters,

Tripti Raghavendra; Divya Sayania; Datta Madamwar

2010-01-01

415

Synthesis of unnatural amino acids via microwave-assisted regio-selective one-pot multi-component reactions of sulfamidates  

EPA Science Inventory

Synthesis of triazole-based unnatural amino acids, triazole bisaminoacids and ß-amino triazole has been described via stereo and regioselective one-pot multi-component reaction of sulfamidates, sodium azide, and alkynes under MW irradiation conditions. The developed method is app...

416

Intramolecular cationic [5 + 2] cycloaddition reactions promoted by trimethylsilyl triflate in 3.0 M lithium perchlorate-ethyl acetate: Application to a formal total synthesis of (±)-isocomene  

Microsoft Academic Search

Trimethylsilyl triflate is an effective reagent in 3.0 M lithium perchlorate-ethyl acetate for promoting intramolecular cationic [5 + 2] cycloaddition reactions. A formal total synthesis of the angular triquinane isocomene (10) is detailed. Cationic [5 + 2] cycloaddition of quinone monoketal 40 gives rise to tricyclic diketone 35 which is subsequently converted into the known tricyclic ketone 33. Addition of

Paul A. Grieco; John K. Walker

1997-01-01

417

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...

418

Synthesis of high specific activity (+)- and (-)-6-( sup 18 F)fluoronorepinephrine via the nucleophilic aromatic substitution reaction  

SciTech Connect

The first example of a no-carrier-added {sup 18}F-labeled catecholamine, 6-({sup 18}F)fluoronorepinephrine (6-({sup 18}F)FNE), has been synthesized via nucleophilic aromatic substitution. The racemic mixture was resolved on a chiral HPLC column to obtain pure samples of (-)-6-({sup 18}F)FNE and (+)6-({sup 18}F)FNE. Radiochemical yields of 20% at the end of bombardment (EOB) for the racemic mixture (synthesis time 93 min), 6% for each enantiomer (synthesis time 128 min) with a specific activity of 2-5 Ci/mumol at EOB were obtained. Chiral HPLC peak assignment for the resolved enantiomers was achieved by using two independent methods: polarimetric determination and reaction with dopamine beta-hydroxylase. Positron emission tomography (PET) studies with racemic 6-({sup 18}F)FNE show high uptake and retention in the baboon heart. This work demonstrates that nucleophilic aromatic substitution by ({sup 18}F)fluoride ion is applicable to systems having electron-rich aromatic rings, leading to high specific activity radiopharmaceuticals. Furthermore, the suitably protected dihydroxynitrobenzaldehyde 1 may serve as a useful synthetic precursor for the radiosynthesis of other complex {sup 18}F-labeled radiotracers.

Ding, Y.S.; Fowler, J.S.; Gatley, S.J.; Dewey, S.L.; Wolf, A.P. (Brookhaven National Laboratory, Upton, NY (USA))

1991-02-01

419

Rapid synthesis of hollow Ag-Au nanodendrites in 15 seconds by combining galvanic replacement and precursor reduction reactions.  

PubMed

Metallic nanomaterials displaying hollow interiors as well as sharp tips/branches at their surface (such as hollow nanodendrites) are attractive, because these features enable higher surface-to-volume ratios than their solid and/or rounded counterparts. This paper describes a simple strategy for the synthesis of Ag-Au nanodendrites in 15?s using Ag nanospheres prepared in a previous synthetic step as seeds. Our approach was based on the utilization of Ag nanospheres as seeds for Au deposition by a combination of galvanic replacement reaction between Ag and AuCl4(-)(aq) and AuCl4(-)(aq) reduction using hydroquinone in the presence of polyvinylpyrrolidone (PVP) as a stabilizer and water as the solvent. The produced Ag-Au nanodendrites presented monodisperse sizes, and their surface morphologies could be tuned as a function of growth time. Owing to their hollow interiors and sharp tips, the Ag-Au nanodendrites performed as effective substrates for surface-enhanced Raman scattering (SERS) detection of 4-MPy (4-mercaptopyridine) and R6G (rhodamine 6G) as probe molecules. We believe that the approach described herein can serve as a protocol for the fast and one-step synthesis of Ag-Au hollow nanondendrites with a wide range of sizes, compositions, and surface morphologies for applications in SERS and catalysis. PMID:25284169

da Silva, Anderson G M; de Souza, Michele L; Rodrigues, Thenner S; Alves, Rafael S; Temperini, Marcia L A; Camargo, Pedro H C

2014-11-10

420

Amide coupling reaction for the synthesis of bispyridine-based ligands and their complexation to platinum as dinuclear anticancer agents.  

PubMed

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is (1)H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand. PMID:24893964

Apps, Michael G; Johnson, Ben W; Sutcliffe, Oliver B; Brown, Sarah D; Wheate, Nial J

2014-01-01

421

Au-ZnO hybrid nanoflowers, nanomultipods and nanopyramids: one-pot reaction synthesis and photocatalytic properties.  

PubMed

The preparation of noble metal-semiconductor hybrid nanocrystals with controlled morphologies has received intensive interest in recent years. In this study, facile one-pot reactions have been developed for the synthesis of Au-ZnO hybrid nanocrystals with different interesting morphologies, including petal-like and urchin-like nanoflowers, nanomultipods and nanopyramids. In the synthesis strategy, oleylamine-containing solution serves as the reaction medium, and the in situ generated Au seeds play an important role in the subsequently induced growth of ZnO nanocrystals. With the aid of several surfactants, hybrid nanocrystals with different morphologies that have considerable influences on their optical and photocatalytic activities are readily achieved. Through high-resolution transmission electron microscopy measurements, an observed common orientation relationship between ZnO and Au is that ZnO nanocrystals prefer to grow with their polar {001} facets on the {111} facets of Au nanocrystals, and well-defined interfaces are evident. Surface plasmon resonance bands of Au with different positions are observed in the UV-vis spectra, and the UV and visible emissions of ZnO are found to be dramatically reduced. Finally, the as-prepared Au-ZnO nanocrystals exhibit excellent photocatalytic activity for the photodegradation of rhodamine B compared with pure ZnO nanocrystals. The Au-ZnO hybrid nanopyramids show the highest catalytic efficiency, which is correlated with the exposed crystal facets, crystallinity and the formation of hybrid nanostructures. The as-prepared Au-ZnO hybrid nanocrystals are expected to find diverse potential applications in the fields such as photocatalysis, solar energy conversion, sensing and biological detection. PMID:24270554

Chen, Yuanzhi; Zeng, Deqian; Zhang, Kun; Lu, Aolin; Wang, Laisen; Peng, Dong-Liang

2014-01-21

422

Chemistry of 1,1,2,2,9,9,10,10-octafluoro-[2,2]-paracyclophane: Its synthesis and reactions  

NASA Astrophysics Data System (ADS)

This dissertation describes the first example of the synthesis of 1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane (AF4) under non-high-dilution conditions. Under very mild reaction conditions, bis-p-(chlorodifluoromethyl)benzene (TFPX dichloride) and its derivatives reacted with Zn dust in N,N-dimethyl acetamide (DMA) (Zinc method) affording the corresponding AF4 and its derivatives in moderate to good yields. Purification of products was also studied and an efficient purification process was developed. A new and very cheap method for preparation of TFPX dichloride is also disclosed. Using the very cheap fluorinating reagent, anhydrous hydrogen fluoride (AHF), 1,4-bis(trichloromethyl)benezene or its derivatives were converted to TFPX and its derivatives in high yields (F/Cl exchange reaction). With the success of the Zinc method and F/Cl exchange reaction, highly pure AF4 thus can be provided to the semiconductor industry and academy research scientists in large quantity and at a very low price. Starting from AF4, numerous AF4 derivatives were synthesized using convenient reaction conditions. Reaction of AF4 with fuming nitric acid at room temperature gave mono-nitroAF4 in almost quantitative yield. Reduction of the mono-nitroAF4 with iron powder in the presence of HCl in alcoholic solvent gave the aminoAF4 in 90% yield. Via the diazonium salt intermediate, iodoAF4 was also obtained in good yield. Under similar reaction conditions, disubstituted AF4 derivatives were also prepared in good yields. Heating a mixture of AF4, trifluoroacetyl peroxide and dichloromethane gave the trifluoromethylated dimeric AF4 as a mixture of diastereomers. When these products were heated to 170--180°C in the presence of I 2, 4-trifluoromethyl-AF4 was obtained in almost 87% yield. X-ray structural analysis showed that the C-C bond connecting the two cyclophane moieties to be longer than the normal C-C bond. Kinetic studies, conducted in the presence of excess amount of hydrogen donor, showed this bond to be quite weak. Oxidation of AF4 with HIO3 in the presence of catalytic amount of H2SO4 in trifluoroacetic acid gave AF4 quinone in one step. AF4 quinone can be easily reduced to the hydroquinone by Na 2S2O4 aqueous solution.

Duan, Jian-Xin

423

Efficient one-step synthesis of pyrrolo[3,4-c]quinoline-1,3-dione derivatives by organocatalytic cascade reactions of isatins and ?-ketoamides.  

PubMed

We describe an efficient one-step synthesis of pyrrolo[3,4-c]quinolinedione derivatives using ethylenediamine diacetate (EDDA)-catalyzed cascade reactions of isatins and ?-ketoamides. It is the first direct conversion of isatins to pyrrolo[3,4-c]quinolinedione derivatives via C-N bond cleavage and isatin ring expansion. Furthermore, this reaction provides a one-step synthetic route for the production of biologically interesting complex molecules that are generally prepared using multi-step reactions. PMID:23824233

Xia, Likai; Lee, Yong Rok

2013-08-28

424

A chemical synthesis of 11-methoxy mitragynine pseudoindoxyl featuring the interrupted Ugi reaction  

PubMed Central

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

Kim, Jimin; Schneekloth, John S.

2013-01-01

425

Silver-promoted Friedel-Crafts reaction: concise total synthesis of (-)-ardeemin, (-)-acetylardeemin and (-)-formylardeemin.  

PubMed

Total syntheses of multidrug resistant inhibitors (-)-acetylardeemin 2a, (-)-ardeemin 2b, and (-)-formylardeemin 3 have been achieved within 10 steps starting from bromopyrroloinoline 13. The key step involves direct alkylation of 13 with prenyl tributylstannane 11 to yield 12 via a silver-promoted asymmetric Friedel-Crafts reaction. Highly efficient installation of the isoprenyl group allowed excellent overall yield. Moreover, the substrate scope of the asymmetric Friedel-Crafts reaction of 13 was expanded to include a variety of arenes 14 to afford natural product-like library analogues 15. PMID:22383065

Wang, Y; Kong, C; Du, Y; Song, H; Zhang, D; Qin, Y

2012-04-14

426

Highly selective synthesis of (E)-alkenyl-(pentafluorosulfanyl)benzenes through Horner-Wadsworth-Emmons reaction.  

PubMed

Diethyl 2-nitro-(pentafluorosulfanyl)benzylphosphonates, available by the vicarious nucleophilic substitution reaction of meta- and para-nitro-(pentafluorosulfanyl)benzenes and diethyl chloromethylphosphonate, undergo Horner-Wadsworth-Emmons reaction with aldehydes in the presence of potassium hydroxide in acetonitrile at ambient temperature to give (E)-2-nitro-1-alkenyl-(pentafluorosulfanyl)benzenes in good yields and high stereoselectivities. Follow-up transformations of the primary products provided (E)-1-alkenyl-(pentafluorosulfanyl)benzenes and 2-(2-arylethyl)-(pentafluorosulfanyl)anilines. PMID:23019446

Iakobson, George; Beier, Petr

2012-01-01

427

Highly selective synthesis of (E)-alkenyl-(pentafluorosulfanyl)benzenes through Horner–Wadsworth–Emmons reaction  

PubMed Central

Summary Diethyl 2-nitro-(pentafluorosulfanyl)benzylphosphonates, available by the vicarious nucleophilic substitution reaction of meta- and para-nitro-(pentafluorosulfanyl)benzenes and diethyl chloromethylphosphonate, undergo Horner–Wadsworth–Emmons reaction with aldehydes in the presence of potassium hydroxide in acetonitrile at ambient temperature to give (E)-2-nitro-1-alkenyl-(pentafluorosulfanyl)benzenes in good yields and high stereoselectivities. Follow-up transformations of the primary products provided (E)-1-alkenyl-(pentafluorosulfanyl)benzenes and 2-(2-arylethyl)-(pentafluorosulfanyl)anilines. PMID:23019446

Iakobson, George

2012-01-01

428

Synthesis of oligonucleotides carrying 5'-5' linkages using copper-catalyzed cycloaddition reactions.  

PubMed

There is considerable interest in coupling oligonucleotides to molecules and surfaces. Although amino- and thiol-containing oligonucleotides are being successfully used for this purpose, cycloaddition reactions may offer greater advantages due to their higher chemoselectivity and speed. In this study, copper-catalyzed 1,3-dipolar cycloaddition reactions between oligonucleotides carrying azido and alkyne groups are examined. For this purpose, several protocols for the preparation of oligonucleotides carrying these two groups are described. The non-templated chemical ligation of two oligonucleotides via copper-catalyzed [3+2] cycloaddition is described. By solid-phase methodology, oligonucleotides carrying 5'-5' linkages can be obtained in good yields. PMID:18081090

Alvira, Margarita; Eritja, Ramon

2007-12-01

429

Ammonia emissions from dairy production in Wisconsin1  

Microsoft Academic Search

Ammonia gas is the only significant basic gas that neutralizes atmospheric acid gases produced from com- bustion of fossil fuels. This reaction produces an aerosol that is a component of atmospheric haze, is implicated in nitrogen (N) deposition, and may be a potential hu- man health hazard. Because of the potential impact of NH3 emissions, environmentally and economically, the objective

L. A. Harper; T. K. Flesch; J. M. Powell; W. K. Coblentz; W. E. Jokela; N. P. Martin

2009-01-01

430

ROADSIDE AMMONIA MEASUREMENTS USING OPTICAL REMOTE SENSING INSTRUMENTS  

EPA Science Inventory

Fine particles less than 2.5 microns in diameter have been identified as a causal agent of excess mortality and other undesirable health impacts. A large part of these airborne particles, generally more than one-half, are formed in the atmosphere by reactions of ammonia with acid...

431

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...

432

Potential Roles of Ammonia in a Hydrogen Economy  

E-print Network

Potential Roles of Ammonia in a Hydrogen Economy A Study of Issues Related to the Use Ammonia..................................................................... 6 II. AMMONIA PROPERTIES......................................................... 6 III. AMMONIA PRODUCTION........................................................ 7 IV. AMMONIA DECOMPOSITION

433

Renal ammonia metabolism and transport.  

PubMed

Renal ammonia metabolism and transport mediates a central role in acid-base homeostasis. In contrast to most renal solutes, the majority of renal ammonia excretion derives from intrarenal production, not from glomerular filtration. Renal ammoniagenesis predominantly results from glutamine metabolism, which produces 2 NH4(+) and 2 HCO3(-) for each glutamine metabolized. The proximal tubule is the primary site for ammoniagenesis, but there is evidence for ammoniagenesis by most renal epithelial cells. Ammonia produced in the kidney is either excreted into the urine or returned to the systemic circulation through the renal veins. Ammonia excreted in the urine promotes acid excretion; ammonia returned to the systemic circulation is metabolized in the liver in a HCO3(-)-consuming process, resulting in no net benefit to acid-base homeostasis. Highly regulated ammonia transport by renal epithelial cells determines the proportion of ammonia excreted in the urine versus returned to the systemic circulation. The traditional paradigm of ammonia transport involving passive NH3 diffusion, protonation in the lumen and NH4(+) trapping due to an inability to cross plasma membranes is being replaced by the recognition of limited plasma membrane NH3 permeability in combination with the presence of specific NH3-transporting and NH4(+)-transporting proteins in specific renal epithelial cells. Ammonia production and transport are regulated by a variety of factors, including extracellular pH and K(+), and by several hormones, such as mineralocorticoids, glucocorticoids and angiotensin II. This coordinated process of regulated ammonia production and transport is critical for the effective maintenance of acid-base homeostasis. PMID:23720285

Weiner, I David; Verlander, Jill W

2013-01-01

434

Renal Ammonia Metabolism and Transport  

PubMed Central

Renal ammonia metabolism and transport mediates a central role in acid-base homeostasis. In contrast to most renal solutes, the majority of renal ammonia excretion derives from intrarenal production, not from glomerular filtration. Renal ammoniagenesis predominantly results from glutamine metabolism, which produces 2 NH4+ and 2 HCO3? for each glutamine metabolized. The proximal tubule is the primary site for ammoniagenesis, but there is evidence for ammoniagenesis by most renal epithelial cells. Ammonia produced in the kidney is either excreted into the urine or returned to the systemic circulation through the renal veins. Ammonia excreted in the urine promotes acid excretion; ammonia returned to the systemic circulation is metabolized in the liver in a HCO3?-consuming process, resulting in no net benefit to acid-base homeostasis. Highly regulated ammonia transport by renal epithelial cells determines the proportion of ammonia excreted in the urine versus returned to the systemic circulation. The traditional paradigm of ammonia transport involving passive NH3 diffusion, protonation in the lumen and NH4+ trapping due to an inability to cross plasma membranes is being replaced by the recognition of limited plasma membrane NH3 permeability in combination with the presence of specific NH3-transporting and NH4+-transporting proteins in specific renal epithelial cells. Ammonia production and transport are regulated by a variety of factors, including extracellular pH and K+, and by several hormones, such as mineralocorticoids, glucocorticoids and angiotensin II. This coordinated process of regulated ammonia production and transport is critical for the effective maintenance of acid-base homeostasis. PMID:23720285

Weiner, I. David; Verlander, Jill W.

2015-01-01

435

A Francisella Virulence Factor Catalyzes an Essential Reaction of Biotin Synthesis  

PubMed Central

Summary We recently identified a gene (FTN_0818) required for Francisella virulence that seemed likely involved in biotin metabolism. However, the molecular function of this virulence determinant was unclear. Here we show that this protein named BioJ is the enzyme of the biotin biosynthesis pathway that determines the chain length of the biotin valeryl side chain. Expression of bioJ allows growth of an E. coli bioH strain on biotin-free medium, indicating functional equivalence of BioJ to the paradigm pimeloyl-ACP methyl ester carboxyl-esterase, BioH. BioJ was purified to homogeneity, shown to be monomeric and capable of hydrolysis of its physiological substrate methyl pimeloyl-ACP to pimeloyl-ACP, the precursor required to begin formation of the fused heterocyclic rings of biotin. Phylogenetic analyses confirmed that distinct from BioH, BioJ represents a novel sub-clade of the ?/?-hydrolase family. Structure-guided mapping combined with site-directed mutagenesis revealed that the BioJ catalytic triad consists of Ser151, Asp248 and His278, all of which are essential for activity and virulence. The biotin synthesis pathway was reconstituted in vitro and the physiological role of BioJ directly assayed. To the best of our knowledge, these data represent further evidence linking biotin synthesis to bacterial virulence. PMID:24313380

Feng, Youjun; Napier, Brooke A.; Manandhar, Miglena; Henke, Sarah K; Weiss, David S.; Cronan, John E.

2014-01-01

436

Synthesis of neplanocin A and its 3'-epimer via an intramolecular Baylis-Hillman reaction.  

PubMed

The key cyclopentenyl intermediate 11b was synthesized in 4 steps from d-ribose in 41% overall yield via an efficient intramolecular Baylis-Hillman reaction. This novel key intermediate can be modified easily and transformed to neplanocin A (1a) and its 3'-epimer (1b). PMID:25122518

Tan, Yun Xuan; Santhanakrishnan, Sridhar; Yang, Hai Yan; Chai, Christina L L; Tam, Eric Kwok Wai

2014-09-01

437

The Petasis Reaction: Microscale Synthesis of a Tertiary Amine Antifungal Analog  

ERIC Educational Resources Information Center

Students prepare a tertiary amine antifungal analog in an upper-level undergraduate organic laboratory. A microscale Petasis reaction is performed to generate a liquid compound readily characterized via IR and proton NMR spectroscopy. The biological relevance of the product is highlighted, with the tertiary amine scaffold being an important…

Koroluk, Katherine J.; Jackson, Derek A.; Dicks, Andrew P.

2012-01-01

438

Polypyrrole-supported graphite felt for Heck reaction in solid phase synthesis  

Microsoft Academic Search

Substrate immobilization on graphite felt for solid phase Heck reaction was achieved by electrochemical polymerization of the substrate precursor containing a pyrrole side chain, where the amount of substrate on the electrode surface was easily controlled by the number of repeated cyclic voltammetric scanning. Couplings between olefins and the 4-iodobenzoic acid-modified graphite felt electrode or aromatic halides and the 4-vinylbenzoic

Yoshitomo Kashiwagi; Shinya Chiba; Hiroshi Ikezoe; Futoshi Kurashima; Tetsuya Ono

2007-01-01

439

Direct Diazo-Transfer Reaction on ?-lactam: Synthesis and Preliminary Biological Activities of 6-Triazolylpenicillanic Acids  

PubMed Central

In this study we report the first example of a direct diazo-transfer reaction on readily available 6-aminopenicillanates to give 6-azidopenicillanates in high yield. Subsequent Cu(I)-catalyzed Huisgen cycloaddition between these 6-azidopenicillanates and assorted terminal alkynes facilely furnished 6-triazolylpenicillanic acids was. Preliminary biological screening indicates that these triazolylpenicillanic acids possess low to moderate antibacterial activities. PMID:17855098

Chen, Po C.; Emrich, Rebekah E.; Patel, Pratiq A.

2009-01-01

440

Synthesis of new heterocycles through a cation-driven tandem ring-enlargement-annulation reaction.  

PubMed

[reaction: see text] The thionium ion, generated through a cyclopropylcarbinyl-cyclobutyl ring expansion, is, for the first time, intramolecularly intercepted by activated aromatic rings to generate new versatile 2a-methyl-8b-(phenylsulfanyl-1,2a,3,8b-tetrahydro-2H-cyclobuta[c]chromenes. PMID:12123377

Bernard, Angela M; Cadoni, Enzo; Frongia, Angelo; Piras, Pier P; Secci, Francesco

2002-07-25

441

Convenient synthesis of alkyl amines via the reaction of organoboranes with ammonium hydroxide  

SciTech Connect

A process for the preparation of alkyl amines in which the reagents are generated in situ under mild and convenient reaction conditions is described. An organoborane is prepared via hydroboration, aqueous ammonium hydroxide is added, and then aqueous sodium hypochlorite is added to the mixture. Two of the alkyl groups in the trialkylborane are converted to the corresponding amines in good yield. (BLM)

Kabalka, G.W.; Sastry, K.A.R.; McCollum, G.W.; Yoshioka, H.

1981-10-09

442

Microwave-Assisted Organic Synthesis Using Benign Reaction Medium and Reagents  

EPA Science Inventory

Account of chemical reactions expedited by microwave (MW) exposure of neat reactants for the rapid one-pot assembly of heterocyclic compounds from in situ generated reactive intermediates via enamines or using hypervalent iodine reagents will be described that can be adapted for ...

443

Synthesis of gallium nitride nanorods through a carbon nanotube-confined reaction  

Microsoft Academic Search

Gallium nitride nanorods were prepared through a carbon nanotube-confined reaction. GaâO vapor was reacted with NHâ gas in the presence of carbon nanotubes to form wurtzite gallium nitride nanorods. The nanorods have a diameter of 4 to 50 nanometers and a length of up to 25 micrometers. It is proposed that the carbon nanotube acts as a template to confine

Weiqiang Han; Shoushan Fan; Qunqing Li; Yongdan Hu

1997-01-01

444

Synthesis, reactions, and electronic properties of 16 pi-electron octaisobutyltetraphenylporphyrin.  

PubMed

The reaction of the doubly oxidized beta-octaisobutyl-meso-tetraphenylporphyrin (OiBTPP, 4), which has a 16 pi-electronic structure at the porphyrin core, with a variety of metal reagents was investigated. The reaction of 4 with SnCl(2) followed by ethanolysis afforded an 18 pi-electron tin complex, (OiBTPP)Sn(OEt)(2) (5), in a redox manner. No reactions were observed using zerovalent metals (Zn, Cu, and Pd). However, the reaction of 16pi [(OiBTPP)Li](+)[BF(4)](-) (6), which was easily derived from 4, with Zn, Cu, and Pd(2)(dba)(3) gave the corresponding 18pi metalloporphyrins (OiBTPP)M (7, M = Zn(EtOH); 8, M = Cu; and 9, M = Pd). One-electron oxidation of the copper complex 8 by AgSbF(6) afforded a 17 pi-electron cation radical complex, [(OiBTPP)Cu](*+)[SbF(6)](-) (10). The UV-visible and electron spin resonance spectra of 10 were quite similar to those of previously reported beta-octaethyl-meso-tetraphenylporphyrin (OETPP) derivatives, [(OETPP)Cu](*+)X(-) (X = ClO(4), I). In contrast to the reaction of 6 with Zn to give the 18pi complex 7, the reaction of 4 with divalent ZnCl(2) enabled us to isolate a new 16pi porphyrin-zinc(II) complex, [(OiBTPP)Zn(Cl)](+)[ZnCl(3)](-) (11), in 92% yield. The solid-state structures of 5 and 7-11 were unambiguously determined by single-crystal X-ray crystallography. The porphyrin cores of 10 (17pi) and 11 (16pi) are much more distorted than those of the 18pi derivatives 5 and 7-9. Furthermore, the bond distances of 10 and 11 clearly showed the presence of bond alternation in contrast to aromatic 18pi species 8 and 7, respectively. Nucleus-independent chemical shift calculations of 4 and some metalated porphyrins indicated that the highly distorted 16pi porphyrins are essentially nonaromatic, with only weak antiaromaticity. Magnetic circular dichroism studies in conjunction with ZINDO/S calculations assisted in identifying the electronic transitions of the UV-vis spectra of key porphyrins. Electrochemical and thin-layer UV-vis spectroelectrochemical experiments on 4 (16pi) and 11 (16pi) indicated that both compounds can be electroreduced to give the 18pi species, with the 16pi/18pi transition being reversible in the case of [(OiBTPP)Zn(Cl)](+)[ZnCl(3)](-) (11). PMID:20731346

Yamamoto, Yohsuke; Hirata, Yusuke; Kodama, Megumi; Yamaguchi, Torahiko; Matsukawa, Shiro; Akiba, Kin-ya; Hashizume, Daisuke; Iwasaki, Fujiko; Muranaka, Atsuya; Uchiyama, Masanobu; Chen, Ping; Kadish, Karl M; Kobayashi, Nagao

2010-09-15

445

Synthesis of Metal Oxide Particles Using Reaction Route from Rare-Earth Metal-EDTA Complexes  

NASA Astrophysics Data System (ADS)

Highly dense, spherical yttria (Y2O3) and erbia (Er2O3) particles were synthesized from their corresponding metal-ethylenediaminetetraacetic (EDTA) complexes. The EDTA·Y·H and EDTA·Er·H complexes were prepared in powdered form. These complexes were used as the staring materials for synthesis of the Y2O3 and Er2O3 particles. The particles were synthesized using an H2-O2 flame produced with a commercial flame spray apparatus. Crystalline structure, surface and cross-sectional morphologies, and elemental distribution of the synthesized particles were investigated. It was confirmed that the crystalline phases of the Y2O3 and Er2O3 particles were homogeneous. In addition, the elemental distribution of the particles was uniform. These results indicate that dense, spherical particles of Y2O3 and Er2O3 have been synthesized with EDTA·Y·H and EDTA·Er·H complexes, respectively.

Komatsu, Keiji; Tsuchiya, Takaaki; Hasebe, Yasuhiro; Sekiya, Tetsuo; Toyama, Ayumu; Nakamura, Atsushi; Akasaka, Hiroki; Saitoh, Hidetoshi

2014-06-01

446

Aminoacyl-nucleotide reactions - Studies related to the origin of the genetic code and protein synthesis  

NASA Technical Reports Server (NTRS)

In the present paper, a report is presented on the effect of pH and carbonate on the hydrolysis rate constants of N-blocked and free aminoacyl adenylate anhydrides. Whereas the hydrolysis of free aminoacyl adenylates seems principally catalyzed by OH(-), the hydrolysis of the N-blocked species is also catalyzed by H(+), giving this compound a U-shaped hydrolysis vs. pH curve. Furthermore, at pH's less than 8, carbonate has an extreme catalytic effect on the hydrolysis of free aminoacyl-AMP anhydride, but essentially no effect on the hydrolysis of N-blocked aminoacyl-AMP anhydride. Furthermore, the N-blocked aminoacyl-AMP anhydride is a very efficient generator of peptides using free glycine as acceptor. The possible significance of the observations to prebiological peptide synthesis is discussed.

Mullins, D. W., Jr.; Senaratne, N.; Lacey, J. C., Jr.

1984-01-01

447

Fischer-Tropsch Synthesis: Characterization and Reaction Testing of Cobalt Carbide  

SciTech Connect

Hydrogenation of carbon monoxide was investigated for cobalt carbide synthesized from Co{sub 3}O{sub 4} by CO carburization in a fixed-bed reactor. The cobalt carbide synthesized was characterized by BET surface area, X-ray diffraction, scanning electron microscopy, X-ray absorption near edge spectroscopy, and extended X-ray absorption fine structure spectroscopy. The catalysts were tested in the slurry phase using a continuously stirred tank reactor at P = 2.0 MPa, H{sub 2}/CO = 2:1 in the temperature range of 493-523 K, and with space velocities varying from 1 to 3 Nl h{sup -1} g{sub cat}{sup -1}. The results strongly suggest that a fraction of cobalt converts to a form with greater metallic character under the conditions employed. This was more pronounced on a Fischer-Tropsch synthesis run conducted at a higher temperature (523 versus 493 K).

Khalid S.; Mohandas J.C.; Gnanamani M.K.; Jacobs G.; Ma W.; Ji Y.; Davis B.H.

2011-08-15

448

Synthesis of Highly Substituted ?-Butyrolactones by a Gold-Catalyzed Cascade Reaction of Benzyl Esters.  

PubMed

Easily accessible benzylic esters of 3-butynoic acids in a gold-catalyzed cyclization/rearrangement cascade reaction provided 3-propargyl ?-butyrolactones with the alkene and the carbonyl group not being conjugated. Crossover experiments showed that the formation of the new C?C bond is an intermolecular process. Initially propargylic-benzylic esters were used, but alkyl-substituted benzylic esters worked equally well. In the case of the propargylic-benzylic products, a simple treatment of the products with aluminum oxide initiated a twofold tautomerization to the allenyl-substituted ?-butyrolactones with conjugation of the carbonyl group, the olefin, and the allene. The synthetic sequence can be conducted stepwise or as a one-pot cascade reaction with similar yields. Even in the presence of the gold catalyst the new allene remains intact. PMID:25352382

Blanco Jaimes, Maria Camila; Ahrens, Alexander; Pflästerer, Daniel; Rudolph, Matthias; Hashmi, A Stephen K

2015-01-01

449

Transition metal promoted reactions of boron hydrides. 13. Platinum catalyzed synthesis of 6,9-dialkyldecaboranes  

SciTech Connect

Both chloroplatinic acid and platinum bromide have been found to catalyze the reactions of decaborane(14) with terminal olefins, including ethylene, propylene, 1-butene, and 1-pentene, to give the corresponding 6,9-R[sub 2]B[sub 10]H[sub 12] derivatives in high yields. Chemical studies of 6,9-(n-C[sub 5]H[sub 11])[sub 2]B[sub 10]H[sub 12] (1) show that, in contrast to decaborane(14), 1 does not react to form dibase adducts with the Lewis bases Et[sub 3]N, Ph[sub 3]P, Et[sub 2]S, or MeCN. However, 1 undergoes many other reactions, including deprotonation to 6,9-(n-C[sub 5]H[sub 11])[sub 2]B[sub 10]H[sub 11][sup [minus

Mazighi, K.; Carroll, P.J.; Sneddon, L.G. (Univ. of Pennsylvania, Philadelphia (United States))

1993-05-12

450

Leuconostoc mesenteroides glucansucrase synthesis of flavonoid glucosides by acceptor reactions in aqueous-organic solvents.  

PubMed

The enzymatic glucosylation of luteolin was attempted using two glucansucrases: the dextransucrase from Leuconostoc mesenteroides NRRL B-512F and the alternansucrase from L. mesenteroides NRRL B-23192. Reactions were carried out in aqueous-organic solvents to improve luteolin solubility. A molar conversion of 44% was achieved after 24h of reaction catalysed by dextransucrase from L. mesenteroides NRRL B-512F in a mixture of acetate buffer (70%)/bis(2-methoxyethyl) ether (30%). Two products were characterised by nuclear magnetic resonance (NMR) spectroscopy: luteolin-3'-O-alpha-d-glucopyranoside and luteolin-4'-O-alpha-d-glucopyranoside. In the presence of alternansucrase from L. mesenteroides NRRL B-23192, three additional products were obtained with a luteolin conversion of 8%. Both enzymes were also able to glucosylate quercetin and myricetin with conversion of 4% and 49%, respectively. PMID:16530175

Bertrand, Anne; Morel, Sandrine; Lefoulon, François; Rolland, Yves; Monsan, Pierre; Remaud-Simeon, Magali

2006-05-22

451

Transition metal dichalcogenide materials: Solid-state reaction synthesis of nanocrystalline nickel disulfide  

Microsoft Academic Search

One novel and convenient synthetic approach has been proposed to prepare the transition metal dichalcogenide material of nanocrystalline nickel disulfide (NiS2) by the solid-state reaction between basic nickel carbonate and elemental sulfur at 400 °C. The as-synthesized product is characterized by X-ray powder Diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and Low-temperature N2 Adsorption (BET method). TEM micrographs

Gaojun An; Liu Chenguang; Yuandong Hou; Xiaoling Zhang; Yunqi Liu

2008-01-01

452

Catalytic enantioselective synthesis of atropisomeric biaryls: a cation-directed nucleophilic aromatic substitution reaction.  

PubMed

A catalytic enantioselective nucleophilic aromatic substitution reaction which yields axially chiral biaryl derivatives in excellent yields with e.r.?values of up to 97:3 has been developed. This process uses a chiral counterion to direct the addition of thiophenolate to a prochiral dichloropyrimidine by a tandem desymmetrization/kinetic resolution mechanism. The products can be derivatized to a range of atropisomeric structures without any reduction in enantioenrichment, thus offering access to unexplored chiral biaryl architectures. PMID:25257677

Armstrong, Roly J; Smith, Martin D

2014-11-17

453

Carbohydrate-2-deoxy-2-phosphonates: simple synthesis and Horner-Emmons reaction.  

PubMed

Phosphorus meets carbohydrates: Dimethyl phosphite reacts with ceric(IV) ammonium nitrate (CAN) to give phosphonyl radicals that add to glycals 1. The derivatives 2 were isolated in high yields and during a subsequent Horner-Emmons reaction underwent an interesting elimination to give 3,6-dihydro-2H-pyrans 3. The short sequence with simple precursors is applicable to the transformation of hexoses, pentoses, and disaccharides. Bn = benzyl. PMID:19170148

Elamparuthi, Elangovan; Linker, Torsten

2009-01-01

454

REACTION SYNTHESIS\\/DYNAMIC COMPACTION OF TITANIUM CARBIDE AND TITANIUM DIBORIDE  

Microsoft Academic Search

Titanium carbide and titanium diboride were synthesized by self-propagating combustion reactions and densified by a high-speed forging technique, in which a hammer strikes the hot and porous ceramic (T - 2O0O0C) at velocities in the range 5 - 15 m\\/s. Compacts with densities higher than 96% of the theoretical density and diameters close to 10 cm were produced by this

M. A. MEYERS; J. C. LA SALVIA; L. W. MEYER; D. HOKE; A. NIILER

1991-01-01

455

Facile Synthesis of 5-Arylidene Thiohydantoin by Sequential Sulfonylation/Desulfination Reaction  

PubMed Central

The sequential sulfonylation/desulfination reactions of 5-benzylthiohydantoin with excess arylsulfonyl chlorides in the presence of triethylamine have been developed to afford a wide range of 5-arylidene thiohydantoin derivatives in moderate to excellent yields. A plausible sulfonylation/desulfination mechanism was proposed. The bioassay showed that these compounds exhibit certain fungicidal activities with the 71.9% inhibition rate of 2K against B. cinerea, and 57.6% inhibition rate of 2m against A. solani, respectively. PMID:23765221

Han, Jintao; Dong, Hongbo; Xu, Zhihong; Lei, Jianping; Wang, Mingan

2013-01-01

456

Functional ionic liquid from biorenewable materials: synthesis and application as a catalyst in direct aldol reactions  

Microsoft Academic Search

A new room temperature ionic liquid (IL) (2-hydroxyethyl)-trimethyl-ammonium (S)-2-pyrrolidinecarboxylic acid salt ([Choline][Pro]) has been synthesized from biorenewable and nontoxic raw materials (choline chloride and l(?)-proline) in a simple and relative green route. The IL has been demonstrated to be the efficient catalyst of the direct aldol reactions between ketones and aromatic aldehydes in water at room temperature. The aldol products

Suqin Hu; Tao Jiang; Zhaofu Zhang; Anlian Zhu; Buxing Han; Jinliang Song; Ye Xie; Wenjing Li

2007-01-01

457

Autophagy and ammonia  

PubMed Central

Autophagy plays an important role in the cellular response to a variety of metabolic stress conditions thus contributing to the maintenance of intracellular homeostasis. Studies in yeast have defined the genetic components involved in the initiation of autophagy as well as the progression through the autophagic cascade. The yeast kinase Atg1 initiates autophagy in response to nutrient limitation in a TOR-dependent manner. The ulk family of genes encodes the mammalian ortholog of yeast Atg1. Our recent work using mouse embryonic fibroblast (MEF) cell lines deficient for both ulk1 and ulk2 has revealed that autophagy induction is more complex in mammals than in yeast. Furthermore, these data confirm the surprising finding that a by-product of amino acid metabolism, ammonia, is a strong inducer of autophagy, as first shown by the Abraham laboratory. PMID:22170154

Cheong, Heesun; Lindsten, Tullia

2012-01-01

458

Ammonia Ice Clouds on Jupiter  

NASA Technical Reports Server (NTRS)

The top cloud layer on Jupiter is thought to consist of ammonia ice, but most of that ammonia 'hides' from spectrometers. It does not absorb light in the same way ammonia does. To many scientists, this implies that ammonia churned up from lower layers of the atmosphere 'ages' in some way after it condenses, possibly by being covered with a photochemically generated hydrocarbon mixture. The New Horizons Linear Etalon Imaging Spectral Array (LEISA), the half of the Ralph instrument that is able to 'see' in infrared wavelengths that are absorbed by ammonia ice, spotted these clouds and watched them evolve over five Jupiter days (about 40 Earth hours). In these images, spectroscopically identified fresh ammonia clouds are shown in bright blue. The largest cloud appeared as a localized source on day 1, intensified and broadened on day 2, became more diffuse on days 3 and 4, and disappeared on day 5. The diffusion seemed to follow the movement of a dark spot along the boundary of the oval region. Because the source of this ammonia lies deeper than the cloud, images like these can tell scientists much about the dynamics and heat conduction in Jupiter's lower atmosphere.

2007-01-01

459

Anhydrous Ammonia Frost on Titan  

NASA Astrophysics Data System (ADS)

Ammonia has been suggested as a probable source for sustaining Titan's thick nitrogen-dominated atmosphere. Ammonia is believed to be important to maintaining nitrogen in Titan's atmosphere. Ammonia is seen in clouds in the atmospheres of Jupiter and Saturn, but has yet to be detected on any of the satellites. This may be because all forms of NH3 are unstable in the ambient conditions of the satellites surfaces or that its spectral features are altered by other components of the surface, and have not been identified. It has recently been demonstrated[1] that brightening occurs in Titan’s atmosphere that is transient on the time-scale of months. The spectral shape of the brightening is more consistent with that of the transient apparition of a pure ammonia frost than of an ammonia monohydrate or ammonia dihydrate frost. However, the phase behavior of the ammonia water system has peritectics at compositions of 1:1 and 1:2. These hydrate forms would be expected to dominate if the frost, or the reservoir from which the frost was derived had any water present. Physical mechanisms for producing measurable quanitities of anhydrous ammonia can include chemical dehydration or dehydration of the vapor phase - but it is challenging to store significant quantities of the anhydrous material because of the phase behavior in the solid state. [1] Nelson, R.M., et al. Saturn’s Titan: Surface Change, Ammonia, and Implications for Atmospheric and Tectonic Activity., Icarus, 199, pp. 429-441, 2009 This work was performed at JPL under contract to NASA

Smythe, W. D.; Nelson, R.; Boryta, M. D.

2009-12-01

460

Low temperature synthesis of LnOF rare-earth oxyfluorides through reaction of the oxides with PTFE  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Low temperature synthesis of LnOF rare-earth oxyfluorides from Ln{sub 2}O{sub 3} and PTFE (CF{sub 2}). Black-Right-Pointing-Pointer Rhombohedral LnOF is the major phase and forms as nanocrystals, 29-103 nm. Black-Right-Pointing-Pointer Expected lanthanide contraction observed in lattice parameters and bond lengths. Black-Right-Pointing-Pointer TbOF orders antiferromagnetically at 10 K and has a metamagnetic transition at 1.8 T. Black-Right-Pointing-Pointer GdOF orders antiferromagnetically at 5 K, other LnOF are paramagnetic. -- Abstract: A low temperature solid-state synthesis route, employing polytetrafluoroethylene (PTFE) and the rare-earth oxides, for the formation of the LnOF rare-earth oxyfluorides (Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), is reported. With the exception of LaOF, which forms in a tetragonal variant, rhomobohedral LnOF is found to be the major product of the reaction. In the case of PrOF, a transition from the rhombohedral to the cubic fluorite phase is observed on heating in air to 500 Degree-Sign C. X-ray diffraction shows the expected lanthanide contraction in the lattice parameters and bond lengths. Magnetic susceptibility measurements show antiferromagnetic-like ordering in TbOF, T{sub m} = 10 K, with a metamagnetic transition at a field {mu}{sub 0}H{sub t} = 1.8 T at 2 K. An antiferromagnetic transition, T{sub N} = 4 K, is observed in GdOF. Paramagnetic behavior is observed above 2 K in PrOF, NdOF, DyOF, HoOF and ErOF. The magnetic susceptibility of EuOF is characteristic of Van Vleck paramagnetism.

Dutton, S.E., E-mail: sdutton@princeton.edu [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States); Hirai, D.; Cava, R.J. [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States)] [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States)

2012-03-15

461

Synthesis of terephthalic acid via Diels-Alder reactions with ethylene and oxidized variants of 5-hydroxymethylfurfural.  

PubMed

Terephthalic acid (PTA), a monomer in the synthesis of polyethylene terephthalate (PET), is obtained by the oxidation of petroleum-derived p-xylene. There is significant interest in the synthesis of renewable, biomass-derived PTA. Here, routes to PTA starting from oxidized products of 5-hydroxymethylfurfural (HMF) that can be produced from biomass are reported. These routes involve Diels-Alder reactions with ethylene and avoid the hydrogenation of HMF to 2,5-dimethylfuran. Oxidized derivatives of HMF are reacted with ethylene over solid Lewis acid catalysts that do not contain strong Brønsted acids to synthesize intermediates of PTA and its equally important diester, dimethyl terephthalate (DMT). The partially oxidized HMF, 5-(hydroxymethyl)furoic acid (HMFA), is reacted with high pressure ethylene over a pure-silica molecular sieve containing framework tin (Sn-Beta) to produce the Diels-Alder dehydration product, 4-(hydroxymethyl)benzoic acid (HMBA), with 31% selectivity at 61% HMFA conversion after 6 h at 190 °C. If HMFA is protected with methanol to form methyl 5-(methoxymethyl)furan-2-carboxylate (MMFC), MMFC can react with ethylene in the presence of Sn-Beta for 2 h to produce methyl 4-(methoxymethyl)benzenecarboxylate (MMBC) with 46% selectivity at 28% MMFC conversion or in the presence of a pure-silica molecular sieve containing framework zirconium (Zr-Beta) for 6 h to produce MMBC with 81% selectivity at 26% MMFC conversion. HMBA and MMBC can then be oxidized to produce PTA and DMT, respectively. When Lewis acid containing mesoporous silica (MCM-41) and amorphous silica, or Brønsted acid containing zeolites (Al-Beta), are used as catalysts, a significant decrease in selectivity/yield of the Diels-Alder dehydration product is observed. PMID:24912153

Pacheco, Joshua J; Davis, Mark E

2014-06-10