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Sample records for epoxidized novolac resin

  1. Nanosized barium hexaferrite in novolac phenolic resin as microwave absorber for X-band application

    NASA Astrophysics Data System (ADS)

    Ozah, S.; Bhattacharyya, N. S.

    2013-09-01

    Nanosized barium ferrite (BaFe12O19) with Novolac phenolic resin (NPR) is developed as a magnetic absorber for application in the frequency range 8.2-12.4 GHz. The absorption is studied by modifying the microstructural properties of the ferrite inclusion with annealing temperature and its content in the composite. Transmission electron microscopy and X-ray diffraction pattern confirms the formation of hexagonal structure of barium ferrite. The crystallite size of the barium ferrite particles is in nano-range and increases with annealing temperature. The BaFe12O19/NPR composite is prepared with different weight percentage of ferrite inclusions. The complex permittivity and complex permeability is measured at X-band and found to increase with annealing temperature and contents of ferrite inclusion. Theoretical study of reflection loss gives that 2 mm absorber samples are showing the best results for X-band application. Reflection loss measurement of the samples shows absorption peak of -24.61 dB at 10.26 GHz for 30 wt%, -28.39 dB at 9.98 GHz for 40 wt% and -37.06 dB at 9.5 GHz for 50 wt% of BaFe12O19 in NPR matrix.

  2. Expanded graphite/Novolac phenolic resin composite as single layer electromagnetic wave absorber for x-band applications

    NASA Astrophysics Data System (ADS)

    Gogoi, Jyoti P.; Bhattacharyya, Nidhi Saxena

    2013-01-01

    Expanded graphite/novolac phenolic resin (EG/NPR) composites are developed as dielectric absorbers with 4mm thickness and its microwave absorption ability studied in the frequency range 8.4 to 12.4 GHz. A high reflection loss ~ -43 dB is observed at 12.4 GHz for 5 wt. % EG/NPR composites. With the increase in EG concentration in the composite the reflection loss decreases and the absorption peak shifts towards lower frequency. 7 wt. %, 8 wt. % and 10 wt. % composites shows a 10dB absorption bandwidth of order of 1GHz. Light weight EG/NPR composite shows potential to be used as cost-effective broadband microwave absorber over the X-band.

  3. Production of carbonaceous adsorbents from agricultural by-products and novolac resin under a continuous countercurrent flow type pyrolysis operation.

    PubMed

    Ioannou, Z; Simitzis, J

    2013-02-01

    Carbonaceous adsorbents based on novolac resin (N) and olive stone biomass (B) in a proportion of 20/80 and 40/60 w./w. N/O were produced. The specimens were cured (c) and pyrolyzed/carbonized (C) up to 1000 °C under a continuous countercurrent flow type pyrolysis operation (N20B-cC, N40B-cC). Commercial activated carbon (AC) was used for comparison reasons. Methylene blue adsorption from its aqueous solutions onto the adsorbents and kinetic analysis were investigated. The specific surface area of adsorbents and the gross calorific values (GCV) of cured materials were determined. The results show that N40B-cC presents lower weight loss and shrinkage but higher methylene blue adsorption than N20B-cC. Pseudo-second order mechanism describes better methylene blue adsorption onto all adsorbents. The specific surface area of carbonaceous and the gross calorific values of cured materials follow the order: AC>N20B-cC>N40B-cC and N100-c>N40B-c>N20B-c>B respectively. Olive stone biomass may constitute a suitable precursor for the production of carbonaceous materials.

  4. Epoxidized natural rubber toughened aqueous resole type liquefied EFB resin: Physical and chemical characterization

    NASA Astrophysics Data System (ADS)

    Amran, Umar Adli; Zakaria, Sarani; Chia, Chin Hua

    2013-11-01

    A preliminary study on the reaction between aqueous resole type resinified liquefied palm oil empty fruit bunches fibres (RLEFB) with epoxidized natural rubber (ENR). Liquefaction of empty fruit bunches (EFB) is carried out at different ratio of phenol to EFB (P:EFB). Resole type phenolic resin is prepared using sodium hydroxide (NaOH) as the catalyst with the ratio of liquefied EFB (LEFB) to formaldehyde (LEFB:F) of 1:1.8. 50% epoxidation of epoxidized natural rubber (ENR-50) is used to react with resole resin by mixing with ENR with aqueous resole resin. The cured resin is characterized with FT-IR and SEM. Aqueous system have been found to be unsuitable medium in the reaction between resin and ENR. This system produced a highly porous product when RLEFB/ENR resin is cured.

  5. Pilot scale production, characterization, and optimization of epoxidized vegetable oil-based resins

    NASA Astrophysics Data System (ADS)

    Monono, Ewumbua Menyoli

    Novel epoxidized sucrose soyate (ESS) resins perform much better than other vegetable oil-based resins; thus, they are of current interest for commercial scale production and for a wide range of applications in coatings and polymeric materials. However, no work has been published that successfully scaled-up the reaction above a 1 kg batch size. To achieve this goal, canola oil was first epoxidized at a 300 g scale to study the epoxidation rate and thermal profile at different hydrogen peroxide (H2O2) addition rates, bath temperatures, and reaction times. At least 83% conversion of double bonds to oxirane was achieved by 2.5 h, and the reaction temperature was 8-15 °C higher than the water bath temperature within the first 30-40 min of epoxidation. A 38 L stainless steel kettle was modified as a reactor to produce 10 kg of ESS. Twenty 7-10 kg batches of ESS were produced with an overall 87.5% resin yield and > 98% conversion after batch three. The conversion and resin quality were consistent across the batches due to the modifications on the reaction that improved mixing and reaction temperature control within 55-65 oC. The total production time was reduced from 8 to 4 days due to the fabrication of a 40 L separatory funnel for both washing and filtration. A math model was developed to optimize the epoxidation process. This was done by using the Box-Behnken design to model the conversion at various acetic acid, H2O2, and Amberlite ratios and at various reaction temperatures and times. The model had an adjusted R2 of 97.6% and predicted R2 of 96.8%. The model showed that reagent amounts and time can be reduced by 18% without compromising the desired conversion value and quality.

  6. ELEVATED TEMPERATURE RESISTANT MODIFIED EPOXIDE RESIN ADHESIVES FOR METALS

    DTIC Science & Technology

    composed of Epon 1001 resin, Plyophen 5023, and dicyandiamide as the curing agent. Al dust was used as the reinforcing filler. The adhesive was cured at...to the development of the following formula (parts by weight): 33 Epon 1001 + 67 Polyophen 5023 + 100 Al dust + 6 dicyandiamide . Higher Epon 1001...or curing without dicyandiamide reduced adhesive shear strength, especially at room temperature.

  7. Novel bio-based thermoset resins based on epoxidized vegetable oils for structural adhesives

    NASA Astrophysics Data System (ADS)

    Sivasubramanian, Shivshankar

    Conventional engineered wood composites are bonded for the most part through formaldehyde-based structural adhesives such as urea formaldehyde (UF), melamine formaldehyde (MF), phenol formaldehyde (PF) and resorcinol formaldehyde (RF). Formaldehyde is a known human carcinogen; the occupational exposure and emission after manufacturing of these binders is raising more and more concern. With increasing emphasis on environmental issues, there is clear incentive to replace these hazardous conventional formaldehyde-based binders with cco-friendly resins having similar properties but derived from renewable sources, bearing in mind the economics of the structural wood composite industry. In this thesis, the curing reaction of bio-derived epoxy thermosets with inexpensive, low-toxicity precursors, including polyimines and amino acids was investigated. Epoxidized linseed oil (ELO) and epoxidized soybean oil (ESO) were successfully crosslinked with both branched polyethyleneimine (PEI) and triethylenetetramine (fETA). Epoxidized castor oil (ECO) was crosslinked with polyethyleneimine (PEI), having different molecular weights. Curing conditions were optimized through solvent uptake and soluble fraction analysis. Finally, the mechanical properties of the optimized compositions of rigid bioepoxies were evaluated using dynamic mechanical rheological testing (DMRT). While not as stiff as conventional materials, optimized materials have sufficient room temperature moduli to show promise for coatings and as binders in engineered wood products.

  8. Effect of annealing temperature of nano-sized BaFe12O19 in Novolac phenolic resin on microwave properties for use as EMI shielding material in X-band

    NASA Astrophysics Data System (ADS)

    Ozah, S.; Bhattacharyya, N. S.

    2013-01-01

    Nanosized barium ferrite (BaFe12O19) powders are synthesized using co-precipitation technique at three different annealing temperatures. The X-Ray Diffraction pattern indicates the presence of hexagonal structure for all the three samples. Transmission electron microscopy (TEM) shows the particles are hexagonal in shape. The synthesized BaFe12O19 powder samples are mechanically mixed with Novolac phenolic resin (NPR) with filler to polymer weight ratio of 30:60 to prepare pellets of BaFe12O19/NPR composites of dimensions, 10.38 mm x 22.94 mm x 4 mm. The complex permittivity, ɛr and complex permeability, μr of the developed samples are measured at X-band by Nicolson-Ross method using Agilent E8362C vector network analyzer. The effect of the annealing temperature on the complex permittivity and permeability in the X-band is studied. The maximum dielectric constant and permeability is obtained of the BaFe12O19/NPR composite with BaFe12O19 annealed at 9000C as 6 and 2 respectively. The composite is a good candidate for microwave absorption study.

  9. Synthesis of improved phenolic resins

    NASA Technical Reports Server (NTRS)

    Delano, C. B.; Mcleod, A. H.

    1979-01-01

    Twenty seven addition cured phenolic resin compositions were prepared and tested for their ability to give char residues comparable to state-of-the-art phenolic resins. Cyanate, epoxy, allyl, acrylate, methacrylate and ethynyl derivatized phenolic oligomers were investigated. The novolac-cyanate and propargyl-novolac resins provided anaerobic char yields at 800 C of 58 percent. A 59 percent char yield was obtained from modified epoxy novolacs. A phosphonitrilic derivative was found to be effective as an additive for increasing char yields. The novolac-cyanate, epoxy-novolac and methacrylate-epoxy-novolac systems were investigated as composite matrices with Thornel 300 graphite fiber. All three resins showed good potential as composite matrices. The free radical cured methacrylate-epoxy-novolac graphite composite provided short beam shear strengths at room temperature of 93.3 MPa (13.5 ksi). The novolac-cyanate graphite composite produced a short beam shear strength of 74 MPa (10.7 ksi) and flexural strength of 1302 MPa (189 ksi) at 177 C. Air heat aging of the novolac-cyanate and epoxy novolac based composites for 12 weeks at 204 C showed good property retention.

  10. A study of the thermal conductivity of composite material Cu-epoxide resin at superfluid helium temperatures

    NASA Astrophysics Data System (ADS)

    Wang, H. L.; Wu, T. H.; Guo, F. Z.

    1994-02-01

    The influence of Kapitza thermal resistance of the composite material at superfluid helium temperatures is studied from the point of view of the heat transfer theory of cryogenics. A numerical model is developed for calculating the effective thermal conductivity coefficient of Cu-epoxide resin with the wires arranged in a square or crosswise. Experimental investigations have also been made at superfluid helium temperatures. The effective thermal conductivity coefficient of this kind of composite material measured by experiment is λ e=0.5929W/m·K.

  11. Thermochemical tests on resins: Char resistance of selected phenolic cured epoxides

    NASA Technical Reports Server (NTRS)

    Keck, F. L.

    1982-01-01

    Curing epoxy resins with novalac phenolic resins is a feasible approach for increasing intact char of the resin system. Char yields above 40% at 700 C were achieved with epoxy novalac (DEN 438)/novalac phenolic (BRWE 5833) resin systems with or without catalyst such as ethyl tri-phenyl phosphonium iodide. These char yields are comparable to commercially used epoxy resin systems like MY-720/DDS/BF3. Stable prepregs are easily made from a solvent solution of the epoxy/phenolic system and this provides a feasible process for fabrication of same into commercial laminates.

  12. Exploration of cardanol-based phenolated and epoxidized resins by size exclusion chromatography and MALDI mass spectrometry.

    PubMed

    Fouquet, Thierry; Puchot, Laura; Verge, Pierre; Bomfim, João A S; Ruch, David

    2014-09-16

    Cardanol and cardanol derivatives are among the most important biobased materials currently investigated in green chemistry, as renewable and promising building blocks in lieu of traditional raw materials from non renewable resources, in particular owing to the olefinic linkages on the C15 alkyl side-chain. Despite the increasing interest they arouse, analytical chemistry dedicated to cardanol and associated resins has been rarely reported in the literature, found even poorer when dealing with chromatography and mass spectrometry. In this work, a thorough molecular characterization was conducted using matrix assisted laser desorption ionization (MALDI) mass spectrometry, size exclusion chromatography (SEC), and SEC-MALDI coupling to gain insights into the composition of phenolated, epoxidized, and epoxidized phenolated cardanol. A nomenclature was proposed to properly describe the numerous species found in these materials, while simulations of the unsaturation patterns and their comparison with the detected patterns in MALDI-MS gave useful details about the phenolation treatment expected to occur on the polyunsaturated C15 side chain. Finally, the SEC-MALDI off-line coupling allowed SEC peaks to be deconvoluted by mass spectrometry and MALDI artefacts related to matrix adduction to be pointed out.

  13. Flexible Bionanocomposites from Epoxidized Hemp Seed Oil Thermosetting Resin Reinforced with Halloysite Nanotubes.

    PubMed

    Shuttleworth, Peter S; Díez-Pascual, Ana M; Marco, Carlos; Ellis, Gary

    2017-03-23

    Hemp seed (Cannabis sativa L.) oil comprises a variety of beneficial unsaturated triglycerides with well-documented nutritional and health benefits. However, it can become rancid over a relatively short time period, leading to increased industrial costs and waste of a valuable product. The development of sustainable polymers is presented as a strategy, where both the presence of unsaturation and peroxide content could be effectively used to alleviate both the waste and financial burden. After the reaction with peroxyacetic acid, the incorporation of halloysite nanotubes (HNTs), and the subsequent thermal curing, without the need for organic solvents or interfacial modifiers, flexible transparent materials with a low glass-transition temperature were developed. The improvement in the thermal stability and both the static and dynamic mechanical properties of the bionanocomposites were significantly enhanced with the well-dispersed HNT filler. At an optimum concentration of 0.5 wt % HNTs, a simultaneous increase in stiffness, strength, ductility, and toughness was observed in comparison to the unfilled cured resin. These sustainable food-waste-derived bionanocomposites may provide an interesting alternative to petroleum-based materials, particularly for low-load-bearing applications, such as packaging.

  14. Jute fiber composites from coal, super clean coal, and petroleum vacuum residue-modified phenolic resin

    SciTech Connect

    Ahmaruzzaman, M.; Sharma, D.K.

    2005-07-01

    Jute fiber composites were prepared with novolac and coal, phenolated-oxidized super clean coal (POS), petroleum vacuum residue (XVR)-modified phenol-formaldehyde (novolac) resin. Five different type of resins, i.e., coal, POS, and XVR-modified resins were used by replacing (10% to 50%) with coal, POS, and XVR. The composites thus prepared have been characterized by tensile strength, hardness, thermogravimetric analysis (TGA), Fourier-transfer infrared (FT-IR), water absorption, steam absorption, and thickness swelling studies. Twenty percent POS-modified novolac composites showed almost the same tensile strength as that of pure novolac composites. After 30% POS incorporation, the tensile strength decreased to 25.84MPa from 33.96MPa in the case of pure novolac resin composites. However, after 50% POS incorporation, the percent retention of tensile strength was appreciable, i.e., 50.80% retention of tensile strength to that of pure novolac jute composites. The tensile strength of coal and XVR-rnodified composites showed a trend similar to that shown by POS-modified novolac resin composites. However, composites prepared from coal and XVR-modified resin with 50% phenol replacement showed 25.4% and 42% tensile strength retention, respectively, compared to that of pure novolac jute composites. It was found that the hardness of the modified composites slightly decreased with an increase in coal, POS, and XVR incorporation in the resin. The XVR-modified composites showed comparatively lower steam absorption than did coal or POS-modified composites. The thermal stability of the POS-modified composites was the highest among the composites studied. The detailed results obtained are being reported.

  15. Heptachlor epoxide

    Integrated Risk Information System (IRIS)

    Heptachlor epoxide ; CASRN 1024 - 57 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogen

  16. Synthesis of improved phenolic and polyester resins

    NASA Technical Reports Server (NTRS)

    Delano, C. B.

    1980-01-01

    Thirty-seven cured phenolic resin compositions were prepared and tested for their ability to provide improved char residues and moisture resistance over state of the art epoxy resin composite matrices. Cyanate, epoxy novolac and vinyl ester resins were investigated. Char promoter additives were found to increase the anaerobic char yield at 800 C of epoxy novolacs and vinyl esters. Moisture resistant cyanate and vinyl ester compositions were investigated as composite matrices with Thornel 300 graphite fiber. A cyanate composite matrix provided state of the art composite mechanical properties before and after humidity exposure and an anaerobic char yield of 46 percent at 800 C. The outstanding moisture resistance of the matrix was not completely realized in the composite. Vinyl ester resins showed promise as candidates for improved composite matrix systems.

  17. On The Molecular Mechanism Of Positive Novolac Resists

    NASA Astrophysics Data System (ADS)

    Huang, Jian-Ping; Kwei, T. K.; Reiser, Arnost

    1989-08-01

    A molecular mechanism for the dissolution of novolac is proposed, based on the idea of a critical degree of deprotonation as being the condition for the transfer of polymer into solution. The rate at which the critical deprotonation condition is achieved is controlled by the supply of developer into a thin penetration zone, and depends in particular on the rate of diffusion of the base cations which are the developer component with the lowest mobility. The penetration zone contains phenolate ions and ion-bound water, but it retains the structure of a rigid polymer membrane, as evidenced by the diffusion coefficient of cations in the pene;tration zone which is several orders of magnitude slower than in an open gel of the same material. When the critical degree of deprotonation is reached, the membrane structure unravels and all subsequent events, chain rearrangement and transfer into solution, occur rapidly. The supralinear dependence of dissolution rate on base concentration and the effect of the size of the base cation are plausibly interpreted by the model. The diffusion of developer components is assumed to occur preferentially via hydrophilic sites in the polymer matrix. These sites define a diffusion path which acts like a hydrophilic diffusion channel. Suitably designed hydrophobic molecules can block some of the channels and in this way alter the dissolution rate. They reduce in effect the diffusion crossect ion of the material. Hydrophilic additives, on the other hand, introduce additional channels into the system and promote dissolution. The concept of diffusion channels appears to provide a unified interpretation for a number of common observations.

  18. Preparation and cured properties of novel cycloaliphatic epoxy resins

    SciTech Connect

    Tokizawa, Makoto; Okada, Hiroyoshi; Wakabayashi, Nobukatsu; Kimura, Tomiaki . Research Center)

    1993-10-20

    Preparation and characterization of novel cycloaliphatic epoxy resins, which are derived from octadienyl compounds, were studied. From a model peracetic acid epoxidation reaction using 2,7-octadienyl acetate-1, the structure of the liquid resins is estimated to be mainly terminal epoxides and some amount of inner epoxide depending on the epoxide content. The epoxy resins offer lower toxicity and lower vapor pressure. The reactivity of the resin with acid anhydrides is moderate but faster than that of traditional cyclohexane epoxide-type resins and slower than that of the glycidyl ester-type resins. This reactivity was also examined using model compounds. The heat deflection temperature of the hexahydro-phthalic anhydride-cured resins is shown to be directly proportional to the number of epoxy groups in the molecules. The flexural strength of the cured resins is nearly equivalent to that of the commercial resins, although the flexural elongation of the resins is larger than that of the rigid cyclohexane epoxide-type resins. The thermal stability of the cured resins is compared to typical rigid cycloaliphatic resins; furthermore, high water resistance of the cured resins is suggested to be attributed to the hydrophobic character of the C[sub 8] chain by cross-linking.

  19. Epoxidation catalyst and process

    DOEpatents

    Linic, Suljo; Christopher, Phillip

    2010-10-26

    Disclosed herein is a catalytic method of converting alkenes to epoxides. This method generally includes reacting alkenes with oxygen in the presence of a specific silver catalyst under conditions suitable to produce a yield of the epoxides. The specific silver catalyst is a silver nanocrystal having a plurality of surface planes, a substantial portion of which is defined by Miller indices of (100). The reaction is performed by charging a suitable reactor with this silver catalyst and then feeding the reactants to the reactor under conditions to carry out the reaction. The reaction may be performed in batch, or as a continuous process that employs a recycle of any unreacted alkenes. The specific silver catalyst has unexpectedly high selectivity for epoxide products. Consequently, this general method (and its various embodiments) will result in extraordinarily high epoxide yields heretofore unattainable.

  20. Succinic anhydrides from epoxides

    DOEpatents

    Coates, Geoffrey W.; Rowley, John M.

    2013-07-09

    Catalysts and methods for the double carbonylation of epoxides are disclosed. Each epoxide molecule reacts with two molecules of carbon monoxide to produce a succinic anhydride. The reaction is facilitated by catalysts combining a Lewis acidic species with a transition metal carbonyl complex. The double carbonylation is achieved in single process by using reaction conditions under which both carbonylation reactions occur without the necessity of isolating or purifying the product of the first carbonylation.

  1. Phenolic dyes as nonbleachable absorbers compatible with novolac resins for linewidth control in photoresists

    DOEpatents

    Renschler, C.L.

    1986-11-25

    Photoresist techniques and compositions are provided employing curcumin as an absorptive dye for the purpose of reducing linewidth non-uniformity caused by scattered and reflective light from the substrate-resist interface. The photoresist compositions containing curcumin as the absorptive dye are used in the production of microelectronic circuitry by both single layer and multilayer photoresist techniques.

  2. Phenolic dyes as nonbleachable absorbers compatible with novolac resins for linewidth control in photoresists

    SciTech Connect

    Renschler, C.L.

    1988-10-17

    Photoresist techniques and compositions are provided employing curcumin as an absorptive dye for the purpose of reducing linewidth non-uniformity caused by scattered and reflective light from the substrate-resist interface. The photoresist compositions containing curcumin as the absorptive dye are used in the production of microelectronic circuitry by both single layer and multilayer photoresist techniques. 2 figs.

  3. Array of Love-wave sensors based on quartz/Novolac to detect CWA simulants.

    PubMed

    Matatagui, D; Fontecha, J; Fernández, M J; Aleixandre, M; Gràcia, I; Cané, C; Horrillo, M C

    2011-09-15

    An array of Love-wave sensors based on quartz and Novolac has been developed to detect chemical warfare agents (CWAs). These weapons are a risk for human health due to their efficiency and high lethality; therefore an early and clear detection is of enormous importance for the people safety. Love-wave devices realized on quartz as piezoelectric substrate and Novolac as guiding layer have been used to make up an array of six sensors, which have been coated with specific polymers by spin coating. The CWAs are very dangerous and for safety reasons their well known simulants have been used: dimethylmethyl phosphonate (DMMP), dipropyleneglycol methyl ether (DPGME), dimethylmethyl acetamide (DMA), dichloroethane (DCE), dichloromethane (DCM) and dichloropentane (DCP). The array has been exposed to these CWA simulants detecting very low concentrations, such as 25 ppb of DMMP, a simulant of nerve agent sarin. Finally, principal component analysis (PCA) as data pre-processing and discrimination technique, and probabilistic neural networks (PNN) as patterns classification technique have been applied. The performance of the sensor array has shown stability, accuracy, high sensitivity and good selectivity to these simulants.

  4. Fabrication and physical testing of graphite composite panels utilizing woven graphite fabric with current and advanced state-of-the-art resin systems

    NASA Technical Reports Server (NTRS)

    Lee, S. C. S.

    1979-01-01

    Three weaves were evaluated; a balanced plain weave, a balanced 8-harness satin weave, and a semiunidirectional crowfoot satin weave. The current state-of-the-art resin system selected was Fiberite's 934 Epoxy; the advanced resin systems evaluated were Phenolic, Phenolic/Novolac, Benzyl and Bismaleimide. The panels were fabricated for testing on NASA/Ames Research Center's Composites Modification Program. Room temperature mechanical tests only were performed by Hitco; the results are presented.

  5. Epoxide-derived organosulfates

    NASA Astrophysics Data System (ADS)

    Schwier, A. N.; Woo, J.; McNeill, V. F.

    2011-12-01

    Organosulfates (OS) are a significant fraction of secondary organic aerosol (SOA) material in the atmosphere. OS are typically surface-active, and have been suggested to cause surface tension depression in aerosols. Recent field studies suggest that epoxide-derived OS are the most abundant OS type in aerosols. Time-dependent surface tension measurements and Aerosol-CIMS characterization of two epoxides and their organosulfate products are shown. α-pinene oxide, derived from α-pinene, shows significant surface tension depression in H2O and ammonium sulfate. Results from cis-2,3-epoxybutane-1,4-diol (BEPOX), a butadiene-derived analog to isoprene-derived epoxydiols, are also shown. In addition, using GAMMA, a photochemical box model using coupled gas- and aqueous-phase chemistry developed in the McNeill laboratory, we show the dominance of epoxide-derived OS formation over other competing OS formation mechanisms, such as radical chemistry, under both high-NOx and low-NOx scenarios.

  6. Investigation of Resin Systems for Improved Ablative Materials

    DTIC Science & Technology

    1966-04-01

    carbon/oxygen atom ratio six times larger than phenol- formaldehyde currently employed as an ablative resin . Table VIII. Carbon Content of Various... Resins Empirical C atoms/- Weight % Weight % Resin System Formula 0 atoms Carbon Hydrocarbon Epoxide C 1 9 H 2 0 0 4 19/4 73. 1 79.5 Phenol- Formaldehyde C...AFSS-A Washington, D. C. 20546 . . . . . .. . . . -" . . . . . L NASA CR-54471 4176-6014-SOOOO FINAL REPORT INVESTIGATION OF RESIN SYSTEMS FOR

  7. The Fracture of Thermosetting Resins after Exposure to Water.

    DTIC Science & Technology

    1980-09-01

    formaldehyde, urea-formaldehyde and melamine - formaldehyde resins , epoxides, unsaturated polyesters, diallyl phthalate resins , furanes and certain kinds...AO0-A099 975 KINGSTON POLYTECHNIC KINGSTON UPON THAMES (ENGLAND) F/G 11/9 THE FRACTURE OF THERMOSETTING RESINS AFTER EXPOSURE TO WATER.(U) SEP 80 6...PERIOD COVERED The Fracture of Thermosetting Resins after First Annual Tech Report Exposure to Water Oct 79 - Oct 80 6. PERFORMING ORG. REPORT

  8. Microwave absorption properties of graphite flakes-phenolic resin composite

    NASA Astrophysics Data System (ADS)

    Gogoi, Jyoti P.; Gogoi, Pragyan J.; Bhattacharyya, Nidhi S.

    2013-01-01

    In the present investigation, microwave absorption properties of a conductor back single layer designed on graphite flakes (GF)-novolac phenolic resin (NPR) composites is studied. The complex permittivity of the developed composite enhance for higher GF percentages. The reflection loss(RL) measured using E8362C VNA shows a maximum RL values -25 dB at 9.8 GHz for 7 wt. % composition with -10 dB bandwidth of 0.3 GHz. The developed composites are being light weight and cost effective shows potential to be used as dielectric absorber.

  9. Assessment of the chemical changes during storage of phenol-formaldehyde resins pyrolysis gas chromatography mass spectrometry, inverse gas chromatography and Fourier transform infra red methods.

    PubMed

    Strzemiecka, B; Voelkel, A; Zięba-Palus, J; Lachowicz, T

    2014-09-12

    The chemical changes occurring in the phenol-formaldehyde resins (resol and novolac type) during their storage were investigated. In this paper the FT-IR, py-GCMS and inverse gas chromatography methods were applied for assessment of the changes occurring during storage of the phenolic resins. We have found that during storage some examined resins occurred partial curing. The results from all techniques applied are consistent. Py-GCMS is useful technique for screening the storage processes but IGC seems to be most sensitive one.

  10. Process for improving moisture resistance of epoxy resins by addition of chromium ions

    NASA Technical Reports Server (NTRS)

    St.clair, A. K.; Stoakley, D. M.; St.clair, T. L.; Singh, J. J. (Inventor)

    1985-01-01

    A process for improving the moisture resistance properties of epoxidized TGMDA and DGEBA resin system by chemically incorporating chromium ions is described. The addition of chromium ions is believed to prevent the absorption of water molecules.

  11. Development and characterization of soy-based epoxy resins and pultruded FRP composites

    NASA Astrophysics Data System (ADS)

    Zhu, Jiang

    This dissertation focuses on the development, manufacture and characterization of novel soy-based epoxy FRP composites. Use of alternative epoxy resin systems derived from a renewable resource holds potential for low cost raw materials for the polymer and composite industries. Epoxidized Allyl Soyate (EAS) and Epoxidized Methyl Soyate (EMS) were developed from soybean oil with two chemical modification procedures: transesterification and epoxidation. This research investigates the curing characteristics and thermal and mechanical properties of the neat soyate resin systems. The derived soyate resins have higher reactivity and superior performance compared to commercially available epoxidized soybean oil. An efficient two-step curing method was developed in order to utilize these soyate resins to their full potential. The epoxy co-resin systems with varied soyate resin content were successfully used to fabricate composite material through pultrusion. The pultrusion resin systems with 30 wt% soyate resins yielded improved, or comparable mechanical properties with neat commercial resins. A finite element analysis of the heat transfer and curing process was performed to study the processing characterization on glass/epoxy composite pultrusion. This model can be used to establish baseline process variables and will benefit subsequent optimization. This research demonstrates that soy-based resins, especially EAS, show considerable promise as an epoxy resin supplement for use in polymer and composite structural applications. The new products derived from soybean oil can provide competitive performance, low cost and environmental advantages.

  12. Effect of network structure on thermal and mechanical properties of cured epoxy resin containing mesogenic group

    SciTech Connect

    Ochi, M.; Shimizu, Y.; Tsuyuno, N.

    1996-10-01

    Epoxy resin containing biphenol group as a mesogenic group was cured with phenol (PN) and catechol (CN) novolacs. In the CN-cured biphenol type epoxy resin, the glass-rubber transition, almost disappeared and thus the very high elastic modulus was obtained in the high temperature region. It is clear that the micro-Brownian motion of the network chains is highly suppressed in this cured system. On the other hand, the PN-cured resin showed the well-defined glass-rubber transition and thus the low rubbery modulus. In addition, in the former system, the characteristic pattern like a schlieren texture was clearly observed in the polarized optical microphotographs. This shows that the mesogenic group contained in the epoxy molecule is oriented in the system cued with catechol novolac, which has neighboring active hydrogens. The computer simulation based on the molecular mechanics also showed that the orientation of the network chains should occur in the CN-cured biphenol epoxy system. Thus, we conclude that the suppression of the micro-Brownian motion in the CN-cured system is due to the orientation of network chains containing a mesogenic group. Moreover, it has been shown that die mechanical and bonding strength at high temperature is considerably improved by the suppression of the network chain in the CN-cured biphenol resin system.

  13. Similarities between catalase and cytosolic epoxide hydrolase.

    PubMed

    Guenthner, T M; Qato, M; Whalen, R; Glomb, S

    1989-01-01

    Cytosolic epoxide hydrolase, measured as trans-stilbene oxide hydrolase activity, was isolated and purified from human and guinea pig liver cytosol. Antiserum to the guinea pig liver preparation reacted strongly with bovine liver catalase. We determined that this lack of selectivity of the antiserum was due to catalase contamination of the epoxide hydrolase preparation. We also determined that several commercial catalase preparations are contaminated with cytosolic epoxide hydrolase. Our human epoxide hydrolase preparation contained no detectable catalase contamination, yet antiserum to this protein also cross-reacted slightly with catalase, indicating some intrinsic similarity between the two enzymes. We conclude that catalase and cytosolic epoxide hydrolase contain some similar immunogenic epitopes, and we surmise that similarities between the subunits of these two enzymes may lead to their partial copurification. Functional similarities between the two enzymes are also demonstrated, as several compounds that inhibit catalase are also shown to inhibit cytosolic epoxide hydrolase activity in the same concentration range and rank order.

  14. Alkene epoxidations catalysed by Mo(VI) supported on imidazole-containing polymers I. Synthesis, characterisation, and activity of catalysts in the epoxidation of cyclohexene

    SciTech Connect

    Miller, M.M.; Sherrington, D.C.

    1995-04-01

    Polystyrene resins functionalised with hydroxylpropyl aminomethyl pyridine, pyridyl imidazole, and carboxybenzimidazole, polyglycidyl methacrylate resins functionalised with aminomethyl pyridine and pyridyl imidazole, and polybenzimidazole resin have all been loaded with Mo(VI). The resulting polymer metal complexes have been activated by treatment with t-butylhydroperoxide, then used as catalysts in the liquid-phase epoxidation of cyclohexene using t-butylhydroperoxide. Polymers containing the imidazole group were particularly active, and unlike the other species did not require preactivation to induce high activity. The complexes formed with the imidazole-containing polymers appear to be monometallic species, whereas the other polymer ligands yield oxybridged bimetallic species. This accounts for the major difference in activity recorded. Possible structures for the catalysts are proposed based on information in the literature. 30 refs., 10 figs., 6 tabs.

  15. Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

    PubMed Central

    2013-01-01

    Summary Enantioselective desymmetrization of meso-aziridines and meso-epoxides with various nucleophiles by organocatalysis has emerged as a cutting-edge approach in recent years. This review summarizes the origin and recent developments of enantioselective desymmetrization of meso-aziridines and meso-epoxides in the presence of organocatalysts. PMID:24062828

  16. Toughening mechanism in elastomer-modified epoxy resins, part 2

    NASA Technical Reports Server (NTRS)

    Yee, A. F.; Pearson, R. A.

    1984-01-01

    The role of matrix ductility on the toughenability and toughening mechanism of elastomer-modified DGEBRA epoxies was investigated. Matrix ductility was varied by using epoxide resins of varying epoxide monomer molecular weights. These epoxide resins were cured using 4,4' diaminodiphenyl sulfone (DDS) and, in some cases, modified with 10% HYCAR(r)CTBN 1300X8. Fracture roughness values for the neat epoxies were found to be almost independent on the monomer molecular weight of the epoxide resin used. However, it was found that the fracture toughness of the elastomer-modified epoxies was very dependent upon the epoxide monomer molecular weight. Tensile dilatometry indicated that the toughening mechanism, when present, is similar to the mechanisms found for the piperidine cured epoxies in Part 1. SEM and OM corroborate this finding. Dynamic mechanical studies were conducted to shed light on the toughenability of the epoxies. The time-dependent small strain behavior of these epoxies were separated into their bulk and shear components. The bulk component is related to brittle fracture, whereas the shear component is related to yielding. It can be shown that the rates of shear and bulk strain energy buildup for a given stress are uniquely determined by the values of Poisson's ratio, nu. It was found that nu increases as the monomer molecular weight of the epoxide resin used increases. This increase in nu can be associated with the low temperature beta relaxation. The effect of increasing cross-link density is to shift the beta relaxation to higher temperatures and to decrease the magnitude of the beta relaxation. Thus, increasing cross-link density decreases nu and increases the tendency towards brittle fracture.

  17. Rheology Analysis of Thermosetting Resin Candidates for Use in Fuel Compacting

    SciTech Connect

    Trammell, Michael P.

    2012-06-01

    The AGR-1 and AGR-2 overcoating and compacting method utilized a wet mixing process where liquid resin (Hexion Durite SC-1008) was blended with natural and synthetic graphite to produce a graphite/resin matrix for overcoating. The matrix production method specified in the scale-up plan is a co-grinding jet mill process where powdered resin and graphite are fed at the same time into a jet mill. Because of the change in matrix production style, SC-1008 cannot be used in the jet milling process because it is a liquid. Also, attempts to dry out matrix made with SC-1008 for use in the overcoating process at B&W had mixed results. The SC-1008 resin became tacky when dried which caused the matrix to build up inside the overcoater. The scale- up jet milling/mixing and overcoating processes required that a suite of solid or powdered resins be identified. Suitable resins candidates were down selected to two resins, specifically Plenco 14838 and Hexion SD-1708. These resins are referred to as novolac or “two-stage” resins because they require the addition of a curing agent such as hexamethylenetetramine (Hexa) to promote an increased level of cross linking. The overcoating matrix is made of 3 components; natural graphite, synthetic graphite, and resin. The most influential component of the compacting process is the resin component and how it behaves with regards to time, temperature, and pressure. The selected scale-up resins are considered fast curing which means that the increase in molecular weight (curing) occurs over a relatively short period of time, ranging from a few seconds to several minutes depending on the temperature. To find the optimal compacting conditions it is useful to quantify this behavior. In this report, rheology is used to investigate viscosity as a function of time at specific temperatures for the previously mentioned resins.

  18. Process for improving mechanical properties of epoxy resins by addition of cobalt ions

    NASA Technical Reports Server (NTRS)

    Stoakley, D. M.; St.clair, A. K. (Inventor)

    1984-01-01

    A resin product useful as an adhesive, composite or casting resin is described as well as the process used in its preparation to improve its flexural strength mechanical property characteristics. Improved flexural strength is attained with little or no change in density, thermal stability or moisture resistance by chemically incorporating 1.2% to 10.6% by weight Co(3) ions in an epoxidized resin system.

  19. Epoxy resin

    DOEpatents

    Wilson, Glenn R.; Salyer, Ival O.; Ball, III, George L.

    1976-07-13

    By mixing one part of a prepolymer containing a polyamine partially polymerized with an organic epoxide and subsequently reacted with a fatty acid containing from 8 to 32 carbon atoms, and then reacting this prepolymer mixture with 3 parts of an organic epoxide, a composition was obtained which made a gas frothable, shear-stable, room temperature curing, low density foam. A particularly advantageous prepolymer was prepared using a polyamine selected from the group consisting of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, partially polymerized with an organic epoxide having an average molecular weight of about 350 and having an epoxide equivalent of 185 to 192, and reacted with 2-10 weight percent linoleic acid. When one part of this prepolymer was reacted with about three parts of epoxy, and frothed by whipping in air or nitrogen an epoxy foam was produced which could be troweled onto surfaces and into corners or crevices, and subsequently cured, at near ambient temperature, to a strong dimensionally stable foam product.

  20. Divergent Reactivity via Cobalt Catalysis: An Epoxide Olefination.

    PubMed

    Jamieson, Megan L; Hume, Paul A; Furkert, Daniel P; Brimble, Margaret A

    2016-02-05

    Cobalt salts exert an unexpected and profound influence on the reactivity of epoxides with dimethylsulfoxonium methylide. In the presence of a cobalt catalyst, conditions for epoxide to an oxetane ring expansion instead deliver homoallylic alcohol products, corresponding to a two-carbon epoxide homologation/ring-opening tandem process. The observed reactivity change appears to be specifically due to cobalt salts and is broadly applicable to a variety of epoxides, retaining the initial stereochemistry. This transformation also provides operationally simple access to enantiopure homoallylic alcohols from chiral epoxides without use of organometallic reagents. Tandem epoxidation-homologation of aldehydes in a single step is also demonstrated.

  1. Cycloaliphatic epoxy resin coating for capillary electrophoresis.

    PubMed

    Shah, Roopa S; Wang, Qinggang; Lee, Milton L

    2002-04-05

    Coating the interior surface of a fused-silica capillary with a polymeric material has long been used in capillary electrophoresis (CE) to reduce or eliminate electroosmotic flow and suppress adsorption. A cycloaliphatic epoxide-based resin was bonded to silane treated capillaries and crosslinked with a curing agent. The epoxy resin coating significantly reduced electroosmotic flow over a pH range of 3-10. This coating was sufficiently hydrophilic to suppress protein adsorption. The epoxy resin coated capillary was used to separate several acidic and basic proteins and peptides. Separation efficiencies greater than 400,000 theoretical plates were achieved. The relative standard deviations in migration times for proteins were <0.8%. Speed and simplicity are important advantages of the coating procedure compared to other published coating methods.

  2. 40 CFR 721.2675 - Perfluoroalkyl epoxide (generic name).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Perfluoroalkyl epoxide (generic name... Substances § 721.2675 Perfluoroalkyl epoxide (generic name). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as perfluoroalkyl epoxide (PMN...

  3. 40 CFR 721.10233 - Linear alkyl epoxide (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Linear alkyl epoxide (generic). 721... Substances § 721.10233 Linear alkyl epoxide (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as linear alkyl epoxide (PMN...

  4. 40 CFR 721.10233 - Linear alkyl epoxide (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Linear alkyl epoxide (generic). 721... Substances § 721.10233 Linear alkyl epoxide (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as linear alkyl epoxide (PMN...

  5. 40 CFR 721.10233 - Linear alkyl epoxide (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Linear alkyl epoxide (generic). 721... Substances § 721.10233 Linear alkyl epoxide (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as linear alkyl epoxide (PMN...

  6. 21 CFR 172.723 - Epoxidized soybean oil.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Epoxidized soybean oil. 172.723 Section 172.723... CONSUMPTION Other Specific Usage Additives § 172.723 Epoxidized soybean oil. Epoxidized soybean oil may be... reacting soybean oil in toluene with hydrogen peroxide and formic acid. (b) It meets the...

  7. 21 CFR 172.723 - Epoxidized soybean oil.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Epoxidized soybean oil. 172.723 Section 172.723....723 Epoxidized soybean oil. Epoxidized soybean oil may be safely used in accordance with the following prescribed conditions: (a) The additive is prepared by reacting soybean oil in toluene with hydrogen...

  8. 21 CFR 172.723 - Epoxidized soybean oil.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Epoxidized soybean oil. 172.723 Section 172.723... CONSUMPTION Other Specific Usage Additives § 172.723 Epoxidized soybean oil. Epoxidized soybean oil may be... reacting soybean oil in toluene with hydrogen peroxide and formic acid. (b) It meets the...

  9. 21 CFR 172.723 - Epoxidized soybean oil.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Epoxidized soybean oil. 172.723 Section 172.723... CONSUMPTION Other Specific Usage Additives § 172.723 Epoxidized soybean oil. Epoxidized soybean oil may be... reacting soybean oil in toluene with hydrogen peroxide and formic acid. (b) It meets the...

  10. 21 CFR 172.723 - Epoxidized soybean oil.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Epoxidized soybean oil. 172.723 Section 172.723... CONSUMPTION Other Specific Usage Additives § 172.723 Epoxidized soybean oil. Epoxidized soybean oil may be... reacting soybean oil in toluene with hydrogen peroxide and formic acid. (b) It meets the...

  11. Quetol 651: Not just a low viscosity resin.

    PubMed

    Ellis, E Ann

    2016-01-01

    Quetol 651, a low viscosity epoxy resin, is miscible with alcohols, acetone, and water. It is versatile and can be used as a single epoxide or mixed with other epoxides and anhydrides. The most important characteristic is that the addition of Quetol 651 to a formulation results in a lower viscosity embedding medium and allows for good detection of antigenic activity. Properly formulated and mixed resins containing Quetol 651 have excellent sectioning properties and good beam stability. The decrease in viscosity lends to lower specific gravity of the embedding medium and less interfering electron density between specimen elements resulting in better spatial resolution. New formulations and viscosity data are presented and compared to long used, embedding formulations and the extensive uses of Quetol 651 are reviewed.

  12. Alkene epoxidation employing metal nitro complexes

    DOEpatents

    Andrews, M.A.; Cheng, C.W.; Kelley, K.P.

    1982-07-15

    Process for converting alkenes to form epoxides utilizes transition metal nitro complexes of the formula: M(RCN)/sub 2/XNO/sub 2/ wherein M is palladium or platinum, R is an alkyl or aryl group containing up to 12 carbon atoms, and X is a monoanionic, monodentate ligand such as chlorine, optionally in the presence of molecular oxygen.

  13. Polymerization of epoxidized triglycerides with fluorosulfonic acid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of triglycerides as agri-based renewable raw materials for the development of new products is highly desirable in view of uncertain future petroleum prices. A new method of polymerizing epoxidized soybean oil has been devised with the use of fluorosulfonic acid. Depending on the reaction con...

  14. Shelf life determination of an epoxy resin by accelerated aging

    SciTech Connect

    Smith, H.M.

    1983-11-01

    The objectives of the study reported were to first define the rate and mode of degradation of an epoxy resin at two storage conditions, 4.4/sup 0/C and 25/sup 0/C, by means of a thermally accelerated aging experiment. Then, samples which had been aged the equivalent of at least 10 years at each storage condition would be tested for conformance to the material specifications. The study's results demonstrate that the commercial resin could be acquired and stored for the required 10 to 11 years without concern over degradation. The expected changes at the two storage temperatures have been defined. Aged resin samples are shown to yield an acceptable product. Sufficient data exist to predict the changes in viscosity and epoxide equivalent of the resin at any other storage temperature of interest. (LEW)

  15. Plastic casting resin poisoning

    MedlinePlus

    Epoxy poisoning; Resin poisoning ... Epoxy and resin can be poisonous if they are swallowed or their fumes are breathed in. ... Plastic casting resins are found in various plastic casting resin products.

  16. Quantification of derivatives of bisphenol A diglycidyl ether (BADGE) and novolac glycidyl ether (NOGE) migrated from can coatings into tuna by HPLC/fluorescence and MS detection.

    PubMed

    Berger, U; Oehme, M; Girardin, L

    2001-01-02

    A reversed phase high performance liquid chromatographic method combined with fluorescence and mass spectrometric detection in series is presented for the separation and quantification of bisphenol A diglycidyl ether (BADGE) and novolac glycidyl ether (NOGE) derivatives in extracts from food can coatings, tuna and oil. Fifteen samples of tuna cans bought in four European countries were investigated. Atmospheric pressure chemical ionization mass spectrometry in the positive ion mode (APCI(+)-MS) allowed to tentatively identify BADGE and NOGE related compounds originating from reactions of the glycidyl ethers with bisphenols, phenol, butanol, water and hydrochloric acid. Quantification was based on the external standard method and fluorescence detection. Mass fractions up to 3.7 micrograms/g were found for hydrochlorination products of bisphenol F diglycidyl ether (BFDGE + 2HCl) in tuna. Furthermore, total migration quantities of phenolic ether compounds were estimated. The highest values found were 20 micrograms/g in tuna and 43 micrograms/g in the oil phase.

  17. Biotechnological production of enantiopure epoxides by enzymatic kinetic resolution.

    PubMed

    Choi, Won Jae

    2009-08-01

    Enantiopure epoxides are high value-added synthons for the production of pharmaceuticals, agrochemicals, as well as versatile fine chemicals and have broad scope of market demand for their applications. A major challenge in conventional organic synthesis is to generate such compounds in high enantiopurity with reasonable yield. Among possible chemical and biological technologies for enantiopure epoxide preparation, enzymatic kinetic resolution has been paid much attention with respect to its high enantioselectivity. Epoxide hydrolase (EH) has shown promising characteristics for the preparation of enantiopure epoxides and vicinal diols during enantioselective hydrolysis of racemic epoxides. EH is readily available from microbial resources thus it is being employed for biohydrolysis of a variety of epoxides. Recent technical progress in EH-catalyzed enantioselective hydrolysis is summarized in terms of exploration of novel EH, its functional improvement, high throughput assay, and preparative scale resolution process.

  18. Mechanics of Crack Growth in Epoxide Adhesives

    DTIC Science & Technology

    1978-05-01

    mind when considering the static G (arrest) values shown in Figure 3. Ic 9 First, Bascom et al 7 ’I 0 have elegantly demonstrated that for rubber ...in limited regions of the material. The diameter of the pores or channels in a craze is typically a few tens of nanometres and the void content is...about 40 to 60%. However, while there is definite proof for craze formation in rubber -modified epoxide 24 materials, the evidence for craze formation in

  19. Mutagenicity of chloroalkene epoxides in bacterial systems.

    PubMed

    Kline, S A; McCoy, E C; Rosenkranz, H S; Van Duuren, B L

    1982-04-01

    6 alpha-chloroepoxides have been tested for in vitro activity in a variety of systems. The epoxides were cis- and trans-1-chloropropene oxide, cis- and trans-1,3-dichloropropene oxide, trichloroethylene oxide and tetrachloroethylene oxide. The epoxides were assayed for mutagenicity in the absence of metabolic activation in S. typhimurium TA1535 and E. coli WP2 uvrA and for preferential inhibition of growth of DNA-repair-deficient E. coli. All 6 epoxides possessed DNA-modifying activity as evidenced by their ability to preferentially inhibit DNA polymerase-deficient E. coli. All of the test chemicals except trichloroethylene oxide were mutagenic for S. typhimurium and all except trichloroethylene oxide and tetrachloroethylene oxide were mutagenic for E. coli Wp2 uvrA. Cis- and trans-1,3-dichloropropene oxide were the most potent mutagens and DNA modifiers. For all cases, the cis isomers were more active than the corresponding trans isomers. alpha-Chloroepoxides are considered likely to be the active intermediates of the carcinogenic parent halo-olefins. These mutagenicity studies are considered relevant in assessing the carcinogenicity of the parent hydrocarbons.

  20. The electron-impact promoted fragmentation of aurone epoxides.

    NASA Technical Reports Server (NTRS)

    Brady, B. A.; O'Sullivan, W. I.; Duffield, A. M.

    1972-01-01

    The mass spectra of six aurone epoxides have been rationalized with the aid of high resolution mass spectrometry and metastable ion evidence. These compounds fragment in a well defined manner and mechanisms are proposed for the formation of their characteristic ions. Some similarity was observed between the mass spectra of 6-methoxyaurone epoxide (II), 4-hydroxy-7-methoxy-3-phenylcoumarin (VII) and 7-methoxyflavonol (IX). The possibility that VII and IX are intermediates in the fragmentation of epoxide II is discussed. Thermal rearrangement of aurone epoxide II was shown to yield the corresponding flavonol IX and coumarin VII.

  1. Simple Epoxide Formation for the Organic Laboratory Using Oxone

    ERIC Educational Resources Information Center

    Broshears, Williams C.; Esteb, John J.; Richter, Jeremy; Wilson, Anne M.

    2004-01-01

    Epoxide chemistry is widely used in organic synthesis and regularly discussed in organic chemistry textbooks. An experiment to generate dimethyldioxirane in situ from acetone using Oxone is explained.

  2. Resin Characterization

    DTIC Science & Technology

    2015-06-01

    international treaties). Environmental testing is performed in a chemical laboratory setting, with the test compounds being exposed to environmental soil or......when it is no longer needed. Do not return it to the originator. ARL-SR-0323 ● JUNE 2015 US Army Research Laboratory Resin

  3. Effect of Monomer Structure on Curing Behavior, CO2 Solubility, and Gas Permeability of Ionic Liquid-Based Epoxy-Amine Resins and Ion-Gels

    SciTech Connect

    McDanel, WM; Cowan, MG; Barton, JA; Gin, DL; Noble, RD

    2015-04-29

    New imidazolium- and pyrrolidinium-based bis(epoxide)-functionalized ionic liquid (IL) monorners were synthesized: and reacted with multifunctional amine monomers to produce cross-linked, epoxy-amine poly(ionic liquid) (PIL) resins and PIL/IL ion-gel membranes. The length and chemical nature (i.e., alkyl versus ether) between the irrildazolium group and epokitie groups were studied to determine their effects on CO2 affinity. The CO2 uptake (millimoles per gram) of the epoxy amine resins (between 0.1 and 1 mmol/g) was found to depend predominately on the epoxide-to-amine ratio and the bis(epoxide) IL molecular weight. The effect of using a primary versus a secondary amine-containing multifunctional monoiner was also assessed for the resin-synthesis. Secondary amines can increase CO2 permeability but also increase the iime required for biS(epoxide) coriversion. When either the epoxide or athine monomer structure is changed, the CO2 solubility and permeability of the resulting PIL resins and ion-sel membranes can be tuned.

  4. Curing agent for polyepoxides and epoxy resins and composites cured therewith. [preventing carbon fiber release

    NASA Technical Reports Server (NTRS)

    Serafini, T. T.; Delvigs, P.; Vannucci, R. D. (Inventor)

    1981-01-01

    A curing for a polyepoxide is described which contains a divalent aryl radical such as phenylene a tetravalent aryl radical such as a tetravalent benzene radical. An epoxide is cured by admixture with the curing agent. The cured epoxy product retains the usual properties of cured epoxides and, in addition, has a higher char residue after burning, on the order of 45% by weight. The higher char residue is of value in preventing release to the atmosphere of carbon fibers from carbon fiber-epoxy resin composites in the event of burning of the composite.

  5. Chiral Ketone and Iminium Catalysts for Olefin Epoxidation

    NASA Astrophysics Data System (ADS)

    Wong, O. Andrea; Shi, Yian

    Organo-catalyzed asymmetric epoxidation has received much attention in the past 30 years and significant progress has been made for various types of olefins. This review will cover the advancement made in the field of chiral ketone and chiral iminium salt-catalyzed epoxidations.

  6. Epoxides--is there a human health problem?

    PubMed Central

    Manson, M M

    1980-01-01

    The purpose of this review is to consider whether epoxides represent a hazard to human health. Possible means of occupational and non-occupational exposure are discussed with reference to the production and uses of industrially important compounds and other epoxides, such as naturally occurring plant and fungal products. In addition to epoxides themselves, unsaturated compounds that may be metabolised in vivo to epoxides are included, since this appears to be a further important means of exposure. The toxicology, in particular carcinogenicity and mutagenicity, is discussed, along with a brief outline of the biochemistry such as metabolism, binding to cell constituents, and DNA repair mechanisms. The question of interactions between different epoxides in vivo is also raised. PMID:7004476

  7. 4D printing smart biomedical scaffolds with novel soybean oil epoxidized acrylate

    PubMed Central

    Miao, Shida; Zhu, Wei; Castro, Nathan J.; Nowicki, Margaret; Zhou, Xuan; Cui, Haitao; Fisher, John P.; Zhang, Lijie Grace

    2016-01-01

    Photocurable, biocompatible liquid resins are highly desired for 3D stereolithography based bioprinting. Here we solidified a novel renewable soybean oil epoxidized acrylate, using a 3D laser printing technique, into smart and highly biocompatible scaffolds capable of supporting growth of multipotent human bone marrow mesenchymal stem cells (hMSCs). Porous scaffolds were readily fabricated by simply adjusting the printer infill density; superficial structures of the polymerized soybean oil epoxidized acrylate were significantly affected by laser frequency and printing speed. Shape memory tests confirmed that the scaffold fixed a temporary shape at −18 °C and fully recovered its original shape at human body temperature (37 °C), which indicated the great potential for 4D printing applications. Cytotoxicity analysis proved that the printed scaffolds had significant higher hMSC adhesion and proliferation than traditional polyethylene glycol diacrylate (PEGDA), and had no statistical difference from poly lactic acid (PLA) and polycaprolactone (PCL). This research is believed to significantly advance the development of biomedical scaffolds with renewable plant oils and advanced 3D fabrication techniques. PMID:27251982

  8. 4D printing smart biomedical scaffolds with novel soybean oil epoxidized acrylate.

    PubMed

    Miao, Shida; Zhu, Wei; Castro, Nathan J; Nowicki, Margaret; Zhou, Xuan; Cui, Haitao; Fisher, John P; Zhang, Lijie Grace

    2016-06-02

    Photocurable, biocompatible liquid resins are highly desired for 3D stereolithography based bioprinting. Here we solidified a novel renewable soybean oil epoxidized acrylate, using a 3D laser printing technique, into smart and highly biocompatible scaffolds capable of supporting growth of multipotent human bone marrow mesenchymal stem cells (hMSCs). Porous scaffolds were readily fabricated by simply adjusting the printer infill density; superficial structures of the polymerized soybean oil epoxidized acrylate were significantly affected by laser frequency and printing speed. Shape memory tests confirmed that the scaffold fixed a temporary shape at -18 °C and fully recovered its original shape at human body temperature (37 °C), which indicated the great potential for 4D printing applications. Cytotoxicity analysis proved that the printed scaffolds had significant higher hMSC adhesion and proliferation than traditional polyethylene glycol diacrylate (PEGDA), and had no statistical difference from poly lactic acid (PLA) and polycaprolactone (PCL). This research is believed to significantly advance the development of biomedical scaffolds with renewable plant oils and advanced 3D fabrication techniques.

  9. Remote cure monitoring of polymeric resins by laser Raman spectroscopy

    SciTech Connect

    Hong, K.C.; Vess, T.M.; Lyon, R.E.; Myrick, M.L.

    1993-05-01

    The validity of using Raman spectroscopy to monitor the cure chemistries of amine-cured epoxy is demonstrated by correlating NIR absorbance measurements with Raman measurements for a concentration series of bisphenol-A diglycidylether in its own reaction product with diethylamine. The intensity of a normalized Raman peak at 1240 cm{sup {minus}l}, assigned to the epoxide functionality, was found to be linearly related to the concentration of epoxide groups in the resin mixtures. Also, it is shown that the Ciba-Geigy Matrimid 5292 system can be monitored by ex-situ FT-Raman spectroscopy by observing changes in the carbonyl stretching (1773 cm{sup {minus}1}) or the C=C stretching of maleimide (1587 cm{sup {minus}1}) during the cure reaction.

  10. Prediction of drug-drug interactions with carbamazepine-10,11-epoxide using a new in vitro assay for epoxide hydrolase inhibition.

    PubMed

    Rosa, Maria; Bonnaillie, Pierre; Chanteux, Hugues

    2016-12-01

    1. Carbamazepine is an antiepileptic drug which is metabolized by CYP3A4 into carbamazepine-10,11-epoxide. This metabolite is then detoxified by epoxide hydrolase. As carbamazepine-10,11-epoxide has been associated with neurotoxicity, it is critical to identify whether a new antiepileptic drug has the potential to inhibit epoxide hydrolase and therefore increase carbamazepine-10,11-epoxide plasma levels. 2. In this study, an in vitro assay was developed to evaluate epoxide hydrolase activity by using carbamazepine-10,11-epoxide as probe substrate. The ability of this assay to predict drug-drug interactions (DDI) at the epoxide hydrolase level was also investigated. 3. To this aim, known inhibitors of epoxide hydrolase for which in vivo data are available were used. Firstly, carbamazepine-10,11-epoxide hydrolase activity was determined in liver microsomes, cytosol and hepatocytes. Thereafter, the IC50 of epoxide hydrolase inhibitors (progabide, valproic acid, valpromide and valnoctamide) was determined in liver microsomes and hepatocytes. Finally, prediction of AUC increase was performed using the in vitro data generated. 4. Interestingly, epoxide hydrolase activity was found to be much higher in human hepatocytes compared to liver microsomes/cytosol. Even though assessed on a limited number of compounds, this study demonstrated that the use of hepatocytes seems to be a more relevant model to assess and predict DDI at the epoxide hydrolase level.

  11. Carcinogenicity and mechanistic insights on the behavior of epoxides and epoxide-forming chemicals.

    PubMed

    Melnick, Ronald L

    2002-12-01

    Many epoxides and their precursors are high production volume chemicals that have major uses in the polymer industry and as intermediates in the manufacture of other chemicals. Several of these chemicals were demonstrated to be carcinogenic in laboratory animal studies conducted by the Ramazzini Foundation (e.g., vinyl chloride, acrylonitrile, styrene, styrene oxide, and benzene) and by the National Toxicology Program (e.g., ethylene oxide, 1,3-butadiene, isoprene, chloroprene, acrylonitrile, glycidol, and benzene). The most common sites of tumor induction were lung, liver, harderian gland, and circulatory system in mice; Zymbal's gland and brain in rats; and mammary gland and forestomach in both species. Differences in cancer outcome among studies of epoxide chemicals may be related to differences in study design (e.g., dose, duration, and route of exposure; observation period; animal strains), as well as biological factors affecting target organ dosimetry of the DNA-reactive epoxide (toxicokinetics) and tissue response (toxicodynamics). N7-Alkylguanine, N1-alkyladenine, and cyclic etheno adducts, as well as K-ras and p53 mutations, have been detected in animals and/or workers exposed to several of these chemicals. The classifications of these chemical carcinogens by IARC and NTP are based on animal and human data and results of mechanistic studies. Reducing occupational and environmental exposures to these chemicals will certainly reduce human cancer risks.

  12. Hydrolysis of the 2',3'-allylic epoxides of allylbenzene, estragole, eugenol, and safrole by both microsomal and cytosolic epoxide hydrolases.

    PubMed

    Luo, G; Qato, M K; Guenthner, T M

    1992-01-01

    2',3'-Allylic epoxide derivatives of allylbenzene and its analogs estragole, eugenol, and safrole were synthesized, and their enzymatic conversion to dihydrodiols by cytosolic and microsomal epoxide hydrolases was examined. All four epoxides were good substrates for both epoxide hydrolases, with Michaelis constants in the low micromolar range. Two putatively selective inhibitors of cytosolic and microsomal epoxide hydrolases, trichloropropylene oxide and nordihydroguaiaretic acid, were used to inhibit the hydrolysis of these allylic epoxides. Minimal selectivity toward either hydrolase was seen with either inhibitor, suggesting that the "selectivity" of these inhibitors is highly substrate-dependent. The susceptibilities of these epoxides to rapid hydrolysis by both epoxide hydrolases may explain their low genotoxic potencies in vivo.

  13. Potent Urea and Carbamate Inhibitors of Soluble Epoxide Hydrolases

    NASA Astrophysics Data System (ADS)

    Morisseau, Christophe; Goodrow, Marvin H.; Dowdy, Deanna; Zheng, Jiang; Greene, Jessica F.; Sanborn, James R.; Hammock, Bruce D.

    1999-08-01

    The soluble epoxide hydrolase (sEH) plays a significant role in the biosynthesis of inflammation mediators as well as xenobiotic transformations. Herein, we report the discovery of substituted ureas and carbamates as potent inhibitors of sEH. Some of these selective, competitive tightbinding inhibitors with nanomolar Ki values interacted stoichiometrically with the homogenous recombinant murine and human sEHs. These inhibitors enhance cytotoxicity of trans-stilbene oxide, which is active as the epoxide, but reduce cytotoxicity of leukotoxin, which is activated by epoxide hydrolase to its toxic diol. They also reduce toxicity of leukotoxin in vivo in mice and prevent symptoms suggestive of acute respiratory distress syndrome. These potent inhibitors may be valuable tools for testing hypotheses of involvement of diol and epoxide lipids in chemical mediation in vitro or in vivo systems.

  14. Synthesis and reactivity of coumarin 3,4-epoxide.

    PubMed

    Born, S L; Rodriguez, P A; Eddy, C L; Lehman-McKeeman, L D

    1997-11-01

    Coumarin is used widely as a fragrance constituent and is administered clinically in the treatment of certain lymphedemas and malignancies. Although toxicity occurs only rarely in humans treated clinically with high-dose coumarin, it is well established that coumarin is hepatotoxic in the rat. This species difference in susceptibility to toxicity reflects the disparate metabolic processes occurring in humans and rodents. In humans, coumarin is converted extensively via cytochrome P450 2A6 to the nontoxic 7-hydroxycoumarin metabolite. In contrast, coumarin 3,4-epoxidation is thought to predominate in rodent species, resulting in the formation of several potentially toxic metabolites. Coumarin epoxide is thought to be highly unstable and has not been isolated synthetically or as a microsomal product. To address this issue, coumarin 3,4-epoxide was synthesized, and its stability and fate have been determined. Coumarin 3,4-epoxide was prepared by reacting coumarin with dimethyldioxirane. The epoxide was stable in organic solvents and survived conditions required for analysis by gas chromotography. Its structure was confirmed via 1H-NMR and gas chromatography-mass spectrometry-infrared spectroscopy (GC-MS-IR). In contrast, coumarin 3,4-epoxide was unstable in aqueous solution, converting within 20 sec to a ring-opened compound. Using GC-MS-IR analysis, the single coumarin 3,4-epoxide product was identified as o-hydroxyphenylacetaldehyde (o-HPA). Although other investigators have suggested that 3-hydroxycoumarin is an intermediate in o-HPA formation from coumarin 3,4-epoxide, we have demonstrated that 3-hydroxycoumarin, incubated in an aqueous system or with liver microsomal proteins, does not form o-HPA. Thus, the results of the present work establish that coumarin 3,4-epoxide can be synthesized and that o-HPA, which has previously been shown to be a prominent coumarin metabolite in rat liver microsomal incubations, is formed directly from coumarin 3,4-epoxide. These

  15. Imide modified epoxy matrix resins

    NASA Technical Reports Server (NTRS)

    Scola, D. A.

    1984-01-01

    The results of a program designed to develop tough imide modified epoxy resins cured by bisimide amine (BIA) hardeners are described. State-of-the-art epoxides MY720 and DER383 were used, and four bismide amines were evaluated. These were the BIA's derived from the 6F anhydride (4,4'-(hexafluoroisopropylidene) bis(phthalic anhydride) and the diamines 3,3'-diaminodiphynyl sulfone, 4,4'-oxygianiline, 4,4'-methylene dianiline, and 1,12-dodecane diamine. A key intermediate, designated 6F anhydride, is required for the synthesis of the bisimide amines. Reaction parameters to synthesize a precursor to the 6F anhydride (6FHC) in high yields were investigated. The catalyst trifluoromethane sulfonic acid was studied. Although small scale runs yielded the 6FHC in 50 percent yield, efforts to ranslate these results to a larger scale synthesis gave the 6FHC in only 9 percent yield. Results show that the concept of using bisimide amine as curing agents to improve the toughness properties of epoxies is valid.

  16. Diversity and Biocatalytic Potential of Epoxide Hydrolases Identified by Genome Analysis†

    PubMed Central

    van Loo, Bert; Kingma, Jaap; Arand, Michael; Wubbolts, Marcel G.; Janssen, Dick B.

    2006-01-01

    Epoxide hydrolases play an important role in the biodegradation of organic compounds and are potentially useful in enantioselective biocatalysis. An analysis of various genomic databases revealed that about 20% of sequenced organisms contain one or more putative epoxide hydrolase genes. They were found in all domains of life, and many fungi and actinobacteria contain several putative epoxide hydrolase-encoding genes. Multiple sequence alignments of epoxide hydrolases with other known and putative α/β-hydrolase fold enzymes that possess a nucleophilic aspartate revealed that these enzymes can be classified into eight phylogenetic groups that all contain putative epoxide hydrolases. To determine their catalytic activities, 10 putative bacterial epoxide hydrolase genes and 2 known bacterial epoxide hydrolase genes were cloned and overexpressed in Escherichia coli. The production of active enzyme was strongly improved by fusion to the maltose binding protein (MalE), which prevented inclusion body formation and facilitated protein purification. Eight of the 12 fusion proteins were active toward one or more of the 21 epoxides that were tested, and they converted both terminal and nonterminal epoxides. Four of the new epoxide hydrolases showed an uncommon enantiopreference for meso-epoxides and/or terminal aromatic epoxides, which made them suitable for the production of enantiopure (S,S)-diols and (R)-epoxides. The results show that the expression of epoxide hydrolase genes that are detected by analyses of genomic databases is a useful strategy for obtaining new biocatalysts. PMID:16597997

  17. Reduced sensitizing capacity of epoxy resin systems: a structure-activity relationship study.

    PubMed

    Niklasson, Ida B; Broo, Kerstin; Jonsson, Charlotte; Luthman, Kristina; Karlberg, Ann-Therese

    2009-11-01

    Epoxy resins can be prepared from numerous chemical compositions. Until recently, alternatives to epoxy resins based on diglycidyl ethers of bisphenol A (DGEBA) or bisphenol F (DGEBF) monomers have not received commercial interest, but are presently doing so, as epoxy resins with various properties are desired. Epoxy resin systems are known to cause allergic contact dermatitis because of contents of uncured monomers, reactive diluents, and hardeners. Reactive diluents, for example, glycidyl ethers, which also contain epoxide moieties, are added to reduce viscosity and improve polymerization. We have investigated the contact allergenic properties of a series of six analogues to phenyl glycidyl ether (PGE), all with similar basic structures but with varying carbon chain lengths and degrees of saturation. The chemical reactivity of the compounds in the test series toward the hexapeptide H-Pro-His-Cys-Lys-Arg-Met-OH was investigated. All epoxides were shown to bind covalently to both cysteine and proline residues. The percent depletion of nonreacted peptide was also studied resulting in 88% depletion when using PGE and 46% when using butyl glycidyl ether (5) at the same time point, thus revealing a large difference between the fastest and the slowest reacting epoxide. The skin sensitization potencies of the epoxides using the murine local lymph node assay (LLNA) were evaluated in relation to the observed physicochemical and reactivity properties. To enable determination of statistical significance between structurally closely related compounds, a nonpooled LLNA was performed. It was found that the compounds investigated ranged from strong to weak sensitizers, congruent with the reactivity data, indicating that even small changes in chemical structure result in significant differences in sensitizing capacity.

  18. Immunohistochemical study of epoxide hydrolase induced by trichloroethylene in rat liver

    SciTech Connect

    Kawamoto, T.; Hobara, T.; Ogino, K.; Takemoto, T.; Nakamura, K.; Imamura, A.; Koshiro, A.; Kobayashi, H.; Iwamoto, S.; Sakai, T.

    1987-10-01

    Epoxide hydrolase catalyzes the hydrolation of potentially toxic, electrophilic epoxides that are often generated during cytochrome P-450 catalyzed monooxigenation, forming the corresponding transdihydrodiols. It is well-known that trichloroethylene is metabolized by cytochrome P-450 containing mixed-function oxidase systems to trichloroethylene oxide, which decomposes to other metabolites. As trichloroethylene is an epoxide, epoxide hydrolase is suspected to catalyze the hydrolation of trichloroethylene oxide. No reports have appeared about the relationship between trichloroethylene and epoxide hydrolase. In this report, the authors studied the effect of trichloroethylene on epoxide hydrolase immunohistochemically.

  19. Asymmetric catalysis of epoxide ring-opening reactions.

    PubMed

    Jacobsen, E N

    2000-06-01

    The discovery of the metal salen-catalyzed asymmetric ring-opening (ARO) of epoxides is chronicled. A screening approach was adopted for the identification of catalysts for the addition of TMSN(3) to meso-epoxides, and the chiral (salen)CrN(3) complex was identified as optimal. Kinetic and structural studies served to elucidate the mechanism of catalysis, which involves cooperative activation of both epoxide and azide by two different metal centers. Covalently linked bimetallic complexes were constructed on the basis of this insight, and shown to catalyze the ARO with identical enantioselectivity but 1-2 orders of magnitude greater reactivity than the monomeric analogues. Extraordinarily high selectivity is observed in the kinetic resolution of terminal epoxides using the (salen)CrN(3)/TMSN(3) system. A search for a practical method for the kinetic resolution reaction led to the discovery of highly enantiomer-selective hydrolytic ring-opening using the corresponding (salen)Co(III) catalyst. This system displays extraordinary substrate generality, and allows practical access to enantiopure terminal epoxides on both laboratory and industrial scales.

  20. Resin-Powder Dispenser

    NASA Technical Reports Server (NTRS)

    Standfield, Clarence E.

    1994-01-01

    Resin-powder dispenser used at NASA's Langley Research Center for processing of composite-material prepregs. Dispenser evenly distributes powder (resin polymer and other matrix materials in powder form) onto wet uncured prepregs. Provides versatility in distribution of solid resin in prepreg operation. Used wherever there is requirement for even, continuous distribution of small amount of powder.

  1. Lithium BINOL Phosphate Catalyzed Desymmetrization of meso-Epoxides with Aromatic Thiols

    PubMed Central

    2015-01-01

    A highly enantioselective method for desymmetrization of meso-epoxides using thiols is reported. This is the first example of epoxide activation achieved using metal BINOL phosphates. The reaction has a broad scope in terms of epoxide substrates and aromatic thiol nucleophiles. The resulting β-hydroxyl sulfides are obtained in excellent yield and enantioselectivity. PMID:25317934

  2. 40 CFR 721.10210 - Soybean oil, epoxidized, reaction products with diethanolamine.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Soybean oil, epoxidized, reaction... Significant New Uses for Specific Chemical Substances § 721.10210 Soybean oil, epoxidized, reaction products... chemical substance identified as soybean oil, epoxidized, reaction products with diethanolamine (PMN...

  3. 40 CFR 721.10210 - Soybean oil, epoxidized, reaction products with diethanolamine.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Soybean oil, epoxidized, reaction... Significant New Uses for Specific Chemical Substances § 721.10210 Soybean oil, epoxidized, reaction products... chemical substance identified as soybean oil, epoxidized, reaction products with diethanolamine (PMN...

  4. 40 CFR 721.10210 - Soybean oil, epoxidized, reaction products with diethanolamine.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Soybean oil, epoxidized, reaction... Significant New Uses for Specific Chemical Substances § 721.10210 Soybean oil, epoxidized, reaction products... chemical substance identified as soybean oil, epoxidized, reaction products with diethanolamine (PMN...

  5. 40 CFR 721.10210 - Soybean oil, epoxidized, reaction products with diethanolamine.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Soybean oil, epoxidized, reaction... Significant New Uses for Specific Chemical Substances § 721.10210 Soybean oil, epoxidized, reaction products... chemical substance identified as soybean oil, epoxidized, reaction products with diethanolamine (PMN...

  6. Formation of furan fatty alkyl esters from their bis-epoxide fatty esters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Epoxidation of vegetable oils and consecutive epoxide ring-opening reaction is a widely investigated path for producing biobased lubricants and polymers. The reaction mechanism and products are considered well-studied and known. In the current study, the reactions of epoxidized alkyl soyate with fou...

  7. Sulfuric acid as a catalyst for ring-opening of biobased bis-epoxides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetable oils can be relatively and easily transformed into bio-based epoxides. Because of this, the acid-catalyzed epoxide ring-opening has been explored for the preparation of bio-based lubricants and polymers. Detailed model studies are carried out only with mono-epoxide made from methyl oleate,...

  8. Soluble epoxide hydrolase: Gene structure, expression and deletion

    PubMed Central

    Harris, Todd R.; Hammock, Bruce D.

    2013-01-01

    Mammalian soluble epoxide hydrolase (sEH) converts epoxides to their corresponding diols through the addition of a water molecule. sEH readily hydrolyzes lipid signaling molecules, including the epoxyeicosatrienoic acids (EETs), epoxidized lipids produced from arachidonic acid by the action of cytochrome p450s. Through its metabolism of the EETs and other lipid mediators, sEH contributes to the regulation of vascular tone, nociception, angiogenesis and the inflammatory response. Because of its central physiological role in disease states such as cardiac hypertrophy, diabetes, hypertension, and pain sEH is being investigated as a therapeutic target. This review begins with a brief introduction to sEH protein structure and function. sEH evolution and gene structure are then discussed before human small nucleotide polymorphisms and mammalian gene expression are described in the context of several disease models. The review ends with an overview of studies that have employed the sEH knockout mouse model. PMID:23701967

  9. Epoxidation of propylene dimers and isomerization of mixtures obtained

    SciTech Connect

    Dobrev, D.M.; Kurtev, K.S.

    1988-05-10

    Mixtures of hexenes are obtained in the dimerization of propylene on a Ziegler catalyst. By the epoxidation of this mixture by organic peroxides, followed by isomerization of the oxides, C/sub 6/ ketones, which are used as solvents, can be obtained. The hexenes were obtained by dimerization of propylene in the presence of a Ni(C/sub 5/H/sub 7/O/sub 2/)/sub 2/-P(C/sub 6/H/sub 5/)/sub 3/-(C/sub 3/H/sub 5/)/sub 2/AlCl catalytic system. The epoxidation was carried with technical grade isopropylbenzyl hydroperoxide (IPBHP). MoO/sub 2/(C/sub 5/H/sub 7/O/sub 2/)/sub 2/ was used as the catalyst. The relative rates of epoxidation of different isomers contained in the dimeric fraction, with respect to 2-methyl-1-pentene, was determined by means of competing reactions.

  10. Reinforcing polymer composites with epoxide-grafted carbon nanotubes.

    PubMed

    Wang, Shiren; Liang, Richard; Wang, Ben; Zhang, Chuck

    2008-02-27

    An in situ functionalization method was used to graft epoxide onto single-walled carbon nanotubes (SWNTs) and improve the integration of SWNTs into epoxy polymer. The characterization results of Raman, FT-IR and transmission electron microscopy (TEM) validated the successful functionalization with epoxide. These functionalized SWNTs were used to fabricate nanocomposites, resulting in uniform dispersion and strong interfacial bonding. The mechanical test demonstrated that, with only 1 wt% loading of functionalized SWNTs, the tensile strength of nanocomposites was improved by 40%, and Young's modulus by 60%.These results suggested that efficient load transfer has been achieved through epoxide-grafting. This investigation provided an efficient way to improve the interfacial bonding of multifunctional high-performance nanocomposites for lightweight structure material applications.

  11. Biocatalytic Synthesis of Epoxy Resins from Fatty Acids as a Versatile Route for the Formation of Polymer Thermosets with Tunable Properties.

    PubMed

    Torron, Susana; Semlitsch, Stefan; Martinelle, Mats; Johansson, Mats

    2016-12-12

    The work herein presented describes the synthesis and polymerization of series of bio-based epoxy resins prepared through lipase catalyzed transesterification. The epoxy-functional polyester resins with various architectures (linear, tri-branched, and tetra-branched) were synthesized through condensation of fatty acids derived from epoxidized soybean oil and linseed oil with three different hydroxyl cores under bulk conditions. The selectivity of the lipases toward esterification/transesterification reactions allowed the formation of macromers with up to 12 epoxides in the backbone. The high degree of functionality of the resins resulted in polymer thermosets with Tg values ranging from -25 to over 100 °C prepared through cationic polymerization. The determining parameters of the synthesis and the mechanism for the formation of the species were determined through kinetic studies by (1)H NMR, SEC, and molecular modeling studies. The correlation between macromer structure and thermoset properties was studied through real-time FTIR measurements, DSC, and DMA.

  12. Analogues of the epoxy resin monomer diglycidyl ether of bisphenol F: effects on contact allergenic potency and cytotoxicity.

    PubMed

    O'Boyle, Niamh M; Delaine, Tamara; Luthman, Kristina; Natsch, Andreas; Karlberg, Ann-Therese

    2012-11-19

    Diglycidyl ethers of bisphenol A (DGEBA) and bisphenol F (DGEBF) are widely used as components in epoxy resin thermosetting products. They are known to cause occupational and nonoccupational allergic contact dermatitis. The aim of this study is to investigate analogues of DGEBF with regard to contact allergy and cytotoxicity. A comprehensive knowledge of the structural features that contribute to the allergenic and cytotoxic effects of DGEBF will guide the development of future novel epoxy resin systems with reduced health hazards for those coming into contact with them. It was found that the allergenic effects of DGEBF were dependent on its terminal epoxide groups. In contrast, it was found that the cytotoxicity in monolayer cell culture was dependent not only on the presence of epoxide groups but also on other structural features.

  13. Multicomponent linchpin couplings. Reaction of dithiane anions with terminal epoxides, epichlorohydrin, and vinyl epoxides: efficient, rapid, and stereocontrolled assembly of advanced fragments for complex molecule synthesis.

    PubMed

    Smith, Amos B; Pitram, Suresh M; Boldi, Armen M; Gaunt, Matthew J; Sfouggatakis, Chris; Moser, William H

    2003-11-26

    The development, application, and advantages of a one-flask multicomponent dithiane linchpin coupling protocol, over the more conventional stepwise addition of dithiane anions to electrophiles leading to the rapid, efficient, and stereocontrolled assembly of highly functionalized intermediates for complex molecule synthesis, are described. Competent electrophiles include terminal epoxides, epichlorohydrin, and vinyl epoxides. High chemoselectivity can be achieved with epichlorohydrin and vinyl epoxides. For vinyl epoxides, the steric nature of the dithiane anion is critical; sterically unencumbered dithiane anions afford S(N)2 adducts, whereas encumbered anions lead primarily to SN2' adducts. Mechanistic studies demonstrate that the SN2' process occurs via syn addition to the vinyl epoxide. Integration of the multicomponent tactic with epichlorohydrin and vinyl epoxides permits the higher-order union of four and five components.

  14. Cure reaction of epoxy resins catalyzed by graphite-based nanofiller

    NASA Astrophysics Data System (ADS)

    Corcione, C. Esposito; Acocella, Maria Rosaria; Giuri, Antonella; Maffezzoli, Alfonso; Guerra, Gaetano

    2015-12-01

    A significant effort was directed to the synthesis of graphene stacks/epoxy nanocomposites and to the analysis of the effect of a graphene precursor on cure reaction of a model epoxy matrix. A comparative thermal analysis of epoxy resins filled with an exfoliated graphite oxide eGO were conducted. The main aim was to understand the molecular origin of the influence of eGO on the Tg of epoxy resins. The higher Tg values previously observed for low curing temperatures, for epoxy resins with graphite-based nanofillers, were easily rationalized by a catalytic activity of graphitic layers on the reaction between the epoxy and amine groups of the resin, which leads to higher crosslinking density in milder conditions. A kinetic analysis of the cure mechanism of the epoxy resin associated to the catalytical activity of the graphite based filler was performed by isothermal DSC measurements. The DSC results showed that the addition of graphite based filler greatly increased the enthalpy of epoxy reaction and the reaction rate, confirming the presence of a catalytic activity of graphitic layers on the crosslinking reaction between the epoxy resin components (epoxide oligomer and di-amine). A kinetic modelling analysis, arising from an auto-catalyzed reaction mechanism, was finally applied to isothermal DSC data, in order to predict the cure mechanism of the epoxy resin in presence of the graphite based nanofiller.

  15. Lutein epoxide cycle, more than just a forest tale

    PubMed Central

    Becerril, José María; García-Plazaola, José Ignacio

    2009-01-01

    Two xanthophyll cycles have been described in higher plants: the ubiquitous violaxanthin (V) cycle and the taxonomically restricted lutein epoxide (Lx) cycle. Both involve the light induced de-epoxidation of an epoxidated xanthophyll (V or Lx) and the epoxidation back in the dark. Evolutionary trends and function of the Lx cycle are still not clear. Up to nowadays, significant amounts of Lx have been found in several unrelated taxa, but it is a character almost exclusive from woody plants (except in the case of the parasitic plant Cuscuta reflexa). We have found an exception to this pattern in Cucumis sativus L., which showed high concentrations of Lx. Since Lx cycle was operative in leaves and cotyledons of this species and Lx concentration were much higher in cotyledons than in leaves, we speculate a role for the early stages of development. To date, this species is the first herbaceous non-parasitic species with operative Lx cycle. Since this species can be much more easily and rapidly grown and investigated than woody plants, these data can open new horizons and new lines of investigation for Lx cycle. PMID:19794858

  16. ULTRASOUND-ASSISTED ORGANIC SYNTHESIS: ALCOHOL OXIDATION AND OLEFIN EPOXIDATION

    EPA Science Inventory

    Ultrasound-assisted Organic Synthesis: Alcohol Oxidation and Olefin Epoxidation

    Unnikrishnan R Pillai, Endalkachew Sahle-Demessie , Vasudevan Namboodiri, Quiming Zhao, Juluis Enriquez
    U.S. EPA , 26 W. Martin Luther King Dr. , Cincinnati, OH 45268
    Phone: 513-569-773...

  17. Hydrolytic and aminolytic kinetic resolution of terminal bis-epoxides.

    PubMed

    Bredihhina, Jevgenia; Villo, Piret; Andersons, Kārlis; Toom, Lauri; Vares, Lauri

    2013-03-15

    Hydrolytic and aminolytic kinetic resolution of terminal bis-epoxides catalyzed by (salen)Co(III) complexes affords epoxy-diols and N-protected epoxy-amino alcohols with excellent enantio- and diastereoselectivity and good yields. An operationally simple procedure gives instant access to valuable building blocks containing two remote stereocenters in highly enantioenriched form.

  18. Novel microbial epoxide hydrolases for biohydrolysis of glycidyl derivatives.

    PubMed

    Kotik, Michael; Brichac, Jiri; Kyslík, Pavel

    2005-12-06

    Microbial isolates from biofilters and petroleum-polluted bioremediation sites were screened for the presence of enantioselective epoxide hydrolases active towards tert-butyl glycidyl ether, benzyl glycidyl ether, and allyl glycidyl ether. Out of 270 isolated strains, which comprised bacteria, yeasts, and filamentous fungi, four were selected based on the enantioselectivities of their epoxide hydrolases determined in biotransformation reactions. The enzyme of Aspergillus niger M200 preferentially hydrolyses (S)-tert-butyl glycidyl ether to (S)-3-tert-butoxy-1,2-propanediol with a relatively high enantioselectivity (the enantiomeric ratio E is about 30 at a reaction temperature of 28 degrees C). Epoxide hydrolases of Rhodotorula mucilaginosa M002 and Rhodococcus fascians M022 hydrolyse benzyl glycidyl ether with relatively low enantioselectivities, the former reacting predominantly with the (S)-enantiomer, the latter preferring the (R)-enantiomer. Enzymatic hydrolysis of allyl glycidyl ether by Cryptococcus laurentii M001 proceeds with low enantioselectivity (E=3). (R)-tert-Butyl glycidyl ether with an enantiomeric excess (ee) of over 99%, and (S)-3-tert-butoxy-1,2-propanediol with an ee-value of 86% have been prepared on a gram-scale using whole cells of A. niger M200. An enantiomeric ratio of approximately 100 has been determined under optimised biotransformation conditions with the partially purified epoxide hydrolase from A. niger M200. The regioselectivity of this enzyme was determined to be total for both (S)-tert-butyl glycidyl ether and (R)-tert-butyl glycidyl ether.

  19. DEVELOPMENT OF METABOLICALLY STABLE INHIBITORS OF MAMMALIAN MICROSOMAL EPOXIDE HYDROLASE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The microsomal epoxide hydrolase (mEH) plays a significant role in the metabolism of xenobiotics such as polyaromatic toxicants. Additionally, polymorphism studies have underlined a potential role of this enzyme in relation to a number of diseases, such as emphysema, spontaneous abortion, eclampsia ...

  20. Ring-opening Polymerization of Epoxidized Soybean Oil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ring opening polymerization of epoxidized soybean oil (ESO) initiated by boron trifluoride diethyl etherate, (BF3•OEt2), in methylene chloride was conducted in an effort to develop useful biodegradable polymers. The resulting polymers (PESO) were characterized using Infrared (IR), differential scan...

  1. Diastereoselective Synthesis of Diketopiperazine Bis-α,β-Epoxides

    PubMed Central

    Ando, Shin; Grote, Amy L.; Koide, Kazunori

    2011-01-01

    Functionalized diketopiperazines (a.k.a. dioxopiperazines) are an important class of molecules in medicinal chemistry and material science. Herein we report a diastereoselective synthesis of diketopiperazine bis-α,β-epoxides via the oxidation of exocyclic olefins. Although six diastereomers may be formed by this approach, only one or two of them were observed. PMID:21250704

  2. Biotransformation of the double bond in allyl glycidyl ether to an epoxide ring. Evidence from hemoglobin adducts in mice.

    PubMed

    Pérez, H L; Osterman-Golkar, S

    2000-02-15

    Allyl glycidyl ether (AGE) is used industrially in the production of various epoxy resins. The compound is mutagenic and evidence for carcinogenicity in mice and rats has been reported. A previous study in mice showed that AGE reacts directly, without metabolic activation, with N-terminal valine in hemoglobin to form adducts (AGEVal). Metabolism of AGE may lead to formation of diglycidyl ether (I) through epoxidation of the double bond or 1-allyloxy-2,3-dihydroxypropane (II) through hydrolysis of the epoxide ring. 2,3-Dihydroxypropyl glycidyl ether (III) may be formed either by hydrolysis of I or epoxidation of II. The main aim of the present study was to investigate if AGE is metabolized to the reactive epoxides I or III by analysis of adducts with hemoglobin. Nine male mice (C3H/Hej) were administered AGE dissolved in tricaprylin, 4 mg/mouse, by intraperitoneal (i.p.) injection. Eleven male mice were administered 4 mg/mouse of AGE dissolved in acetone, by skin application. Adducts of I or III with N-terminal valine, N-(2-hydroxy-3-(2,3-dihydroxy)propyloxy)propylvaline (diOHPrGEVal), were demonstrated in mice administered AGE by i.p. injection. The levels were in the range 1600-5600 pmol/g globin. The level of diOHPrGEVal in mice administered AGE by skin application (n = 5) was below the detection limit of the analytical method, 20 pmol/g globin. The level of AGEVal, analyzed in mice administered AGE by skin application (n = 6), was about 20 pmol/g globin (median value), as compared with 1600 pmol/g globin previously found in mice administered AGE by i.p. injection. Neither AGEVal nor diOHPrGEVal were detected in control animals. Both adducts were analyzed using a modified Edman method for derivatization and using gas chromatography/tandem mass spectrometry for detection. The hydroxyl groups of the Edman derivative of diOHPrGEVal were protected by acetylation.

  3. Effect of epoxidation level on thermal properties and ionic conductivity of epoxidized natural rubber solid polymer nanocomposite electrolytes

    NASA Astrophysics Data System (ADS)

    Harun, Fatin; Chan, Chin Han; Sim, Lai Har; Winie, Tan; Zainal, Nurul Fatahah Asyqin

    2015-08-01

    Effect of epoxide content on the thermal and conductivity properties of epoxidized natural rubber (ENR) solid polymer nanocomposite electrolytes was investigated. Commercial available epoxidized natural rubber having 25 (ENR25) and 50 mole% (ENR50) epoxide, respectively were incorporated with lithium perchlorate (LiClO4) salt and titanium dioxide (TiO2) nanofiller via solution casting method. The solid polymer nanocomposite electrolytes were characterized by differential scanning calorimetry (DSC) and impedance spectroscopy (IS) for their thermal properties and conductivity, respectively. It was evident that introduction of LiClO4 causes a greater increase in glass transition temperature (Tg) and ionic conductivity of ENR50 as compared to ENR25. Upon addition of TiO2 in ENR/LiClO4 system, a remarkable Tg elevation was observed for both ENRs where ENR50 reveals a more pronounced changes. It is interesting to note that they exhibit different phenomenon in ionic conductivity with TiO2 loading where ENR25 shows enhancement of conductivity while ENR50 shows declination.

  4. Effect of epoxidation level on thermal properties and ionic conductivity of epoxidized natural rubber solid polymer nanocomposite electrolytes

    SciTech Connect

    Harun, Fatin; Chan, Chin Han; Winie, Tan; Sim, Lai Har; Zainal, Nurul Fatahah Asyqin

    2015-08-28

    Effect of epoxide content on the thermal and conductivity properties of epoxidized natural rubber (ENR) solid polymer nanocomposite electrolytes was investigated. Commercial available epoxidized natural rubber having 25 (ENR25) and 50 mole% (ENR50) epoxide, respectively were incorporated with lithium perchlorate (LiClO{sub 4}) salt and titanium dioxide (TiO{sub 2}) nanofiller via solution casting method. The solid polymer nanocomposite electrolytes were characterized by differential scanning calorimetry (DSC) and impedance spectroscopy (IS) for their thermal properties and conductivity, respectively. It was evident that introduction of LiClO{sub 4} causes a greater increase in glass transition temperature (T{sub g}) and ionic conductivity of ENR50 as compared to ENR25. Upon addition of TiO{sub 2} in ENR/LiClO{sub 4} system, a remarkable T{sub g} elevation was observed for both ENRs where ENR50 reveals a more pronounced changes. It is interesting to note that they exhibit different phenomenon in ionic conductivity with TiO{sub 2} loading where ENR25 shows enhancement of conductivity while ENR50 shows declination.

  5. Polyester Resin Hazards

    PubMed Central

    Bourne, L. B.; Milner, F. J. M.

    1963-01-01

    Polyester resins are being increasingly used in industry. These resins require the addition of catalysts and accelerators. The handling of polyester resin system materials may give rise to skin irritations, allergic reactions, and burns. The burns are probably due to styrene and organic peroxides. Atmospheric pollution from styrene and explosion and fire risks from organic peroxides must be prevented. Where dimethylaniline is used scrupulous cleanliness and no-touch technique must be enforced. Handling precautions are suggested. Images PMID:14014495

  6. Expanded graphite—Phenolic resin composites based double layer microwave absorber for X-band applications

    NASA Astrophysics Data System (ADS)

    Gogoi, Jyoti Prasad; Bhattacharyya, Nidhi Saxena

    2014-11-01

    In this investigation, double layer microwave absorbers are designed and developed with paired combination of 5 wt. %, 7 wt. %, 8 wt. %, and 10 wt. % expanded graphite-novolac phenolic resin (EG-NPR) composites, in the frequency range of 8.2-12.4 GHz. The thickness and compositional combination of the two layers constituting the absorber are optimized to achieve minimum value of reflection loss (dB) and a broad microwave absorption bandwidth. Double layer combinations showing -25 dB absorption bandwidth >2 GHz and -30 dB absorption bandwidth >1 GHz are chosen for fabrication. The total thickness of the fabricated double layer microwave absorber is varied from 3 mm to 3.4 mm. Absorption bandwidths at -10 dB, -20 dB, -25 dB and -30 dB are determined for the fabricated structure. The maximum -25 dB and -30 dB absorption bandwidth of 2.47 GHz and 1.77 GHz, respectively, are observed for the double layer structure with (5 wt. %-8 wt. %) EG-NPR composites with total thickness of 3.2 mm, while -10 dB bandwidth covers the entire X-band range.

  7. Identification and characterization of a new epoxide hydrolase from mouse liver microsomes.

    PubMed

    Guenthner, T M; Oesch, F

    1983-12-25

    A new microsomal epoxide hydrolase (mEH2) has been identified and characterized. This enzyme has properties which distinguish it from previously described cytosolic (cEH) or membrane-bound (mEH1) epoxide hydrolases. The enzyme is an integral microsomal protein which is not dissociated from the membrane by repeated washing, high ionic strength salt, or chaotropic agent solutions, or by sonication. It is very different from the normally described microsomal epoxide hydrolase (mEH1) as shown by its different substrate specificity and kinetic properties and by immunological criteria. In contrast to the hitherto described microsomal epoxide hydrolase, mEH1, the new enzyme effectively catalyzes the hydration of transdisubstituted oxiranes such as trans-stilbene oxide and trans-beta-ethyl styrene oxide and has no appreciable activity toward benzo(a)pyrene 4,5-oxide. It is also structurally distinct, in that it does not cross-react with antibodies raised against the normally described microsomal epoxide hydrolase mEH1. This newly described microsomal epoxide hydrolase probably represents an important factor in the control of reactive epoxides; its location in the membrane ensures access to lipophilic epoxides generated by membrane-bound monooxygenases, and its substrate specificity is such that it can hydrolyze epoxides poorly metabolized by the previously described microsomal epoxide hydrolase.

  8. Modeling Epoxidation of Drug-like Molecules with a Deep Machine Learning Network

    PubMed Central

    2015-01-01

    Drug toxicity is frequently caused by electrophilic reactive metabolites that covalently bind to proteins. Epoxides comprise a large class of three-membered cyclic ethers. These molecules are electrophilic and typically highly reactive due to ring tension and polarized carbon–oxygen bonds. Epoxides are metabolites often formed by cytochromes P450 acting on aromatic or double bonds. The specific location on a molecule that undergoes epoxidation is its site of epoxidation (SOE). Identifying a molecule’s SOE can aid in interpreting adverse events related to reactive metabolites and direct modification to prevent epoxidation for safer drugs. This study utilized a database of 702 epoxidation reactions to build a model that accurately predicted sites of epoxidation. The foundation for this model was an algorithm originally designed to model sites of cytochromes P450 metabolism (called XenoSite) that was recently applied to model the intrinsic reactivity of diverse molecules with glutathione. This modeling algorithm systematically and quantitatively summarizes the knowledge from hundreds of epoxidation reactions with a deep convolution network. This network makes predictions at both an atom and molecule level. The final epoxidation model constructed with this approach identified SOEs with 94.9% area under the curve (AUC) performance and separated epoxidized and non-epoxidized molecules with 79.3% AUC. Moreover, within epoxidized molecules, the model separated aromatic or double bond SOEs from all other aromatic or double bonds with AUCs of 92.5% and 95.1%, respectively. Finally, the model separated SOEs from sites of sp2 hydroxylation with 83.2% AUC. Our model is the first of its kind and may be useful for the development of safer drugs. The epoxidation model is available at http://swami.wustl.edu/xenosite. PMID:27162970

  9. Incombustible resin composition

    NASA Technical Reports Server (NTRS)

    Akima, T.

    1982-01-01

    Incombustible resin compositions composed of aromatic compounds were obtained through (1) combustion polymer material and (2) bisphenol A or halogenated bisphenol A and bisphenol A diglycidl ether or halogenated bisphenol A diglycidyl ether. The aromatic compound is an adduct of bifunctional phenols and bifunctional epoxy resins.

  10. Delayed cure bismaleimide resins

    DOEpatents

    Not Available

    1982-08-12

    Prior art polybismaleimides begin to polymerize at or just above the melting point of the monomer. This patent describes new bismaleimide resins which have an increased pot life and provide longer time periods in which the monomer remains fluid. The resins can be polymerized into molded articles with a high uniformity of properties. (DLC)

  11. Acute and chronic toxicity toward the bacteria Vibrio fischeri of organic narcotics and epoxides: structural alerts for epoxide excess toxicity.

    PubMed

    Blaschke, Ulrike; Paschke, Albrecht; Rensch, Ines; Schüürmann, Gerrit

    2010-12-20

    The acute and chronic bacterial toxicity of 34 organic compounds comprising 19 baseline narcotics and 15 epoxides has been determined with regard to 30-min bioluminescence and 24-h growth inhibition in terms of EC50 (effective concentration 50%) values employing Vibrio fischeri. For the narcotics, linear regression of log EC50 on log Kow (octanol/water partition coefficient) yields r2 (squared correlation coefficient) and rms (root-mean-square error) values of 0.95 and 0.44 (30-min), and 0.94 and 0.34 (24-h), respectively. Employing the resultant baseline narcosis models, toxicity enhancement (Te) values were derived as a ratio of narcosis-predicted over experimental EC50 for the epoxides. For seven aliphatic epoxides, log Te was below 1 in both assays, indicating narcosis-range toxicity with regard to 30-min bioluminescence and 24-h growth inhibition. Concerning eight nonaliphatic epoxides, log Te values up to 2.4 were observed, reflecting excess toxicity through an enhanced electrophilic reactivity of the compounds. Here, however, the intercorrelation between both assays was very low (r2 = 0.09). The results are discussed in terms of electronic substituent effects activating an SN2-type epoxide reaction with nucleophilic protein sites and side-chain activation offering alternative electrophile-nucleophile reaction routes at side-chain sites, leading to respective structural alerts as indicators of excess toxicity. Surprisingly, 30-min bioluminescence appears to be slightly more sensitive to chemical stress than 24-h growth, which holds both for baseline narcotics and for most of the epoxides. This is also reflected by effective narcosis doses 50%, ED50, of 7.1 mmol/kg (30-min) and 7.7 mmol/kg (24-h) estimated from narcosis theory. Keeping in mind the different end points (bioluminescence vs growth) involved, this finding demonstrates that chronic toxicity is not always more sensitive than acute toxicity, calling for analyses with regard to further respective

  12. Styrene-butadiene rubber/halloysite nanotubes composites modified by epoxidized natural rubber.

    PubMed

    Jia, Zhixin; Luo, Yuanfang; Yang, Shuyan; Du, Mingliang; Guo, Baochun; Jia, Demin

    2011-12-01

    The reinforcement effects of halloysite nanotubes on styrene-butadiene rubber and the modification effect of epoxidized natural rubber on styrene-butadiene rubber/halloysite nanotubes composites were studied. The structure, morphology and properties of styrene-butadiene rubber/halloysite nanotubes composites before and after the incorporation of epoxidized natural rubber were investigated. The results indicated that epoxidized natural rubber can promote the dispersion and orientation of halloysite nanotubes in styrene-butadiene rubber matrix at nanoscale and strengthen interfacial combination between halloysite nanotubes and styrene-butadiene rubber by the formation of covalent bonds and hydrogen bonds between epoxidized natural rubber and halloysite nanotubes. Consequently epoxidized natural rubber can improve the mechanical properties of the vulcanizates of styrene-butadiene rubber/halloysite nanotubes composites. Besides epoxidized natural rubber can decrease the rolling resistance of the vulcanizates and increase the wet grip property of the vulcanizates.

  13. Asymmetric catalysis with water: efficient kinetic resolution of terminal epoxides by means of catalytic hydrolysis.

    PubMed

    Tokunaga, M; Larrow, J F; Kakiuchi, F; Jacobsen, E N

    1997-08-15

    Epoxides are versatile building blocks for organic synthesis. However, terminal epoxides are arguably the most important subclass of these compounds, and no general and practical method exists for their production in enantiomerically pure form. Terminal epoxides are available very inexpensively as racemic mixtures, and kinetic resolution is an attractive strategy for the production of optically active epoxides, given an economical and operationally simple method. Readily accessible synthetic catalysts (chiral cobalt-based salen complexes) have been used for the efficient asymmetric hydrolysis of terminal epoxides. This process uses water as the only reagent, no added solvent, and low loadings of a recyclable catalyst (<0.5 mole percent), and it affords highly valuable terminal epoxides and 1, 2-diols in high yield with high enantiomeric enrichment.

  14. Ionic Liquid Epoxy Resin Monomers

    NASA Technical Reports Server (NTRS)

    Paley, Mark S. (Inventor)

    2013-01-01

    Ionic liquid epoxide monomers capable of reacting with cross-linking agents to form polymers with high tensile and adhesive strengths. Ionic liquid epoxide monomers comprising at least one bis(glycidyl) N-substituted nitrogen heterocyclic cation are made from nitrogen heterocycles corresponding to the bis(glycidyl) N-substituted nitrogen heterocyclic cations by a method involving a non-nucleophilic anion, an alkali metal cation, epichlorohydrin, and a strong base.

  15. Direct Epoxidation of Propylene over Stabilized Cu+ Surface Sites on Ti Modified Cu2O

    DOE PAGES

    Yang, X.; Kattel, S.; Xiong, K.; ...

    2015-07-17

    Direct propylene epoxidation by O2 is a challenging reaction because of the strong tendency for complete combustion. Results from the current study demonstrate the feasibility to tune the epoxidation selectivity by generating highly dispersed and stabilized Cu+ active sites in a TiCuOx mixed oxide. The TiCuOx surface anchors the key surface intermediate, oxametallacycle, leading to higher selectivity for epoxidation of propylene.

  16. Isolation and characterization of Xenopus soluble epoxide hydrolase.

    PubMed

    Purba, Endang R; Oguro, Ami; Imaoka, Susumu

    2014-07-01

    Soluble epoxide hydrolase (sEH) contributes to cell growth, but the contribution of sEH to embryonic development is not well understood. In this study, Xenopus sEH cDNA was isolated from embryos of Xenopus laevis. The Xenopus sEH was expressed in Escherichia coli and was purified. The epoxide hydrolase and phosphatase activities of purified sEH were investigated. The Xenopus sEH did not show phosphatase activity toward 4-methylumbelliferyl phosphate or several lysophosphatidic acids although it had EH activity. The amino acid sequence of Xenopus sEH was compared with that reported previously. We found amino acid substitutions of the 29th Thr to Asn and the 146th Arg to His and prepared a sEH mutant (N29T/H146R), designed as mutant 1. Neither wild-type sEH nor mutant 1 had phosphatase activity. Additional substitution of the 11th Gly with Asp was found by comparison with human sEH which has phosphatase activity, but the Xenopus sEH mutant G11D prepared as mutant 2 did not have phosphatase activity. The epoxide hydrolase activity of sEH seemed to be similar to that of human sEH, while Xenopus sEH did not have phosphatase activity toward several substrates that human sEH metabolizes.

  17. Nickel-Catalyzed Regiodivergent Opening of Epoxides with Aryl Halides: Co-Catalysis Controls Regioselectivity

    PubMed Central

    Zhao, Yang; Weix, Daniel J.

    2014-01-01

    Epoxides are versatile intermediates in organic synthesis, but have rarely been employed in cross-coupling reactions. We report that bipyridine-ligated nickel can mediate the addition of functionalized aryl halides, a vinyl halide, and a vinyl triflate to epoxides under reducing conditions. For terminal epoxides, the regioselectivity of the reaction depends upon the co-catalyst employed. Iodide co-catalysis results in opening at the less hindered position via an iodohydrin intermediate. Titanocene co-catalysis results in opening at the more hindered position, presumably via TiIII-mediated radical generation. 1,2-Disubstituted epoxides are opened under both conditions to form predominantly the trans product. PMID:24341892

  18. Cytosolic and microsomal epoxide hydrolases are immunologically distinguishable from each other in the rat and mouse.

    PubMed

    Guenthner, T M; Hammock, B D; Vogel, U; Oesch, F

    1981-04-10

    Antibodies raised to homogeneous rat liver microsomal epoxide hydrolase were used to distinguish microsomal epoxide hydrolase from epoxide hydrolase of cytosolic origin in mice and rats. Using double diffusion analysis in agarose gels, we show that anti-rat liver microsomal epoxide hydrolase forms a single precipitin line with solubilized microsomes from rat and mouse liver, but no reaction is seen with the corresponding cytosolic fractions. Rat or mouse microsomal epoxide hydrolase activity (using benzo[a]pyrene 4,5-oxide as substrate) can be completely precipitated out of solubilized preparations by the antibody, which is equipotent against rat and mouse microsomal epoxide hydrolase. No precipitation of cytosolic hydrolase activity (using trans-beta-ethyl styrene oxide as substrate) is seen with any concentration of the antibody tested. Thus, in the case of microsomal epoxide hydrolase, extensive immunological cross-reactivity exists between the two species, rat and mouse. In contrast, no cross-reactivity is detectable between cytosolic and microsomal epoxide hydrolase, even when enzymes from the same species are compared. We conclude that microsomal and cytosolic epoxide hydrolase activities represent distinct and immunologically non-cross-reactive protein species.

  19. Direct observation of enantiomer discrimination of epoxides by chiral salen complexes using ENDOR.

    PubMed

    Fallis, Ian A; Murphy, Damien M; Willock, David J; Tucker, Richard J; Farley, Robert D; Jenkins, Robert; Strevens, Robert R

    2004-12-08

    Electron nuclear double resonance (ENDOR) spectroscopy was used to investigate the weak enantioselective binding between chiral salen complexes [VO(1)] ((R,R)- and (S,S)-vanadyl N,N'-bis(3,5-di-tert-butylsalcylidene)-1,2-cyclohexanediamine) and chiral epoxides (e.g., (R)-/(S)-propylene epoxide, 5) in frozen (10 K) solution. Differences in epoxide binding by enatiomers of [VO(1)] was evidenced by changes to the 1H epoxide derived peaks in the ENDOR spectra, such that (R,R)-[VO(1)] + (R)-5 and (R,R)-[VO(1)] + (S)-5 yield noticeably different spectra. These changes were assigned to the small structural differences between the diastereomeric metal-epoxide adducts. Simulation of the spectra revealed differences in the VO...1Hepoxide distances for the diastereomeric pairs, which was confirmed by a complementary set of density functional theory (DFT) calculations. While the epoxide molecule is very weakly coordinated, ENDOR measurements of the racemic complex in racemic epoxide nevertheless indicated the preferential coordination of the (R)-5 to (R,R)-[VO(1)] (likewise (S)-(5) to (S,S)-[VO(1)]), which is favored over the binding of (S)-5 epoxide to (R,R)-[VO(1)] (and likewise (R)-5 epoxide to (S,S)-[VO(1)]). This demonstrates the unique power of the ENDOR technique to resolve weak chiral interactions for which EPR spectroscopy alone lacks sufficient resolution.

  20. Biocidal quaternary ammonium resin

    NASA Technical Reports Server (NTRS)

    Janauer, G. E.

    1983-01-01

    Activated carbon (charcoal) and polymeric resin sorbents are widely used in the filtration and treatment of drinking water, mainly to remove dissolved organic and inorganic impurities and to improve the taste. Earlier hopes that activated carbon might "disinfect' water proved to be unfounded. The feasibility of protecting against microbial infestation in charcoal and resin beds such as those to be incorporated into total water reuse systems in spacecraft was investigated. The biocidal effect of IPCD (insoluable polymeric contact disinfectants) in combination with a representative charcoal was assessed. The ion exchange resins (IPCD) were shown to adequately protect charcoal and ion exchange beds.

  1. Biocompatibility of composite resins

    PubMed Central

    Mousavinasab, Sayed Mostafa

    2011-01-01

    Dental materials that are used in dentistry should be harmless to oral tissues, so they should not contain any leachable toxic and diffusible substances that can cause some side effects. Reports about probable biologic hazards, in relation to dental resins, have increased interest to this topic in dentists. The present paper reviews the articles published about biocompatibility of resin-restorative materials specially resin composites and monomers which are mainly based on Bis-GMA and concerns about their degradation and substances which may be segregated into oral cavity. PMID:23372592

  2. Biosynthesis, isolation, and NMR analysis of leukotriene A epoxides: substrate chirality as a determinant of the cis or trans epoxide configuration[S

    PubMed Central

    Jin, Jing; Zheng, Yuxiang; Boeglin, William E.; Brash, Alan R.

    2013-01-01

    Leukotriene (LT)A4 and closely related allylic epoxides are pivotal intermediates in lipoxygenase (LOX) pathways to bioactive lipid mediators that include the leukotrienes, lipoxins, eoxins, resolvins, and protectins. Although the structure and stereochemistry of the 5-LOX product LTA4 is established through comparison to synthetic standards, this is the exception, and none of these highly unstable epoxides has been analyzed in detail from enzymatic synthesis. Understanding of the mechanistic basis of the cis or trans epoxide configuration is also limited. To address these issues, we developed methods involving biphasic reaction conditions for the LOX-catalyzed synthesis of LTA epoxides in quantities sufficient for NMR analysis. As proof of concept, human 15-LOX-1 was shown to convert 15S-hydroperoxy-eicosatetraenoic acid (15S-HPETE) to the LTA analog 14S,15S-trans-epoxy-eicosa-5Z,8Z,10E,12E-tetraenoate, confirming the proposed structure of eoxin A4. Using this methodology we then showed that recombinant Arabidopsis AtLOX1, an arachidonate 5-LOX, converts 5S-HPETE to the trans epoxide LTA4 and converts 5R-HPETE to the cis epoxide 5-epi-LTA4, establishing substrate chirality as a determinant of the cis or trans epoxide configuration. The results are reconciled with a mechanism based on a dual role of the LOX nonheme iron in LTA epoxide biosynthesis, providing a rational basis for understanding the stereochemistry of LTA epoxide intermediates in LOX-catalyzed transformations. PMID:23242647

  3. Impact of a heteroatom in a structure-activity relationship study on analogues of phenyl glycidyl ether (PGE) from epoxy resin systems.

    PubMed

    Niklasson, Ida B; Delaine, Tamara; Luthman, Kristina; Karlberg, Ann-Therese

    2011-04-18

    Epoxy resins are among the most common causes of occupational contact dermatitis. They are normally used in so-called epoxy resin systems (ERS). These commercial products are combinations of epoxy resins, curing agents, modifiers, and reactive diluents. The most frequently used resins are diglycidyl ethers based on bisphenol A (DGEBA) and bisphenol F (DGEBF). In this study, we have investigated the contact allergenic properties of a series of analogues to the reactive diluent phenyl glycidyl ether (PGE), all with similar basic structures but with varying heteroatoms or with no heteroatom present. The chemical reactivity of the compounds in the test series toward the hexapeptide H-Pro-His-Cys-Lys-Arg-Met-OH was investigated. All epoxides were shown to bind covalently to both cysteine and proline residues. The percent depletion of nonreacted peptide was also studied resulting in ca. 60% depletion when using either PGE, phenyl 2,3-epoxypropyl sulfide (2), or N-(2,3-epoxypropyl)aniline (3), and only 15% when using 1,2-epoxy-4-phenylbutane (4) at the same time point. The skin sensitization potencies of the epoxides using the murine local lymph node assay (LLNA) were evaluated in relation to the observed physicochemical and reactivity properties. To enable determination of statistical significance between structurally closely related compounds, a nonpooled LLNA was performed. It was found that all investigated compounds containing a heteroatom in the α-position to the epoxide were strong sensitizers, congruent with the reactivity data, indicating that the impact of a heteroatom is crucial for the sensitizing capacity for this type of epoxides.

  4. Inhibition of soluble epoxide hydrolase modulates inflammation and autophagy in obese adipose tissue and liver: role for omega-3 epoxides.

    PubMed

    López-Vicario, Cristina; Alcaraz-Quiles, José; García-Alonso, Verónica; Rius, Bibiana; Hwang, Sung H; Titos, Esther; Lopategi, Aritz; Hammock, Bruce D; Arroyo, Vicente; Clària, Joan

    2015-01-13

    Soluble epoxide hydrolase (sEH) is an emerging therapeutic target in a number of diseases that have inflammation as a common underlying cause. sEH limits tissue levels of cytochrome P450 (CYP) epoxides derived from omega-6 and omega-3 polyunsaturated fatty acids (PUFA) by converting these antiinflammatory mediators into their less active diols. Here, we explored the metabolic effects of a sEH inhibitor (t-TUCB) in fat-1 mice with transgenic expression of an omega-3 desaturase capable of enriching tissues with endogenous omega-3 PUFA. These mice exhibited increased CYP1A1, CYP2E1, and CYP2U1 expression and abundant levels of the omega-3-derived epoxides 17,18-epoxyeicosatetraenoic acid (17,18-EEQ) and 19,20-epoxydocosapentaenoic (19,20-EDP) in insulin-sensitive tissues, especially liver, as determined by LC-ESI-MS/MS. In obese fat-1 mice, t-TUCB raised hepatic 17,18-EEQ and 19,20-EDP levels and reinforced the omega-3-dependent reduction observed in tissue inflammation and lipid peroxidation. t-TUCB also produced a more intense antisteatotic action in obese fat-1 mice, as revealed by magnetic resonance spectroscopy. Notably, t-TUCB skewed macrophage polarization toward an antiinflammatory M2 phenotype and expanded the interscapular brown adipose tissue volume. Moreover, t-TUCB restored hepatic levels of Atg12-Atg5 and LC3-II conjugates and reduced p62 expression, indicating up-regulation of hepatic autophagy. t-TUCB consistently reduced endoplasmic reticulum stress demonstrated by the attenuation of IRE-1α and eIF2α phosphorylation. These actions were recapitulated in vitro in palmitate-primed hepatocytes and adipocytes incubated with 19,20-EDP or 17,18-EEQ. Relatively similar but less pronounced actions were observed with the omega-6 epoxide, 14,15-EET, and nonoxidized DHA. Together, these findings identify omega-3 epoxides as important regulators of inflammation and autophagy in insulin-sensitive tissues and postulate sEH as a druggable target in metabolic

  5. Thermally stable laminating resins

    NASA Technical Reports Server (NTRS)

    Jones, R. J.; Vaughan, R. W.; Burns, E. A.

    1972-01-01

    Improved thermally stable laminating resins were developed based on the addition-type pyrolytic polymerization. Detailed monomer and polymer synthesis and characterization studies identified formulations which facilitate press molding processing and autoclave fabrication of glass and graphite fiber reinforced composites. A specific resin formulation, termed P10P was utilized to prepare a Courtaulds HMS reinforced simulated airfoil demonstration part by an autoclave molding process.

  6. Acetylene terminated matrix resins

    NASA Technical Reports Server (NTRS)

    Goldfarb, I. J.; Lee, Y. C.; Arnold, F. E.; Helminiak, T. E.

    1985-01-01

    The synthesis of resins with terminal acetylene groups has provided a promising technology to yield high performance structural materials. Because these resins cure through an addition reaction, no volatile by-products are produced during the processing. The cured products have high thermal stability and good properties retention after exposure to humidity. Resins with a wide variety of different chemical structures between the terminal acetylene groups are synthesized and their mechanical properties studied. The ability of the acetylene cured polymers to give good mechanical properties is demonstrated by the resins with quinoxaline structures. Processibility of these resins can be manipulated by varying the chain length between the acetylene groups or by blending in different amounts of reactive deluents. Processing conditions similar to the state-of-the-art epoxy can be attained by using backbone structures like ether-sulfone or bis-phenol-A. The wide range of mechanical properties and processing conditions attainable by this class of resins should allow them to be used in a wide variety of applications.

  7. Towards a General Understanding of Carbonyl‐Stabilised Ammonium Ylide‐Mediated Epoxidation Reactions

    PubMed Central

    Novacek, Johanna; Roiser, Lukas; Zielke, Katharina

    2016-01-01

    Abstract The key factors for carbonyl‐stabilised ammonium ylide‐mediated epoxidation reactions were systematically investigated by experimental and computational means and the hereby obtained energy profiles provide explanations for the observed experimental results. In addition, we were able to identify the first tertiary amine‐based chiral auxiliary that allows for high enantioselectivities and high yields for such epoxidation reactions. PMID:27381752

  8. 40 CFR 721.7210 - Epoxidized copolymer of phenol and substituted phenol.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Epoxidized copolymer of phenol and substituted phenol. 721.7210 Section 721.7210 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.7210 Epoxidized copolymer of phenol and substituted phenol. (a)...

  9. Inversion of product selectivity in an enzyme-inspired metallosupramolecular tweezer catalyzed epoxidation reaction†

    PubMed Central

    Ulmann, Pirmin A.; Braunschweig, Adam B.; Lee, One-Sun; Wiester, Michael J.

    2014-01-01

    This study describes a heteroligated, hemilabile PtII–P,S tweezer coordination complex that combines a chiral Jacobsen–Katsuki MnIII-salen epoxidation catalyst with an amidopyridine receptor, which leads to an inversion of the major epoxide product compared to catalysts without a recognition group. PMID:20448966

  10. COMPARATIVE STUDIES OF THE EFFECT OF POLYCYCLIC AROMATIC HYDROCARBON GEOMETRY ON THE HYDROLYSIS OF DIOL EPOXIDES

    EPA Science Inventory

    Comparative studies of the effect of polycyclic aromatic hydrocarbon geometry on the hydrolysis of diol epoxides

    The interaction of the diol epoxides (DEs) of both planar and non-planar PAHs with water have been examined using quantum mechanical and molecular dynamics. Th...

  11. Asymmetric Epoxidation: A Twinned Laboratory and Molecular Modeling Experiment for Upper-Level Organic Chemistry Students

    ERIC Educational Resources Information Center

    Hii, King Kuok; Rzepa, Henry S.; Smith, Edward H.

    2015-01-01

    The coupling of a student experiment involving the preparation and use of a catalyst for the asymmetric epoxidation of an alkene with computational simulations of various properties of the resulting epoxide is set out in the form of a software toolbox from which students select appropriate components. At the core of these are the computational…

  12. Structure-Potency Relationships for Epoxides in Allergic Contact Dermatitis.

    PubMed

    Roberts, David W; Aptula, Aynur; Api, Anne Marie

    2017-02-20

    Epoxides are known or proposed to be involved in skin sensitization in various ways. Some are encountered directly, and others have been shown to be formed abiotically and metabolically from various unsaturated chemicals. They can react as SN2 electrophiles. To date no quantitative mechanistic models (QMMs) are known for skin sensitization potency of this subcategory of SN2 electrophiles. Here we have considered the reaction mechanistic chemistry of epoxides and combined published experimental kinetic data (rate constants k for reaction with a cysteine-based peptide) together with calculated hydrophobicity data (logP) to derive a QMM correlating potency in the local lymph node assay (LLNA), expressed as EC3, with a relative alkylation index (RAI, calculated as logk + 0.4 logP). The QMM equation, pEC3 = 2.42(±0.26) RAI + 4.04 (±0.25), n = 9, R(2) = 0.928, R(2)(adj) = 0.917, F = 90, s = 0.18, fits the data well, with one positive outlier. The outlier can be rationalized by its exhibiting an alert for oxidation of an amine moiety to give, in this case, the highly reactive glycidaldehyde. The epoxide QMM predicts the potency of a nonepoxide SN2 electrophile (predicted EC3, 0.48%; observed EC3, 0.5%), which suggests that it could form the basis for a more general H-polar SN2 QMM that could be a valuable tool in skin sensitization risk assessment for this quite extensive and structurally diverse reaction mechanistic domain.

  13. Detoxication of the 2',3'-epoxide metabolites of allylbenzene and estragole. Conjugation with glutathione.

    PubMed

    Luo, G; Guenthner, T M

    1994-01-01

    The enzymatic detoxication in vitro of the 2',3'-epoxide derivatives of allylbenzene and estragole was examined, and the relative rates of enzymatic glutathione conjugation and epoxide hydrolysis were compared with those for styrene 1',2'-oxide. HPLC was used to determine the amounts of dihydrodiol and glutathione conjugate metabolites formed by cell extracts from several sources. Although some differences among species were observed, in general, the rates of epoxide inactivation by both pathways are similar. We conclude that one explanation for the apparent lack of genotoxicity of these allylic epoxides in vivo may be their rapid metabolic inactivation by both glutathione S-transferases and epoxide hydrolases, which occur to approximately equal degrees in vitro.

  14. Direct epoxidation in Candida antarctica lipase B studied by experiment and theory.

    PubMed

    Svedendahl, Maria; Carlqvist, Peter; Branneby, Cecilia; Allnér, Olof; Frise, Anton; Hult, Karl; Berglund, Per; Brinck, Tore

    2008-10-13

    Candida antarctica lipase B (CALB) is a promiscuous serine hydrolase that, besides its native function, catalyzes different side reactions, such as direct epoxidation. A single-point mutant of CALB demonstrated a direct epoxidation reaction mechanism for the epoxidation of alpha,beta-unsaturated aldehydes by hydrogen peroxide in aqueous and organic solution. Mutation of the catalytically active Ser105 to alanine made the previously assumed indirect epoxidation reaction mechanism impossible. Gibbs free energies, activation parameters, and substrate selectivities were determined both computationally and experimentally. The energetics and mechanism for the direct epoxidation in CALB Ser105Ala were investigated by density functional theory calculations, and it was demonstrated that the reaction proceeds through a two step-mechanism with formation of an oxyanionic intermediate. The active-site residue His224 functions as a general acid-base catalyst with support from Asp187. Oxyanion stabilization is facilitated by two hydrogen bonds from Thr40.

  15. Photoaffinity labeling of opioid receptor with morphine-7,8-oxide (morphine epoxide)

    SciTech Connect

    Takayanagi, I.; Shibata, R.; Miyata, N.; Hirobe, M.

    1982-05-01

    The opioid receptor mediating inhibitory action of morphine in the electrically stimulated guinea pig ileum was irreversibly photoinactivated by morphine epoxide (3 X 10(-6) M). Morphine epoxide (up to 3 X 10(-5) M) did not influence the responses of rat vas deferens (epsilon-receptor) or rabbit vas deferens (kappa-receptor) to electrical stimulation. Effective concentrations of morphine epoxide were much lower in the guinea pig ileum (mu-receptor) than in the mouse vas deference (delta-receptor). The inhibitory action of (Met)-enkephalin on the twitch responses of the rat vas deferens and mouse vas deferens to electrical stimulation were not influenced after irradiation in the presence of morphine epoxide (3 X 10(-6) M). Therefore, morphine epoxide is probably a useful probe for photoaffinity labeling of the mu-receptor in vitro.

  16. Graphite fiber reinforced thermoplastic resins

    NASA Technical Reports Server (NTRS)

    Novak, R. C.

    1975-01-01

    Mechanical properties of neat resin samples and graphite fiber reinforced samples of thermoplastic resins were characterized with particular emphasis directed to the effects of environmental exposure (humidity, temperature and ultraviolet radiation). Tensile, flexural, interlaminar shear, creep and impact strengths were measured for polysulfone, polyarylsulfone and a state-of-the-art epoxy resin samples. In general, the thermoplastic resins exhibited environmental degradation resistance equal to or superior to the reference epoxy resin. Demonstration of the utility and quality of a graphite/thermoplastic resin system was accomplished by successfully thermoforming a simulated compressor blade and a fan exit guide vane.

  17. Catalysts for CO2/epoxide ring-opening copolymerization

    PubMed Central

    Trott, G.; Saini, P. K.; Williams, C. K.

    2016-01-01

    This article summarizes and reviews recent progress in the development of catalysts for the ring-opening copolymerization of carbon dioxide and epoxides. The copolymerization is an interesting method to add value to carbon dioxide, including from waste sources, and to reduce pollution associated with commodity polymer manufacture. The selection of the catalyst is of critical importance to control the composition, properties and applications of the resultant polymers. This review highlights and exemplifies some key recent findings and hypotheses, in particular using examples drawn from our own research. PMID:26755758

  18. Method for removing contaminants from plastic resin

    DOEpatents

    Bohnert, George W.; Hand, Thomas E.; DeLaurentiis, Gary M.

    2008-12-09

    A resin recycling method that produces essentially contaminant-free synthetic resin material in an environmentally safe and economical manner. The method includes receiving the resin in container form. The containers are then ground into resin particles. The particles are exposed to a solvent, the solvent contacting the resin particles and substantially removing contaminants on the resin particles. After separating the particles and the resin, a solvent removing agent is used to remove any residual solvent remaining on the resin particles after separation.

  19. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1995-09-12

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 10 figs.

  20. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1995-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  1. Selective inhibition and selective induction of multiple microsomal epoxide hydrolases.

    PubMed

    Guenthner, T M

    1986-03-01

    The inhibition in vitro and induction in vivo of microsomal trans-stilbene oxide hydrolase have been studied. This microsomal epoxide hydrolase activity is distinguishable from the previously well-defined microsomal arene oxide hydrolase by a number of catalytic criteria. Two substituted chalcone oxides, 4-phenylchalcone oxide and 4'-phenylchalcone oxide, are potent inhibitors of microsomal trans-stilbene oxide hydrolase, but have no apparent activity against benzo[a]pyrene 4,5-oxide hydrolase. Conversely, compounds that are potent inhibitors of benzo[a]pyrene 4,5-oxide hydrolase, including styrene oxide, cyclohexene oxide, and trichloropropene oxide, inhibit microsomal trans-stilbene oxide hydrolase only at very high (millimolar) concentrations. The chalcone oxides inhibit microsomal trans-stilbene oxide hydrolase noncompetitively, and have micromolar or nanomolar affinity constants for the enzyme. Attempts were made to induce microsomal trans-stilbene oxide hydrolase in vivo. Compounds that induced microsomal benzo[a]pyrene 4,5-oxide hydrolase levels in mice did not simultaneously induce trans-stilbene oxide hydrolase levels. Clofibrate was an exception; it induced levels of both enzymes to a small but statistically significant degree. The two microsomal hydrolase activities have, therefore, very different catalytic sites and appear to be under separate genetic control. 4-Phenylchalcone oxide and 4'-phenylchalcone oxide are selective inhibitors of microsomal trans-stilbene oxide hydrolase and may prove to be very useful in assessing the involvement of this enzyme in the metabolism of endogenous or xenobiotic epoxides.

  2. Epoxide hydrolase of Trichoderma reesei: Biochemical properties and conformational characterization.

    PubMed

    de Oliveira, Gabriel Stephani; Adriani, Patricia Pereira; Borges, Flavia Garcia; Lopes, Adriana Rios; Campana, Patricia T; Chambergo, Felipe S

    2016-08-01

    Epoxide hydrolases (EHs) are enzymes that are present in all living organisms and catalyze the hydrolysis of epoxides to the corresponding vicinal diols. EHs have biotechnological potential in chiral chemistry. We report the cloning, purification, enzymatic activity, and conformational analysis of the TrEH gene from Trichoderma reesei strain QM9414 using circular dichroism spectroscopy. The EH gene has an open reading frame encoding a protein of 343 amino acid residues, resulting in a molecular mass of 38.2kDa. The enzyme presents an optimum pH of 7.2, and it is highly active at temperatures ranging from 23 to 50°C and thermally inactivated at 70°C (t1/2=7.4min). The Michaelis constants (Km) were 4.6mM for racemic substrate, 21.7mM for (R)-(+)-styrene oxide and 3.0mM for (S)-(-)-styrene oxide. The kcat/Km analysis indicated that TrEH is enantioselective and preferentially hydrolyzes (S)-(-)-styrene oxide. The conformational stability studies suggested that, despite the extreme conditions (high temperatures and extremely acid and basic pHs), TrEH is able to maintain a considerable part of its regular structures, including the preservation of the native cores in some cases. The recombinant protein showed enantioselectivity that was distinct from other fungus EHs, making this protein a potential biotechnological tool.

  3. Peripheral FAAH and soluble epoxide hydrolase inhibitors are synergistically antinociceptive.

    PubMed

    Sasso, Oscar; Wagner, Karen; Morisseau, Christophe; Inceoglu, Bora; Hammock, Bruce D; Piomelli, Daniele

    2015-07-01

    We need better medicines to control acute and chronic pain. Fatty acid amide hydrolase (FAAH) and soluble epoxide hydrolase (sEH) catalyze the deactivating hydrolysis of two classes of bioactive lipid mediators--fatty acid ethanolamides (FAEs) and epoxidized fatty acids (EpFAs), respectively--which are biogenetically distinct but share the ability to attenuate pain responses and inflammation. In these experiments, we evaluated the antihyperalgesic activity of small-molecule inhibitors of FAAH and sEH, administered alone or in combination, in two pain models: carrageenan-induced hyperalgesia in mice and streptozocin-induced allodynia in rats. When administered separately, the sEH inhibitor 1-trifluoromethoxyphenyl-3-(1-propionylpiperidine-4-yl)urea (TPPU) and the peripherally restricted FAAH inhibitor URB937 were highly active in the two models. The combination TPPU plus URB937 was markedly synergistic, as assessed using isobolographic analyses. The results of these experiments reveal the existence of a possible functional crosstalk between FAEs and EpFAs in regulating pain responses. Additionally, the results suggest that combinations of sEH and FAAH inhibitors might be exploited therapeutically to achieve greater analgesic efficacy.

  4. Integrated process and dual-function catalyst for olefin epoxidation

    DOEpatents

    Zhou, Bing; Rueter, Michael

    2003-01-01

    The invention discloses a dual-functional catalyst composition and an integrated process for production of olefin epoxides including propylene oxide by catalytic reaction of hydrogen peroxide from hydrogen and oxygen with olefin feeds such as propylene. The epoxides and hydrogen peroxide are preferably produced simultaneously in situ. The dual-functional catalyst comprises noble metal crystallites with dimensions on the nanometer scale (on the order of <1 nm to 10 nm), specially dispersed on titanium silicalite substrate particles. The dual functional catalyst catalyzes both the direct reaction of hydrogen and oxygen to generate hydrogen peroxide intermediate on the noble metal catalyst surface and the reaction of the hydrogen peroxide intermediate with the propylene feed to generate propylene oxide product. Combining both these functions in a single catalyst provides a very efficient integrated process operable below the flammability limits of hydrogen and highly selective for the production of hydrogen peroxide to produce olefin oxides such as propylene oxide without formation of undesired co-products.

  5. Imide Modified Epoxy Matrix Resin.

    DTIC Science & Technology

    1981-02-01

    the bisimide amine cured epoxies (IME’s) were considerably lower than the state-of-the-art epoxies . The strain-to-failure of the control resin system ...nine epoxy resin systems which were prepared from tetraglycidyl methylenedianiline (MY 720) cured with a stoichiometric quantity of bisimide-amine and...graphite imide modified cured epoxy resin composites. The designation for each material is also listed in Table 1. The composition of each resin system

  6. Impact of structure and functionality of core polyol in highly functional biobased epoxy resins.

    PubMed

    Pan, Xiao; Webster, Dean C

    2011-09-01

    Highly functional biobased epoxy resins were prepared using dipentaerythritol (DPE), tripentaerythritol (TPE), and sucrose as core polyols that were substituted with epoxidized soybean oil fatty acids, and the impact of structure and functionality of the core polyol on the properties of the macromolecular resins and their epoxy-anhydride thermosets was explored. The chemical structures, functional groups, molecular weights, and compositions of epoxies were characterized using nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI MS). The epoxies were also studied for their bulk viscosity, intrinsic viscosity, and density. Crosslinked with dodecenyl succinic anhydride (DDSA), epoxy-anhydride thermosets were evaluated using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile tests, and tests of coating properties. Epoxidized soybean oil (ESO) was used as a control. Overall, the sucrose-based thermosets exhibited the highest moduli, having the most rigid and ductile performance while maintaining the highest biobased content. DPE/TPE-based thermosets showed modestly better thermosetting performance than the control ESO thermoset.

  7. Exported Epoxide Hydrolases Modulate Erythrocyte Vasoactive Lipids during Plasmodium falciparum Infection

    PubMed Central

    Dalmia, Varun K.

    2016-01-01

    ABSTRACT Erythrocytes are reservoirs of important epoxide-containing lipid signaling molecules, including epoxyeicosatrienoic acids (EETs). EETs function as vasodilators and anti-inflammatory modulators in the bloodstream. Bioactive EETs are hydrolyzed to less active diols (dihydroxyeicosatrienoic acids) by epoxide hydrolases (EHs). The malaria parasite Plasmodium falciparum infects host red blood cells (RBCs) and exports hundreds of proteins into the RBC compartment. In this study, we show that two parasite epoxide hydrolases, P. falciparum epoxide hydrolases 1 (PfEH1) and 2 (PfEH2), both with noncanonical serine nucleophiles, are exported to the periphery of infected RBCs. PfEH1 and PfEH2 were successfully expressed in Escherichia coli, and they hydrolyzed physiologically relevant erythrocyte EETs. Mutations in active site residues of PfEH1 ablated the ability of the enzyme to hydrolyze an epoxide substrate. Overexpression of PfEH1 or PfEH2 in parasite-infected RBCs resulted in a significant alteration in the epoxide fatty acids stored in RBC phospholipids. We hypothesize that the parasite disruption of epoxide-containing signaling lipids leads to perturbed vascular function, creating favorable conditions for binding and sequestration of infected RBCs to the microvascular endothelium. PMID:27795395

  8. Synthesis and characterization of molybdenum/phenolic resin composites binding with aluminum nitride particles for diamond cutters

    NASA Astrophysics Data System (ADS)

    Lin, Chun-Te; Lee, Hsun-Tsing; Chen, Jem-Kun

    2013-11-01

    Novolac-type bisphenol-F based molybdenum-phenolic resins/silane-modified aluminum nitride (Mo-BPF/m-AlN) composites were successfully prepared. In the preparation process, molybdate reacted with bisphenol-F based phenolic resins (BPF) to form a low cross-linked Mo-BPF with new Mosbnd O bonds which were confirmed by the FTIR and XPS spectra. Simultaneously, a special silane-modified aluminum nitride (m-AlN) was prepared with 3-aminopropyltriethoxysilane (APTES) modifier. Then, this m-AlN was fully mixed with Mo-BPF to form Mo-BPF/m-AlN which can be further cured with hexamethylenetetramine at 200 °C. The structure and characterization of BPF, Mo-BPF and Mo-BPF/m-AlN were determined by using FTIR, DSC, DMA, TGA, SEM, mechanical properties and contact angle measurements. SEM photographs show that m-AlN particles are uniformly distributed in the Mo-BPF/m-AlN composites. Also there are no gaps or void between m-AlN and Mo-BPF phases, which implies a strong physical bonding between the two phases. The glass transition temperature, thermal resistance, flexural strength, and hardness of Mo-BPF are respectively higher than those of BPF. This is due to the presence of Mosbnd O cross-linking bonds in Mo-BPF. When the m-AlN was additionally incorporated into Mo-BPF, the well-dispersed and well-adhered m-AlN can further promote all the above-mentioned properties of the composites. Typically, the glass transition temperature, decomposition temperature at 5% weight loss and flexural strength of Mo-BPF/m-AlN are 245 °C, 428 °C and 82.7 MPa respectively, which are much higher than the corresponding values of 184 °C, 358 °C and 58.2 MPa for BPF. In addition, the hygroscopic nature of BPF can be inhibited by treating with molybdate or incorporating with m-AlN. This is due to that the m-AlN is hydrophobic and Mosbnd O groups in Mo-BPF are more hydrophobic than OH groups in BPF. Furthermore, Mo-BPF/m-AlN was compared with BPF in the performance as a binder for diamond cutting

  9. Resin impregnation process for producing a resin-fiber composite

    NASA Technical Reports Server (NTRS)

    Palmer, Raymond J. (Inventor); Moore, William E. (Inventor)

    1994-01-01

    Process for vacuum impregnation of a dry fiber reinforcement with a curable resin to produce a resin-fiber composite, by drawing a vacuum to permit flow of curable liquid resin into and through a fiber reinforcement to impregnate same and curing the resin-impregnated fiber reinforcement at a sufficient temperature and pressure to effect final curing. Both vacuum and positive pressure, e.g. autoclave pressure, are applied to the dry fiber reinforcement prior to application of heat and prior to any resin flow to compact the dry fiber reinforcement, and produce a resin-fiber composite of reduced weight, thickness and resin content, and improved mechanical properties. Preferably both a vacuum and positive pressure, e.g. autoclave pressure, are also applied during final curing.

  10. Hydration of arene and alkene oxides by epoxide hydrase in human liver microsomes.

    PubMed

    Kapitulnik, J; Levin, W; Morecki, R; Dansette, P M; Jerina, D M; Conney, A H

    1977-02-01

    The comparative hydration of styrene 7,8-oxide, octene 1,2-oxide, naphthalene 1,2-oxide, phenanthrene 9,10-oxide, benzo[a]anthracene 5,6-oxide, 3-methylcholanthrene 11,12-oxide, dibenzo[a,h]anthracene 5,6-oxide, and benzo[a, 7,8-, 9,10-, and 11,12-oxides to their respective dihydrodiols was investigated in microsomes from nine human autopsy livers. The substrate specificity of the epoxide hydrase in human liver microsomes was very similar to that of the epoxide hydrase in rat liver microsomes. Phenanthrene 9,10-oxide was the best substrate for the human and rat epoxide hydrases and dibenzo[a,h]anthracene 5,6-oxide and benzo[a-a)pyrene 11, 12-oxide were the poorest substrates. Plotting epoxide hydrase activity obtained with one substrate against epoxide hydrase activity for another substrate for each of the nine human livers revealed excellent correlations for all combinations of the 11 substrates studied (r = 0.87 to 0.99). The data suggest the presence in human liver of a single epoxide hydrase with broad substrate specificity. However, the results do not exclude the possible presence in human liver of several epoxide hydrases that are under similar regulatory control. These results suggest the need for further investigation to determine whether there is a safe epoxide of a drug whose in vivo metabolism is predictive of the capacity of different individuals to metabolize a wide variety of epoxides of drugs and environmental chemicals.

  11. Nontoxic Resins Advance Aerospace Manufacturing

    NASA Technical Reports Server (NTRS)

    2009-01-01

    The 2008 NASA Commercial Invention of the Year, PETI-330, is a polyimide matrix resin that performs well at high temperatures and is easily processed into composites in a simple, short curing cycle. Invented by scientists at Langley Research Center, PETI-330 is now licensed to Ube Industries, based in Japan with its American headquarters in New York. In addition to being durable and lightweight, the resin is also nontoxic, which makes it safe for workers to handle. PETI-330 was created specifically for heat-resistant composites formed with resin transfer molding and resin infusion, which formerly could only be used with low temperature resin systems.

  12. New Low Cost Resin Systems

    DTIC Science & Technology

    2006-05-31

    difference between resins 1 and 2 was the type of phosphorous containing compound, where resin 3 was the same as resin 1 with the addition of melamine ...SBIR N03-120 New Low Cost Resin Systems Applied Poleramic, Inc. Final Report Report Documentation Page Form ApprovedOMB No. 0704-0188 Public...Feb 2004 4. TITLE AND SUBTITLE New Low Cost Resin Systems 5a. CONTRACT NUMBER N00014-03-M-0304 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6

  13. Mechanism of olefin epoxidation in the presence of a titanium-containing zeolite

    NASA Astrophysics Data System (ADS)

    Danov, S. M.; Krasnov, V. L.; Sulimov, A. V.; Ovcharova, A. V.

    2013-11-01

    The effect of the nature of a solvent on the liquid-phase epoxidation of olefins with an aqueous solution of hydrogen peroxide over a titanium-containing zeolite is studied. Butanol-1, butanol-2, propanol-1, isopropanol, methanol, ethanol, water, acetone, methyl ethyl ketone, isobutanol, and tert-butanol are examined as solvents. A mechanism of olefin epoxidation with hydrogen peroxide in an alcohol medium over a titanium-containing zeolite is proposed. Epoxidation reactions involving hydrogen peroxide and different olefins are studied experimentally.

  14. First-Principles Chemical Kinetic Modeling of Methyl trans-3-Hexenoate Epoxidation by HO2.

    PubMed

    Cagnina, S; Nicolle, A; de Bruin, T; Georgievskii, Y; Klippenstein, S J

    2017-03-09

    The design of innovative combustion processes relies on a comprehensive understanding of biodiesel oxidation kinetics. The present study aims at unraveling the reaction mechanism involved in the epoxidation of a realistic biodiesel surrogate, methyl trans-3-hexenoate, by hydroperoxy radicals using a bottom-up theoretical kinetics methodology. The obtained rate constants are in good agreement with experimental data for alkene epoxidation by HO2. The impact of temperature and pressure on epoxidation pathways involving H-bonded and non-H-bonded conformers was assessed. The obtained rate constant was finally implemented into a state-of-the-art detailed combustion mechanism, resulting in fairly good agreement with engine experiments.

  15. Data set of optimal parameters for colorimetric red assay of epoxide hydrolase activity.

    PubMed

    de Oliveira, Gabriel Stephani; Adriani, Patricia Pereira; Borges, Flavia Garcia; Lopes, Adriana Rios; Campana, Patricia T; Chambergo, Felipe S

    2016-09-01

    The data presented in this article are related to the research article entitled "Epoxide hydrolase of Trichoderma reesei: Biochemical properties and conformational characterization" [1]. Epoxide hydrolases (EHs) are enzymes that catalyze the hydrolysis of epoxides to the corresponding vicinal diols. This article describes the optimal parameters for the colorimetric red assay to determine the enzymatic activity, with an emphasis on the characterization of the kinetic parameters, pH optimum and thermal stability of this enzyme. The effects of reagents that are not resistant to oxidation by sodium periodate on the reactions can generate false positives and interfere with the final results of the red assay.

  16. Cellulose whisker/epoxy resin nanocomposites.

    PubMed

    Tang, Liming; Weder, Christoph

    2010-04-01

    New nanocomposites composed of cellulose nanofibers or "whiskers" and an epoxy resin were prepared. Cellulose whiskers with aspect ratios of approximately 10 and approximately 84 were isolated from cotton and sea animals called tunicates, respectively. Suspensions of these whiskers in dimethylformamide were combined with an oligomeric difunctional diglycidyl ether of bisphenol A with an epoxide equivalent weight of 185-192 and a diethyl toluenediamine-based curing agent. Thin films were produced by casting these mixtures and subsequent curing. The whisker content was systematically varied between 4 and 24% v/v. Electron microscopy studies suggest that the whiskers are evenly dispersed within the epoxy matrix. Dynamic mechanical thermoanalysis revealed that the glass transition temperature (T(g)) of the materials was not significantly influenced by the incorporation of the cellulose filler. Between room temperature and 150 degrees C, i.e., below T(g), the tensile storage moduli (E') of the nanocomposites increased modestly, for example from 1.6 GPa for the neat polymer to 4.9 and 3.6 GPa for nanocomposites comprising 16% v/v tunicate or cotton whiskers. The relative reinforcement was more significant at 185 degrees C (i.e., above T(g)), where E' was increased from approximately 16 MPa (neat polymer) to approximately 1.6 GPa (tunicate) or approximately 215 MPa (cotton). The mechanical properties of the new materials are well-described by the percolation model and are the result of the formation of a percolating whisker network in which stress transfer is facilitated by strong interactions between the whiskers.

  17. Epoxidation reactions of unsaturated fatty esters with potassium peroxomonosulfate.

    PubMed

    Lie Ken Jie, M S; Pasha, M K

    1998-06-01

    Epoxidation of the double bond in methyl oleate, octadec-11E-en-9-ynoate, ricinoleate (12-hydroxy-octadec-9Z-enoate), iso-ricinoleate (9-hydroxy-octadec-12Z-enoate), and 12-oxo-octadec-9Z-enoate with potassium peroxomonosulfate (oxone, 2 KHSO5.KHSO4.K2SO4) in the presence of trifluoroacetone or methyl pyruvate gave the corresponding monoepoxy derivatives. Reaction of Oxone with methyl linoleate and octadeca-9Z,11E-dienoate furnished the corresponding diepoxystearate derivative. Methyl 9,12-dioxo-octadec-10Z-enoate was obtained when a C18 furanoid fatty ester (methyl 9,12-epoxy-9,11-octadecadienoate) was treated with Oxone. The yield of these reactions was very high (85-99%), and the epoxy derivatives were readily isolated by solvent extraction. The products were identified by spectroscopic methods.

  18. Vitamin K epoxide reductase: homology, active site and catalytic mechanism.

    PubMed

    Goodstadt, Leo; Ponting, Chris P

    2004-06-01

    Vitamin K epoxide reductase (VKOR) recycles reduced vitamin K, which is used subsequently as a co-factor in the gamma-carboxylation of glutamic acid residues in blood coagulation enzymes. VKORC1, a subunit of the VKOR complex, has recently been shown to possess this activity. Here, we show that VKORC1 is a member of a large family of predicted enzymes that are present in vertebrates, Drosophila, plants, bacteria and archaea. Four cysteine residues and one residue, which is either serine or threonine, are identified as likely active-site residues. In some plant and bacterial homologues the VKORC1 homologous domain is fused with domains of the thioredoxin family of oxidoreductases. These might reduce disulfide bonds of VKORC1-like enzymes as a prerequisite for their catalytic activities.

  19. Cesium promotion in styrene epoxidation on silver catalysts.

    PubMed

    Zhou, Ling; Gorin, Craig F; Madix, Robert J

    2010-01-20

    The adsorption of a small amount of cesium on Ag(110) redirects the partial oxidation products of styrene from phenylacetaldehyde and phenylketene to styrene oxide. The cesium stabilizes the oxametallacycle intermediate and hinders its transformation to the intermediate that leads to the other products. Cesium does not appear to create any electronic effects on the bonding of the intermediates. Low coverages of cesium induce a (1 x 2) missing-row reconstruction of the entire clean Ag(110) surface and a (3 x 5) surface oxide structure on the cesium-reconstructed Ag(110) surface. This (3 x 5)-ordered surface oxide is superimposed on the Ag(111) microfacets produced by the cesium-induced reconstruction, which leads to selectivity and reactivity very similar to those of the extended (111) surface. These studies provide insight into the microscopic origins of the structural effects of cesium in styrene epoxidation on silver catalysts.

  20. Characteristics of polyaniline cobalt supported catalysts for epoxidation reactions.

    PubMed

    Kowalski, Grzegorz; Pielichowski, Jan; Grzesik, Mirosław

    2014-01-01

    A study of polyaniline (PANI) doping with various cobalt compounds, that is, cobalt(II) chloride, cobalt(II) acetate, and cobalt(II) salen, is presented. The catalysts were prepared by depositing cobalt compounds onto the polymer surface. PANI powders containing cobalt ions were obtained by one- or two-step method suspending PANI in the following acetonitrile/acetic acid solution or acetonitrile and then acetic acid solution. Moreover different ratios of Co(II) : PANI were studied. Catalysts obtained with both methods and at all ratios were investigated using various techniques including AAS and XPS spectroscopy. The optimum conditions for preparation of PANI/Co catalysts were established. Catalytic activity of polyaniline cobalt(II) supported catalysts was tested in dec-1-ene epoxidation with molecular oxygen at room temperature. The relationship between the amount of cobalt species, measured with both AAS and XPS techniques, and the activity of PANI-Co catalysts has been established.

  1. Characteristics of Polyaniline Cobalt Supported Catalysts for Epoxidation Reactions

    PubMed Central

    Kowalski, Grzegorz; Pielichowski, Jan; Grzesik, Mirosław

    2014-01-01

    A study of polyaniline (PANI) doping with various cobalt compounds, that is, cobalt(II) chloride, cobalt(II) acetate, and cobalt(II) salen, is presented. The catalysts were prepared by depositing cobalt compounds onto the polymer surface. PANI powders containing cobalt ions were obtained by one- or two-step method suspending PANI in the following acetonitrile/acetic acid solution or acetonitrile and then acetic acid solution. Moreover different ratios of Co(II) : PANI were studied. Catalysts obtained with both methods and at all ratios were investigated using various techniques including AAS and XPS spectroscopy. The optimum conditions for preparation of PANI/Co catalysts were established. Catalytic activity of polyaniline cobalt(II) supported catalysts was tested in dec-1-ene epoxidation with molecular oxygen at room temperature. The relationship between the amount of cobalt species, measured with both AAS and XPS techniques, and the activity of PANI-Co catalysts has been established. PMID:24701183

  2. Structure of a bacterial homologue of vitamin K epoxide reductase

    SciTech Connect

    Li, Weikai; Schulman, Sol; Dutton, Rachel J.; Boyd, Dana; Beckwith, Jon; Rapoport, Tom A.

    2010-03-19

    Vitamin K epoxide reductase (VKOR) generates vitamin K hydroquinone to sustain {gamma}-carboxylation of many blood coagulation factors. Here, we report the 3.6 {angstrom} crystal structure of a bacterial homologue of VKOR from Synechococcus sp. The structure shows VKOR in complex with its naturally fused redox partner, a thioredoxin-like domain, and corresponds to an arrested state of electron transfer. The catalytic core of VKOR is a four transmembrane helix bundle that surrounds a quinone, connected through an additional transmembrane segment with the periplasmic thioredoxin-like domain. We propose a pathway for how VKOR uses electrons from cysteines of newly synthesized proteins to reduce a quinone, a mechanism confirmed by in vitro reconstitution of vitamin K-dependent disulphide bridge formation. Our results have implications for the mechanism of the mammalian VKOR and explain how mutations can cause resistance to the VKOR inhibitor warfarin, the most commonly used oral anticoagulant.

  3. Detoxication strategy of epoxide hydrolase-the basis for a novel threshold for definable genotoxic carcinogens.

    PubMed

    Oesch, Franz; Hengstler, Jan Georg; Arand, Michael

    2004-01-01

    From our recent work on the three-dimensional structure of epoxide hydrolases we theoretically deduced the likelihood of a two-step catalytic mechanism that we and others have subsequently experimentally confirmed. Analysis of the rate of the two steps by us and by others show that the first step-responsible for removal of the reactive epoxide from the system-works extraordinarily fast (typically three orders of magnitude faster than the second step), sucking up the epoxide like a sponge. Regeneration of the free enzyme (the second step of the catalytic mechanism) is slow. This becomes a toxicological problem only at doses of the epoxide that titrate the enzyme out. Our genotoxicity work shows that indeed this generates a practical threshold below which no genotoxicity is observed. This shows that-contrary to old dogma-practical thresholds exist for definable genotoxic carcinogens.

  4. A Computational Study of Acid Catalyzed Aerosol Reactions of Atmospherically Relevant Epoxides

    EPA Science Inventory

    Epoxides are important intermediates of atmospheric isoprene oxidation. Their subsequent reactions in the particle phase lead to the production of organic compounds detected in ambient aerosols. We apply density functional theory to determine the important kinetic factors that ...

  5. Biobased composites from thermoplastic polyurethane elastomer and cross-linked acrylated-epoxidized soybean oil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean oil is an important sustainable material. Crosslinked acrylated epoxidized soybean oil (AESO) is brittle without flexibility and the incorporation of thermoplastic polyurethane improves its toughness for industrial applications. The hydrophilic functional groups from both oil and polyurethan...

  6. The Role of Long Chain Fatty Acids and Their Epoxide Metabolites in Nociceptive Signaling

    PubMed Central

    Wagner, Karen; Vito, Steve; Inceoglu, Bora; Hammock, Bruce D.

    2014-01-01

    Lipid derived mediators contribute to inflammation and the sensing of pain. The contributions of omega-6 derived prostanoids in enhancing inflammation and pain sensation are well known. Less well explored are the opposing anti-inflammatory and analgesic effects of the omega-6 derived epoxyeicosatrienoic acids. Far less has been described about the epoxidized metabolites derived from omega-3 long chain fatty acids. The epoxide metabolites are turned over rapidly with enzymatic hydrolysis by the soluble epoxide hydrolase being the major elimination pathway. Despite this, the overall understanding of the role of lipid mediators in the pathology of chronic pain is growing. Here we review the role of long chain fatty acids and their metabolites in alleviating both acute and chronic pain conditions. We focus specifically on the epoxidized metabolites of omega-6 and omega-3 long chain fatty acids as well as a novel strategy to modulate their activity in vivo. PMID:25240260

  7. Poly(monothiocarbonate)s from the Alternating and Regioselective Copolymerization of Carbonyl Sulfide with Epoxides.

    PubMed

    Luo, Ming; Zhang, Xing-Hong; Darensbourg, Donald J

    2016-10-18

    Carbonyl sulfide (COS) is an air pollutant that causes acid rain, ozonosphere damage, and carbon dioxide (CO2) generation. It is a heterocumulene and structural analogue of CO2. Relevant to organic synthesis, it is a source of C═O or C═S groups and thus an ideal one-carbon (C1) building block for synthesizing sulfur-containing polymers through the similar route of CO2 copolymerization. In contrast, traditional synthesis of sulfur-containing polymers often involves the condensation of thiols with phosgene and ring-opening polymerization of cyclic thiocarbonates that are generally derived from thiols and phosgene; thus, COS/epoxide copolymerization is a "greener" route to supplement or supplant current processes for the production of sulfur-containing polymers. This Accounts highlights our efforts on the discovery of the selective formation of poly(monothiocarbonate)s from COS with epoxides via heterogeneous zinc-cobalt double metal cyanide complex (Zn-Co(III) DMCC) and homogeneous (salen)CrX complexes. The catalytic activity and selectivity of Zn-Co(III) DMCC for COS/epoxide copolymerization are similar to those for CO2/epoxide copolymerization. (salen)CrX complexes accompanied by onium salts exhibited high activity and selectivity for COS/epoxide copolymerization under mild conditions, affording copolymers with >99% monothiocarbonate units and high tail-to-head content up to 99%. By way of contrast, these catalysts often show moderate or low activity for CO2/epoxide copolymerization. Of note, a specialty of COS/epoxide copolymerization is the occurrence of an oxygen-sulfur exchange reaction (O/S ER), which may produce carbonate and dithiocarbonate units. O/S ER, which are induced by the metal-OH bond regenerated by chain transfer reactions, can be kinetically inhibited by changing the reaction conditions. We provide a thorough mechanistic understanding of the electronic/steric effect of the catalysts on the regioselectivity of COS copolymerization. The

  8. System for removing contaminants from plastic resin

    DOEpatents

    Bohnert, George W.; Hand, Thomas E.; DeLaurentiis, Gary M.

    2010-11-23

    A resin recycling system that produces essentially contaminant-free synthetic resin material in an environmentally safe and economical manner. The system includes receiving the resin in container form. A grinder grinds the containers into resin particles. The particles are exposed to a solvent in one or more solvent wash vessels, the solvent contacting the resin particles and substantially removing contaminants on the resin particles. A separator is used to separate the resin particles and the solvent. The resin particles are then placed in solvent removing element where they are exposed to a solvent removing agent which removes any residual solvent remaining on the resin particles after separation.

  9. A domino ring-opening/epoxidation of 1,2-dioxines.

    PubMed

    Greatrex, Ben W; Taylor, Dennis K; Tiekink, Edward R T

    2004-04-02

    When allowed to react with alkaline hydrogen peroxide, monocyclic 1,2-dioxines ring-open to their isomeric gamma-hydroxyenone intermediates which are rapidly epoxidized to afford trans-4-hydroxy-2,3-epoxyketones in 21-81% yield. In the case of meso-1,2-dioxines, Co(II) complex catalyzed asymmetric ring-opening of the 1,2-dioxine may be employed to furnish enantioenriched epoxides

  10. Hydroxyl-Substituted Ladder Polyethers via Selective Tandem Epoxidation/Cyclization Sequence

    PubMed Central

    Czabaniuk, Lara C.; Jamison, Timothy F.

    2015-01-01

    A new and highly selective method for the synthesis of hydroxyl-substituted tetrahydropyrans is described. This method utilizes titanium(IV) iso-propoxide and diethyl tartrate to perform a diastereoselective epoxidation followed by in situ epoxide activation and highly selective endo-cyclization to form the desired tetrahydropyran ring. The HIJ ring fragment of the marine ladder polyether yessotoxin was synthesized using this two-stage tactic that proceeds with high efficiency and excellent regioselectivity. PMID:25647091

  11. Mechanistic investigation leads to a synthetic improvement in the hydrolytic kinetic resolution of terminal epoxides.

    PubMed

    Nielsen, Lars P C; Stevenson, Christian P; Blackmond, Donna G; Jacobsen, Eric N

    2004-02-11

    The mechanism of the hydrolytic kinetic resolution (HKR) of terminal epoxides was investigated by kinetic analysis using reaction calorimetry. The chiral (salen)Co-X complex (X = OAc, OTs, Cl) undergoes irreversible conversion to (salen)Co-OH during the course of the HKR and thus serves as both precatalyst and cocatalyst in a cooperative bimetallic catalytic mechanism. This insight led to the identification of more active catalysts for the HKR of synthetically useful terminal epoxides.

  12. Hydroxyl-substituted ladder polyethers via selective tandem epoxidation/cyclization sequence.

    PubMed

    Czabaniuk, Lara C; Jamison, Timothy F

    2015-02-20

    A new and highly selective method for the synthesis of hydroxyl-substituted tetrahydropyrans is described. This method utilizes titanium(IV) isopropoxide and diethyl tartrate to perform a diastereoselective epoxidation followed by in situ epoxide activation and highly selective endo-cyclization to form the desired tetrahydropyran ring. The HIJ ring fragment of the marine ladder polyether yessotoxin was synthesized using this two-stage tactic that proceeds with high efficiency and excellent regioselectivity.

  13. Opening of Aryl-Substituted Epoxides to form Quaternary Stereogenic Centers: Synthesis of (−)-Mesembrine

    PubMed Central

    Taber, Douglass F.; He, Yigang

    2011-01-01

    Cycloalkanones are easily converted into aryl-substituted cyclic alkenes by the addition of an aryl Grignard reagent followed by dehydration. These alkenes are good substrates for asymmetric epoxidation. We have found that the addition of allylic and benzylic Grignard reagents can occur preferentially at the benzylic position of the derived epoxides, to give the quaternary stereogenic center. This approach led to a short synthesis of the nanomolar serotonin re-uptake inhibitor (−)-mesembrine. PMID:16149803

  14. Flame Retardant Epoxy Resins

    NASA Technical Reports Server (NTRS)

    Thompson, C. M.; Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.; Lyon, R. E.

    2004-01-01

    As part of a program to develop fire resistant exterior composite structures for future subsonic commercial aircraft, flame retardant epoxy resins are under investigation. Epoxies and their curing agents (aromatic diamines) containing phosphorus were synthesized and used to prepare epoxy formulations. Phosphorus was incorporated within the backbone of the epoxy resin and not used as an additive. The resulting cured epoxies were characterized by thermogravimetric analysis, propane torch test, elemental analysis and microscale combustion calorimetry. Several formulations showed excellent flame retardation with phosphorous contents as low as 1.5% by weight. The fracture toughness of plaques of several cured formulations was determined on single-edge notched bend specimens. The chemistry and properties of these new epoxy formulations are discussed.

  15. Epoxidation of Short-Chain Alkenes by Resting-Cell Suspensions of Propane-Grown Bacteria

    PubMed Central

    Hou, Ching T.; Patel, Ramesh; Laskin, Allen I.; Barnabe, Nancy; Barist, Irene

    1983-01-01

    Sixteen new cultures of propane-utilizing bacteria were isolated from lake water from Warinanco Park, Linden, N.J. and from lake and soil samples from Bayway Refinery, Linden, N.J. In addition, 19 known cultures obtained from culture collections were also found to be able to grow on propane as the sole carbon and energy source. In addition to their ability to oxidize n-alkanes, resting-cell suspensions of both new cultures and known cultures grown on propane oxidize short-chain alkenes to their corresponding 1,2-epoxides. Among the substrate alkenes, propylene was oxidized at the highest rate. In contrast to the case with methylotrophic bacteria, the product epoxides are further metabolized. Propane and other gaseous n-alkanes inhibit the epoxidation of propylene. The optimum conditions for in vivo epoxidation are described. Results from inhibition studies indicate that a propane monooxygenase system catalyzes both the epoxidation and hydroxylation reactions. Experiments with cell-free extracts show that both hydroxylation and epoxidation activities are located in the soluble fraction obtained after 80,000 × g centrifugation. PMID:16346338

  16. Advanced thermoplastic resins, phase 1

    NASA Technical Reports Server (NTRS)

    Hendricks, C. L.; Hill, S. G.; Falcone, A.; Gerken, N. T.

    1991-01-01

    Eight thermoplastic polyimide resin systems were evaluated as composite matrix materials. Two resins were selected for more extensive mechanical testing and both were versions of LaRC-TPI (Langley Research Center - Thermoplastic Polyimide). One resin was made with LaRC-TPI and contained 2 weight percent of a di(amic acid) dopant as a melt flow aid. The second system was a 1:1 slurry of semicrystalline LaRC-TPI powder in a polyimidesulfone resin diglyme solution. The LaRC-TPI powder melts during processing and increases the melt flow of the resin. Testing included dynamic mechanical analysis, tension and compression testing, and compression-after-impact testing. The test results demonstrated that the LaRC-TPI resins have very good properties compared to other thermoplastics, and that they are promising matrix materials for advanced composite structures.

  17. Dry PMR-15 Resin Powders

    NASA Technical Reports Server (NTRS)

    Vannucci, Raymond D.; Roberts, Gary D.

    1988-01-01

    Shelf lives of PMR-15 polymides lengthened. Procedure involves quenching of monomer reactions by vacuum drying of PRM-15 resin solutions at 70 to 90 degree F immediately after preparation of solutions. Absence of solvent eliminates formation of higher esters and reduces formation of imides to negligible level. Provides fully-formulated dry PMR-15 resin powder readily dissolvable in solvent at room temperature immediately before use. Resins used in variety of aerospace, aeronautical, and commercial applications.

  18. Vitrification of ion exchange resins

    DOEpatents

    Cicero-Herman, Connie A.; Workman, Rhonda Jackson

    2001-01-01

    The present invention relates to vitrification of ion exchange resins that have become loaded with hazardous or radioactive wastes, in a way that produces a homogenous and durable waste form and reduces the disposal volume of the resin. The methods of the present invention involve directly adding borosilicate glass formers and an oxidizer to the ion exchange resin and heating the mixture at sufficient temperature to produce homogeneous glass.

  19. 40 CFR 414.40 - Applicability; description of the thermoplastic resins subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Polyethylene *Polyethylene—Ethyl Acrylate Resins *Polyethylene—Polyvinyl Acetate Copolymers Polyethylene Resin (HDPE) Polyethylene Resin (LPDE) Polyethylene Resin, Scrap Polyethylene Resin, Wax (Low M.W.) Polyethylene Resin, Latex Polyethylene Resins *Polyethylene Resins, Compounded *Polyethylene,...

  20. 40 CFR 414.40 - Applicability; description of the thermoplastic resins subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Polyethylene *Polyethylene—Ethyl Acrylate Resins *Polyethylene—Polyvinyl Acetate Copolymers Polyethylene Resin (HDPE) Polyethylene Resin (LPDE) Polyethylene Resin, Scrap Polyethylene Resin, Wax (Low M.W.) Polyethylene Resin, Latex Polyethylene Resins *Polyethylene Resins, Compounded *Polyethylene,...

  1. 40 CFR 414.40 - Applicability; description of the thermoplastic resins subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Polyethylene *Polyethylene—Ethyl Acrylate Resins *Polyethylene—Polyvinyl Acetate Copolymers Polyethylene Resin (HDPE) Polyethylene Resin (LPDE) Polyethylene Resin, Scrap Polyethylene Resin, Wax (Low M.W.) Polyethylene Resin, Latex Polyethylene Resins *Polyethylene Resins, Compounded *Polyethylene,...

  2. 40 CFR 414.40 - Applicability; description of the thermoplastic resins subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Polyethylene *Polyethylene—Ethyl Acrylate Resins *Polyethylene—Polyvinyl Acetate Copolymers Polyethylene Resin (HDPE) Polyethylene Resin (LPDE) Polyethylene Resin, Scrap Polyethylene Resin, Wax (Low M.W.) Polyethylene Resin, Latex Polyethylene Resins *Polyethylene Resins, Compounded *Polyethylene,...

  3. Phosphorus-containing bisimide resins

    NASA Technical Reports Server (NTRS)

    Varma, I. K.; Fohlen, G. M.; Parker, J. A. (Inventor)

    1981-01-01

    The production of fire-resistant resins particularly useful for making laminates with inorganic fibers such as graphite fibers is discussed. The resins are by (1) condensation of an ethylenically unsaturated cyclic anhydride with a bis(diaminophenyl) phosphine oxide, and (2) by addition polymerization of the bisimide so obtained. Up to about 50%, on a molar basis, of benzophenonetetracarboxylic acid anhydride can be substituted for some of the cyclic anhydride to alter the properties of the products. Graphite cloth laminates made with these resins show 800 C char yields greater than 70% by weight in nitrogen. Limiting oxygen indexes of more than 100% are determined for these resins.

  4. Epoxidation Activities of Human Cytochromes P450c17 and P450c21

    PubMed Central

    2015-01-01

    Some cytochrome P450 enzymes epoxidize unsaturated substrates, but this activity has not been described for the steroid hydroxylases. Physiologic steroid substrates, however, lack carbon–carbon double bonds in the parts of the pregnane molecules where steroidogenic hydroxylations occur. Limited data on the reactivity of steroidogenic P450s toward olefinic substrates exist, and the study of occult activities toward alternative substrates is a fundamental aspect of the growing field of combinatorial biosynthesis. We reasoned that human P450c17 (steroid 17-hydroxylase/17,20-lyase, CYP17A1), which 17- and 16α-hydroxylates progesterone, might catalyze the formation of the 16α,17-epoxide from 16,17-dehydroprogesterone (pregna-4,16-diene-3,20-dione). CYP17A1 catalyzed the novel 16α,17-epoxidation and the ordinarily minor 21-hydroxylation of 16,17-dehydroprogesterone in a 1:1 ratio. CYP17A1 mutation A105L, which has reduced progesterone 16α-hydroxylase activity, gave a 1:5 ratio of epoxide:21-hydroxylated products. In contrast, human P450c21 (steroid 21-hydroxylase, CYP21A2) converted 16,17-dehydroprogesterone to the 21-hydroxylated product and only a trace of epoxide. CYP21A2 mutation V359A, which has significant 16α-hydroxylase activity, likewise afforded the 21-hydroxylated product and slightly more epoxide. CYP17A1 wild-type and mutation A105L do not 21- or 16α-hydroxylate pregnenolone, but the enzymes 21-hydroxylated and 16α,17-epoxidized 16,17-dehydropregnenolone (pregna-5,16-diene-3β-ol-20-one) in 4:1 or 12:1 ratios, respectively. Catalase and superoxide dismutase did not prevent epoxide formation. The progesterone epoxide was not a time-dependent, irreversible CYP17A1 inhibitor. Our substrate modification studies have revealed occult epoxidase and 21-hydroxylase activities of CYP17A1, and the fraction of epoxide formed correlated with the 16α-hydroxylase activity of the enzymes. PMID:25386927

  5. Impact of Stereochemistry on Ligand Binding: X-ray Crystallographic Analysis of an Epoxide-Based HIV Protease Inhibitor.

    PubMed

    Benedetti, Fabio; Berti, Federico; Campaner, Pietro; Fanfoni, Lidia; Demitri, Nicola; Olajuyigbe, Folasade M; De March, Matteo; Geremia, Silvano

    2014-09-11

    A new pseudopeptide epoxide inhibitor, designed for irreversible binding to HIV protease (HIV-PR), has been synthesized and characterized in solution and in the solid state. However, the crystal structure of the complex obtained by inhibitor-enzyme cocrystallization revealed that a minor isomer, with inverted configuration of the epoxide carbons, has been selected by HIV-PR during crystallization. The structural characterization of the well-ordered pseudopeptide, inserted in the catalytic channel with its epoxide group intact, provides deeper insights into inhibitor binding and HIV-PR stereoselectivity, which aids development of future epoxide-based HIV inhibitors.

  6. Occupational skin diseases from epoxy compounds. Epoxy resin compounds, epoxy acrylates and 2,3-epoxypropyl trimethyl ammonium chloride.

    PubMed

    Jolanki, R

    1991-01-01

    Of a total of 3731 patients investigated between 1974 and 1990, 1844 (49.4%) had an occupational skin disease. Of them 142 (7.7%) had an occupational skin disease caused by epoxy compounds--135 patients (95%) had allergic contact dermatitis, five had irritant contact dermatitis, and two had contact urticaria. Apart from dermatoses, two patients had IgE-mediated asthma from exposure to DGEBA epoxy resins. Thus epoxy compounds are one of the main causes of occupational allergic contact dermatoses and can be considered potential causes of occupational asthma. The most frequent causes were epoxy resin compounds, which together induced 93% (132 cases) of all epoxy compound dermatoses. The three most common causative products were epoxy paints and their raw materials (31%, 41 cases), epoxy resin compounds used in electrical insulation (29%, 38 cases) and epoxy glues (18%, 24 cases). Fewer cases were caused by products containing epoxy acrylate and EPTMAC. The present study found that, in addition to contact allergy to DGEBA epoxy resins, contact allergy to epoxy hardeners, non-DGEBA resins and reactive diluents is common. Polyamine hardeners, most frequently MDA, DETA and TETA, rarely IPDA, tris-DMP, EDA, TMD and XDA, were the second commonest causes of contact allergy induced by epoxy resin compounds, after DGEBA epoxy resins. Cycloaliphatic epoxy resins and other non-DGEBA epoxy resins, including heterocyclic dimethyl hydantoin, phenol novolak and brominated epoxy resins, were the third commonest causes, and reactive diluents the fourth commonest cause of allergic dermatitis due to epoxy resin compounds. Most patients sensitized to reactive diluents were allergic to PGE, ortho-CGE, HDDGE and BDDGE, whereas fewer patients were sensitized to AGE, NPGDGE and BGE. Cross-sensitization between reactive diluents was common. Cardura E 10 and Epoxide 8 provoked no reactions. The present study also indicated that DGEBA epoxy resins with a high average MW ought to be regarded as

  7. Final Report: Experimental and Theoretical Studies of Surface Oxametallacycles - Connections to Heterogeneous Olefin Epoxidation

    SciTech Connect

    Mark A. Barteau

    2009-09-15

    This project has aimed at the rational design of catalysts for direct epoxidation of olefins. This chemistry remains one of the most challenging problems in heterogeneous catalysis. Although the epoxidation of ethylene by silver catalysts to form ethylene oxide (EO) has been practiced for decades, little progress has been made in expanding this technology to other products and processes. We have made significant advances through the combination of surface science experiments, Density Functional Theory (DFT) calculations, and catalytic reactor experiments, toward understanding the mechanism of this reaction on silver catalysts, and to the rational improvement of selectivity. The key has been our demonstration of surface oxametallacycle intermediates as the species that control reaction selectivity. This discovery permits the influence of catalyst promoters on selectivity to be probed, and new catalyst formulations to be developed. It also guides the development of new chemistry with potential for direct epoxidation of more complex olefins. During the award period we have focused on 1. the formation and reaction selectivity of complex olefin epoxides on silver surfaces, and 2. the influence of co-adsorbed oxygen atoms on the reactions of surface oxametallacycles on silver, and 3. the computational prediction, synthesis, characterization and experimental evaluation of bimetallic catalysts for ethylene epoxidation. The significance of these research thrusts is as follows. Selective epoxidation of olefins more complex than ethylene requires suppression of not only side reactions available to the olefin such as C-H bond breaking, but it requires formation and selective ring closure of the corresponding oxametallacycle intermediates. The work carried out under this grant has significantly advanced the field of catalyst design from first principles. The combination of computational tools, surface science, and catalytic reactor experiments in a single laboratory has few

  8. Epoxide-mediated differential packaging of Cif and other virulence factors into outer membrane vesicles.

    PubMed

    Ballok, Alicia E; Filkins, Laura M; Bomberger, Jennifer M; Stanton, Bruce A; O'Toole, George A

    2014-10-01

    Pseudomonas aeruginosa produces outer membrane vesicles (OMVs) that contain a number of secreted bacterial proteins, including phospholipases, alkaline phosphatase, and the CFTR inhibitory factor (Cif). Previously, Cif, an epoxide hydrolase, was shown to be regulated at the transcriptional level by epoxides, which serve as ligands of the repressor, CifR. Here, we tested whether epoxides have an effect on Cif levels in OMVs. We showed that growth of P. aeruginosa in the presence of specific epoxides but not a hydrolysis product increased Cif packaging into OMVs in a CifR-independent fashion. The outer membrane protein, OprF, was also increased under these conditions, but alkaline phosphatase activity was not significantly altered. Additionally, we demonstrated that OMV shape and density were affected by epoxide treatment, with two distinct vesicle fractions present when cells were treated with epibromohydrin (EBH), a model epoxide. Vesicles isolated from the two density fractions exhibited different protein profiles in Western blotting and silver staining. We have shown that a variety of clinically or host-relevant treatments, including antibiotics, also alter the proteins packaged in OMVs. Proteomic analysis of purified OMVs followed by an analysis of transposon mutant OMVs yielded mutants with altered vesicle packaging. Finally, epithelial cell cytotoxicity was reduced in the vesicles formed in the presence of EBH, suggesting that this epoxide alters the function of the OMVs. Our data support a model whereby clinically or host-relevant signals mediate differential packaging of virulence factors in OMVs, which results in functional consequences for host-pathogen interactions.

  9. Patulin biosynthesis: Epoxidation of toluquinol and gentisyl alcohol by particulate preparations from Penicillium patulum

    SciTech Connect

    Priest, J.W.; Light, R.J. )

    1989-11-14

    A crude extract that catalyzes the epoxidation of toluquinol and gentisyl alcohol was isolated from cultures of Penicillium patulum. About 60% of the activity sedimented from crude extract upon centrifugation at 105000g for 2 h, and at 30000g for 30 min after precipitation with 30% ammonium sulfate and resuspension in buffer. The quinone epoxide phyllostine, a product of gentisyl alcohol epoxidation, has previously been shown to be an intermediate in the biosynthesis of patulin and was shown to be further converted to neopatulin by the extract. The epoxide product of toluquinol, desoxyphyllostine (2-methyl-5,6-epoxy-1,4-benzoquinone), has not been reported previously from fungal cultures. Its structure was confirmed by GC-mass spectrometry and proton and {sup 13}C NMR. Its CD spectrum showed the same shape and signs as that of phyllostine, indicating that it too is an enzymatic product with a similar absolute configuration. Whereas chemical epoxidation of toluquinone and gentisly quinone occurs with hydrogen peroxide, the enzymatic epoxidation utilized oxygen and the hydroquinone. The epoxidation was inhibited by 1,10-phenanthroline, EDTA, and {rho}-(chloromercuri)benzenesulfonic acid and by degassing with nitrogen, but no inhibition was observed with KCN, catalase, or CO. The apparent K{sub m}'s were similar for the two substrates with both substrates showing inhibition at 1.0 mM. The rate of desoxyphyllostine formation was more than 10 times that of phyllostine formation at equivalent substrate concentrations. Gentisaldehyde was not a substrate for the enzyme. The epoxidase was induced in late fermentor cultures of P. patulum with the same kinetics as m-hydroxybenzyl alcohol dehydrogenase, another enzyme associated with the induction of patulin biosynthesis.

  10. Highly selective hydrolytic kinetic resolution of terminal epoxides catalyzed by chiral (salen)Co(III) complexes. Practical synthesis of enantioenriched terminal epoxides and 1,2-diols.

    PubMed

    Schaus, Scott E; Brandes, Bridget D; Larrow, Jay F; Tokunaga, Makoto; Hansen, Karl B; Gould, Alexandra E; Furrow, Michael E; Jacobsen, Eric N

    2002-02-20

    The hydrolytic kinetic resolution (HKR) of terminal epoxides catalyzed by chiral (salen)Co(III) complex 1 x OAc affords both recovered unreacted epoxide and 1,2-diol product in highly enantioenriched form. As such, the HKR provides general access to useful, highly enantioenriched chiral building blocks that are otherwise difficult to access, from inexpensive racemic materials. The reaction has several appealing features from a practical standpoint, including the use of H(2)O as a reactant and low loadings (0.2-2.0 mol %) of a recyclable, commercially available catalyst. In addition, the HKR displays extraordinary scope, as a wide assortment of sterically and electronically varied epoxides can be resolved to > or = 99% ee. The corresponding 1,2-diols were produced in good-to-high enantiomeric excess using 0.45 equiv of H(2)O. Useful and general protocols are provided for the isolation of highly enantioenriched epoxides and diols, as well as for catalyst recovery and recycling. Selectivity factors (k(rel)) were determined for the HKR reactions by measuring the product ee at ca. 20% conversion. In nearly all cases, k(rel) values for the HKR exceed 50, and in several cases are well in excess of 200.

  11. Discovery of enantioselectivity of urea inhibitors of soluble epoxide hydrolase.

    PubMed

    Manickam, Manoj; Pillaiyar, Thanigaimalai; Boggu, PullaReddy; Venkateswararao, Eeda; Jalani, Hitesh B; Kim, Nam-Doo; Lee, Seul Ki; Jeon, Jang Su; Kim, Sang Kyum; Jung, Sang-Hun

    2016-07-19

    Soluble epoxide hydrolase (sEH) hydrolyzes epoxyeicosatrienoic acids (EETs) in the metabolic pathway of arachidonic acid and has been considered as an important therapeutic target for chronic diseases such as hypertension, diabetes and inflammation. Although many urea derivatives are known as sEH inhibitors, the enantioselectivity of the inhibitors is not highlighted in spite of the stereoselective hydrolysis of EETs by sEH. In an effort to explore the importance of enantioselectivity in the urea scaffold, a series of enantiomers with the stereocenter adjacent to the urea nitrogen atom were prepared. The selectivity of enantiomers of 1-(α-alkyl-α-phenylmethyl)-3-(3-phenylpropyl)ureas showed wide range differences up to 125 fold with the low IC50 value up to 13 nM. The S-configuration with planar phenyl and small alkyl groups at α-position is crucial for the activity and selectivity. However, restriction of the free rotation of two α-groups with indan-1-yl or 1,2,3,4-tetrahydronaphthalen-1-yl moiety abolishes the selectivity between the enantiomers, despite the increase in activity up to 13 nM. The hydrophilic group like sulfonamido group at para position of 3-phenylpropyl motif of 1-(α-alkyl-α-phenylmethyl-3-(3-phenylpropyl)urea improves the activity as well as enantiomeric selectivity. All these ureas are proved to be specific inhibitor of sEH without inhibition against mEH.

  12. Soluble epoxide hydrolase inhibitory activity of anthraquinone components from Aloe.

    PubMed

    Sun, Ya Nan; Kim, Jang Hoon; Li, Wei; Jo, A Reum; Yan, Xi Tao; Yang, Seo Young; Kim, Young Ho

    2015-10-15

    Aloe is a short-stemmed succulent herb widely used in traditional medicine to treat various diseases and as raw material in cosmetics and heath foods. In this study, we isolated and identified two new anthraquinone derivatives, aloinoside C (6) and aloinoside D (7), together with six known compounds from an aqueous dissolved Aloe exudate. Their structures were identified by spectroscopic analysis. The inhibitory effects of the isolated compounds on soluble epoxide hydrolase (sEH) were evaluated. Compounds 1-8 inhibited sEH activity potently, with IC50 values ranging from 4.1±0.6 to 41.1±4.2 μM. A kinetic analysis of compounds 1-8 revealed that the inhibitory actions of compounds 1, 6 and 8 were non-competitive, whereas those of compounds 2-5 and 7 were the mixed-type. Molecular docking increases our understanding of receptor-ligand binding of all compounds. These results demonstrate that compounds 1-8 from Aloe are potential sEH inhibitors.

  13. Cure shrinkage in casting resins

    SciTech Connect

    Spencer, J. Brock

    2015-02-01

    A method is described whereby the shrinkage of a casting resin can be determined. Values for the shrinkage of several resin systems in frequent use by Sandia have been measured. A discussion of possible methods for determining the stresses generated by cure shrinkage and thermal contraction is also included.

  14. Imide modified epoxy matrix resins

    NASA Technical Reports Server (NTRS)

    Scola, D. A.; Pater, R. H.

    1981-01-01

    High char yield epoxy using novel bisimide amines (BIA's) as curing agents with a state of the art epoxy resin was developed. Stoichiometric quantities of the epoxy resin and the BIA's were studied to determine the cure cycle required for preparation of resin specimens. The bisimide cured epoxies were designated IME's (imide modified epoxy). The physical, thermal and mechanical properties of these novel resins were determined. The levels of moisture absorption exhibited by the bisimide amine cured expoxies (IME's) were considerably lower than the state of the art epoxies. The strain-to-failure of the control resin system was improved 25% by replacement of DDS with 6F-DDS. Each BIA containing resin exhibited twice the char yield of the control resin MY 720/DDS. Graphite fiber reinforced control (C) and IME resins were fabricated and characterized. Two of the composite systems showed superior properties compared to the other Celion 6000/IME composite systems and state of the art graphite epoxy systems. The two systems exhibited excellent wet shear and flexural strengths and moduli at 300 and 350 F.

  15. A2E-epoxides damage DNA in retinal pigment epithelial cells. Vitamin E and other antioxidants inhibit A2E-epoxide formation.

    PubMed

    Sparrow, Janet R; Vollmer-Snarr, Heidi R; Zhou, Jilin; Jang, Young P; Jockusch, Steffen; Itagaki, Yasuhiro; Nakanishi, Koji

    2003-05-16

    The autofluorescent pigments that accumulate in retinal pigment epithelial cells with aging and in some retinal disorders have been implicated in the etiology of macular degeneration. The major constituent is the fluorophore A2E, a pyridinium bisretinoid. Light-exposed A2E-laden retinal pigment epithelium exhibits a propensity for apoptosis with light in the blue region of the spectrum being most damaging. Efforts to understand the events precipitating the death of the cells have revealed that during irradiation (430 nm), A2E self-generates singlet oxygen with the singlet oxygen in turn reacting with A2E to generate epoxides at carbon-carbon double bonds. Here we demonstrate that A2E-epoxides, independent of singlet oxygen, exhibit reactivity toward DNA with oxidative base changes being at least one of these lesions. Mass spectrometry revealed that the antioxidants vitamins E and C, butylated hydroxytoluene, resveratrol, a trolox analogue (PNU-83836-E), and bilberry extract reduce A2E-epoxidation, whereas single cell gel electrophoresis and cell viability studies revealed a corresponding reduction in the incidence of DNA damage and cell death. Vitamin E, a lipophilic antioxidant, produced a more pronounced decrease in A2E-epoxidation than vitamin C, and treatment with both vitamins simultaneously did not confer additional benefit. Studies in which singlet oxygen was generated by endoperoxide in the presence of A2E revealed that vitamin E, butylated hydroxytoluene, resveratrol, the trolox analogue, and bilberry reduced A2E-epoxidation by quenching singlet oxygen. Conversely, vitamin C and ginkgolide B were not efficient quenchers of singlet oxygen under these conditions.

  16. High performance phenolic pultrusion resin

    SciTech Connect

    Qureshi, S.P.; Ingram, W.H.; Smith, C.

    1996-11-01

    Today, Phenol-Formaldehyde (PF) resins are the materials of choice for aerospace interior applications, primarily due to low FST (flame, smoke and toxicity). Since 1990, growth of PF resins has been steadily increasing in non-aerospace applications (which include mass transit, construction, marine, mine ducting and offshore oil) due to low FST and reasonable cost. This paper describes one component phenol-formaldehyde resin that was jointly developed with Morrison Molded Fiber Glass for their pultrusion process. Physical properties of the resin with flame/smoke/toxicity, chemical resistance and mechanical performance of the pultruded RP are discussed. Neat resin screening tests to identify high-temperature formulations are explored. Research continues at Georgia-Pacific to investigate the effect of formulation variables on processing and mechanical properties.

  17. Reactions of epoxide monomers in food simulants used to test plastics for migration.

    PubMed

    Philo, M R; Damant, A P; Castle, L

    1997-01-01

    The reactions of four epoxides used as monomers for food contact plastics were studied in the food simulants distilled water, 15% aqueous ethanol, 3% aqueous acetic acid and olive oil. Loss of the parent substance and formation of products was monitored to establish the transformation products to be expected in each simulant following migration testing of plastics. Each epoxide was stable in olive oil but suffered extensive loss in the three aqueous simulants. Reaction half-lives were from < 1 to 10 h in aqueous acetic acid, 25-63 h in distilled water, and 33-87 h in aqueous ethanol simulant. Hydrolysis to the diol was the main reaction pathway. Epoxide ring opening in aqueous ethanol simulant gave the diol and also the diol monoethyl ether. It is concluded that, for aqueous simulants and by implication for most foods, testing plastics against specific migration limits for epoxides is not likely to give reliable results due to their reactivity. The present EC mode of control for these reactive monomers, via compositional limits in food contact plastics, is more practical since the hydrolysis products are less toxic than the parent epoxide.

  18. Synthesis and physicochemical properties of epoxidized Tmp trioleate by in situ method

    SciTech Connect

    Samidin, Salma; Salimon, Jumat

    2014-09-03

    Tmp trioleate was initially synthesized via esterification of trimetilolprapane and oleic acid (90%) using 1.5% of H{sub 2}SO{sub 4} as a catalyst. The production of Tmp trioleate was observed at 98% (w/w). The iodine value of Tmp trioleate was analyzed for further reaction of epoxidation. Epoxide was important reaction as an intermediate for preparation of chemical modified lubricants from vegetable oils. Finding the best way of epoxidation process will give high quality for further modification of oil instead of reduce the cost and time for the preparation process during reaction of epoxidation. In this study, the epoxidation of unsaturation Tmp trioleate with peroxyformic acid generated in-situ from hydrogen peroxide 30% in H{sub 2}O{sub 2} with formic acid was studied. 95% conversion to oxygen oxirane content (OOC) ring was obtained. The derivatization showed an improvement of the compound's oxidative stability evidenced from pressurized differential scanning calorimetry (PDSC) data which are 177°C to 200°C. Physicochemical properties showed increasing of temperature of flash point from 280°C to 300°C and viscosity index (VI) from 146 to 154. However, the pour point showed increasing temperature which was −58.81°C to −17.32°C. From the data obtained, these derivatives have shown better performance of lubricity properties. Overall, the data indicates that these performances are compatible to the commercial lubricants.

  19. Synthesis and physicochemical properties of epoxidized Tmp trioleate by in situ method

    NASA Astrophysics Data System (ADS)

    Samidin, Salma; Salimon, Jumat

    2014-09-01

    Tmp trioleate was initially synthesized via esterification of trimetilolprapane and oleic acid (90%) using 1.5% of H2SO4 as a catalyst. The production of Tmp trioleate was observed at 98% (w/w). The iodine value of Tmp trioleate was analyzed for further reaction of epoxidation. Epoxide was important reaction as an intermediate for preparation of chemical modified lubricants from vegetable oils. Finding the best way of epoxidation process will give high quality for further modification of oil instead of reduce the cost and time for the preparation process during reaction of epoxidation. In this study, the epoxidation of unsaturation Tmp trioleate with peroxyformic acid generated in-situ from hydrogen peroxide 30% in H2O2 with formic acid was studied. 95% conversion to oxygen oxirane content (OOC) ring was obtained. The derivatization showed an improvement of the compound's oxidative stability evidenced from pressurized differential scanning calorimetry (PDSC) data which are 177°C to 200°C. Physicochemical properties showed increasing of temperature of flash point from 280°C to 300°C and viscosity index (VI) from 146 to 154. However, the pour point showed increasing temperature which was -58.81°C to -17.32°C. From the data obtained, these derivatives have shown better performance of lubricity properties. Overall, the data indicates that these performances are compatible to the commercial lubricants.

  20. Developmental toxicity of bisphenol A diglycidyl ether (epoxide resin badge) during the early life cycle of a native amphibian species.

    PubMed

    Hutler Wolkowicz, Ianina; Svartz, Gabriela V; Aronzon, Carolina M; Pérez Coll, Christina

    2016-12-01

    Bisphenol A diglycidyl ether (BADGE) is used in packaging materials, in epoxy adhesives, and as an additive for plastics, but it is also a potential industrial wastewater contaminant. The aim of the present study was to evaluate the adverse effects of BADGE on Rhinella arenarum by means of standardized bioassays at embryo-larval development. The results showed that BADGE was more toxic to embryos than to larvae at all exposure times. At acute exposure, lethality rates of embryos exposed to concentrations of 0.0005 mg/L BADGE and greater were significantly higher than rates in the vehicle control, whereas lethality rates of larvae were significantly higher in concentrations of 10 mg/L BADGE and greater. The toxicity then increased significantly, with 96-h median lethal concentrations (LC50s) of 0.13 mg/L and 6.9 mg/L BADGE for embryos and larvae, respectively. By the end of the chronic period, the 336-h LC50s were 0.04 mg/L and 2.2 mg/L BADGE for embryos and larvae, respectively. This differential sensitivity was also ascertained by the 24-h pulse exposure experiments, in which embryos showed a stage-dependent toxicity, with blastula being the most sensitive stage and S.23 the most resistant. The most important sublethal effects in embryos were cell dissociation and delayed development, whereas the main abnormalities observed in larvae related to neurotoxicity, as scare response to stimuli and narcotic effect. Environ Toxicol Chem 2016;35:3031-3038. © 2016 SETAC.

  1. 40 CFR 721.10313 - Fatty acids, C16-18 and C18-unsatd., Me esters, epoxidized.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...., Me esters, epoxidized. 721.10313 Section 721.10313 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10313 Fatty acids, C16-18 and C18-unsatd., Me esters... identified as fatty acids, C16-18 and C18-unsatd., Me esters, epoxidized (PMN P-02-249; CAS No....

  2. 40 CFR 721.10313 - Fatty acids, C16-18 and C18-unsatd., Me esters, epoxidized.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...., Me esters, epoxidized. 721.10313 Section 721.10313 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10313 Fatty acids, C16-18 and C18-unsatd., Me esters... identified as fatty acids, C16-18 and C18-unsatd., Me esters, epoxidized (PMN P-02-249; CAS No....

  3. 40 CFR 721.10313 - Fatty acids, C16-18 and C18-unsatd., Me esters, epoxidized.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...., Me esters, epoxidized. 721.10313 Section 721.10313 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10313 Fatty acids, C16-18 and C18-unsatd., Me esters... identified as fatty acids, C16-18 and C18-unsatd., Me esters, epoxidized (PMN P-02-249; CAS No....

  4. Epoxidation of alkenes through oxygen activation over a bifunctional CuO/Al2O3 catalyst.

    PubMed

    Scotti, Nicola; Ravasio, Nicoletta; Zaccheria, Federica; Psaro, Rinaldo; Evangelisti, Claudio

    2013-03-07

    The epoxidation of alkenes was carried out over a CuO/Al(2)O(3) catalyst using cumene as an oxygen carrier, through a one-pot reaction, giving high conversion and selectivity with different substrates. Trans-β-methylstyrene gave the corresponding epoxide in 95% yield after 3 h.

  5. Soluble epoxide hydrolase limits mechanical hyperalgesia during inflammation

    PubMed Central

    2011-01-01

    Background Cytochrome-P450 (CYP450) epoxygenases metabolise arachidonic acid (AA) into four different biologically active epoxyeicosatrienoic acid (EET) regioisomers. Three of the EETs (i.e., 8,9-, 11,12- and 14,15-EET) are rapidly hydrolysed by the enzyme soluble epoxide hydrolase (sEH). Here, we investigated the role of sEH in nociceptive processing during peripheral inflammation. Results In dorsal root ganglia (DRG), we found that sEH is expressed in medium and large diameter neurofilament 200-positive neurons. Isolated DRG-neurons from sEH-/- mice showed higher EET and lower DHET levels. Upon AA stimulation, the largest changes in EET levels occurred in culture media, indicating both that cell associated EET concentrations quickly reach saturation and EET-hydrolyzing activity mostly effects extracellular EET signaling. In vivo, DRGs from sEH-deficient mice exhibited elevated 8,9-, 11,12- and 14,15-EET-levels. Interestingly, EET levels did not increase at the site of zymosan-induced inflammation. Cellular imaging experiments revealed direct calcium flux responses to 8,9-EET in a subpopulation of nociceptors. In addition, 8,9-EET sensitized AITC-induced calcium increases in DRG neurons and AITC-induced calcitonin gene related peptide (CGRP) release from sciatic nerve axons, indicating that 8,9-EET sensitizes TRPA1-expressing neurons, which are known to contribute to mechanical hyperalgesia. Supporting this, sEH-/- mice showed increased nociceptive responses to mechanical stimulation during zymosan-induced inflammation and 8,9-EET injection reduced mechanical thresholds in naive mice. Conclusion Our results show that the sEH can regulate mechanical hyperalgesia during inflammation by inactivating 8,9-EET, which sensitizes TRPA1-expressing nociceptors. Therefore we suggest that influencing the CYP450 pathway, which is actually highly considered to treat cardiovascular diseases, may cause pain side effects. PMID:21970373

  6. Soluble epoxide hydrolase: a novel therapeutic target in stroke

    PubMed Central

    Zhang, Wenri; Koerner, Ines P; Noppens, Ruediger; Grafe, Marjorie; Tsai, Hsing-Ju; Morisseau, Christophe; Luria, Ayala; Hammock, Bruce D; Falck, John R; Alkayed, Nabil J

    2009-01-01

    The P450 eicosanoids epoxyeicosatrienoic acids (EETs) are produced in brain and perform important biological functions, including protection from ischemic injury. The beneficial effect of EETs, however, is limited by their metabolism via soluble epoxide hydrolase (sEH). We tested the hypothesis that sEH inhibition is protective against ischemic brain damage in vivo by a mechanism linked to enhanced cerebral blood flow (CBF). We determined expression and distribution of sEH immunoreactivity (IR) in brain, and examined the effect of sEH inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic acid butyl ester (AUDA-BE) on CBF and infarct size after experimental stroke in mice. Mice were administered a single intraperitoneal injection of AUDA-BE (10 mg/kg) or vehicle at 30 mins before 2-h middle cerebral artery occlusion (MCAO) or at reperfusion, in the presence and absence of P450 epoxygenase inhibitor N-methylsulfonyl-6-(2-propargyloxyphenyl) hexanamide (MS-PPOH). Immunoreactivity for sEH was detected in vascular and non-vascular brain compartments, with predominant expression in neuronal cell bodies and processes. 12-(3-Adamantan-1-yl-ureido)-dodecanoic acid butyl ester was detected in plasma and brain for up to 24 h after intraperitoneal injection, which was associated with inhibition of sEH activity in brain tissue. Finally, AUDA-BE significantly reduced infarct size at 24 h after MCAO, which was prevented by MS-PPOH. However, regional CBF rates measured by iodoantipyrine (IAP) autoradiography at end ischemia revealed no differences between AUDA-BE- and vehicle-treated mice. The findings suggest that sEH inhibition is protective against ischemic injury by non-vascular mechanisms, and that sEH may serve as a therapeutic target in stroke. PMID:17440491

  7. Increased silver activity for direct propylene epoxidation via subnanometer size effects.

    SciTech Connect

    Lei, Y.; Mehmood, F.; Lee, S.; Greeley, J. P.; Lee, B.; Seifert, S.; Winans, R. E.; Elam, J. E.; Meyer, R. J.; Redfern, P. C.; Teschner, D.; Schlogl, R.; Pellin, M. J.; Curtiss, L. A.; Vajda, S.; Univ. of Illinois at Chicago; Fritz-Haber Inst. der Max-Planck-Gesellschaft; Yale Univ.

    2010-04-09

    Production of the industrial chemical propylene oxide is energy-intensive and environmentally unfriendly. Catalysts based on bulk silver surfaces with direct propylene epoxidation by molecular oxygen have not resolved these problems because of substantial formation of carbon dioxide. We found that unpromoted, size-selected Ag{sub 3} clusters and {approx}3.5-nanometer Ag nanoparticles on alumina supports can catalyze this reaction with only a negligible amount of carbon dioxide formation and with high activity at low temperatures. Density functional calculations show that, relative to extended silver surfaces, oxidized silver trimers are more active and selective for epoxidation because of the open-shell nature of their electronic structure. The results suggest that new architectures based on ultrasmall silver particles may provide highly efficient catalysts for propylene epoxidation.

  8. Increased Silver Activity for Direct Propylene Epoxidation via Subnanometer Size Effects

    SciTech Connect

    Lei, Y.; Mehmood, Faisal; Lee, Sang Soo; Greeley, Jeffrey P.; Lee, Byeongdu; Seifert, Soenke; Winans, R. E.; Elam, J. W.; Meyer, R. J.; Redfern, Paul C.; Teschner, D.; Schlogl, Robert; Pellin, M. J.; Curtiss, Larry A.; Vajda, S.

    2010-04-09

    Production of the industrial chemical propylene oxide is energy-intensive and environmentally unfriendly. Catalysts based on bulk silver surfaces with direct propylene epoxidation by molecular oxygen have not resolved these problems because of substantial formation of carbon dioxide. We found that unpromoted, size-selected Ag3 clusters and ~3.5-nanometer Ag nanoparticles on alumina supports can catalyze this reaction with only a negligible amount of carbon dioxide formation and with high activity at low temperatures. Density functional calculations show that, relative to extended silver surfaces, oxidized silver trimers are more active and selective for epoxidation because of the open-shell nature of their electronic structure. The results suggest that new architectures based on ultrasmall silver particles may provide highly efficient catalysts for propylene epoxidation.

  9. A broadly applicable and practical oligomeric (salen) Co catalyst for enantioselective epoxide ring-opening reactions

    PubMed Central

    White, David E.; Tadross, Pamela M.; Lu, Zhe

    2014-01-01

    The (salen) Co catalyst (4a) can be prepared as a mixture of cyclic oligomers in a short, chromatography-free synthesis from inexpensive, commercially available precursors. This catalyst displays remarkable enhancements in reactivity and enantioselectivity relative to monomeric and other multimeric (salen) Co catalysts in a wide variety of enantioselective epoxide ring-opening reactions. The application of catalyst 4a is illustrated in the kinetic resolution of terminal epoxides by nucleophilic ring-opening with water, phenols, and primary alcohols; the desymmetrization of meso epoxides by addition of water and carbamates; and the desymmetrization of oxetanes by intramolecular ring opening with alcohols and phenols. The favorable solubility properties of complex 4a under the catalytic conditions facilitated mechanistic studies, allowing elucidation of the basis for the beneficial effect of oligomerization. Finally, a catalyst selection guide is provided to delineate the specific advantages of oligomeric catalyst 4a relative to (salen) Co monomer 1 for each reaction class. PMID:25045188

  10. A broadly applicable and practical oligomeric (salen) Co catalyst for enantioselective epoxide ring-opening reactions.

    PubMed

    White, David E; Tadross, Pamela M; Lu, Zhe; Jacobsen, Eric N

    2014-07-08

    The (salen) Co catalyst (4a) can be prepared as a mixture of cyclic oligomers in a short, chromatography-free synthesis from inexpensive, commercially available precursors. This catalyst displays remarkable enhancements in reactivity and enantioselectivity relative to monomeric and other multimeric (salen) Co catalysts in a wide variety of enantioselective epoxide ring-opening reactions. The application of catalyst 4a is illustrated in the kinetic resolution of terminal epoxides by nucleophilic ring-opening with water, phenols, and primary alcohols; the desymmetrization of meso epoxides by addition of water and carbamates; and the desymmetrization of oxetanes by intramolecular ring opening with alcohols and phenols. The favorable solubility properties of complex 4a under the catalytic conditions facilitated mechanistic studies, allowing elucidation of the basis for the beneficial effect of oligomerization. Finally, a catalyst selection guide is provided to delineate the specific advantages of oligomeric catalyst 4a relative to (salen) Co monomer 1 for each reaction class.

  11. Inhibiting an Epoxide Hydrolase Virulence Factor from Pseudomonas aeruginosa Protects CFTR.

    PubMed

    Bahl, Christopher D; Hvorecny, Kelli L; Bomberger, Jennifer M; Stanton, Bruce A; Hammock, Bruce D; Morisseau, Christophe; Madden, Dean R

    2015-08-17

    Opportunistic pathogens exploit diverse strategies to sabotage host defenses. Pseudomonas aeruginosa secretes the CFTR inhibitory factor Cif and thus triggers loss of CFTR, an ion channel required for airway mucociliary defense. However, the mechanism of action of Cif has remained unclear. It catalyzes epoxide hydrolysis, but there is no known role for natural epoxides in CFTR regulation. It was demonstrated that the hydrolase activity of Cif is strictly required for its effects on CFTR. A small-molecule inhibitor that protects this key component of the mucociliary defense system was also uncovered. These results provide a basis for targeting the distinctive virulence chemistry of Cif and suggest an unanticipated role of physiological epoxides in intracellular protein trafficking.

  12. Enantioselective epoxidation with chiral MN(III)(salen) catalysts: kinetic resolution of aryl-substituted allylic alcohols.

    PubMed

    Adam, W; Humpf, H U; Roschmann, K J; Saha-Möller, C R

    2001-08-24

    A set of aryl-substituted allylic alcohols rac-2 has been epoxidized by chiral Mn(salen*) complexes 1 as the catalyst and iodosyl benzene (PhIO) as the oxygen source. Whereas one enantiomer of the allylic alcohol 2 is preferentially epoxidized to give the threo- or cis-epoxy alcohol 3 (up to 80% ee) as the main product (dr up to >95:5), the other enantiomer of 2 is enriched (up to 53% ee). In the case of 1,1-dimethyl-1,2-dihydronaphthalen-2-ol (2c), the CH oxidation to the enone 4c proceeds enantioselectively and competes with the epoxidation. The absolute configurations of the allylic alcohols 2 and their epoxides 3 have been determined by chemical correlation or CD spectroscopy. The observed diastereo- and enantioselectivities in the epoxidation reactions are rationalized in terms of a beneficial interplay between the hydroxy-directing effect and the attack along the Katsuki trajectory.

  13. A simple and effective catalytic system for epoxidation of aliphatic terminal alkenes with manganese(II) as the catalyst.

    PubMed

    Ho, Kam-Piu; Wong, Wing-Leung; Lam, Kin-Ming; Lai, Cheuk-Piu; Chan, Tak Hang; Wong, Kwok-Yin

    2008-01-01

    A simple catalytic system that uses commercially available manganese(II) perchlorate as the catalyst and peracetic acid as the oxidant is found to be very effective in the epoxidation of aliphatic terminal alkenes with high product selectivity at ambient temperature. Many terminal alkenes are epoxidised efficiently on a gram scale in less than an hour to give excellent yields of isolated product (>90 %) of epoxides in high purity. Kinetic studies with some C9-alkenes show that the catalytic system is more efficient in epoxidising terminal alkenes than internal alkenes, which is contrary to most commonly known epoxidation systems. The reaction rate for epoxidation decreases in the order: 1-nonene>cis-3-nonene>trans-3-nonene. ESI-MS and EPR spectroscopic studies suggest that the active form of the catalyst is a high-valent oligonuclear manganese species, which probably functions as the oxygen atom-transfer agent in the epoxidation reaction.

  14. Indirect resin composites

    PubMed Central

    Nandini, Suresh

    2010-01-01

    Aesthetic dentistry continues to evolve through innovations in bonding agents, restorative materials, and conservative preparation techniques. The use of direct composite restoration in posterior teeth is limited to relatively small cavities due to polymerization stresses. Indirect composites offer an esthetic alternative to ceramics for posterior teeth. This review article focuses on the material aspect of the newer generation of composites. This review was based on a PubMed database search which we limited to peer-reviewed articles in English that were published between 1990 and 2010 in dental journals. The key words used were ‘indirect resin composites,’ composite inlays,’ and ‘fiber-reinforced composites.’ PMID:21217945

  15. Chromatography resin support

    DOEpatents

    Dobos, James G.

    2002-01-01

    An apparatus and method of using an improved chromatography resin support is disclosed. The chromatography support platform is provided by a stainless steel hollow cylinder adapted for being inserted into a chromatography column. An exterior wall of the stainless steel cylinder defines a groove for carrying therein an "O"-ring. The upper surface of the stainless steel column is covered by a fine stainless steel mesh welded to the edges of the stainless steel cylinder. When placed upon a receiving ledge defined within a chromatography column, the "O"-ring provides a fluid tight seal with the inner edge wall of the chromatography cylinder. The stainless steel mesh supports the chromatography matrix and provides a back flushable support which is economical and simple to construct.

  16. Flammability screening tests of resins

    NASA Technical Reports Server (NTRS)

    Arhart, R. W.; Farrar, D. G.; Hughes, B. M.

    1979-01-01

    Selected flammability characteristics of glass cloth laminates of thermosetting resins are evaluated. A protocol for the evaluation of the flammability hazards presented by glass cloth laminates of thermosetting resins and the usefulness of that protocol with two laminates are presented. The glass laminates of an epoxy resin, M-751 are evaluated for: (1) determination of smoke generation from the laminates; (2) analysis of products of oxidative degradation of the laminates; (3) determination of minimum oxygen necessary to maintain flaming oxidation; (4) evaluation of toxicological hazards.

  17. Resin/graphite fiber composites

    NASA Technical Reports Server (NTRS)

    Cavano, P. J.; Jones, R. J.; Vaughan, R. W.

    1972-01-01

    High temperature resin matrices suitable for use in advanced graphite fiber composites for jet engine applications were evaluated. A series of planned, sequential screening experiments with resin systems in composite form were performed to reduce the number of candidates to a single A-type polyimide resin that repetitively produced void-free, high strength and modulus composites acceptable for use in the 550 F range for 1000 hours. An optimized processing procedure was established for this system. Extensive mechanical property studies characterized this single system, at room temperature, 500 F, 550 F and 600 F, for various exposure times.

  18. Grafted methylenediphosphonate ion exchange resins

    DOEpatents

    Trochimcznk, A.W.; Gatrone, R.C.; Alexandratos, S.; Horwitz, E.P.

    1997-04-08

    An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorus. The pendent groups have the formula as shown in the patent wherein R is hydrogen, a cation or mixtures thereof; and R{sup 1} is hydrogen or an C{sub 1}-C{sub 2} alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange resin are also disclosed.

  19. Grafted methylenediphosphonate ion exchange resins

    DOEpatents

    Trochimcznk, Andrzej W.; Gatrone, Ralph C.; Alexandratos, Spiro; Horwitz, E. Philip

    1998-01-27

    An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorous. The pendent groups have the formula ##STR1## wherein R is hydrogen, a cation or mixtures thereof; and R.sup.1 is hydrogen or an C.sub.1 -C.sub.2 alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange-resin are also disclosed.

  20. Grafted methylenediphosphonate ion exchange resins

    DOEpatents

    Trochimcznk, Andrzej W.; Gatrone, Ralph C.; Alexandratos, Spiro; Horwitz, E. Philip

    1997-01-01

    An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorous. The pendent groups have the formula ##STR1## wherein R is hydrogen, a cation or mixtures thereof; and R.sup.1 is hydrogen or an C.sub.1 -C.sub.2 alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange resin are also disclosed.

  1. Asymmetric epoxidation of allylic alcohols catalyzed by vanadium-binaphthylbishydroxamic Acid complex.

    PubMed

    Noji, Masahiro; Kobayashi, Toshihiro; Uechi, Yuria; Kikuchi, Asami; Kondo, Hisako; Sugiyama, Shigeo; Ishii, Keitaro

    2015-03-20

    A vanadium-binaphthylbishydroxamic acid (BBHA) complex-catalyzed asymmetric epoxidation of allylic alcohols is described. The optically active binaphthyl-based ligands BBHA 2a and 2b were synthesized from (S)-1,1'-binaphthyl-2,2'-dicarboxylic acid and N-substituted-O-trimethylsilyl (TMS)-protected hydroxylamines via a one-pot, three-step procedure. The epoxidations of 2,3,3-trisubstituted allylic alcohols using the vanadium complex of 2a were easily performed in toluene with a TBHP water solution to afford (2R)-epoxy alcohols in good to excellent enantioselectivities.

  2. Synthesis of Marine Polycyclic Polyethers via Endo-Selective Epoxide-Opening Cascades

    PubMed Central

    Vilotijevic, Ivan; Jamison, Timothy F.

    2010-01-01

    The proposed biosynthetic pathways to ladder polyethers of polyketide origin and oxasqualenoids of terpenoid origin share a dramatic epoxide-opening cascade as a key step. Polycyclic structures generated in these biosynthetic pathways display biological effects ranging from potentially therapeutic properties to extreme lethality. Much of the structural complexity of ladder polyether and oxasqualenoid natural products can be traced to these hypothesized cascades. In this review we summarize how such epoxide-opening cascade reactions have been used in the synthesis of ladder polyethers and oxasqualenoid natural products. PMID:20411125

  3. Enantioselective epoxidation of non-functionalized alkenes using carbohydrate based salen-Mn(III) complexes.

    PubMed

    Zhao, Shanshan; Zhao, Jiquan; Zhao, Dongmin

    2007-02-05

    Three new salen ligands with carbohydrate moieties were prepared from a salicylaldehyde derivative obtained by reaction of 1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose with 3-tert-butyl-5-(chloro-methyl)-2-hydroxybenzaldehyde. These ligands were coordinated with Mn(III) to give three chiral salen-Mn(III) complexes. The complexes were characterized and employed in the asymmetric epoxidation of unfunctionalized alkenes. Catalytic results showed that although there are no chiral groups on the diimine bridge, these complexes had some enantioselectivity, which indicates the carbohydrate moiety has an asymmetric inducing effect in the epoxidation reaction.

  4. The selection reaction of homogeneous catalyst in soy-epoxide hydroxylation

    NASA Astrophysics Data System (ADS)

    Elvistia Firdaus, Flora

    2014-04-01

    Hydroxylation reaction of soy-epoxide has resulted soy-polyol; a prepolymeric material for polyurethane. The conversion and selectivity of soy-epoxide butanol based to hydroxylation was found higher than soy-ethylene glycol (EG) based. These reactions were performed by sulfur acid which commonly known as homogeneous catalyst. Conversion and selectivity of homogeneous catalyst compared to bentonite; a heteregeneous catalyst was lower as in fact the mixtures were more viscous. The catalysis were significantly effected to cell morphology. Foams were conducted by heterogeneous catalyst resulted an irregular form of windows while homogeneous catalyst are more ordered.

  5. Miscibility study of hexanoyl chitosan in blend with epoxidized natural rubber by viscometric analysis

    NASA Astrophysics Data System (ADS)

    Jamal, Asheila; Chan, C. H.; Muhammad, F. H.; Winie, Tan

    2015-08-01

    Miscibility of blends of hexanoyl chitosan and epoxidized natural rubber with 25 mol% epoxidation level (ENR25) was investigated by dilute solution viscometry (DSV). Experimental results obey the Huggins' equation in the concentration range under investigation. Intrinsic viscosities are found to vary linearly with blend composition. The difference between experimental and ideal Huggins coefficients, κ =K12-√{K1ṡK2 } is proposed to evaluate the miscibility behavior of the blends. Negative deviations from the ideal behavior indicated immiscibility between hexanoyl chitosan and ENR25.

  6. Allergic contact dermatitis from formaldehyde textile resins.

    PubMed

    Reich, Hilary C; Warshaw, Erin M

    2010-01-01

    Formaldehyde-based resins have been used to create permanent-press finishes on fabrics since the 1920s. These resins have been shown to be potent sensitizers in some patients, leading to allergic contact dermatitis. This review summarizes the history of formaldehyde textile resin use, the diagnosis and management of allergic contact dermatitis from these resins, and current regulation of formaldehyde resins in textiles.

  7. Epoxy hydantoins as matrix resins

    NASA Technical Reports Server (NTRS)

    Weiss, J.

    1983-01-01

    Tensile strength and fracture toughness of castings of the hydantoin resins cured with methylenedianiline are significantly higher than MY 720 control castings. Water absorption of an ethyl, amyl hydantoin formulation is 2.1 percent at equilibrium and Tg's are about 160 C, approximately 15 deg below the final cure temperature. Two series of urethane and ester-extended hydantoin epoxy resins were synthesized to determine the effect of crosslink density and functional groups on properties. Castings cured with methylenedianiline or with hexahydrophthalic anhydride were made from these compounds and evaluated. The glass transition temperatures, tensile strengths and moduli, and fracture toughness values were all much lower than that of the simple hydantoin epoxy resins. Using a methylene bishydantoin epoxy with a more rigid structure gave brittle, low-energy fractures, while a more flexible, ethoxy-extended hydantoin epoxy resin gave a very low Tg.

  8. Phthalonitrile Resins and Preparation Thereof.

    DTIC Science & Technology

    The present invention pertains generally to organic synthesis and in particular to a rapid synthesis of a diether-linked polyphthalonitrile resin by polymerizing a phthalonitrile monomer with a primary amine.

  9. Regenerating Water-Sterilizing Resins

    NASA Technical Reports Server (NTRS)

    Colombo, G. V.; Putnam, D. F.

    1982-01-01

    Iodine-dispensing resin can be regenerated after iodine content has been depleted, without being removed from water system. Resin is used to make water potable by killing bacteria, fungi, and viruses. Regeneration technique may be come basis of water purifier for very long space missions. Enough crystalline iodine for multiple regenerations during mission can be stored in one small cartridge. Cartridge could be inserted in waterline as necessary on signal from iodine monitor or timer.

  10. Liquid monobenzoxazine based resin system

    DOEpatents

    Tietze, Roger; Nguyen, Yen-Loan; Bryant, Mark

    2014-10-07

    The present invention provides a liquid resin system including a liquid monobenzoxazine monomer and a non-glycidyl epoxy compound, wherein the weight ratio of the monobenzoxazine monomer to the non-glycidyl epoxy compound is in a range of about 25:75 to about 60:40. The liquid resin system exhibits a low viscosity and exceptional stability over an extended period of time making its use in a variety of composite manufacturing methods highly advantageous.

  11. Investigation of the role of the 2',3'-epoxidation pathway in the bioactivation and genotoxicity of dietary allylbenzene analogs.

    PubMed

    Guenthner, T M; Luo, G

    2001-03-07

    The genotoxic potential of naturally occurring allylbenzene analogs, including safrole, eugenol, estragole, and others, has been examined in many studies over the past 30 years. It has been established that these compounds are subject to biotransformation in the liver, which can lead to the formation of reactive electrophilic intermediates. The major route of bioactivation is via hydroxylation of the 1' carbon atom of the allylic side chain. We have synthesized 2',3'- (allylic) epoxide derivatives of allylbenzene, estragole eugenol and safrole, and have used them to characterize the genotoxic potential of epoxidation at the allylic double bond for allylbenzene and its naturally occurring analogs. In order to assert that this pathway has the potential for genotoxicity, it is necessary to demonstrate (1) that epoxide metabolites of these compounds are capable of forming covalent adducts with DNA bases; and (2) that these epoxide metabolites are actually formed in vivo. We have demonstrated that allylic epoxides derived from allylbenzene and estragole are capable of forming covalent adducts with all four deoxyribonucleotides in vitro and, in the case of deoxyguanosine, form at least four different adducts. We also deduce, from evidence obtained using the isolated perfused rat liver, that formation of potentially genotoxic 2',3' epoxide metabolites occurs readily in vivo, but that these metabolites are rapidly further metabolized to less toxic dihydrodiol or glutathione conjugates. We conclude that 2',3' epoxide metabolites of allylbenzene analogs are formed in vivo and that these epoxides are sufficiently reactive to facilely form covalent bonds with DNA bases. Epoxide formation at the allylic double bond represents, therefore, a potentially genotoxic bioactivation pathway for allylbenzene analogs. However, comparison of the relative kinetics of epoxide metabolism and epoxide formation suggests that a wide margin of protection from DNA covalent adduct formation exists

  12. Recyclable polyurea-microencapsulated Pd(0) nanoparticles: an efficient catalyst for hydrogenolysis of epoxides.

    PubMed

    Ley, Steven V; Mitchell, Claire; Pears, David; Ramarao, Chandrashekar; Yu, Jin-Quan; Zhou, Wuzong

    2003-11-27

    [reaction: see text] Pd nanoparticles (approximately 2 nm in size) microencapsulated in polyurea is an efficient and recyclable catalyst for reductive ring-opening hydrogenolysis of epoxides, using either HCOOH/Et(3)N or H(2) as a hydrogen donor.

  13. A new efficient iron catalyst for olefin epoxidation with hydrogen peroxide.

    PubMed

    Mikhalyova, Elena A; Makhlynets, Olga V; Palluccio, Taryn D; Filatov, Alexander S; Rybak-Akimova, Elena V

    2012-01-18

    A new aminopyridine ligand derived from bipiperidine (the product of full reduction of bipyridine, bipy) coordinates to iron(II) in a cis-α fashion, yielding a new selective catalyst for olefin epoxidation with H(2)O(2) under limiting substrate conditions.

  14. Synthesis of epoxidized cardanol and its antioxidative properties for vegetable oils and biodiesel

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A novel antioxidant epoxidized cardanol (ECD), derived from cardanol, was synthesized and characterized by FT-IR, 1H-NMR and 13C-NMR. Oxidative stability of ECD used in vegetable oils and biodiesel was evaluated by pressurized differential scanning calorimetry (PDSC) and the Rancimat method, respect...

  15. Jacobsen protocols for large-scale epoxidation of cyclic dienyl sulfones: application to the (+)-pretazettine core.

    PubMed

    Ebrahimian, G Reza; du Jourdin, Xavier Mollat; Fuchs, Philip L

    2012-05-18

    A Jacobsen epoxidation protocol using H2O2 as oxidant was designed for the large-scale preparation of various epoxy vinyl sulfones. A number of cocatalysts were screened, and pH control led to increased reaction rate, higher turnover number, and improved reliability.

  16. Characterization of multiple epoxide hydrolase activities in mouse liver nuclear envelope.

    PubMed

    Guenthner, T M

    1986-10-01

    A nuclear envelope-associated epoxide hydrolase in mouse liver that hydrates trans-stilbene oxide has been identified and characterized. This epoxide hydrolase is distinct from the enzyme in nuclear envelopes that hydrates benzo[a]pyrene 4,5-oxide and other arene oxides. This distinction was demonstrated by the criteria of pH optima, response to specific inhibitors in vitro, and precipitation by specific antibodies. The new epoxide hydrolase had a pH optimum of 6.8, was poorly inhibited by trichloropropene oxide, was potently inhibited by 4-phenylchalcone oxide, and did not bind to antiserum against benzo[a]pyrene 4,5-oxide hydrolase. This nuclear enzyme is similar in many of its properties to cytosolic and microsomal trans-stilbene oxide hydrolases and may be nuclear envelope-bound form of these other epoxide hydrolases. It differed from these other trans-stilbene oxide hydrolases in that its affinities for both trans-stilbene oxide (measured as apparent Km) and 4-phenylchalcone oxide (measured as I50) were 4- to 20-fold lower than those of either the cytosolic or microsomal forms.

  17. Epoxide hydrolase activities and epoxy fatty acids in the mosquito Culex quinquefasciatus

    PubMed Central

    Xu, Jiawen; Morisseau, Christophe; Yang, Jun; Mamatha, Dadala M.

    2015-01-01

    Culex mosquitoes have emerged as important model organisms for mosquito biology, and are disease vectors for multiple mosquito-borne pathogens, including West Nile virus. We characterized epoxide hydrolase activities in the mosquito Culex quinquefasciatus, which suggested multiple forms of epoxide hydrolases were present. We found EH activities on epoxy eicosatrienoic acids (EETs). EETs and other eicosanoids are well-established lipid signaling molecules in vertebrates. We showed EETs can be synthesized in vitro from arachidonic acids by mosquito lysate, and EETs were also detected in vivo both in larvae and adult mosquitoes by LC-MS/MS. The EH activities on EETs can be induced by blood feeding, and the highest activity was observed in the midgut of female mosquitoes. The enzyme activities on EETs can be inhibited by urea-based inhibitors designed for mammalian soluble epoxide hydrolases (sEH). The sEH inhibitors have been shown to play diverse biological roles in mammalian systems, and they can be useful tools to study the function of EETs in mosquitoes. Besides juvenile hormone metabolism and detoxification, insect epoxide hydrolases may also play a role in regulating lipid signaling molecules, such as EETs and other epoxy fatty acids, synthesized in vivo or obtained from blood feeding by female mosquitoes. PMID:25686802

  18. Application of hydrated and anhydrous fluroantimonic acids in the polymerization of epoxidized soybean oil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Polymerizations of epoxidized soybean oil (ESO) were catalyzed by the superacids, fluroantimonic acid hexahydrate (HSbF6•6H2O) and anhydrous fluroantimonic acid (HSbF6) using ethyl acetate solvent. This work was conducted in an effort to develop useful biodegradable polymers from renewable resources...

  19. Catalyzed ring-opening polymerization of epoxidized soybean oil by hydrated and anhydrous fluoroantimonic acids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ring-opening polymerization of epoxidized soybean oil (ESO) catalyzed by the super acid, fluroantimonic acid hexahydrate (HSbF6-6H2O), and the anhydrous form (HSbF6) in ethyl acetate was conducted in an effort to develop useful biodegradable polymers. The resulting polymerized ESO (SA-RPESO and SAA-...

  20. Catalytic epoxidation activity of keplerate polyoxomolybdate nanoball toward aqueous suspension of olefins under mild aerobic conditions.

    PubMed

    Rezaeifard, Abdolreza; Haddad, Reza; Jafarpour, Maasoumeh; Hakimi, Mohammad

    2013-07-10

    Catalytic efficiency of a sphere-shaped nanosized polyoxomolybdate {Mo132} in the aerobic epoxidation of olefins in water at ambient temperature and pressure in the absence of reducing agent is exploited which resulted good-to-high yields and desired selectivity.

  1. Engineering of an epoxide hydrolase for efficient bioresolution of bulky pharmaco substrates

    PubMed Central

    Kong, Xu-Dong; Yuan, Shuguang; Li, Lin; Chen, She; Xu, Jian-He; Zhou, Jiahai

    2014-01-01

    Optically pure epoxides are essential chiral precursors for the production of (S)-propranolol, (S)-alprenolol, and other β-adrenergic receptor blocking drugs. Although the enzymatic production of these bulky epoxides has proven difficult, here we report a method to effectively improve the activity of BmEH, an epoxide hydrolase from Bacillus megaterium ECU1001 toward α-naphthyl glycidyl ether, the precursor of (S)-propranolol, by eliminating the steric hindrance near the potential product-release site. Using X-ray crystallography, mass spectrum, and molecular dynamics calculations, we have identified an active tunnel for substrate access and product release of this enzyme. The crystal structures revealed that there is an independent product-release site in BmEH that was not included in other reported epoxide hydrolase structures. By alanine scanning, two mutants, F128A and M145A, targeted to expand the potential product-release site displayed 42 and 25 times higher activities toward α-naphthyl glycidyl ether than the wild-type enzyme, respectively. These results show great promise for structure-based rational design in improving the catalytic efficiency of industrial enzymes for bulky substrates. PMID:25331869

  2. Iron(II)-Catalyzed Asymmetric Epoxidation of Trisubstituted α,β-Unsaturated Esters

    PubMed Central

    Luo, Lan

    2015-01-01

    An asymmetric epoxidation of trisubstituted α,β-unsaturated esters is described. The oxidation utilizes a pseudo-C2-symmetric iron(II) catalyst [Fe(L*)2(CH3CN)(OTf)](OTf) and peracetic acid as oxidant, yielding the α,β-epoxyesters in high enantiomeric purity (up to 99% ee). PMID:26146482

  3. (Salen)Mn(III) Catalyzed Asymmetric Epoxidation Reactions by Hydrogen Peroxide in Water: A Green Protocol

    PubMed Central

    Ballistreri, Francesco Paolo; Gangemi, Chiara M. A.; Pappalardo, Andrea; Tomaselli, Gaetano A.; Toscano, Rosa Maria; Trusso Sfrazzetto, Giuseppe

    2016-01-01

    Enantioselective epoxidation reactions of some chosen reactive alkenes by a chiral Mn(III) salen catalyst were performed in H2O employing H2O2 as oxidant and diethyltetradecylamine N-oxide (AOE-14) as surfactant. This procedure represents an environmentally benign protocol which leads to e.e. values ranging from good to excellent (up to 95%). PMID:27420047

  4. Thermal behavior of epoxidized cardanol diethyl phosphate as novel renewable plasticizer for poly(vinyl chloride)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A novel plasticizer, epoxidized cardanol diethyl phosphate (ECEP), based on cardanol was synthesized. Chemical structure of ECEP was characterized by fourier transform infrared (FTIR), 1H-nuclear magnetic resonance(1H NMR) and 13C-nuclear magnetic resonance(13C NMR) spectroscopy. Effects of ECEP sub...

  5. Signature motifs identify an Acinetobacter Cif virulence factor with epoxide hydrolase activity.

    PubMed

    Bahl, Christopher D; Hvorecny, Kelli L; Bridges, Andrew A; Ballok, Alicia E; Bomberger, Jennifer M; Cady, Kyle C; O'Toole, George A; Madden, Dean R

    2014-03-14

    Endocytic recycling of the cystic fibrosis transmembrane conductance regulator (CFTR) is blocked by the CFTR inhibitory factor (Cif). Originally discovered in Pseudomonas aeruginosa, Cif is a secreted epoxide hydrolase that is transcriptionally regulated by CifR, an epoxide-sensitive repressor. In this report, we investigate a homologous protein found in strains of the emerging nosocomial pathogens Acinetobacter nosocomialis and Acinetobacter baumannii ("aCif"). Like Cif, aCif is an epoxide hydrolase that carries an N-terminal secretion signal and can be purified from culture supernatants. When applied directly to polarized airway epithelial cells, mature aCif triggers a reduction in CFTR abundance at the apical membrane. Biochemical and crystallographic studies reveal a dimeric assembly with a stereochemically conserved active site, confirming our motif-based identification of candidate Cif-like pathogenic EH sequences. Furthermore, cif expression is transcriptionally repressed by a CifR homolog ("aCifR") and is induced in the presence of epoxides. Overall, this Acinetobacter protein recapitulates the essential attributes of the Pseudomonas Cif system and thus may facilitate airway colonization in nosocomial lung infections.

  6. Surprising unreactivity of cholesterol-5,6-epoxides towards nucleophiles[S

    PubMed Central

    Paillasse, Michael R.; Saffon, Nathalie; Gornitzka, Heinz; Silvente-Poirot, Sandrine; Poirot, Marc; de Medina, Philippe

    2012-01-01

    We recently established that drugs used for the treatment and the prophylaxis of breast cancers, such as tamoxifen, were potent inhibitors of cholesterol-5,6-epoxide hydrolase (ChEH), which led to the accumulation of 5,6α-epoxy-cholesterol (5,6α-EC) and 5,6β-epoxy-cholesterol (5,6β-EC). This could be considered a paradox because epoxides are known as alkylating agents with putative carcinogenic properties. We report here that, as opposed to the carcinogen styrene-oxide, neither of the ECs reacted spontaneously with nucleophiles. Under catalytic conditions, 5,6β-EC remains unreactive whereas 5,6α-EC gives cholestan-3β,5α-diol-6β-substituted compounds. These data showed that 5,6-ECs are stable epoxides and unreactive toward nucleophiles in the absence of a catalyst, which contrasts with the well-known reactivity of aromatic and aliphatic epoxides. These data rule out 5,6-EC acting as spontaneous alkylating agents. In addition, these data support the existence of a stereoselective metabolism of 5,6α-EC. PMID:22285872

  7. Boron Trifluoride Catalized Ring-Opening Polymerization of Epoxidized Soybean Oil in Liquid Carbon Dioxide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Boron trifluoride diethyl etherate (BF3.OEt2) catalyzed ring-opening polymerization of epoxidized soybean oil (ESO), in liquid carbon dioxide, was conducted in an effort to develop useful biobased biodegradable polymers. The resulting polymers (RPESO) were characterized by FTIR spectroscopy, differ...

  8. Lewis Acid Catalyzed Ring-opening Polymerization of Epoxidized Soybean Oil in Liquid Carbon Dioxide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ring-opening polymerization of epoxidized soybean oil (ESO) catalyzed by boron trifluoride diethyl etherate (BF3•OEt2), in liquid carbon dioxide, was conducted in an effort to develop useful biobased biodegradable polymers. The resulting polymers (RPESO) were characterized by FTIR spectroscopy, diff...

  9. Formation of furan fatty alkyl esters from their bis-epoxide fatty esters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reactions of epoxidized alkyl soyate with four different alcohols: ethanol, isopropyl alcohol, 2-ethylhexanol, benzyl alcohol, in the presence of Bronsted acid catalyst, were investigated. Products that were not reported in prior studies of similar reactions were found. These were furan fatty acid a...

  10. Formation of furan fatty alkyl esters from their bis-epoxide fatty esters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reactions of epoxidized alkyl soyate with four different alcohols: ethanol, isopropyl alcohol, 2-ethylhexanol, and benzyl alcohol were investigated in the presence of Bronsted acid catalyst. Products not reported in prior studies of similar reactions were found. These were furan fatty acid alkyl est...

  11. INTERACTION OF BENZO(A)PYRENE DIOL EPOXIDE WITH SVAO MINICHROMOSOMES

    SciTech Connect

    Gamper, Howard B.; Yokota, Hisao A.; Bartholomew, James C.

    1980-03-01

    SV40 minichromosomes were reacted with (+)7{beta},8{alpha}-dihydroxy-9{alpha},10{alpha}-epoxy- 7,8,9,10-tetrahydrobenzo[a]pyrene (BaP diol epoxide). Low levels of modification (< 5 DNA adducts/minichromosome) did not detectably alter the structure of the minichromosomes but high levels (> 200 DNA adducts/minichromosome) led to extensive fragmentation. Relative to naked SV40 DNA BaP diol epoxide induced alkylation and strand scission of minichromosomal DNA was reduced or enhanced by factors of 1.5 and 2.0, respectively. The reduction in covalent binding was attributed to the presence of histones, which competed with DNA for the hydrocarbon and reduced the probability of BaP diol epoxide intercalation by tightening the helix. The enhancement of strand scission was probably due to the catalytic effect of histones on the rate of S-elimination at apurinic sites, although an altered adduct profile or the presence of a repair endonuclease were not excluded. Staphylococcal nuclease digestion indicated that BaP dial epoxide randomly alkylated the minichromosomal DNA. This is in contrast to studies with cellular chromatin where internucleosomal DNA was preferentially modified. Differences in the minichromosomal protein complement were responsible for this altered susceptibility.

  12. Assessment of rat liver microsomal epoxide hydrolase as a marker of hepatocarcinogenesis.

    PubMed

    Kizer, D E; Clouse, J A; Ringer, D P; Hanson-Painton, O; Vaz, A D; Palakodety, R B; Griffin, M J

    1985-05-15

    The influence of eleven xenobiotics on the activity and amount of hepatic microsomal epoxide hydrolase was determined. Activity was assayed using three different substrates after rats were fed, throughout 3 weeks, diets containing one of six hepatocarcinogens, viz. 2-acetylaminofluorene, 3'-methyl-4-dimethylaminoazobenzene, 4'-fluoro-4-dimethylaminoazobenzene, thioacetamide, aflatoxin B1 and ethionine. Five hepatocarcinogens induced activity 4- to 10-fold; ethionine was relatively ineffective as an inducer. Two non-carcinogenic analogues of hepatocarcinogens, viz. fluorene and p-aminoazobenzene, caused no appreciable increase in enzyme activity, but phenobarbital, barbital and 1-naphthylisothiocyanate induced activity 2- to 3-fold. All eleven xenobiotics increased the amount of microsomal epoxide hydrolase 2- to 9-fold when examined immunochemically using either a radial diffusion assay or an enzyme-linked immunosorbent assay (ELISA). Serum glutamic oxaloacetic acid transaminase activity was not appreciably elevated by feeding ten of the xenobiotics, suggesting that inductions were not owing to toxicity. Using ELISA, microsomal epoxide hydrolase was detected in post-microsomal (PM) supernatant fractions from control rat liver, thus confirming an earlier report by Gill et al. [Carcinogenesis 3, 1307 (1982)]. The eleven xenobiotics induced the amount of ELISA-detectable antigen in PM supernatant fractions by 3- to 34-fold. Longer centrifugation of PM supernatant fractions yielded a pellet fraction that contained 92 +/- 1.2% of the ELISA-detectable antigen irrespective of the xenobiotic regimen. Relationships between xenobiotic induction of microsomal epoxide hydrolase activity and amount and hepatocarcinogenesis are discussed.

  13. Synthesis of an Epoxide Carbonylation Catalyst: Exploration of Contemporary Chemistry for Advanced Undergraduates

    ERIC Educational Resources Information Center

    Getzler, Yutan D. Y. L.; Schmidt, Joseph A. R.; Coates, Geoffrey W.

    2005-01-01

    A class of highly active, well-defined compounds for the catalytic carbonylation of epoxides and aziridines to beta-lactones and beta-lactams are introduced. The synthesis of one of the catalysts involves a simple imine condensation to form the ligand followed by air-sensitive metalation and salt metathesis steps.

  14. The strained sesquiterpene β-caryophyllene as a probe for the solvent-assisted epoxidation mechanism.

    PubMed

    Steenackers, Bart; Neirinckx, Alexander; De Cooman, Luc; Hermans, Ive; De Vos, Dirk

    2014-04-04

    In our attempt to synthesize β-caryophyllene oxide in food-compatible conditions, we observed the uncatalyzed and highly selective epoxidation of β-caryophyllene, a strained bicyclic sesquiterpene, in ethanol with aqueous H2 O2 under radical-suppressing conditions without the addition of a catalyst. The unusual reactivity of β-caryophyllene allowed us to use it as a probe for the mechanism of the solvent-assisted epoxidation in a wide range of organic solvents. A kinetic study was performed to investigate the epoxidation mechanism; an excellent correlation was found between the observed epoxidation rates in different solvents and the Abraham's hydrogen bond formation parameters of these solvents. By means of computational analysis, it was found that the main role of the solvent consists of the stabilization of the elongated OO bond of H2 O2 in the transition state through hydrogen-bond donation to the leaving OH moiety of H2 O2 . α-Humulene was found to possess similar reactivity as β-caryophyllene whereas isocaryophyllene-the unstrained isomer of β-caryophyllene-was unreactive.

  15. EPOXIDATION OF SMALL ORGANIC MOLECULES USING A SPINNING TUBE-IN-TUBE REACTOR

    EPA Science Inventory

    The commodity-scale epoxidation of several organic molecules has been carried out using a Spinning Tube-in-Tube (STTr) reactor (manufactured by Kreido Laboratories). This reactor, which embodies and facilitates the use of Green Chemistry principles and Process Intensification, a...

  16. On the interaction between supercritical CO2 and epoxides combining infrared absorption spectroscopy and quantum chemistry calculations.

    PubMed

    Foltran, Stéphanie; Méreau, Raphaël; Tassaing, Thierry

    2011-05-28

    The nature and strength of the interactions occurring between epoxides and CO(2) have been investigated by combining infrared spectroscopy with quantum chemistry calculations. A series of infrared absorption experiments on four model epoxide molecules highly diluted in supercritical CO(2) have been performed at constant temperature T = 40 °C for various CO(2) pressures varying from 1 to 30 MPa. Then, we carried out a theoretical analysis based on quantum chemistry calculations using Density Functional Theory (B3PW91 and CAM-B3LYP) and ab initio (MP2) computational methods. A very good agreement between experimental and calculated vibrational frequency shifts of the epoxide ring vibrations group was obtained using the CAM-B3LYP functional, hence validating the calculated optimized geometries of the epoxide-CO(2) complexes. Whatever the epoxide considered, CO(2) is found to be on average above the oxygen atom of the epoxy ring and interacts with the carbon atom of CO(2) through a Lewis acid-Lewis base type of interaction. The substituents on the epoxide ring are found to influence the stability of the epoxide-CO(2) complexes mainly because of the partial charge on the oxygen atom that is sensitive to the nature of the substituent.

  17. FB-Line resin testing final report

    SciTech Connect

    Bannochie, C.J.

    1992-01-23

    The Dowex 50W-X8 and 50W-Xl2 resin samples are both strong acid cation materials in the hydrogen form. Each material has a water retention capacity characteristic of its respective marketed degree of cross-linking. Dowex 21K gives confirmatory responses to tests for a strong anion exchange resin in the nitrate form. All three resins have the manufacturer`s specified ionic type and form, and the Dowex 50W resins have characteristic water retention capacities. These tests conclude that the ion exchange resins in use in FB-Line meet the approved safety document criteria for cross-linking, ionic form, and resin type.

  18. FB-Line resin testing final report

    SciTech Connect

    Bannochie, C.J.

    1992-01-23

    The Dowex 50W-X8 and 50W-Xl2 resin samples are both strong acid cation materials in the hydrogen form. Each material has a water retention capacity characteristic of its respective marketed degree of cross-linking. Dowex 21K gives confirmatory responses to tests for a strong anion exchange resin in the nitrate form. All three resins have the manufacturer's specified ionic type and form, and the Dowex 50W resins have characteristic water retention capacities. These tests conclude that the ion exchange resins in use in FB-Line meet the approved safety document criteria for cross-linking, ionic form, and resin type.

  19. Dysregulation of Soluble Epoxide Hydrolase and Lipidomic Profiles in Anorexia Nervosa

    PubMed Central

    Shih, Pei-an Betty; Yang, Jun; Morisseau, Christophe; German, J. Bruce; Van Zeeland, Ashley; Armando, Aaron M.; Quehenberger, Oswald; Bergen, Andrew W.; Magistretti, Pierre; Berrettini, Wade; Halmi, Katherine Ann; Schork, Nicholas; Hammock, Bruce D.; Kaye, Walter

    2015-01-01

    Individuals with anorexia nervosa (AN) restrict eating and become emaciated. AN tend to have an aversion to foods rich in fat. Because Epoxide Hydrolase 2 (EPHX2) was identified as a novel AN susceptibility gene, and because its protein product, soluble epoxide hydrolase (sEH), converts bioactive epoxides of polyunsaturated fatty acid (PUFA) to the corresponding diols, lipidomic and metabolomic targets of EPHX2 were assessed to evaluate the biological functions of EPHX2 and their role in AN. Epoxide substrates of sEH and associated oxylipins were measured in ill AN, recovered AN, and gender- and race-matched controls. PUFA and oxylipin markers were tested as potential biomarkers for AN. Oxylipin ratios were calculated as proxy markers of in vivo sEH activity. Several free- and total PUFAs were associated with AN diagnosis and with AN recovery. AN displayed elevated n-3 PUFAs and may differ from controls in PUFA elongation and desaturation processes. Cytochrome P450 pathway oxylipins from arachidonic acid, linoleic acid, alpha-linolenic acid, and docosahexaenoic acid PUFAs are associated with AN diagnosis. The diol:epoxide ratios suggest the sEH activity is higher in AN compared to controls. Multivariate analysis illustrates normalization of lipidomic profiles in recovered ANs. EPHX2 influences AN risk through in vivo interaction with dietary PUFAs. PUFA composition and concentrations as well as sEH activity may contribute to the pathogenesis and prognosis of AN. Our data support the involvement of EPHX2-associated lipidomic and oxylipin dysregulations in AN, and reveal their potential as biomarkers to assess responsiveness to future intervention or treatment. PMID:25824304

  20. Kinetics and mechanism of styrene epoxidation by chlorite: role of chlorine dioxide.

    PubMed

    Leigh, Jessica K; Rajput, Jonathan; Richardson, David E

    2014-07-07

    An investigation of the kinetics and mechanism for epoxidation of styrene and para-substituted styrenes by chlorite at 25 °C in the pH range of 5-6 is described. The proposed mechanism in water and water/acetonitrile includes seven oxidation states of chlorine (-I, 0, I, II, III, IV, and V) to account for the observed kinetics and product distributions. The model provides an unusually detailed quantitative mechanism for the complex reactions that occur in mixtures of chlorine species and organic substrates, particularly when the strong oxidant chlorite is employed. Kinetic control of the reaction is achieved by the addition of chlorine dioxide to the reaction mixture, thereby eliminating a substantial induction period observed when chlorite is used alone. The epoxidation agent is identified as chlorine dioxide, which is continually formed by the reaction of chlorite with hypochlorous acid that results from ClO produced by the epoxidation reaction. The overall stoichiometry is the result of two competing chain reactions in which the reactive intermediate ClO reacts with either chlorine dioxide or chlorite ion to produce hypochlorous acid and chlorate or chloride, respectively. At high chlorite ion concentrations, HOCl is rapidly eliminated by reaction with chlorite, minimizing side reactions between HOCl and Cl2 with the starting material. Epoxide selectivity (>90% under optimal conditions) is accurately predicted by the kinetic model. The model rate constant for direct reaction of styrene with ClO2(aq) to produce epoxide is (1.16 ± 0.07) × 10(-2) M(-1) s(-1) for 60:40 water/acetonitrile with 0.20 M acetate buffer. Rate constants for para substituted styrenes (R = -SO3(-), -OMe, -Me, -Cl, -H, and -NO2) with ClO2 were determined. The results support the radical addition/elimination mechanism originally proposed by Kolar and Lindgren to account for the formation of styrene oxide in the reaction of styrene with chlorine dioxide.

  1. Trigger factor assisted folding of the recombinant epoxide hydrolases identified from C. pelagibacter and S. nassauensis.

    PubMed

    Saini, Priya; Wani, Shadil Ibrahim; Kumar, Ranjai; Chhabra, Ravneet; Chimni, Swapandeep Singh; Sareen, Dipti

    2014-12-01

    Epoxide hydrolases (EHs), are enantioselective enzymes as they catalyze the kinetic resolution of racemic epoxides into the corresponding enantiopure vicinal diols, which are useful precursors in the synthesis of chiral pharmaceutical compounds. Here, we have identified and cloned two putative epoxide hydrolase genes (cpeh and sneh) from marine bacteria, Candidatus pelagibacter ubique and terrestrial bacteria, Stackebrandtia nassauensis, respectively and overexpressed them in pET28a vector in Escherichia coli BL21(DE3). The CPEH protein (42kDa) was found to be overexpressed as inactive inclusion bodies while SNEH protein (40kDa) was found to form soluble aggregates. In this study, the recombinant CPEH was successfully transformed from insoluble aggregates to the soluble and functionally active form, using pCold TF vector, though with low EH activity. To prevent the soluble aggregate formation of SNEH, it was co-expressed with GroEL/ES chaperone and was also fused with trigger factor (TF) chaperone at its N-terminus. The TF chaperone-assisted correct folding of SNEH led to a purified active EH with a specific activity of 3.85μmol/min/mg. The pure enzyme was further used to biocatalyze the hydrolysis of 10mM benzyl glycidyl ether (BGE) and α-methyl styrene oxide (MSO) with an enantiomeric excess of the product (eep) of 86% and 73% in 30 and 15min, respectively. In conclusion, this is the first report about the heterologous expression of epoxide hydrolases using TF as a molecular chaperone in pCold TF expression vector, resulting in remarkable increase in the solubility and activity of the otherwise improperly folded recombinant epoxide hydrolases.

  2. Discrete metal-based catalysts for the copolymerization of CO2 and epoxides: discovery, reactivity, optimization, and mechanism.

    PubMed

    Coates, Geoffrey W; Moore, David R

    2004-12-10

    Most synthetic polymers are made from petroleum feedstocks. Given the non-renewable nature of these materials, there is increasing interest in developing routes to polymeric materials from renewable resources. In addition, there is a growing demand for biodegradable polymeric materials. Polycarbonates made from CO(2) and epoxides have the potential to meet these goals. Since the discovery of catalysts for the copolymerization of CO(2) and epoxides in the late 1960's by Inoue, a significant amount of research has been directed toward the development of catalysts of improved activity and selectivity. Reviewed here are well-defined catalysts for epoxide-CO(2) copolymerization and related reactions.

  3. Low Melt Viscosity Resins for Resin Transfer Molding

    NASA Technical Reports Server (NTRS)

    Harris, Frank W.

    2002-01-01

    In recent years, resin transfer molding (RTM) has become one of the methods of choice for high performance composites. Its cost effectiveness and ease of fabrication are major advantages of RTM. RTM process usually requires resins with very low melt viscosity (less than 10 Poise). The optimum RTM resins also need to display high thennal-oxidative stability, high glass transition temperature (T(sub g)), and good toughness. The traditional PMR-type polyimides (e.g. PMR-15) do not fit this requirement, because the viscosities are too high and the nadic endcap cures too fast. High T(sub g), low-melt viscosity resins are highly desirable for aerospace applications and NASA s Reusable Launch Vehicle (RLV) program. The objective of this work is to prepare low-melt viscosity polyimide resins for RTM or resin film infusion (RFI) processes. The approach involves the synthesis of phenylethynyl-terminated imide oligomers. These materials have been designed to minimize their melt viscosity so that they can be readily processed. During the cure, the oligomers undergo both chain extension and crosslinking via the thermal polymerization of the phenylethynyl groups. The Phenylethynyl endcap is preferred over the nadic group due to its high curing temperature, which provides broader processing windows. This work involved the synthesis and polymerization of oligomers containing zig-zag backbones and twisted biphenyl structures. Some A-B type precursors which possessed both nitro and anhydride functionality, or both nitro and amine functionality, were also synthesized in order to obtain the well defined oligomers. The resulting zig-zag structured oligomers were then end-capped with 4-phenylethynylphthalic anhydride (PEPA) for further cure. The properties of these novel imide oligomers are evaluated.

  4. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1996-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  5. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

    1994-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene disphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  6. 21 CFR 177.1585 - Polyestercarbonate resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... intrinsic viscosity of the polyestercarbonate resins shall be a minimum of 0.44 deciliter per gram, as determined by a method entitled “Intrinsic Viscosity (IV) of Lexan ® Polyestercarbonate Resin by a...

  7. 40 CFR 63.1427 - Process vent requirements for processes using extended cookout as an epoxide emission reduction...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... constant, 1/hr. t = Time, hours. Note: This equation assumes a first order reaction with respect to epoxide... concentration in the vapor space using Raoult's Law or another appropriate phase equilibrium equation and...

  8. 40 CFR 63.1427 - Process vent requirements for processes using extended cookout as an epoxide emission reduction...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... constant, 1/hr. t = Time, hours. Note: This equation assumes a first order reaction with respect to epoxide... concentration in the vapor space using Raoult's Law or another appropriate phase equilibrium equation and...

  9. A mechanistic study into the epoxidation of carboxylic acid and alkene in a mono, di-acylglycerol lipase.

    PubMed

    Wang, Xuping; Tang, Qingyun; Popowicz, Grzegorz Maria; Yang, Bo; Wang, Yonghua

    2015-05-01

    More and more industrial chemistry reactions rely on green technologies. Enzymes are finding increasing use in diverse chemical processes. Epoxidized vegetable oils have recently found applications as plasticizers and additives for PVC production. We report here an unusual activity of the Malassezia globosa lipase (SMG1) that is able to catalyze epoxidation of alkenes. SMG1 catalyzes formation of peroxides from long chain carboxylic acids that subsequently react with double bonds of alkenes to produce epoxides. The SMG1 is selective towards carboxylic acids and active also as a mutant lacking hydrolase activity. Moreover we present previously unobserved mechanism of catalysis that does not rely on acyl-substrate complex nor tetrahedral intermediate. Since SMG1 lipase is activated by allosteric change upon binding to the lipophilic-hydrophilic phase interface we reason that it can be used to drive the epoxidation in the lipophilic phase exclusively.

  10. Epoxide pathways improve model predictions of isoprene markers and reveal key role of acidity in aerosol formation

    EPA Science Inventory

    Isoprene significantly contributes to organic aerosol in the southeastern United States where biogenic hydrocarbons mix with anthropogenic emissions. In this work, the Community Multiscale Air Quality model is updated to predict isoprene aerosol from epoxides produced under both ...

  11. Method for loading resin beds

    DOEpatents

    Notz, Karl J.; Rainey, Robert H.; Greene, Charles W.; Shockley, William E.

    1978-01-01

    An improved method of preparing nuclear reactor fuel by carbonizing a uranium loaded cation exchange resin provided by contacting a H.sup.+ loaded resin with a uranyl nitrate solution deficient in nitrate, comprises providing the nitrate deficient solution by a method comprising the steps of reacting in a reaction zone maintained between about 145.degree.-200.degree. C, a first aqueous component comprising a uranyl nitrate solution having a boiling point of at least 145.degree. C with a second aqueous component to provide a gaseous phase containing HNO.sub.3 and a reaction product comprising an aqueous uranyl nitrate solution deficient in nitrate.

  12. 21 CFR 177.1585 - Polyestercarbonate resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    .... 10. (i) Polyestercarbonate resins, when extracted with distilled water at reflux temperature for 6... water at reflux temperature for 6 hours, shall yield total nonvolatile extractives not to exceed 0.005 percent by weight of the resins. (iii) Polyestercarbonate resins, when extracted with n-heptane at...

  13. 21 CFR 177.1680 - Polyurethane resins.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Polyurethane resins. 177.1680 Section 177.1680... Components of Single and Repeated Use Food Contact Surfaces § 177.1680 Polyurethane resins. The polyurethane...) For the purpose of this section, polyurethane resins are those produced when one or more of...

  14. 21 CFR 172.280 - Terpene resin.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Terpene resin. 172.280 Section 172.280 Food and..., Films and Related Substances § 172.280 Terpene resin. The food additive terpene resin may be safely used... polymer obtained by polymerizing terpene hydrocarbons derived from wood. It has a softening point of...

  15. SRM filament wound case resin characterization studies

    NASA Technical Reports Server (NTRS)

    Chou, L. W.

    1985-01-01

    The amine cured epoxy wet winding resin used in fabrication of the SRM filament wound case is analyzed. High pressure liquid chromatography (HPSC) is utilized extensively to study lot-to-lot variation in both resin and curing agent. The validity of quantitative hplc methodology currently under development in-process resin/catalyst assay is assessed.

  16. Method of removing contaminants from plastic resins

    DOEpatents

    Bohnert,George W.; Hand,Thomas E.; Delaurentiis,Gary M.

    2007-08-07

    A method for removing contaminants from synthetic resin material containers using a first organic solvent system and a second carbon dioxide system. The organic solvent is utilized for removing the contaminants from the synthetic resin material and the carbon dioxide is used to separate any residual organic solvent from the synthetic resin material.

  17. Method for removing contaminants from plastic resin

    DOEpatents

    Bohnert, George W.; Hand, Thomas E.; DeLaurentiis, Gary M.

    2008-12-30

    A method for removing contaminants from synthetic resin material containers using a first organic solvent system and a second carbon dioxide system. The organic solvent is utilized for removing the contaminants from the synthetic resin material and the carbon dioxide is used to separate any residual organic solvent from the synthetic resin material.

  18. Method of removing contaminants from plastic resins

    DOEpatents

    Bohnert, George W.; Hand, Thomas E.; DeLaurentiis, Gary M.

    2008-11-18

    A method for removing contaminants from synthetic resin material containers using a first organic solvent system and a second carbon dioxide system. The organic solvent is utilized for removing the contaminants from the synthetic resin material and the carbon dioxide is used to separate any residual organic solvent from the synthetic resin material.

  19. 21 CFR 177.1550 - Perfluorocarbon resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    .... Perfluorocarbon resins can be identified by their characteristic infrared spectra. (2) Melt-viscosity. (i) The per-fluoro-carbon resins identified in paragraph (a)(1) of this section shall have a melt viscosity of not... viscosity of the perfluorocarbon resins identified in paragraph (a)(1) of this section shall not vary...

  20. 21 CFR 177.1550 - Perfluorocarbon resins.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    .... Perfluorocarbon resins can be identified by their characteristic infrared spectra. (2) Melt-viscosity. (i) The per-fluoro-carbon resins identified in paragraph (a)(1) of this section shall have a melt viscosity of not... viscosity of the perfluorocarbon resins identified in paragraph (a)(1) of this section shall not vary...

  1. 21 CFR 177.1550 - Perfluorocarbon resins.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    .... Perfluorocarbon resins can be identified by their characteristic infrared spectra. (2) Melt-viscosity. (i) The per-fluoro-carbon resins identified in paragraph (a)(1) of this section shall have a melt viscosity of not... viscosity of the perfluorocarbon resins identified in paragraph (a)(1) of this section shall not vary...

  2. 21 CFR 177.1550 - Perfluorocarbon resins.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    .... Perfluorocarbon resins can be identified by their characteristic infrared spectra. (2) Melt-viscosity. (i) The per-fluoro-carbon resins identified in paragraph (a)(1) of this section shall have a melt viscosity of not... viscosity of the perfluorocarbon resins identified in paragraph (a)(1) of this section shall not vary...

  3. In Vivo Anti-Tumor Activity and Toxicological Evaluations of Perillaldehyde 8,9-Epoxide, a Derivative of Perillyl Alcohol

    PubMed Central

    Andrade, Luciana Nalone; Amaral, Ricardo Guimarães; Dória, Grace Anne Azevedo; Fonseca, Cecília Santos; da Silva, Tayane Kayane Mariano; Albuquerque Júnior, Ricardo Luiz Cavalcante; Thomazzi, Sara Maria; do Nascimento, Lázaro Gomes; Carvalho, Adriana Andrade; de Sousa, Damião Pergentino

    2016-01-01

    Recent studies have revealed the high cytotoxicity of p-menthane derivatives against human tumor cells. In this study, the substance perillaldehyde 8,9-epoxide, a p-menthane class derivative obtained from (S)-(−)-perillyl alcohol, was selected in order to assess antitumor activity against experimental sarcoma 180 tumors. Toxicological effects related to the liver, spleen, kidneys and hematology were evaluated in mice submitted to treatment. The tumor growth inhibition rate was 38.4%, 58.7%, 35.3%, 45.4% and 68.1% at doses of 100 and 200 mg/kg/day for perillaldehyde 8,9-epoxide, perillyl alcohol and 25 mg/kg/day for 5-FU intraperitoneal treatments, respectively. No toxicologically significant effect was found in liver and kidney parameters analyzed in Sarcoma 180-inoculated mice treated with perillaldehyde 8,9-epoxide. Histopathological analyses of the liver, spleen, and kidneys were free from any morphological changes in the organs of the animals treated with perillaldehyde 8,9-epoxide. In conclusion, the data suggest that perillaldehyde 8,9-epoxide possesses significant antitumor activity without systemic toxicity for the tested parameters. By comparison, there was no statistical difference for the antitumor activity between perillaldehyde 8,9-epoxide and perillyl alcohol. PMID:26742032

  4. Theoretical determination of molecular structure and conformation. 18. On the formation of epoxides during the ozonolysis of alkenes

    SciTech Connect

    Cremer, D.; Bock, C.W.

    1986-06-11

    The reaction of carbonyl oxide (CH/sub 2/OO) and ethylene has been investigated by ab initio techniques. According to theoretical results, carbonyl oxide can act as an oxygen-transfer agent, thus leading to epoxide and aldehyde: C/sub 2/H/sub 4/ + CH/sub 2/OO ..-->.. CH/sub 2/OCH/sub 2/ + CH/sub 2/O. The calculated transition-state energies of the various epoxidation modes are 4-8 kcal/mol, which are comparable to activation energies of cycloaddition (cycloreversion) reactions encountered in the ozonolysis of alkenes. Epoxidation of alkene by carbonyl oxide is best described as a S/sub N/2 reaction on the terminal oxygen atom of carbonyl oxide. The preferred collision mode of the O-transfer reaction can be rationalized on the basis of frontier orbital interactions. Apart from epoxidation, carbonyl oxide can add to ethylene, yielding 1,2-dioxolane. The energy requirements of the cycloaddition are equivalent to those of the epoxidation. However, 1,2-dioxolanes will only be observed under normal ozonolysis conditions if the excess energy generated in the cycloaddition reaction is readily dissipated. Otherwise, 1,2-dioxolanes will immediately decompose, again yielding, among other products, epoxides.

  5. Fractionation and utilization of gossypol resin

    SciTech Connect

    Tursunov, A.K.; Dzhailov, A.T.; Fatkhullaev, E.; Sadykov, A.A.

    1985-10-01

    Gossypol resin is formed as a secondary waste product during distillation of fatty acides isolated from cottonseed oil soap stocks; it is insoluble in water but soluble in products of petroleum distillation. For fractionation, gossypol resin was saponified with caustic soda or caustic potash. Using this method, the resin was separated into unsaponifiable (21-24%) and saponifiable (76-79%) parts. Details of the individual fractions of gossypol resin are presented. The unsaponifiable fraction contains hydrocarbons, alcohols, beta-sito-sterol, beta-amyrin, and vitamin E. The fatty acid fraction of the resin is a mixture of fatty acids and lactones.

  6. A Method for Characterizing PMR-15 Resin

    NASA Technical Reports Server (NTRS)

    Roberts, G. D.; Lauver, R. W.

    1986-01-01

    Quantitative analysis technique based on reverse-phase, highperformance liquid chromatography (HPLC) and paired-ion chromatography (PIC) developed for PMR-15 resins. In reverse-phase HPLC experiment, polar solvent containing material to be analyzed passed through column packed with nonpolar substrate. Composition of PMR-15 Resin of 50 weight percent changes as resin ages at room temperature. Verification of proper resin formulation and analysis of changes in resin composition during storage important to manufacturers of PMR-15 polymer matrix composite parts. Technique especially suitable for commercial use by manufacturers of high-performance composite components.

  7. Process for curing bismaleimide resins

    NASA Technical Reports Server (NTRS)

    Parker, John A. (Inventor); OTHY S.imides alone. (Inventor)

    1986-01-01

    This invention relates to vinyl pyridine group containing compounds and oligomers, their advantageous copolymerization with bismaleimide resins, and the formation of reinforced composites based on these copolymers. When vinyl pyridines including vinyl stilbazole materials and vinyl styrylpyridine oligomer materials are admixed with bismaleimides and cured to form copolymers the cure temperatures of the copolymers are substantially below the cure temperatures of the bismaleimides alone.

  8. Fiber reinforced composite resin systems.

    PubMed

    Giordano, R

    2000-01-01

    The Targis/Vectris and Sculpture/FibreKor systems were devised to create a translucent maximally reinforced resin framework for fabrication of crowns, bridges, inlays, and onlays. These materials are esthetic, have translucency similar to castable glass-ceramics such as OPC and Empress, and have fits that are reported to be acceptable in clinical and laboratory trials. These restorations rely on proper bonding to the remaining tooth structure; therefore, careful attention to detail must be paid to this part of the procedure. Cementation procedures should involve silane treatment of the cleaned abraded internal restoration surface, application of bonding agent to the restoration as well as the etched/primed tooth, and finally use of a composite resin. Each manufacturer has a recommended system which has been tested for success with its resin system. These fiber reinforced resins are somewhat different than classical composites, so not all cementation systems will necessarily work with them. Polishing of the restoration can be accomplished using diamond or alumina impregnated rubber wheels followed by diamond paste. The glass fibers can pose a health risk. They are small enough to be inhaled and deposited in the lungs, resulting in a silicosis-type problem. Therefore, if fibers are exposed and ground on, it is extremely important to wear a mask. Also, the fibers can be a skin irritant, so gloves also should be worn. If the fibers become exposed intraorally, they can cause gingival inflammation and may attract plaque. The fibers should be covered with additional composite resin. If this cannot be accomplished, the restoration should be replaced. The bulk of these restorations are formed using a particulate filled resin, similar in structure to conventional composite resins. Therefore, concerns as to wear resistance, color stability, excessive expansion/contraction, and sensitivity remain until these materials are proven in long-term clinical trials. They do hold the

  9. Epoxidation of 1-Octene with hydrogen peroxide aqueous catalyzed by titania supported sulfonated coal

    NASA Astrophysics Data System (ADS)

    Nurhadi, Mukhamad

    2017-02-01

    Titania supported sulfonated coal was created as heterogeneous catalyst for epoxidation of 1-octene with aqueous hydrogen peroxide as oxidant at room temperature. The catalysts were prepared from coal that was sulfonated with H2SO4 (97%) and impregnated 7.2%wt with titanium(IV) isopropoxide (Ti(PrO)4). All catalysts coal (C), CS, Ti(7.2)-CS and Ti(7.2)-CSC were characterized by FTIR. The catalytic performance was tested for epoxidation of 1-octene with H2O2 aqueous as oxidant. It is found that Ti(7.2)-CS possessed the best catalytic performance and it gave the highest 1,2 epoxyoctene 322 µmol.

  10. Block Copolymerization of Lactide and an Epoxide Facilitated by a Redox Switchable Iron-Based Catalyst.

    PubMed

    Biernesser, Ashley B; Delle Chiaie, Kayla R; Curley, Julia B; Byers, Jeffery A

    2016-04-18

    A cationic iron(III) complex was active for the polymerization of various epoxides, whereas the analogous neutral iron(II) complex was inactive. Cyclohexene oxide polymerization could be "switched off" upon in situ reduction of the iron(III) catalyst and "switched on" upon in situ oxidation, which is orthogonal to what was observed previously for lactide polymerization. Conducting copolymerization reactions in the presence of both monomers resulted in block copolymers whose identity can be controlled by the oxidation state of the catalyst: selective lactide polymerization was observed in the iron(II) oxidation state and selective epoxide polymerization was observed in the iron(III) oxidation state. Evidence for the formation of block copolymers was obtained from solubility differences, GPC, and DOSY-NMR studies.

  11. From epoxidized linseed oil to bioresin: an overall approach of epoxy/anhydride cross-linking.

    PubMed

    Pin, Jean-Mathieu; Sbirrazzuoli, Nicolas; Mija, Alice

    2015-04-13

    Biorenewable resources can be used as green monomers to design tailored structures for formulations that can play an important role as functional materials. The choice of optimal structures depends on the targeted properties and applications. This work focuses on the elaboration of biobased materials with toughened mechanical properties based on epoxidized linseed oil. This result was obtained by an overall approach of cross-linking process, that is, starting with the optimal choice of hardeners and finally favoring the side reactions of polymerization. Therefore, the anionic alternating copolymerization of epoxide with mono- and dianhydrides was investigated to tailor the parameters that led to maximal conversions and properties. The obtained highly cross-linked networks perform well, as demonstrated by good impact strengths, high glass transition temperatures, and excellent thermal stability, which opens up the possibility of using these emergent materials for industrial applications.

  12. Ladder Polyether Synthesis via Epoxide-Opening Cascades Directed by a Disappearing Trimethylsilyl Group

    PubMed Central

    Heffron, Timothy P.; Simpson, Graham L.; Merino, Estibaliz; Jamison, Timothy F.

    2010-01-01

    Epoxide-opening cascades offer the potential to construct complex polyether natural products expeditiously and in a manner that emulates the biogenesis proposed for these compounds. Herein we provide a full account of our development of a strategy that addresses several important challenges of such cascades. The centerpiece of the method is a trimethylsilyl (SiMe3) group that serves several purposes and leaves no trace of itself by the time the cascade has come to an end. The main function of the SiMe3 group is to dictate the regioselectivity of epoxide opening. This strategy is the only general method of effecting endo-selective cascades under basic conditions. PMID:20302314

  13. CO2 copolymers from epoxides: catalyst activity, product selectivity, and stereochemistry control.

    PubMed

    Lu, Xiao-Bing; Ren, Wei-Min; Wu, Guang-Peng

    2012-10-16

    The use of carbon dioxide as a carbon source for the synthesis of organic chemicals can contribute to a more sustainable chemical industry. Because CO(2) is such a thermodynamically stable molecule, few effective catalysts are available to facilitate this transformation. Currently, the major industrial processes that convert CO(2) into viable products generate urea and hydroxybenzoic acid. One of the most promising new technologies for the use of this abundant, inexpensive, and nontoxic renewable resource is the alternating copolymerization of CO(2) and epoxides to provide biodegradable polycarbonates, which are highly valuable polymeric materials. Because this process often generates byproducts, such as polyether or ether linkages randomly dispersed within the polycarbonate chains and/or the more thermodynamically stable cyclic carbonates, the choice of catalyst is critical for selectively obtaining the expected product. In this Account, we outline our efforts to develop highly active Co(III)-based catalysts for the selective production of polycarbonates from the alternating copolymerization of CO(2) with epoxides. Binary systems consisting of simple (salen)Co(III)X and a nucleophilic cocatalyst exhibited high activity under mild conditions even at 0.1 MPa CO(2) pressure and afforded copolymers with >99% carbonate linkages and a high regiochemical control (∼95% head-to-tail content). Discrete, one-component (salen)Co(III)X complexes bearing an appended quaternary ammonium salt or sterically hindered Lewis base showed excellent activity in the selectively alternating copolymerization of CO(2) with both aliphatic epoxides and cyclohexene oxide at high temperatures with low catalyst loading and/or low pressures of CO(2). Binary or one-component catalysts based on unsymmetric multichiral Co(III) complexes facilitated the efficient enantioselective copolymerization of CO(2) with epoxides, providing aliphatic polycarbonates with >99% head-to-tail content. These

  14. Copolymerization of CO2 and epoxides catalyzed by metal salen complexes.

    PubMed

    Darensbourg, Donald J; Mackiewicz, Ryan M; Phelps, Andrea L; Billodeaux, Damon R

    2004-11-01

    The design of efficient metal catalysts for the selective coupling of epoxides and carbon dioxide to afford completely alternating copolymers has made significant gains over the past decade. Hence, it is becoming increasingly clear that this "greener" route to polycarbonates has the potential to supplement or supplant current processes for the production of these important thermoplastics, which involve the condensation polymerization of diols and phosgene or organic carbonates. On the basis of the experiences in our laboratory, this Account summarizes our efforts at optimizing (salen)CrIIIX catalysts for the selective formation of polycarbonates from alicyclic and aliphatic epoxides with CO2. An iterative catalyst design process is employed in which the salen ligand, initiator, cocatalyst, and reaction conditions are systematically varied, with the reaction rates and product selectivity being monitored by in situ infrared spectroscopy.

  15. Synthesis of cyclic sulfites from epoxides and sulfur dioxide with silica-immobilized homogeneous catalysts.

    PubMed

    Takenaka, Yasumasa; Kiyosu, Takahiro; Mori, Goro; Choi, Jun-Chul; Fukaya, Norihisa; Sakakura, Toshiyasu; Yasuda, Hiroyuki

    2012-01-09

    Quaternary ammonium- and amino-functionalized silica catalysts have been prepared for the selective synthesis of cyclic sulfites from epoxides and sulfur dioxide, demonstrating the effects of immobilizing the homogeneous catalysts on silica. The cycloaddition of sulfur dioxide to various epoxides was conducted under solvent-free conditions at 100 °C. The quaternary ammonium- and amino-functionalized silica catalysts produced cyclic sulfites in high yields (79-96 %) that are comparable to those produced by the homogeneous catalysts. The functionalized silica catalysts could be separated from the product solution by filtration, thereby avoiding the catalytic decomposition of the cyclic sulfite products upon distillation of the product solution. Heterogenization of a homogeneous catalyst by immobilization can, therefore, improve the efficiency of the purification of crude reaction products. Despite a decrease in catalytic activity after each recycling step, the heterogeneous pyridine-functionalized silica catalyst provided high yields after as many as five recycling processes.

  16. Phenoxy resins containing pendent ethynyl groups

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M.; Jensen, B. J.; Havens, S. J.

    1984-01-01

    As part of an effort on tougher/solvent resistant matrix resins for composites, research was directed towards exploring methods to improve the solvent resistance of linear amorphous thermoplastics. Ethyl reactive groups were placed on the ends of oligomers and pendent along the polymer chain and subsequently thermally reacted to provide crosslinking and thus improvement in solvent resistance. This concept is extended to another thermoplastic, a phenoxy resin. A commercially available phenoxy resin (PKHH) was systematically modified by reaction of the pendent hydroxyl groups on the phenoxy resin with various amounts of 4-ethynylbenzoyl chloride. As the pendent ethynyl group content in the phenoxy resin increased, the cured resin exhibited a higher glass transition temperature, better solvent resistance and less flexibility. The solvent resistance was further improved by correcting a low molecular weight diethynyl compound, 2,2-bis(4-ethynylbenzoyloxy-4'-phenyl)propane, with a phenoxy resin containing pendent ethynyl groups.

  17. Dichlorodioxomolybdenum(VI) complexes bearing oxygen-donor ligands as olefin epoxidation catalysts.

    PubMed

    Oliveira, Tânia S M; Gomes, Ana C; Lopes, André D; Lourenço, João P; Almeida Paz, Filipe A; Pillinger, Martyn; Gonçalves, Isabel S

    2015-08-21

    Treatment of the solvent adduct [MoO2Cl2(THF)2] with either 2 equivalents of N,N-dimethylbenzamide (DMB) or 1 equivalent of N,N'-diethyloxamide (DEO) gave the dioxomolybdenum(vi) complexes [MoO2Cl2(DMB)2] () and [MoO2Cl2(DEO)] (). The molecular structures of and were determined by single-crystal X-ray diffraction. Both complexes present a distorted octahedral geometry and adopt the cis-oxo, trans-Cl, cis-L configuration typical of complexes of the type [MoO2X2(L)n], with either the monodentate DMB or bidentate DEO oxygen-donor ligands occupying the equatorial positions trans to the oxo groups. The complexes were applied as homogeneous catalysts for the epoxidation of olefins, namely cis-cyclooctene (Cy), 1-octene, trans-2-octene, α-pinene and (R)-(+)-limonene, using tert-butylhydroperoxide (TBHP) as oxidant. In the epoxidation of Cy at 55 °C, the desired epoxide was the only product and turnover frequencies in the range of ca. 3150-3200 mol molMo(-1) h(-1) could be reached. The catalytic production of cyclooctene oxide was investigated in detail, varying either the reaction temperature or the cosolvent. Complexes and were also applied in liquid-liquid biphasic catalytic epoxidation reactions by using an ionic liquid of the type [C4mim][X] (C4mim = 1-n-butyl-3-methylimidazolium; X = NTf2, BF4 or PF6] as a solvent to immobilise the metal catalysts. Recycling for multiple catalytic runs was achieved without loss of activity.

  18. Cholesterol-5,6-epoxides: chemistry, biochemistry, metabolic fate and cancer.

    PubMed

    Poirot, Marc; Silvente-Poirot, Sandrine

    2013-03-01

    In the nineteen sixties it was proposed that cholesterol might be involved in the etiology of cancers and cholesterol oxidation products were suspected of being causative agents. Researchers had focused their attention on cholesterol-5,6-epoxides (5,6-ECs) based on several lines of evidence: 1) 5,6-ECs contained an oxirane group that was supposed to confer alkylating properties such as those observed for aliphatic and aromatic epoxides. 2) cholesterol-5,6-epoxide hydrolase (ChEH) was induced in pre-neoplastic lesions of skin from rats exposed to ultraviolet irradiations and ChEH was proposed to be involved in detoxification processes like other epoxide hydrolases. However, 5,6-ECs failed to induce carcinogenicity in rodents which ruled out a potent carcinogenic potential for 5,6-ECs. Meanwhile, clinical studies revealed an anomalous increase in the concentrations of 5,6β-EC in the nipple fluids of patients with pre-neoplastic breast lesions and in the blood of patients with endometrious cancers, suggesting that 5,6-ECs metabolism could be linked with cancer. Paradoxically, ChEH has been recently shown to be totally inhibited by therapeutic concentrations of tamoxifen (Tam), which is one of the main drugs used in the hormonotherapy and the chemoprevention of breast cancers. These data would suggest that the accumulation of 5,6-ECs could represent a risk factor, but we found that 5,6-ECs were involved in the induction of breast cancer cell differentiation and death induced by Tam suggesting a positive role of 5,6-ECs. These observations meant that the biochemistry and the metabolism of 5,6-ECs needed to be extensively studied. We will review the current knowledge and the future direction of 5,6-ECs chemistry, biochemistry, metabolism, and relationship with cancer.

  19. Salen-complex-mediated formation of cyclic carbonates by cycloaddition of CO2 to epoxides.

    PubMed

    Decortes, Antonello; Castilla, Ana M; Kleij, Arjan W

    2010-12-17

    Metal complexes of salen ligands are an important class of compounds, and they have been widely studied in the past. Among their successful catalytic applications, the synthesis of cyclic carbonates by the coupling reaction of epoxides with CO(2) has received increased attention; this is mostly due to the importance of using a greenhouse gas as a feedstock for the synthesis of useful molecules. Herein the most relevant past and present research surrounding this topic is presented.

  20. Chiral Co(III)(salen)-catalysed hydrolytic kinetic resolution of racemic epoxides in ionic liquids.

    PubMed

    Oh, Chun Rim; Choo, Dong Joon; Shim, Woo Ho; Lee, Dong Hoon; Roh, Eun Joo; Lee, Sang-gi; Song, Choong Eui

    2003-05-07

    In the chiral Co(III)(salen)-catalysed HKR of racemic epoxides, in the presence of ionic liquids, Co(II)(salen) complex is oxidised without acetic acid to catalytically active Co(III)(salen) complex during reaction and, moreover, this oxidation state is stabilised against reduction to Co(II) complex which enables the reuse of the recovered catalyst for consecutive reactions without extra reoxidation.

  1. Exploring dual electrophiles in peptide-based proteasome inhibitors: carbonyls and epoxides.

    PubMed

    Xin, Bo-Tao; de Bruin, Gerjan; Verdoes, Martijn; Filippov, Dmitri V; van der Marel, Gijs A; Overkleeft, Herman S

    2014-08-14

    Peptide epoxyketones are potent and selective proteasome inhibitors. Selectivity is governed by the epoxyketone dual electrophilic warhead, which reacts with the N-terminal threonine 1,2-amino alcohol uniquely present in proteasome active sites. We studied a series of C-terminally modified oligopeptides featuring adjacent electrophiles based on the epoxyketone warhead. We found that the carbonyl moiety in the natural warhead is essential, but that the adjacent epoxide can be replaced by a carbonyl, though with considerable loss of activity.

  2. Chiral epoxide production using mycobacterium solubilized in a water-in-oil microemulsion.

    PubMed

    Prichanont; Leak; Stuckey

    2000-07-01

    The application of many biotransformation processes is limited because the substrates/products are poorly water soluble, can be further metabolized, or are inhibitory. Hence non-aqueous media (e.g. two-phase systems, low water environments) are being examined to determine whether they can be used to overcome these problems. One novel approach is to encapsulate whole cells in water-in-oil (w/o) microemulsions (reverse micelles). In this study we have investigated the influence of key system parameters on system stability and epoxidation activity of Mycobacterium M156 cells in reverse micelles comprised of a mixture of Tween 85 and Span 80 (10-20 w%, with an hydrophilic/lipophilic balance [HLB] of 10 and a weight ratio of Tween 85 to Span 80 = 5.7) in n-hexadecane. It was found that the minimum allyl phenyl ether (APE) concentration required in the bulk hexadecane solvent phase for epoxidation to occur was 15 mM, whereas the minimum molar ratio of water to surfactant (W(0)) was 35. The optimum epoxidation rate achieved was 3.8 nmol/mg dwt-min with an APE concentration of 50 mM, and a W(0) of 50, with an enantiomeric excess (ee) of 86%. However, epoxidation was found to terminate approximately 3 h after initiation, and the causes for this were postulated to be either: the deleterious effect of the solvent on the Mycobacteria; inactivation of the energy generating system; an insufficient energy supply, or; the instability of the monooxygenase enzyme. It was concluded that on balance emulsion systems are not an economically viable system for producing phenyl glycidyl ether (PGE).

  3. The stability of the three transmembrane and the four transmembrane human vitamin K epoxide reductase models

    NASA Astrophysics Data System (ADS)

    Wu, Sangwook

    2016-04-01

    The three transmembrane and the four transmembrane helix models are suggested for human vitamin K epoxide reductase (VKOR). In this study, we investigate the stability of the human three transmembrane/four transmembrane VKOR models by employing a coarse-grained normal mode analysis and molecular dynamics simulation. Based on the analysis of the mobility of each transmembrane domain, we suggest that the three transmembrane human VKOR model is more stable than the four transmembrane human VKOR model.

  4. Association of DDT and heptachlor epoxide in human blood with diabetic nephropathy.

    PubMed

    Everett, Charles J; Thompson, Olivia M

    2015-01-01

    Six organochlorine pesticides and pesticide metabolites in human blood were tested to determine their relationships with diabetic nephropathy. The data were derived from the National Health and Nutrition Examination Survey (NHANES) 1999-2004 (unweighted, n=2992, population estimate=133,088,752). The six chemicals were p,p'-DDT (dichlorodiphenyltrichloroethane), p,p'-DDE (dichlorodiphenyltrichloroethylene), beta-hexachlorocyclohexane, oxychlordane, trans-nonachlor and heptachlor epoxide. In this research, total diabetes included diagnosed and undiagnosed diabetes (glycohemoglobin, A1c ≥6.5%), and nephropathy was defined as a urinary albumin to creatinine ratio >30 mg/g, representing microalbuminuria and macroalbuminuria. The pesticide p,p'-DDT and pesticide metabolite heptachlor epoxide were significantly associated with total diabetes with nephropathy, with odds ratios of 2.08 (95% CI 1.06-4.11) and 1.75 (95% CI 1.05-2.93), respectively. Organochlorine pesticides are thought to act through the constitutive androstane receptor/pregnane X receptor disease pathway, but this is not well established. When p,p'-DDT and heptachlor epoxide were both elevated, the odds ratio for diabetic nephropathy was 2.76 (95% CI 1.31-5.81), and when six of six organochlorine pesticides and pesticide metabolites, were elevated, the odds ratio for diabetic nephropathy was 3.00 (95% CI 1.08-8.36). The differences in the odds ratios for these groups appear to be due to differences in the mean heptachlor epoxide concentration of each category. Organochlorine pesticides and pesticide metabolites are known to have estrogenic, antiestrogenic or antiandrogenic activity. The constitutive androstane receptor/pregnane X receptor pathway is thought to interact with the aryl hydrocarbon receptor pathway, and the associations noted may be due to that interaction.

  5. Monolithic Nickel (II) Oxide Aerogels Using an Organic Epoxide: The Importance of the Counter Ion

    SciTech Connect

    Gash, A E; Satcher, J H; Simpson, R L

    2004-01-13

    The synthesis and characterization of nickel (II) oxide aerogel materials prepared using the epoxide addition method is described. The addition of the organic epoxide propylene oxide to an ethanolic solution of NiCl{sub 2} 6H{sub 2}O resulted in the formation of an opaque light green monolithic gel and subsequent drying with supercritical CO{sub 2} gave a monolithic aerogel material of the same color. This material has been characterized using powder X-ray diffraction, electron microscopy, elemental analysis, and nitrogen adsorption/desorption analysis. The results indicate that the nickel (II) oxide aerogel has very low bulk density (98 kg/m{sup 3} ({approx}98 %porous)), high surface area (413 m{sup 2}/g), and has a particulate-type aerogel microstructure made up of very fine spherical particles with an open porous network. By comparison, a precipitate of Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} is obtained when the same preparation is attempted with the common Ni(NO{sub 3}){sub 2} 6H{sub 2}O salt as the precursor. The implications of the difference of reactivity of the two different precursors are discussed in the context of the mechanism of gel formation via the epoxide addition method. The synthesis of nickel (II) oxide aerogel, using the epoxide addition method, is especially unique in our experience. It is our first example of the successful preparation of a metal oxide aerogel using a metal divalent metal ion and may have implications for the application of this method to the preparation of aerogels or nanoparticles of other divalent metal oxides. To our knowledge this is the first report of a monolithic pure nickel (II) oxide aerogel materials.

  6. Direct Epoxidation of Propylene over Stabilized Cu+ Surface Sites on Ti Modified Cu2O

    SciTech Connect

    Yang, X.; Kattel, S.; Xiong, K.; Mudiyanselage, K.; Rykov, S.; Senanayake, S. D.; Rodriguez, J. A.; Liu, P.; Stacchiola, D. J.; Chen, J. G.

    2015-07-17

    Direct propylene epoxidation by O2 is a challenging reaction because of the strong tendency for complete combustion. Results from the current study demonstrate the feasibility to tune the epoxidation selectivity by generating highly dispersed and stabilized Cu+ active sites in a TiCuOx mixed oxide. The TiCuOx surface anchors the key surface intermediate, oxametallacycle, leading to higher selectivity for epoxidation of propylene.

  7. Complex Cure Kinetics of the Hydroxyl-Epoxide Reaction in DGEBA Epoxy Hardened with Diethanolamine

    NASA Astrophysics Data System (ADS)

    Ancipink, Windy; McCoy, John; Kropka, Jamie; Celina, Mathias

    The curing of a diglycidyl ether of bisphenol-A Epoxy (Epon 828) with diethanolamine (DEA) involves a fast amine-epoxide reaction followed by a slower hydroxyl-epoxide reaction. At curing temperatures below 100°C, the time scales of these two reactions are well separated, and the hydroxyl addition can be studied as an ''isolated'' reaction. The hydroxyl-epoxide reaction is of great interest due to the complex kinetics involved, which are brought about by competing reactions. The reaction kinetics are believed to be tertiary amine catalyzed and are well fit to a modified form of the Kamal-type equation. Here we study the complex long term reaction kinetics at various temperatures, by using isothermal modulated differential scanning calorimetry, micro calorimetry, and infrared spectroscopy. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  8. Purification and characterisation of a novel enantioselective epoxide hydrolase from Aspergillus niger M200.

    PubMed

    Kotik, Michael; Kyslík, Pavel

    2006-02-01

    Purification of a novel enantioselective epoxide hydrolase from Aspergillus niger M200 has been achieved using ammonium sulphate precipitation, ionic exchange, hydrophobic interaction, and size-exclusion chromatography, in conjunction with two additional chromatographic steps employing hydroxylapatite, and Mimetic Green. The enzyme was purified 186-fold with a yield of 15%. The apparent molecular mass of the enzyme was determined to be 77 kDa under native conditions and 40 kDa under denaturing conditions, implying a dimeric structure of the native enzyme. The isoelectric point of the enzyme was estimated to be 4.0 by isoelectric focusing electrophoresis. The enzyme has a broad substrate specificity with highest specificities towards tert-butyl glycidyl ether, para-nitrostyrene oxide, benzyl glycidyl ether, and styrene oxide. Enantiomeric ratios of 30 to more than 100 were determined for the hydrolysis reactions of 4 epoxidic substrates using the purified enzyme at a reaction temperature of 10 degrees C. Product inhibition studies suggest that the enzyme is able to differentiate to a high degree between the (R)-diol and (S)-diol product of the hydrolysis reaction with tert-butyl glycidyl ether as the substrate. The highest activity of the enzyme was at 42 degrees C and a pH of 6.8. Six peptide sequences, which were obtained by cleavage of the purified enzyme with trypsin and mass spectrometry analysis of the tryptic peptides, show high similarity with corresponding sequences originated from the epoxide hydrolase from Aspergillus niger LCP 521.

  9. Cloning and characterization of three epoxide hydrolases from a marine bacterium, Erythrobacter litoralis HTCC2594.

    PubMed

    Woo, Jung-Hee; Hwang, Young-Ok; Kang, Sung Gyun; Lee, Hyun Sook; Cho, Jang-Cheon; Kim, Sang-Jin

    2007-08-01

    Previously, we reported that ten strains belonging to Erythrobacter showed epoxide hydrolase (EHase) activities toward various epoxide substrates. Three genes encoding putative EHases were identified by analyzing open reading frames of Erythrobacter litoralis HTCC2594. Despite low similarities to reported EHases, the phylogenetic analysis of the three genes showed that eeh1 was similar to microsomal EHase, while eeh2 and eeh3 could be grouped with soluble EHases. The three EHase genes were cloned, and the recombinant proteins (rEEH1, rEEH2, and rEEH3) were purified. The functionality of purified proteins was proved by hydrolytic activities toward styrene oxide. EEH1 preferentially hydrolyzed (R)-styrene oxide, whereas EEH3 preferred to hydrolyze (S)-styrene oxide, representing enantioselective hydrolysis of styrene oxide. On the other hand, EEH2 could hydrolyze (R)- and (S)-styrene oxide at an equal rate. The optimal pH and temperature for the EHases occurred largely at neutral pHs and 40-55 degrees C. The substrate selectivity of rEEH1, rEEH2, and rEEH3 toward various epoxide substrates were also investigated. This is the first representation that a strict marine microorganism possessed three EHases with different enantioselectivity toward styrene oxide.

  10. Effect of the synthetic method on the catalytic activity of alumina: Epoxidation of cyclohexene

    SciTech Connect

    Valderruten, N.E.; Peña, W.F.; Ramírez, A.E.; Rodríguez-Páez, J.E.

    2015-02-15

    Graphical abstract: Temperature influence on percent conversion and selectivity in the epoxidation of cyclohexene using commercial alumina as a catalyst. - Highlights: • Aluminum oxide was synthesized using Pechini method. • The alumina obtained showed a mix of boehmite and γ-alumina phases. • We research an economically feasible method to obtain alumina for use as a catalyst. • Alumina obtained by Pechini showed high percent conversion and/or selectivity. • The best results were 78% conversion and 78% selectivity to epoxidation reactions. - Abstract: Al{sub 2}O{sub 3} was prepared from different inorganic precursors via the Pechini method and compared with Al{sub 2}O{sub 3} prepared by the sol–gel method. Structural characterization of these materials was carried out by FTIR, X-ray diffraction (XRD), N{sub 2} adsorption at −196 °C and transmission electron microscopy (TEM). The solids were tested in the epoxidation of cyclohexene and a difference in their catalytic activities was observed. The characterization results indicate that the samples prepared by Pechini have a mixture of γ-alumina and boehmite, a condition favoring catalytic activity, whereas the sol–gel sample is less crystalline due to higher boehmite content. These results indicate that both the nature of the precursor and the method of synthesis strongly affect the catalytic activity of Al{sub 2}O{sub 3}.

  11. Rate-Enhancing Roles of Water Molecules in Methyltrioxorhenium-Catalyzed Olefin Epoxidation by Hydrogen Peroxide.

    PubMed

    Goldsmith, Bryan R; Hwang, Taeho; Seritan, Stefan; Peters, Baron; Scott, Susannah L

    2015-08-05

    Olefin epoxidation catalyzed by methyltrioxorhenium (MTO, CH3ReO3) is strongly accelerated in the presence of H2O. The participation of H2O in each of the elementary steps of the catalytic cycle, involving the formation of the peroxo complexes (CH3ReO2(η(2)-O2), A, and CH3ReO(η(2)-O2)2(H2O), B), as well as in their subsequent epoxidation of cyclohexene, was examined in aqueous acetonitrile. Experimental measurements demonstrate that the epoxidation steps exhibit only weak [H2O] dependence, attributed by DFT calculations to hydrogen bonding between uncoordinated H2O and a peroxo ligand. The primary cause of the observed H2O acceleration is the strong co-catalytic effect of water on the rates at which A and B are regenerated and consequently on the relative abundances of the three interconverting Re-containing species at steady state. Proton transfer from weakly coordinated H2O2 to the oxo ligands of MTO and A, resulting in peroxo complex formation, is directly mediated by solvent H2O molecules. Computed activation parameters and kinetic isotope effects, in combination with proton-inventory experiments, suggest a proton shuttle involving one or (most favorably) two H2O molecules in the key ligand-exchange steps to form A and B from MTO and A, respectively.

  12. Persistence and changes in bioavailability of dieldrin, DDE and heptachlor epoxide in earthworms over 45 years

    USGS Publications Warehouse

    Beyer, W. Nelson; Gale, Robert W.

    2013-01-01

    The finding of dieldrin (88 ng/g), DDE (52 ng/g), and heptachlor epoxide (19 ng/g) in earthworms from experimental plots after a single moderate application (9 kg/ha) 45 years earlier attests to the remarkable persistence of these compounds in soil and their continued uptake by soil organisms. Half-lives (with 95 % confidence intervals) in earthworms, estimated from exponential decay equations, were as follows: dieldrin 4.9 (4.3-5.7) years, DDE 5.3 (4.7-6.1) years, and heptachlor epoxide 4.3 (3.8-4.9) years. These half-lives were not significantly different from those estimated after 20 years. Concentration factors (dry weight earthworm tissue/dry weight soil) were initially high and decreased mainly during the first 11 years after application. By the end of the study, average concentration factors were 1.5 (dieldrin), 4.0 (DDE), and 1.8 (heptachlor epoxide), respectively.

  13. Epoxidation of cottonseed oil by aqueous hydrogen peroxide catalysed by liquid inorganic acids.

    PubMed

    Dinda, Srikanta; Patwardhan, Anand V; Goud, Vaibhav V; Pradhan, Narayan C

    2008-06-01

    The kinetics of epoxidation of cottonseed oil by peroxyacetic acid generated in situ from hydrogen peroxide and glacial acetic acid in the presence of liquid inorganic acid catalysts were studied. It was possible to obtain up to 78% relative conversion to oxirane with very less oxirane cleavage by in situ technique. The rate constants for sulphuric acid catalysed epoxidation of cottonseed oil were in the range 0.39-5.4 x 10(-6)L mol(-1)s(-1) and the activation energy was found to be 11.7 kcal mol(-1). Some thermodynamic parameters such as enthalpy, entropy, and free energy of activation were determined to be of 11.0 kcal mol(-1), -51.4 cal mol(-1)K(-1) and 28.1 kcal mol(-1), respectively. The order of effectiveness of catalysts was found to be sulphuric acid>phosphoric acid>nitric acid>hydrochloric acid. Acetic acid was found to be superior to formic acid for the in situ cottonseed oil epoxidation.

  14. Facile immobilization of biomolecules onto various surfaces using epoxide-containing antibiofouling polymers.

    PubMed

    Sung, Daekyung; Park, Sangjin; Jon, Sangyong

    2012-03-06

    The surface modifications of plastic or glass substrate and the subsequent immobilization of biomolecules onto the surfaces has been a central feature of the fabrication of biochips. To this end, we designed and synthesized new epoxide-containing random copolymers that form stable polymer adlayers on plastic or glass surface and subsequently react with amine or sulfhydryl functional groups of biomolecules under aqueous conditions. Epoxide-containing random copolymers were synthesized by radical polymerization of three functional monomers: a monomer acting as an anchor to the surfaces, a PEG group for preventing nonspecific protein adsorption, and an epoxide group for conjugating to biomolecules. Polymer coating layers were facilely formed on cyclic olefin copolymer (COC) or glass substrate by simply dipping each substrate into a solution of each copolymer. The polymer-coated surfaces characterized by a contact angle analyzer and X-ray photoelectron spectroscopy (XPS) showed very low levels of nonspecific immunoglobulin G (IgG) adsorption compared to the uncoated bare surface (control). Using a microcontact printing (μCP) method, antibodies as representative biomolecules could be selectively attached onto the copolymers-coated glass or COC surface with high signal-to-noise ratios.

  15. Reduction of epoxidized vegetable oils: a novel method to prepare bio-based polyols for polyurethanes.

    PubMed

    Zhang, Chaoqun; Ding, Rui; Kessler, Michael R

    2014-06-01

    A novel method, epoxidation/reduction of vegetable oils, is developed to prepare bio-based polyols for the manufacture of polyurethanes (PUs). These polyols are synthesized from castor oil (CO), epoxidized soybean oil, and epoxidized linseed oil and their molecular structures are characterized. They are used to prepare a variety of PUs, and their thermomechanical properties are compared to those of PU made with petroleum-based polyol (P-450). It is shown that PUs made with polyols from soybean and linseed oil exhibit higher glass transition temperatures, tensile strength, and Young's modulus and PU made with polyol from CO exhibits higher elongation at break and toughness than PU made with P-450. However, PU made with P-450 displays better thermal resistance because of tri-ester structure and terminal functional groups. The method provides a versatile way to prepare bio-polyols from vegetable oils, and it is expected to partially or completely replace petroleum-based polyols in PUs manufacture.

  16. Soluble epoxide hydrolase inhibition alleviates neuropathy in Akita (Ins2 Akita) mice.

    PubMed

    Wagner, Karen; Gilda, Jennifer; Yang, Jun; Wan, Debin; Morisseau, Christophe; Gomes, Aldrin V; Hammock, Bruce D

    2017-03-01

    The soluble epoxide hydrolase (sEH) is a regulatory enzyme responsible for the metabolism of bioactive lipid epoxides of both omega-6 and omega-3 long chain polyunsaturated fatty acids. These natural epoxides mediate cell signaling in several physiological functions including blocking inflammation, high blood pressure and both inflammatory and neuropathic pain. Inhibition of the sEH maintains the level of endogenous bioactive epoxy-fatty acids (EpFA) and allows them to exert their generally beneficial effects. The Akita (Ins2(Akita) or Ins2(C96Y)) mice represent a maturity-onset of diabetes of the young (MODY) model in lean, functionally unimpaired animals, with a sexually dimorphic disease phenotype. This allowed for a test of male and female mice in a battery of functional and nociceptive assays to probe the role of sEH in this system. The results demonstrate that inhibiting the sEH is analgesic in diabetic neuropathy and this occurs in a sexually dimorphic manner. Interestingly, sEH activity is also sexually dimorphic in the Akita model, and moreover correlates with disease status particularly in the hearts of male mice. In addition, in vivo levels of oxidized lipid metabolites also correlate with increased sEH expression and the pathogenesis of disease in this model. Thus, sEH is a target to effectively block diabetic neuropathic pain but also demonstrates a potential role in mitigating the progression of this disease.

  17. Lutein epoxide cycle, light harvesting and photoprotection in species of the tropical tree genus Inga.

    PubMed

    Matsubara, Shizue; Krause, G Heinrich; Seltmann, Martin; Virgo, Aurelio; Kursar, Thomas A; Jahns, Peter; Winter, Klaus

    2008-04-01

    Dynamics and possible function of the lutein epoxide (Lx) cycle, that is, the reversible conversion of Lx to lutein (L) in the light-harvesting antennae, were investigated in leaves of tropical tree species. Photosynthetic pigments were quantified in nine Inga species and species from three other genera. In Inga, Lx levels were high in shade leaves (mostly above 20 mmol mol(-1) chlorophyll) and low in sun leaves. In Virola surinamensis, both sun and shade leaves exhibited very high Lx contents (about 60 mmol mol(-1) chlorophyll). In Inga marginata grown under high irradiance, Lx slowly accumulated within several days upon transfer to deep shade. When shade leaves of I. marginata were briefly exposed to the sunlight, both violaxanthin and Lx were quickly de-epoxidized. Subsequently, overnight recovery occurred only for violaxanthin, not for Lx. In such leaves, containing reduced levels of Lx and increased levels of L, chlorophyll fluorescence induction showed significantly slower reduction of the photosystem II electron acceptor, Q(A), and faster formation as well as a higher level of non-photochemical quenching. The results indicate that slow Lx accumulation in Inga leaves may improve light harvesting under limiting light, while quick de-epoxidation of Lx to L in response to excess light may enhance photoprotection.

  18. Alteration of the mutagenicity 3,3'-dichlorobenzidine by modifiers of rat hepatic epoxide hydrolase activity

    SciTech Connect

    Iba, M.M.

    1986-03-05

    The involvement of arene oxides in the activation of benzidines was assessed by examining the effect of (I) the epoxide hydrolase inhibitor trichloropropylene oxide (TCPO), (II) purified rat liver microsomal (P) epoxide hydrolase (EH), and (III) pretreatment of rats with phenobarbital (PB) on hepatic Sg- or P-catalyzed mutagenicity of benzidine (BZ) and 3,3'-dichlorobenzidine (DCB) to Salmonella TA 98. When catalyzed by Sg from untreated rats, the mutagenicity of DCB and BZ was 601 +/- 101 and 79 +/- 25 (His/sup +/ revertants/plate) respectively, but was 345 +/- 55 and 226 +/- 30 respectively, when catalyzed by microsomes (P) from untreated rats. PB-pretreatment enhanced the Sg-catalyzed mutagenicity of DCB and BZ (2.3-fold and 1.7-fold, respectively) and the P-catalyzed mutagenicity of DCB (1.7-fold), but totally inhibited the P-catalyzed mutagenicity of BZ. In TCPO-supplemented activating systems from PB-pretreated rats, the mutagenicity of DCB was enhanced in both Sg and P (1.9-fold and 1.6-fold, respectively), whereas that of BZ was unchanged. Added EH enhanced the P-catalyzed mutagenicity of DCB (1.4-fold) but had no effect on that of BZ, suggesting that the activity of the enzyme on DCB metabolites may not be entirely detoxifying. The data suggest that epoxidation may contribute to the activation of DCB but not BZ.

  19. Stereoelectronic Factors in the Stereoselective Epoxidation of Glycals and 4-Deoxypentenosides

    PubMed Central

    Alberch, Laura; Cheng, Gang; Seo, Seung-Kee; Li, Xuehua; Boulineau, Fabien P.; Wei, Alexander

    2011-01-01

    Glycals and 4-deoxypentenosides (4-DPs), unsaturated pyranosides with similar structures and reactivity profiles, can exhibit a high degree of stereoselectivity upon epoxidation with dimethyldioxirane (DMDO). In most cases, the glycals and their corresponding 4-DP isosteres share the same facioselectivity, implying that the pyran substituents are largely responsible for the stereodirecting effect. Fully substituted dihydropyrans are subject to a “majority rule,” in which the epoxidation is directed toward the face opposite to two of the three groups. Removing one of the substituents has a variable effect on the epoxidation outcome, depending on its position and also on the relative stereochemistry of the remaining two groups. Overall, we observe that the greatest loss in facioselectivity for glycals and 4-DPs is caused by removal of the C3 oxygen, followed by the C5/anomeric substituent, and least of all by the C4/C2 oxygen. DFT calculations based on polarized-π frontier molecular orbital (PPFMO) theory support a stereoelectronic role for the oxygen substituents in 4-DP facioselectivity, but less clearly so in the case of glycals. We conclude that the anomeric oxygen in 4-DPs contributes toward a stereoelectronic bias in facioselectivity whereas the C5 alkoxymethyl in glycals imparts a steric bias, which at times can compete with the stereodirecting effects from the other oxygen substituents. PMID:21417287

  20. Epoxides, cyclic sulfites, and sulfate from natural pentacyclic triterpenoids: theoretical calculations and chemical transformations.

    PubMed

    García-Granados, Andrés; López, Pilar E; Melguizo, Enrique; Moliz, Juan N; Parra, Andrés; Simeó, Yolanda; Dobado, José A

    2003-06-13

    Several triterpenic derivatives, with the A-ring functionalized, were semisynthesized from oleanolic and maslinic acids. The reactivities of sulfites, sulfate, and epoxides in these triterpene compounds were investigated under different reaction conditions. Moreover, contracted A-ring triterpenes (five-membered rings) were obtained, by different treatments of the sulfate 7. From the epoxide 8, deoxygenated and halohydrin derivatives were semisynthesized with several nucleophiles. Ozonolysis and Beckmann reactions were used to yield 4-aza compounds, from five-membered ring olanediene triterpenes. The X-ray structure of sulfate 7 is given and compared with density functional theory geometries. Theoretical (13)C and (1)H chemical shifts (gauge-invariant atomic orbital method at the B3LYP/6-31G*//B3LYP/6-31G* level) and (3)J(H,H) coupling constants were calculated for compounds 5-9 and 34-36, identifying the (R)- or (S)-sulfur and alpha- or beta-epoxide configurations together with 4-aza or 3-aza structures.

  1. Foam, Foam-resin composite and method of making a foam-resin composite

    NASA Technical Reports Server (NTRS)

    Cranston, John A. (Inventor); MacArthur, Doug E. (Inventor)

    1995-01-01

    This invention relates to a foam, a foam-resin composite and a method of making foam-resin composites. The foam set forth in this invention comprises a urethane modified polyisocyanurate derived from an aromatic amino polyol and a polyether polyol. In addition to the polyisocyanurate foam, the composite of this invention further contains a resin layer, wherein the resin may be epoxy, bismaleimide, or phenolic resin. Such resins generally require cure or post-cure temperatures of at least 350.degree. F.

  2. Expression and characterization of an epoxide hydrolase from Anopheles gambiae with high activity on epoxy fatty acids

    PubMed Central

    Xu, Jiawen; Morisseau, Christophe; Hammock, Bruce D.

    2014-01-01

    In insects, epoxide hydrolases (EHs) play critical roles in the metabolism of xenobiotic epoxides from the food resources and in the regulation of endogenous chemical mediators, such as juvenile hormones. Using the baculovirus expression system, we expressed and characterized an epoxide hydrolase from Anopheles gambiae (AgEH) that is distinct in evolutionary history from insect juvenile hormone epoxide hydrolases (JHEHs). We partially purified the enzyme by ion exchange chromatography and isoelectric focusing. The experimentally determined molecular weight and pI were estimated to be 35kD and 6.3 respectively, different than the theoretical ones. The AgEH had the greatest activity on long chain epoxy fatty acids such as 14,15-epoxyeicosatrienoic acids (14,15-EET) and 9,10-epoxy-12Z-octadecenoic acids (9,10-EpOME or leukotoxin) among the substrates evaluated. Juvenile hormone III, a terpenoid insect growth regulator, was the next best substrate tested. The AgEH showed kinetics comparable to the mammalian soluble epoxide hydrolases, and the activity could be inhibited by AUDA [12-(3-adamantan-1-yl-ureido) dodecanoic acid], a urea-based inhibitor designed to inhibit the mammalian soluble epoxide hydrolases. The rabbit serum generated against the soluble epoxide hydrolase of Mus musculus can both cross-react with natural and denatured forms of the AgEH, suggesting immunologically they are similar. The study suggests there are mammalian sEH homologs in insects, and epoxy fatty acids may be important chemical mediators in insects. PMID:25173592

  3. Short and long term behaviour of externally bonded fibre reinforced polymer laminates with bio-based resins for flexural strengthening of concrete beams

    NASA Astrophysics Data System (ADS)

    McSwiggan, Ciaran

    The use of bio-based resins in composites for construction is emerging as a way to reduce of embodied energy produced by a structural system. In this study, two types of bio-based resins were explored: an epoxidized pine oil resin blend (EP) and a furfuryl alcohol resin (FA) derived from corn cobs and sugar cane. Nine large-scale reinforced concrete beams strengthened using externally bonded carbon and glass fibre reinforced bio-based polymer (CFRP and GFRP) sheets were tested. The EP resin resulted in a comparable bond strength to conventional epoxy (E) when used in wet layup, with a 7% higher strength for CFRP. The FA resin, on the other hand, resulted in a very weak bond, likely due to concrete alkalinity affecting curing. However, when FA resin was used to produce prefabricated cured CFRP plates which were then bonded to concrete using conventional epoxy paste, it showed an excellent bond strength. The beams achieved an increase in peak load ranging from 18-54% and a 9-46% increase in yielding load, depending on the number of FRP layers and type of fibres and resin. Additionally, 137 concrete prisms with a mid-span half-depth saw cut were used to test CFRP bond durability, and 195 CFRP coupons were used to examine tensile strength durability. Specimens were conditioned in a 3.5% saline solution at 23, 40 or 50°C, for up to 240 days. Reductions in bond strength did not exceed 15%. Bond failure of EP was adhesive with traces of cement paste on CFRP, whereas that of FA was cohesive with a thicker layer of concrete on CFRP, suggesting that the bond between FA and epoxy paste is excellent. EP tension coupons had similar strength and modulus to E resin, whereas FA coupons had a 9% lower strength and 14% higher modulus. After 240 days of exposure, maximum reductions in tensile strength were 8, 19 and 10% for EP, FA and E resins, respectively. Analysis of Variance (ANOVA) was also performed to assess the significance of the reductions observed. High degrees of

  4. 21 CFR 177.2510 - Polyvinylidene fluoride resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Polyvinylidene fluoride resins. 177.2510 Section... Repeated Use § 177.2510 Polyvinylidene fluoride resins. Polyvinylidene fluoride resins may be safely used... fluoride resins consist of basic resins produced by the polymerization of vinylidene fluoride. (b)...

  5. High Temperature Transfer Molding Resins

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)

    2000-01-01

    High temperature resins containing phenylethynyl groups that are processable by transfer molding have been prepared. These phenylethynyl containing oligomers were prepared from aromatic diamines containing phenylethynyl groups and various ratios of phthalic anhydride and 4-phenylethynlphthalic anhydride in glacial acetic acid to form a mixture of imide compounds in one step. This synthetic approach is advantageous since the products are a mixture of compounds and consequently exhibit a relatively low melting temperature. In addition, these materials exhibit low melt viscosities which are stable for several hours at 210-275 C, and since the thermal reaction of the phenylethynyl group does not occur to any appreciable extent at temperatures below 300 C, these materials have a broad processing window. Upon thermal cure at approximately 300-350 C, the phenylethynyl groups react to provide a crosslinked resin system. These new materials exhibit excellent properties and are potentially useful as adhesives, coatings, films, moldings and composite matrices.

  6. Advanced thermoplastic resins, phase 2

    NASA Technical Reports Server (NTRS)

    Brown, A. M.; Hill, S. G.; Falcone, A.

    1991-01-01

    High temperature structural resins are required for use on advanced aerospace vehicles as adhesives and composite matrices. NASA-Langley developed polyimide resins were evaluated as high temperature structural adhesives for metal to metal bonding and as composite matrices. Adhesive tapes were prepared on glass scrim fabric from solutions of polyamide acids of the semicrystalline polyimide LARC-CPI, developed at the NASA-Langley Research Center. Using 6Al-4V titanium adherends, high lap shear bond strengths were obtained at ambient temperature (45.2 MPa, 6550 psi) and acceptable strengths were obtained at elevated temperature (14.0 MPa, 2030 psi) using the Pasa-Jell 107 conversion coating on the titanium and a bonding pressure of 1.38 MPa (200 psi). Average zero degree composite tensile and compressive strengths of 1290 MPa (187 ksi) and 883 MPa (128 ksi) respectively were obtained at ambient temperature with unsized AS-4 carbon fiber reinforcement.

  7. Petroleum resins and their production

    SciTech Connect

    Luvinh, Q.

    1989-04-25

    A process is described for the production of petroleum resins compatible with base polymers in hot melt formulations and having a softening point of from about 60/sup 0/C. to about 120/sup 0/C. and Gardner color of about 4 or less, comprising copolymerizing using a Friedel-Crafts catalyst. The mixture is substantially free form cyclopentadiene and dicyclopentadiene. This patent also describes a resin consisting essentially of a copolymer containing from 5 to 80 wt. % of units derived from an olefinically unsaturated aromatic compound form 5 to 80 wt. % of units derived from C/sub 5/ olefines or diolefines or C/sub 6/ olefines diolefines or a mixture of C/sub 5/ and C/sub 6/ olefines or diolefines and from 7 to 45 wt. % of units derived from a terpene.

  8. Phosphorus-containing imide resins

    NASA Technical Reports Server (NTRS)

    Varma, I. K.; Fohlen, G. M.; Parker, J. A. (Inventor)

    1984-01-01

    Flame-resistant reinforced bodies are disclosed which are composed of reinforcing fibers, filaments or fabrics in a cured body of bis- and tris-imide resins derived from tris(m-aminophenyl) phosphine oxides by reaction with maleic anhydride or its derivatives, or of addition polymers of such imides, including a variant in which a mono-imide is condensed with a dianhydride and the product is treated with a further quantity of maleic anhydride.

  9. Synthesis of Improved Polyester Resins.

    DTIC Science & Technology

    1979-07-05

    peroxides as initiator. The peroxides used were benzoyl peroxide , cumene hydroperoxide, t-butyl peroxybenzoate and 2,5... benzoyl peroxide , while allyl type polyester resins require a higher temperature cure and use a peroxide such as dicumyl peroxide . Numerous other peroxides ...using MEKP (methylethylketone peroxide ) or BZP ( benzoyl peroxide ) catalysts. 47 01 "I 4 C C~ >~> .0 00 Q) . x> x (. C. a, 0 + 0) 0. 0 0 a,. E S- >0>

  10. ELUTION OF URANIUM FROM RESIN

    DOEpatents

    McLEan, D.C.

    1959-03-10

    A method is described for eluting uranium from anion exchange resins so as to decrease vanadium and iron contamination and permit recycle of the major portion of the eluats after recovery of the uranium. Diminution of vanadium and iron contamination of the major portion of the uranium is accomplished by treating the anion exchange resin, which is saturated with uranium complex by adsorption from a sulfuric acid leach liquor from an ore bearing uranium, vanadium and iron, with one column volume of eluant prepared by passing chlorine into ammonium hydroxide until the chloride content is about 1 N and the pH is about 1. The resin is then eluted with 8 to 9 column volumes of 0.9 N ammonium chloride--0.1 N hydrochloric acid solution. The eluants are collected separately and treated with ammonia to precipitate ammonium diuranate which is filtered therefrom. The uranium salt from the first eluant is contaminated with the major portion of ths vanadium and iron and is reworked, while the uranium recovered from the second eluant is relatively free of the undesirable vanadium and irons. The filtrate from the first eluant portion is discarded. The filtrate from the second eluant portion may be recycled after adding hydrochloric acid to increase the chloride ion concentration and adjust the pH to about 1.

  11. Synthesis of improved polyester resins

    NASA Technical Reports Server (NTRS)

    Mcleod, A. H.; Delano, C. B.

    1979-01-01

    Eighteen aromatic unsaturated polyester prepolymers prepared by a modified interfacial condensation technique were investigated for their solubility in vinyl monomers and ability to provide high char yield forming unsaturated polyester resins. The best resin system contained a polyester prepolymer of phthalic, fumaric and diphenic acids reacted with 2,7-naphthalene diol and 9,9-bis(4-hydroxyphenyl)fluorene. This prepolymer is very soluble in styrene, divinyl benzene, triallyl cyanurate, diallyl isophthalate and methylvinylpyridine. It provided anaerobic char yields as high as 41 percent at 800 C. The combination of good solubility and char yield represents a significant improvement over state-of-the-art unsaturated polyester resins. The majority of the other prepolymers had only low or no solubility in vinyl monomers. Graphite composites from this prepolymer with styrene were investigated. The cause for the observed low shear strengths of the composites was not determined, however 12-week aging of the composites at 82 C showed that essentially no changes in the composites had occurred.

  12. Scintillating 99Tc Selective Ion Exchange Resins

    SciTech Connect

    Mitchell Greenhalgh; Richard D. Tillotson

    2012-07-01

    Scintillating technetium (99Tc) selective ion exchange resins have been developed and evaluated for equilibrium capacities and detection efficiencies. These resins can be utilized for the in-situ concentration and detection of low levels of pertechnetate anions (99TcO4-) in natural waters. Three different polystyrene type resin support materials were impregnated with varying amounts of tricaprylmethylammonium chloride (Aliquat 336) extractant, several different scintillating fluors and wavelength shifters. The prepared resins were contacted batch-wise to equilibrium over a wide range of 99TcO4- concentrations in natural water. The measured capacities were used to develop Langmuir adsorption isotherms for each resin. 99Tc detection efficiencies were determined and up to 71.4 ± 2.6% was achieved with some resins. The results demonstrate that a low level detection limit for 99TcO4- in natural waters can be realized.

  13. Development of tough, moisture resistant laminating resins

    NASA Technical Reports Server (NTRS)

    Brand, R. A.; Harrison, E. S.

    1982-01-01

    Tough, moisture resistant laminating resins for employment with graphite fibers were developed. The new laminating resins exhibited cost, handleability and processing characteristics equivalent to 394K (250 F) curing epoxies. The laminating resins were based on bisphenol A dicyanate and monofunctional cyanates with hydrophobic substituents. These resins sorb only small quantities of moisture at equilibrium (0.5% or less) with minimal glass transition temperature depression and represent an improvement over epoxies which sorb around 2% moisture at equilibrium. Toughening was accomplished by the precipitation of small diameter particles of butadiene nitrile rubber throughout the resin matrix. The rubber domains act as microcrack termini and energy dissipation sites, allowing increased stress accommodation prior to catastrophic failure. A unique blend of amine terminated butadiene nitrile elastomer (MW 2,000) and a high nitrile content butadiene nitrile rubber yielded the desired resin morphology.

  14. Lycopene epoxides and apo-lycopenals formed by chemical reactions and autoxidation in model systems and processed foods.

    PubMed

    Rodriguez, Evelyn B; Rodriguez-Amaya, Delia B

    2009-01-01

    To gain a better understanding of the reactions and the underlying mechanisms of the oxidative degradation of lycopene, the products formed by epoxidation with m-chloroperbenzoic acid (MCPBA), oxidative cleavage with KMnO(4), and autoxidation in low-moisture and aqueous model systems, under light exposure, at ambient temperature were identified. The presence of oxidation products was also verified in processed products (tomato juice, tomato paste, tomato puree, guava juice, "goiabada"). A total of 8 lycopene epoxides and a cyclolycopene diol were formed by the reaction of lycopene with MCPBA and 6 apo-lycopenals were produced with KMnO(4). Some of these oxidation products were not detected in the model systems and in the foods analyzed, but the acid-catalyzed rearrangement product 2,6-cyclolycopene-1,5-diol and apo-12'-lycopenal were found in all model and food systems and lycopene-1,2-epoxide and 2,6-cyclolycopene-1,5-epoxide were found in the model systems and in all but 1 ("goiabada") of the 5 foods analyzed. Other epoxides and apo-lycopenals were found in some systems. The inability to detect an intermediate product could be due to a fast turn over. Increased Z-isomerization was also observed and Z-isomers of the oxidation products were detected.

  15. Substrate range and enantioselectivity of epoxidation reactions mediated by the ethene-oxidising Mycobacterium strain NBB4.

    PubMed

    Cheung, Samantha; McCarl, Victoria; Holmes, Andrew J; Coleman, Nicholas V; Rutledge, Peter J

    2013-02-01

    Mycobacterium strain NBB4 is an ethene-oxidising micro-organism isolated from estuarine sediments. In pursuit of new systems for biocatalytic epoxidation, we report the capacity of strain NBB4 to convert a diverse range of alkene substrates to epoxides. A colorimetric assay based on 4-(4-nitrobenzyl)pyridine) has been developed to allow the rapid characterisation and quantification of biocatalytic epoxide synthesis. Using this assay, we have demonstrated that ethene-grown NBB4 cells epoxidise a wide range of alkenes, including terminal (propene, 1-butene, 1-hexene, 1-octene and 1-decene), cyclic (cyclopentene, cyclohexene), aromatic (styrene, indene) and functionalised substrates (allyl alcohol, dihydropyran and isoprene). Apparent specific activities have been determined and range from 2.5 to 12.0 nmol min(-1) per milligram of cell protein. The enantioselectivity of epoxidation by Mycobacterium strain NBB4 has been established using styrene as a test substrate; (R)-styrene oxide is produced in enantiomeric excesses greater than 95%. Thus, the ethene monooxygenase of Mycobacterium NBB4 has a broad substrate range and promising enantioselectivity, confirming its potential as a biocatalyst for alkene epoxidation.

  16. Porous Ceramic Spheres from Ion Exchange Resin

    NASA Technical Reports Server (NTRS)

    Dynys, Fred

    2005-01-01

    A commercial cation ion exchange resin, cross-linked polystyrene, has been successfully used as a template to fabricate 20 to 50 micron porous ceramic spheres. Ion exchange resins have dual template capabilities. Pore architecture of the ceramic spheres can be altered by changing the template pattern. Templating can be achieved by utilizing the internal porous structure or the external surface of the resin beads. Synthesis methods and chemical/physical characteristics of the ceramic spheres will be reported.

  17. Sand control with resin and explosive

    SciTech Connect

    Dees, J.M.; Begnaud, W.J.; Sahr, N.L.

    1992-09-08

    This patent describes a method for treating a well having perforated casing to prevent solids movement through the perforations and into the wellbore. It comprises positioning a quantity of liquid resin solution such that the solution occupies the interval of the casing having perforations; positioning an explosive in proximity with the liquid resin solution; detonating the explosive; displacing the liquid resin solution remaining in the wellbore after step (c) through the perforations with a displacing fluid; and injecting a chemical solution through the perforations to cause the resin to polymerize to form a consolidated permeable matrix.

  18. Characterization of PMR polyimide resin and prepreg

    NASA Technical Reports Server (NTRS)

    Lindenmeyer, P. H.; Sheppard, C. H.

    1984-01-01

    Procedures for the chemical characterization of PMR-15 resin solutions and graphite-reinforced prepregs were developed, and a chemical data base was established. In addition, a basic understanding of PMR-15 resin chemistry was gained; this was translated into effective processing procedures for the production of high quality graphite composites. During the program the PMR monomers and selected model compounds representative of postulated PMR-15 solution chemistry were acquired and characterized. Based on these data, a baseline PMR-15 resin was formulated and evaluated for processing characteristics and composite properties. Commercially available PMR-15 resins were then obtained and chemically characterized. Composite panels were fabricated and evaluated.

  19. Novel silica-based ion exchange resin

    SciTech Connect

    1997-11-01

    Eichrom`s highly successful Diphonixo resin resembles a conventional ion exchange resin in its use of sulfonic acid ligands on a styrene- divinylbenzene matrix. Diphonix resin exhibits rapid exchange kinetics that allow economical operation of ion exchange systems. Unlike conventional resins, Diphonix resin contains chelating ligands that are diphosphonic acid groups that recognize and remove the targeted metals and reject the more common elements such as sodium, calcium and magnesium. This latter property makes Diphonix ideal for many industrial scale applications, including those involving waste treatment. For treatment of low-level, transuranic (TRU) and high- level radioactive wastes, Diphonix`s polystyrene backbone hinders its application due to radiolytic stability of the carbon-hydrogen bonds and lack of compatibility with expected vitrification schemes. Polystyrene-based Diphonix is approximately 60% carbon- hydrogen. In response to an identified need within the Department of Energy for a resin with the positive attributes of Diphonix that also exhibits greater radiolytic stability and final waste form compatibility, Eichrom has successfully developed a new, silica-based resin version of Diphonix. Target application for this new resin is for use in environmental restoration and waste management situations involving the processing of low-level, transuranic and high-level radioactive wastes. The resin can also be used for processing liquid mixed waste (waste that contains low level radioactivity and hazardous constituents) including mixed wastes contaminated with organic compounds. Silica-based Diphonix is only 10% carbon-hydrogen, with the bulk of the matrix silica.

  20. Asymmetric aminolytic kinetic resolution of racemic epoxides using recyclable chiral polymeric Co(III)-salen complexes: a protocol for total utilization of racemic epoxide in the synthesis of (R)-Naftopidil and (S)-Propranolol.

    PubMed

    Kumar, Manish; Kureshy, Rukhsana I; Shah, Arpan K; Das, Anjan; Khan, Noor-ul H; Abdi, Sayed H R; Bajaj, Hari C

    2013-09-20

    Chiral polymeric Co(III) salen complexes with chiral ((R)/(S)-BINOL, diethyl tartrate) and achiral (piperazine and trigol) linkers with varying stereogenic centers were synthesized for the first time and used as catalysts for aminolytic kinetic resolution (AKR) of a variety of terminal epoxides and glycidyl ethers to get enantio-pure epoxides (ee, 99%) and N-protected β-amino alcohols (ee, 99%) with quantitative yield in 16 h at RT under optimized reaction conditions. This protocol was also used for the synthesis of two enantiomerically pure drug molecules (R)-Naftopidil (α1-blocker) and (S)-Propranolol (β-blocker) as a key step via AKR of single racemic naphthylglycidyl ether with Boc-protected isoproylamine with 100% epoxide utilization at 1 g level. The catalyst 1 was successfully recycled for a number of times.

  1. Strategic use of nickel(0)-catalyzed enyne-epoxide reductive coupling towards the synthesis of (−)-cyatha-3,12-diene

    PubMed Central

    Sparling, Brian A.; Simpson, Graham L.; Jamison, Timothy F.

    2009-01-01

    Various situations are explored in which the nickel(0)-catalyzed enyne-epoxide reductive coupling was utilized to access key intermediates towards the total synthesis of (−)-cyatha-3,12-diene (1). Enantioenriched 3,5-dien-1-ols with a variety of functionality were obtained in a straightforward manner from easily accessible 1,3-enynes and terminal epoxides. PMID:20161213

  2. (Salen)Mn-catalyzed epoxidation of alkenes: a two-zone process with different spin-state channels as suggested by DFT study.

    PubMed

    Abashkin, Yuri G; Burt, Stanley K

    2004-01-08

    [structure: see text] A novel (two-zone process with different spin-state channels) mechanistic picture for the Jacobsen-Katsuki reaction is presented that provides insight into the still elusive understanding of the epoxidation mechanism. For the first time, we show that the salen moiety of the catalyst can be explicitly involved in the epoxidation process.

  3. Co(III)(salen)-catalyzed HKR of two stereocentered alkoxy- and azido epoxides: a concise enantioselective synthesis of (S,S)-reboxetine and (+)-epi-cytoxazone.

    PubMed

    Reddy, R Santhosh; Chouthaiwale, Pandurang V; Suryavanshi, Gurunath; Chavan, Vilas B; Sudalai, Arumugam

    2010-07-21

    The HKR of racemic syn- or anti- alkoxy- and azido epoxides catalyzed by Co(salen) complex affords a practical access to a series of enantioenriched syn- or anti- alkoxy- and azido epoxides and the corresponding 1,2-diols. This strategy has been successfully employed in the concise, enantioselective synthesis of bioactive molecules such as (S,S)-reboxetine and (+)-epi-cytoxazone.

  4. Cloning, expression, purification, crystallization and preliminary X-ray studies of epoxide hydrolases A and B from Mycobacterium tuberculosis

    SciTech Connect

    Biswal, Bichitra K.; Garen, Grace; Cherney, Maia M.; Garen, Craig; James, Michael N. G.

    2006-02-01

    Epoxide hydrolases A (Rv3617) and B (Rv1938), detoxification enzymes from M. tuberculosis, have been cloned, expressed, purified and crystallized. Crystals of Rv3617 and Rv1938 diffracted to 3.0 and 2.1 Å resolution, respectively. Mycobacterium tuberculosis epoxide hydrolases A and B, corresponding to open reading frames Rv3617 and Rv1938, are detoxification enzymes against epoxides. The recombinant forms of these enzymes have been expressed in Escherichia coli and purified to homogeneity. Diffraction-quality crystals of Rv3617 and Rv1938 were obtained by the hanging-drop vapour-diffusion technique. Crystals of Rv3617 and Rv1938 diffracted to 3.0 and 2.1 Å resolution, respectively, at the ALS synchrotron at Berkeley, CA, USA.

  5. A novel and enantioselective epoxide hydrolase from Aspergillus brasiliensis CCT 1435: purification and characterization.

    PubMed

    Beloti, Lilian L; Costa, Bruna Z; Toledo, Marcelo A S; Santos, Clelton A; Crucello, Aline; Fávaro, Marianna T P; Santiago, André S; Mendes, Juliano S; Marsaioli, Anita J; Souza, Anete P

    2013-10-01

    A novel epoxide hydrolase from Aspergillus brasiliensis CCT1435 (AbEH) was cloned and overexpressed in Escherichia coli cells with a 6xHis-tag and purified by nickel affinity chromatography. Gel filtration analysis and circular dichroism measurements indicated that this novel AbEH is a homodimer in aqueous solution and contains the typical secondary structure of an α/β hydrolase fold. The activity of AbEH was initially assessed using the fluorogenic probe O-(3,4-epoxybutyl) umbelliferone and was active in a broad range of pH (6-9) and temperature (25-45°C); showing optimum performance at pH 6.0 and 30°C. The Michaelis constant (KM) and maximum rate (Vmax) values were 495μM and 0.24μM/s, respectively. Racemic styrene oxide (SO) was used as a substrate to assess the AbEH activity and enantioselectivity, and 66% of the SO was hydrolyzed after only 5min of reaction, with the remaining (S)-SO ee exceeding 99% in a typical kinetic resolution behavior. The AbEH-catalyzed hydrolysis of SO was also evaluated in a biphasic system of water:isooctane; (R)-diol in 84% ee and unreacted (S)-SO in 36% ee were produced, with 43% conversion in 24h, indicating a discrete enantioconvergent behavior for AbEH. This novel epoxide hydrolase has biotechnological potential for the preparation of enantiopure epoxides or vicinal diols.

  6. A stable epoxide of estrone: Evidence for formation of a 'new' estrogen metabolite.

    PubMed

    Raeside, James I; Christie, Heather L

    2017-03-01

    Oxidative metabolism of estrogens is an important feature in liver and some non-hepatic tissues. In initial studies on estrogen metabolism in tissues from the reproductive tract of the stallion, where testicular estrogen secretion is remarkably high, a prominent radiolabeled product from [(3)H]-estrone (E1) was noted on chromatography; it had a retention time (Rt) between 17β-estradiol (E2) and E1. Unexpectedly, when non-radiolabeled E1 was the substrate no UV absorption at 280nm was seen at the Rt for the [(3)H]-labeled product-suggesting a non-aromatic ring A. The following efforts were made to reveal more about the nature of the "unknown" compound. Reduction and acetylation showed, separately, the presence of a single keto and hydroxyl group. Exposure to acid gave a single radiolabeled peak with Rt of 6α-hydroxy-E1-suggesting the presence of a third molecule of oxygen. Mass spectrometry with limited material was inconclusive but supportive for a formula of C18H22O3. Thus, an epoxide involving the aromatic ring of E1 is suggested as a labile intermediate in the formation of the "unknown" metabolite. Estrogen epoxides as labile, reactive intermediates have been considered as potential precursors of the 2- and 4-hydroxy catechol estrogens with implications in breast cancer [Soloway, 2007]. Because of the association of the "unknown" metabolite with 6α-hydroxy-E1, the structural form proposed for the stable epoxide is that for 5α,6α-epoxy-estrone. This represents an alternative to the production of the 2- and 4-hydroxy-catechol estrogens. The broad range in normal tissues where the "unknown" compound was shown to be a persistent metabolite (e.g. mouse mammary glands, ovary, uterus, brain, muscle, equine conceptus, stallion and domestic boar reproductive tracts) suggests more general biological implications.

  7. Assessing the oxidative potential of isoprene-derived epoxides and secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Kramer, Amanda J.; Rattanavaraha, Weruka; Zhang, Zhenfa; Gold, Avram; Surratt, Jason D.; Lin, Ying-Hsuan

    2016-04-01

    Fine particulate matter (PM2.5) is known to contribute to adverse health effects, such as asthma, cardiopulmonary disease, and lung cancer. Secondary organic aerosol (SOA) is a major component of PM2.5 and can be enhanced by atmospheric oxidation of biogenic volatile organic compounds in the presence of anthropogenic pollutants, such as nitrogen oxides (NOx) and sulfur dioxide. However, whether biogenic SOA contributes to adverse health effects remains unclear. The objective of this study was to assess the potential of isoprene-derived epoxides and SOA for generating reactive oxygen species (ROS) in light of the recent recognition that atmospheric oxidation of isoprene in the presence of acidic sulfate aerosol is a major contributor to the global SOA burden. The dithiothreitol (DTT) assay was used to characterize the ROS generation by the isoprene-derived epoxides, trans-β-isoprene epoxydiol (trans-β-IEPOX) and methacrylic acid epoxide (MAE), and their hydrolysis products, the 2-methyltetrol diastereomers (2-MT), 2-methylglyceric acid (2-MG), their organosulfate derivatives, as well as an isoprene-derived hydroxyhydroperoxide (ISOPOOH). In addition, ROS generation potential was evaluated for total SOA produced from photooxidation of isoprene and methacrolein (MACR) as well as from the reactive uptake of trans-β-IEPOX and MAE onto acidified sulfate aerosol. The high-NOx regime, which yields 2-MG-, MAE- and MACR-derived SOA has a higher ROS generation potential than the low-NOx regime, which yields 2-MT, IEPOX- and isoprene-derived SOA. ISOPOOH has an ROS generation potential similar to 1,4-naphthoquinone (1,4-NQ), suggesting a significant contribution of aerosol-phase organic peroxides to PM oxidative potential. MAE- and MACR-derived SOA show equal or greater ROS generation potential than reported in studies on diesel exhaust PM, highlighting the importance of a comprehensive investigation of the toxicity of isoprene-derived SOA.

  8. 21 CFR 175.380 - Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... condensation of xylene-formaldehyde resin and 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins, to... include resins produced by the condensation of allyl ether of mono-, di-, or trimethylol phenol and...

  9. Living carbocationic polymerization of isobutylene by epoxide/Lewis acid systems: The mechanism of initiation

    NASA Astrophysics Data System (ADS)

    Hayat Soytas, Serap

    The objective of the work presented in this dissertation was to generate a fundamental understanding of the synthesis of star-branched polyisobutylenes (PIBs) arising from hexaepoxysqualene (HES)/Lewis acid (LA) initiating systems, using BCl3 and TiCl4 as LAs. The understanding of initiation and propagation mechanisms by HES is crucial to control the number of arms and arm lengths of star PIBs expected from this initiator. The initiation by monofunctional epoxides, such as alpha-methylstyrene epoxide (MSE), 1,2-epoxy-2,4,4-trimethylpentane (TMPO-1), and 2,3-epoxy-2,4,4-trimethylpentane (TMPO-2), was investigated. In situ FTIR spectroscopy, which was highly utilized in this research, provided valuable information. Most importantly, the ability to identify the head group by in situ FTIR of growing PIB chains initiated by an epoxide, i.e. the --C--O--LA complex, contributed significantly to the understanding of initiation of IB polymerization. This technique allowed the monitoring of the rate of initiation with the multifunctional epoxy initiator. Previous research showed that TiCl4 gave 40% initiating efficiency in conjunction with the aromatic epoxy initiator MSE, whereas the aliphatic initiators TMPO-1 and TMPO-2 gave only 3 and 10% efficiency, respectively. In this research it was found that BCl3 is more efficient with the aliphatic initiator, TMPO-1, yielding an asymmetric telechelic PIB carrying an alpha-primary OH and an o-tertiary Cl functional group with 70% initiator efficiency, while MSE gave only 1--4% efficiency. The TMPO-2/BCl3 system gave 20% initiator efficiency. The various initiation mechanisms were discussed. IB polymerization was successfully initiated by HES in the presence of excess BCl3 and monitored by in situ FTIR spectroscopy. The gradual increase of the IR band assigned to the --C--O--BCl 2 group demonstrated that slow initiation was occurring. Chain extension with the HES/BCl3 initiated PIB was achieved leading to high molecular weight PIBs

  10. Synthesis and characterization of new magnetically recoverable molybdenum nanocatalyst for epoxidation of olefins

    NASA Astrophysics Data System (ADS)

    Masteri-Farahani, M.; Kashef, Z.

    2012-04-01

    New heterogeneous molybdenum catalyst was prepared through covalent attachment of a Schiff base ligand on the surface of silica coated magnetite nanoparticles via aminopropyl spacer and subsequent complexation with MoO2(acac)2. The prepared nanocatalyst was characterized with Fourier transform infrared spectroscopy, X-ray diffraction, scanning and transmission electron microscopies and vibrating sample magnetometry. Catalytic epoxidation of some olefins and allylic alcohols by prepared nanocatalyst using tert-butyl hydroperoxide and cumene hydroperoxide as oxidants was achieved with good activities and selectivities.

  11. How the Proximal Pocket May Influence the Enantiospecificities of Chloroperoxidase-Catalyzed Epoxidations of Olefins

    PubMed Central

    Morozov, Alexander N.; Chatfield, David C.

    2016-01-01

    Chloroperoxidase-catalyzed enantiospecific epoxidations of olefins are of significant biotechnological interest. Typical enantiomeric excesses are in the range of 66%–97% and translate into free energy differences on the order of 1 kcal/mol. These differences are generally attributed to the effect of the distal pocket. In this paper, we show that the influence of the proximal pocket on the electron transfer mechanism in the rate-limiting event may be just as significant for a quantitatively accurate account of the experimentally-measured enantiospecificities. PMID:27517911

  12. Quantitative DFT modeling of the enantiomeric excess for dioxirane-catalyzed epoxidations

    PubMed Central

    Schneebeli, Severin T.; Hall, Michelle Lynn

    2009-01-01

    Herein we report the first fully quantum mechanical study of enantioselectivity for a large dataset. We show that transition state modeling at the UB3LYP-DFT/6-31G* level of theory can accurately model enantioselectivity for various dioxirane-catalyzed asymmetric epoxidations. All the synthetically useful high selectivities are successfully “predicted” by this method. Our results hint at the utility of this method to further model other asymmetric reactions and facilitate the discovery process for the experimental organic chemist. Our work suggests the possibility of using computational methods not simply to explain organic phenomena, but also to predict them quantitatively. PMID:19243187

  13. Alloy Catalyst in a Reactive Environment: The Example of Ag-Cu Particles for Ethylene Epoxidation

    SciTech Connect

    Piccinin, Simone; Zafeiratos, Spiros; Stampfl, Catherine; Hansen, Thomas W.; Haevecker, Michael; Teschner, Detre; Girgsdies, Frank; Knop-Gericke, Axel; Schloegl, Robert; Scheffler, Matthias; Bukhtiyarov, Valerii I.

    2010-01-22

    Combining first-principles calculations and in situ photoelectron spectroscopy, we show how the composition and structure of the surface of an alloy catalyst is affected by the temperature and pressure of the reagents. The Ag-Cu alloy, recently proposed as an improved catalyst for ethylene epoxidation, forms a thin Cu-O surface oxide, while a Ag-Cu surface alloy is found not to be stable. Several possible surface structures are identified, among which the catalyst surface is likely to dynamically evolve under reaction conditions.

  14. Enantioselective hydrolysis of racemic epichlorohydrin using an epoxide hydrolase from Novosphingobium aromaticivorans.

    PubMed

    Woo, Jung-Hee; Hwang, Young-Ok; Kang, Ji-Hyun; Lee, Hyun Sook; Kim, Sang-Jin; Kang, Sung Gyun

    2010-09-01

    Previously we reported that an epoxide hydrolase (EHase) from Novosphingobium aromaticivorans could preferentially hydrolyze (R)-styrene oxide. In this study, we demonstrate that the purified NEH could be also effective in chiral resolution of racemic epichlorohydrin (ECH). Particularly, the purified NEH showed excellent hydrolyzing activity toward ECH to complete the reaction at a short period of incubation time. Enantiopure (S)-ECH could be obtained with a high enantiopurity of more than 99.99% enantiomeric excess (ee) and yield of 20.7% (theoretical, 50%). The chiral resolution of the purified NEH toward ECH was not susceptible to substrate inhibition by 500 mM racemic ECH.

  15. Chiral nanoporous metal-metallosalen frameworks for hydrolytic kinetic resolution of epoxides.

    PubMed

    Zhu, Chengfeng; Yuan, Guozan; Chen, Xu; Yang, Zhiwei; Cui, Yong

    2012-05-16

    Chiral nanoporous metal-organic frameworks are constructed by using dicarboxyl-functionalized chiral Ni(salen) and Co(salen) ligands. The Co(salen)-based framework is shown to be an efficient and recyclable heterogeneous catalyst for hydrolytic kinetic resolution (HKR) of racemic epoxides with up to 99.5% ee. The MOF structure brings Co(salen) units into a highly dense arrangement and close proximity that enhances bimetallic cooperative interactions, leading to improved catalytic activity and enantioselectivity in HKR compared with its homogeneous analogues, especially at low catalyst/substrate ratios.

  16. Imide modified epoxy matrix resins

    NASA Technical Reports Server (NTRS)

    Scola, D. A.

    1982-01-01

    Results of a program designed to develop tough imide modified epoxy (IME) resins cured by bisimide amine (BIA) hardeners are presented. State of the art epoxy resin, MY720, was used. Three aromatic bisimide amines and one aromatic aliphatic BIA were evaluated. BIA's derived from 6F anhydride (3,3 prime 4,4 prime-(hexafluoro isopropyl idene) bis (phthalic anhydride) and diamines, 3,3 prime-diam nodiphenyl sulfone (3,3 prime-DDS), 4,4 prime-diamino diphenyl sulfone (4,4 prime-DDS), 1.12-dodecane diamine (1,12-DDA) were used. BIA's were abbreviated 6F-3,3 prime-DDS, 6F-4,4 prime-DDS, 6F-3,3 prime-DDS-4,4 prime DDS, and 6F-3,3 prime-DDS-1,12-DDA corresponding to 6F anhydride and diamines mentioned. Epoxy resin and BIA's (MY720/6F-3,3 prime-DDS, MY720/6F-3,3 prime-DDS-4,4 prime-DDS, MY720/6F-3,3 prime-DDS-1,12-DDA and a 50:50 mixture of a BIA and parent diamine, MY720/6F-3,3 prime-DDS/3,3 prime-DDS, MY720/6F-3,3 prime-DDS-4,4 prime-DDS/3,3 prime-DDS, MY720/6F-3,3 prime-DDS-1,12-DDA/3,3 prime-DDS were studied to determine effect of structure and composition. Effect of the addition of two commercial epoxies, glyamine 200 and glyamine 100 on the properties of several formulations was evaluated. Bisimide amine cured epoxies were designated IME's (imide modified epoxy). Physical, thermal and mechanical properties of these resins were determined. Moisture absorption in boiling water exhibited by several of the IME's was considerably lower than the state of the art epoxies (from 3.2% for the control and state of the art to 2.0 wt% moisture absorption). Char yields are increased from 20% for control and state of the art epoxies to 40% for IME resins. Relative toughness characteristics of IME resins were measured by 10 deg off axis tensile tests of Celion 6000/IME composites. Results show that IME's containing 6F-3,3 prime-DDS or 6F-3,3 prime-DDS-1,12-DDA improved the "toughness" characteristics of composites by about 35% (tensile strength), about 35% (intralaminar shear

  17. Dentine sealing provided by smear layer/smear plugs vs. adhesive resins/resin tags.

    PubMed

    Carrilho, Marcela R; Tay, Franklin R; Sword, Jeremy; Donnelly, Adam M; Agee, Kelli A; Nishitani, Yoshihiro; Sadek, Fernanda T; Carvalho, Ricardo M; Pashley, David H

    2007-08-01

    The aim of this study was to evaluate the ability of five experimental resins, which ranged from hydrophobic to hydrophilic blends, to seal acid-etched dentine saturated with water or ethanol. The experimental resins (R1, R2, R3, R4, and R5) were evaluated as neat bonding agents (100% resin) or as solutions solvated with absolute ethanol (70% resin/30% ethanol). Fluid conductance was measured at 20 cm H(2)O hydrostatic pressure after sound dentine surfaces were: (i) covered with a smear layer; (ii) acid-etched; or (iii) bonded with neat or solvated resins, which were applied to acid-etched dentine saturated with water or ethanol. In general, the fluid conductance of resin-bonded dentine was significantly higher than that of smear layer-covered dentine. However, when the most hydrophobic neat resins (R1 and R2) were applied to acid-etched dentine saturated with ethanol, the fluid conductance was as low as that produced by smear layers. The fluid conductance of resin-bonded dentine saturated with ethanol was significantly lower than for resin bonded to water-saturated dentine, except for resin R4. Application of more hydrophobic resins may provide better sealing of acid-etched dentine if the substrate is saturated with ethanol instead of with water.

  18. Polyimide Resins Resist Extreme Temperatures

    NASA Technical Reports Server (NTRS)

    2009-01-01

    Spacecraft and aerospace engines share a common threat: high temperature. The temperatures experienced during atmospheric reentry can reach over 2,000 F, and the temperatures in rocket engines can reach well over 5,000 F. To combat the high temperatures in aerospace applications, Dr. Ruth Pater of Langley Research Center developed RP-46, a polyimide resin capable of withstanding the most brutal temperatures. The composite material can push the service temperature to the limits of organic materials. Designed as an environmentally friendly alternative to other high-temperature resins, the RP-46 polyimide resin system was awarded a 1992 "R&D 100" award, named a "2001 NASA Technology of the Year," and later, due to its success as a spinoff technology, "2004 NASA Commercial Invention of the Year." The technology s commercial success also led to its winning the Langley s "Paul F. Holloway Technology Transfer Award" as well as "Richard T. Whitcom Aerospace Technology Transfer Award" both for 2004. RP-46 is relatively inexpensive and it can be readily processed for use as an adhesive, composite, resin molding, coating, foam, or film. Its composite materials can be used in temperatures ranging from minus 150 F to 2,300 F. No other organic materials are known to be capable of such wide range and extreme high-temperature applications. In addition to answering the call for environmentally conscious high-temperature materials, RP-46 provides a slew of additional advantages: It is extremely lightweight (less than half the weight of aluminum), chemical and moisture resistant, strong, and flexible. Pater also developed a similar technology, RP-50, using many of the same methods she used with RP-46, and very similar in composition to RP-46 in terms of its thermal capacity and chemical construction, but it has different applications, as this material is a coating as opposed to a buildable composite. A NASA license for use of this material outside of the Space Agency as well as

  19. Coupling Agents - HME Resin System.

    DTIC Science & Technology

    1977-12-01

    and test results of the sized fiber impregnated with lIME 5803—53 resin and laminated are shown in Table 2. The slig htl y improved SBS strength of...inherent in the 9 - - -~~~~ . ~~~~~~~~~~~~~~~~ ~~- % . - ~, - • - - - ~~~~~~~~~~~~ — — ~~~~~~~~ free radical—induced crosslink cures. As this shrinkage

  20. Phosphorus-containing imide resins

    NASA Technical Reports Server (NTRS)

    Varma, I. K.; Fohlen, G. M.; Parker, J. A. (Inventor)

    1985-01-01

    Cured polymers of bis and tris-imides derived from tris(m-aminophenyl) phosphine oxides by reaction with maleic anhydride or its derivatives, and addition polymers of such imides, including a variant in which a monoimide is condensed with a dianhydride and the product is treated with a further quantity of maleic anhydride prior to curing are disclosed and claimed. Such polymers are flame resistant. Also disclosed are an improved method of producing tris(m-aminophenyl) phosphine oxides from the nitro analogues by reduction with hydrazine hydrate using palladized charcoal or Raney nickel as the catalyst and fiber reinforced cured resin composites.

  1. Robust bifunctional aluminium-salen catalysts for the preparation of cyclic carbonates from carbon dioxide and epoxides.

    PubMed

    Rulev, Yuri A; Gugkaeva, Zalina; Maleev, Victor I; North, Michael; Belokon, Yuri N

    2015-01-01

    Two new one-component aluminium-based catalysts for the reaction between epoxides and carbon dioxide have been prepared. The catalysts are composed of aluminium-salen chloride complexes with trialkylammonium groups directly attached to the aromatic rings of the salen ligand. With terminal epoxides, the catalysts induced the formation of cyclic carbonates under mild reaction conditions (25-35 °C; 1-10 bar carbon dioxide pressure). However, with cyclohexene oxide under the same reaction conditions, the same catalysts induced the formation of polycarbonate. The catalysts could be recovered from the reaction mixture and reused.

  2. Robust bifunctional aluminium–salen catalysts for the preparation of cyclic carbonates from carbon dioxide and epoxides

    PubMed Central

    Rulev, Yuri A; Gugkaeva, Zalina; Maleev, Victor I

    2015-01-01

    Summary Two new one-component aluminium-based catalysts for the reaction between epoxides and carbon dioxide have been prepared. The catalysts are composed of aluminium–salen chloride complexes with trialkylammonium groups directly attached to the aromatic rings of the salen ligand. With terminal epoxides, the catalysts induced the formation of cyclic carbonates under mild reaction conditions (25–35 °C; 1–10 bar carbon dioxide pressure). However, with cyclohexene oxide under the same reaction conditions, the same catalysts induced the formation of polycarbonate. The catalysts could be recovered from the reaction mixture and reused. PMID:26664580

  3. Shell cross-linked micelle-based nanoreactors for the substrate-selective hydrolytic kinetic resolution of epoxides.

    PubMed

    Liu, Yu; Wang, Yu; Wang, Yufeng; Lu, Jie; Piñón, Victor; Weck, Marcus

    2011-09-14

    Shell cross-linked micelles (SCMs) containing Co(III)-salen cores were prepared from amphiphilic poly(2-oxazoline) triblock copolymers. The catalytic activity of these nanoreactors for the hydrolytic kinetic resolution of various terminal epoxides was investigated. The SCM catalysts showed high catalytic efficiency and, more significantly, substrate selectivity based on the hydrophobic nature of the epoxide. Moreover, because of the nanoscale particle size and the high stability, the catalyst could be recovered easily by ultrafiltration and reused with high activity for eight cycles.

  4. Cp2TiCl-promoted isomerization of trisubstituted epoxides to exo-methylene allylic alcohols on carvone derivatives.

    PubMed

    Bermejo, Francisco; Sandoval, Celso

    2004-08-06

    The ring-opening reaction of trisubstituted epoxides promoted by Cp2TiCl led to exo-methylene allylic alcohols as major compounds when 0.5 M solutions of the epoxides were added to 0.1 M solutions of the reagent at room temperature in THF. In most cases, the allylic alcohols were contaminated with saturated alcohols. Normal and reverse addition modes led to the alternate product being favored. The different stereochemical outcome of cis- and trans-epoxy acetates is rationalized in terms of mechanistically biased elimination processes.

  5. Experience with NuResin, a mobile ion exchange resin reprocessing system

    SciTech Connect

    Palazzi, K.R.; Bell, M.J.; Concklin, J.R.

    1995-12-31

    Ion exchange resin used in condensate polishing, steam generator blowdown, and radwaste systems is a major contributor to the volume of low-level waste (LLW) at operating nuclear plants. Plant regeneration systems for resins use large quantities of demineralized water for cleaning, separating, and regenerating resins. These systems generate a tremendous volume of LLW from boiling water reactors (BWRs) and those pressurized water reactors (PWRs) that have experienced steam generator tube leaks. At essentially all BWRs and those PWRs that replace rather than regenerate condensate polishing resin, the LLW volume contribution from the resin alone is significant. This report describes a process for the treatment of resins with the objective of returning the resin to service.

  6. Modified resins for solid-phase extraction

    DOEpatents

    Fritz, James S.; Sun, Jeffrey J.

    1993-07-27

    A process of treating aqueous solutions to remove organic solute contaminants by contacting an aqueous solution containing polar organic solute contaminants with a functionalized polystyrene-divinyl benzene adsorbent resin, with the functionalization of said resin being accomplished by organic hydrophilic groups such as hydroxymethyl, acetyl and cyanomethyl.

  7. Modified resins for solid-phase extraction

    DOEpatents

    Fritz, James S.; Sun, Jeffrey J.

    1991-12-10

    A process of treating aqueous solutions to remove organic solute contaminants by contacting an aqueous solution containing polar organic solute contaminants with a functionalized polystyrene-divinyl benzene adsorbent resin, with the functionalization of said resin being accomplished by organic hydrophilic groups such as hydroxymethyl, acetyl and cyanomethyl.

  8. Silicone modified resins for graphite fiber laminates

    NASA Technical Reports Server (NTRS)

    Frost, L. W.; Bower, G. M.

    1980-01-01

    Six silicone modified resins were selected for evaluation in unidirectional filament wound graphite laminates. Neat samples of these resins had 1,000 C char residues of 6-63%. The highest flexural values measured for the laminates were a strength of 1,220 MPa and a modulus of 105 GPa. The highest interlaminar shear strength was 72 MPa.

  9. VOLUMETRIC POLYMERIZATION SHRINKAGE OF CONTEMPORARY COMPOSITE RESINS

    PubMed Central

    Nagem, Halim; Nagem, Haline Drumond; Francisconi, Paulo Afonso Silveira; Franco, Eduardo Batista; Mondelli, Rafael Francisco Lia; Coutinho, Kennedy Queiroz

    2007-01-01

    The polymerization shrinkage of composite resins may affect negatively the clinical outcome of the restoration. Extensive research has been carried out to develop new formulations of composite resins in order to provide good handling characteristics and some dimensional stability during polymerization. The purpose of this study was to analyze, in vitro, the magnitude of the volumetric polymerization shrinkage of 7 contemporary composite resins (Definite, Suprafill, SureFil, Filtek Z250, Fill Magic, Alert, and Solitaire) to determine whether there are differences among these materials. The tests were conducted with precision of 0.1 mg. The volumetric shrinkage was measured by hydrostatic weighing before and after polymerization and calculated by known mathematical equations. One-way ANOVA (á=0.05) was used to determine statistically significant differences in volumetric shrinkage among the tested composite resins. Suprafill (1.87±0.01) and Definite (1.89±0.01) shrank significantly less than the other composite resins. SureFil (2.01±0.06), Filtek Z250 (1.99±0.03), and Fill Magic (2.02±0.02) presented intermediate levels of polymerization shrinkage. Alert and Solitaire presented the highest degree of polymerization shrinkage. Knowing the polymerization shrinkage rates of the commercially available composite resins, the dentist would be able to choose between using composite resins with lower polymerization shrinkage rates or adopting technical or operational procedures to minimize the adverse effects deriving from resin contraction during light-activation. PMID:19089177

  10. Fluorinated diamond bonded in fluorocarbon resin

    DOEpatents

    Taylor, Gene W.

    1982-01-01

    By fluorinating diamond grit, the grit may be readily bonded into a fluorocarbon resin matrix. The matrix is formed by simple hot pressing techniques. Diamond grinding wheels may advantageously be manufactured using such a matrix. Teflon fluorocarbon resins are particularly well suited for using in forming the matrix.

  11. TMI-2 purification demineralizer resin study

    SciTech Connect

    Thompson, J D; Osterhoudt, T R

    1984-05-01

    Study of the Makeup and Purification System demineralizers at TMI-2 has established that fuel quantities in the vessels are low, precluding criticality, that the high radioactive cesium concentration on the demineralizer resins can be chemically removed, and that the demineralizer resins can probably be removed from the vessels by sluicing through existing plant piping. Radiation measurements from outside the demineralizers establishing that there is between 1.5 and 5.1 (probably 3.3) lb of fuel in the A vessel and less than that amount in the B vessel. Dose rates up to 2780 R per hour were measured on contact with the A demineralizer. Remote visual observation of the A demineralizer showed a crystalline crust overlaying amber-colored resins. The cesium activity in solid resin samples ranged from 220 to 16,900 ..mu..Ci/g. Based on this information, researchers concluded that the resins cannot be removed through the normal pathway in their present condition. Studies do show that the resins will withstand chemical processing designed to rinse and elute cesium from the resins. The process developed should work on the TMI-2 resins.

  12. 21 CFR 177.1550 - Perfluorocarbon resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... resins can be identified by their characteristic infrared spectra. (2) Melt-viscosity. (i) The per-fluoro-carbon resins identified in paragraph (a)(1) of this section shall have a melt viscosity of not less than.../federal_register/code_of_federal_regulations/ibr_locations.html. The melt viscosity of the...

  13. 21 CFR 177.1500 - Nylon resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...: Nylon resins Specific gravity Melting point(degrees Fahrenheit) Solubilityin boiling 4.2N HC1 Viscosity... by 100. (5) Viscosity number (VN). (i) The viscosity number (VN) for Nylon 6/12 resin in a 96 percent... ISO 307-1984(E), “Plastics-Polyamides-Determination of Viscosity Number,” which is incorporated...

  14. Release and toxicity of dental resin composite.

    PubMed

    Gupta, Saurabh K; Saxena, Payal; Pant, Vandana A; Pant, Aditya B

    2012-09-01

    Dental resin composite that are tooth-colored materials have been considered as possible substitutes to mercury-containing silver amalgam filling. Despite the fact that dental resin composites have improved their physico-chemical properties, the concern for its intrinsic toxicity remains high. Some components of restorative composite resins are released in the oral environment initially during polymerization reaction and later due to degradation of the material. In vitro and in vivo studies have clearly identified that these components of restorative composite resins are toxic. But there is a large gap between the results published by research laboratories and clinical reports. The objective of this manuscript was to review the literature on release phenomenon as well as in vitro and in vivo toxicity of dental resin composite. Interpretation made from the recent data was also outlined.

  15. Release and toxicity of dental resin composite

    PubMed Central

    Gupta, Saurabh K.; Saxena, Payal; Pant, Vandana A.; Pant, Aditya B.

    2012-01-01

    Dental resin composite that are tooth-colored materials have been considered as possible substitutes to mercury-containing silver amalgam filling. Despite the fact that dental resin composites have improved their physico-chemical properties, the concern for its intrinsic toxicity remains high. Some components of restorative composite resins are released in the oral environment initially during polymerization reaction and later due to degradation of the material. In vitro and in vivo studies have clearly identified that these components of restorative composite resins are toxic. But there is a large gap between the results published by research laboratories and clinical reports. The objective of this manuscript was to review the literature on release phenomenon as well as in vitro and in vivo toxicity of dental resin composite. Interpretation made from the recent data was also outlined. PMID:23293458

  16. Chemoviscosity modeling for thermosetting resins, 2

    NASA Technical Reports Server (NTRS)

    Hou, T. H.

    1985-01-01

    A new analytical model for simulating chemoviscosity of thermosetting resin was formulated. The model is developed by modifying the Williams-Landel-Ferry (WLF) theory in polymer rheology for thermoplastic materials. By assuming a linear relationship between the glass transition temperature and the degree of cure of the resin system under cure, the WLF theory can be modified to account for the factor of reaction time. Temperature dependent functions of the modified WLF theory constants were determined from the isothermal cure data of Lee, Loos, and Springer for the Hercules 3501-6 resin system. Theoretical predictions of the model for the resin under dynamic heating cure cycles were shown to compare favorably with the experimental data reported by Carpenter. A chemoviscosity model which is capable of not only describing viscosity profiles accurately under various cure cycles, but also correlating viscosity data to the changes of physical properties associated with the structural transformations of the thermosetting resin systems during cure was established.

  17. Physical Properties of Synthetic Resin Materials

    NASA Technical Reports Server (NTRS)

    Fishbein, Meyer

    1939-01-01

    A study was made to determine the physical properties of synthetic resins having paper, canvas, and linen reinforcements, and of laminated wood impregnated with a resin varnish. The results show that commercial resins have moduli of elasticity that are too low for structural considerations. Nevertheless, there do exist plastics that have favorable mechanical properties and, with further development, it should be possible to produce resin products that compare favorably with the light-metal alloys. The results obtained from tests on Compound 1840, resin-impregnated wood, show that this material can stand on its own merit by virtue of a compressive strength four times that of the natural wood. This increase in compressive strength was accomplished with an increase of density to a value slightly below three times the normal value and corrected one of the most serious defects of the natural product.

  18. Solidification of ion exchange resin wastes

    SciTech Connect

    Not Available

    1982-08-01

    Solidification media investigated included portland type I, portland type III and high alumina cements, a proprietary gypsum-based polymer modified cement, and a vinyl ester-styrene thermosetting plastic. Samples formulated with hydraulic cement were analyzed to investigate the effects of resin type, resin loading, waste-to-cement ratio, and water-to-cement ratio. The solidification of cation resin wastes with portland cement was characterized by excessive swelling and cracking of waste forms, both after curing and during immersion testing. Mixed bed resin waste formulations were limited by their cation component. Additives to improve the mechanical properties of portland cement-ion exchange resin waste forms were evaluated. High alumina cement formulations dislayed a resistance to deterioration of mechanical integrity during immersion testing, thus providing a significant advantage over portland cements for the solidification of resin wastes. Properties of cement-ion exchange resin waste forms were examined. An experiment was conducted to study the leachability of /sup 137/Cs, /sup 85/Sr, and /sup 60/Co from resins modified in portland type III and high alumina cements. The cumulative /sup 137/Cs fraction release was at least an order of magnitude greater than that of either /sup 85/Sr or /sup 60/Co. Release rates of /sup 137/Cs in high alumina cement were greater than those in portland III cement by a factor of two.Compressive strength and leach testing were conducted for resin wastes solidified with polymer-modified gypsum based cement. /sup 137/Cs, /sup 85/Sr, and /sup 60/Co fraction releases were about one, two and three orders of magnitude higher, respectively, than in equivalent portland type III cement formulations. As much as 28.6 wt % dry ion exchange resin was successfully solidified using vinyl ester-styrene compared with a maximum of 25 wt % in both portland and gypsum-based cement.

  19. Terpenoid Oligomers of Dammar Resin.

    PubMed

    Bonaduce, Ilaria; Di Girolamo, Francesca; Corsi, Iacopo; Degano, Ilaria; Tinè, Maria Rosaria; Colombini, Maria Perla

    2016-04-22

    Dammar is a triterpenoid resin containing a volatile fraction, a monomeric fraction, and a high-molecular weight fraction. Although the low-molecular-weight components comprising sesquiterpenoids and triterpenoids have been extensively studied, the nature of the macromolecular components is still not fully understood, and different and sometimes contradictory theories have been proposed. The aim of this paper is to clarify the nature of the macromolecular components of dammar resin. A multianalytical approach was adopted based on thermoanalytical-thermogravimetric analysis (TGA), and thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TGA/FTIR)--and mass spectrometric techniques-direct exposure mass spectrometry (DE/MS), pyrolysis coupled to gas chromatography and mass spectrometry (Py/GC/MS), flow injection analysis electrospray ionization mass spectrometry (FIA/ESI/MS), and gas chromatography/mass spectrometry (GC/MS). The data indicate that the oligomeric fraction comprises triterpenoids bound through ester bonds, and that these triterpenoids are the same as those found in the free terpenoid fraction. The oligomeric fraction also includes triterpenoids containing carbonyl moieties, such as formyl groups, thus suggesting that these are involved in the esters in their corresponding enolic form.

  20. Resin/graphite fiber composites

    NASA Technical Reports Server (NTRS)

    Cavano, P. J.

    1974-01-01

    Techniques were developed that provided thermo-oxidatively stable A-type polyimide/graphite fiber composites using the approach of in situ polymerization of monomeric reactants directly on reinforcing fibers, rather than employing separately prepared prepolymer varnish. This was accomplished by simply mixing methylene dianiline and two ester-acids and applying this solution to the fibers for subsequent molding. Five different formulated molecular weight resins were examined, and an optimized die molding procedure established for the 1500 formulated molecular weight system. Extensive ultrasonic inspection of composites was successfully utilized as a technique for monitoring laminate quality. Composite mechanical property studies were conducted with this polyimide resin at room temperature and after various time exposures in a thermo-oxidative environment at 561 K (550 F), 589 K (600 F) and 617 K (650 F). It was determined that such composites have a long term life in the temperature range of 561 K to 589 K. The final phase involved the fabrication and evaluation of a series of demonstration airfoil specimens.

  1. Adsorption of pesticides on resins.

    PubMed

    Kyriakopoulos, Grigorios; Hourdakis, Adamadia; Doulia, Danae

    2003-03-01

    The objective of this work was to assess the capability of organic hydrophobic polymeric resins Amberlite XAD-4 and XAD-7 to remove the pesticides alachlor and amitrole from water. The pesticides adsorption on the two different adsorbents was measured by batch equilibrium technique and isotherm types and parameters were estimated. Two theoretical models were applied based on a Freundlich and a Langmuir isotherms. The effect of pesticides chemical composition and structure as well as the nature of solid surface on the efficiency of adsorption was evaluated. The influence of pH also was studied. In low pH solutions adsorption of amitrole was higher upon the nonionic aliphatic acrylic ester copolymer XAD-7 in comparison to the nonionic, crosslinked macroreticular copolymer of styrene divinylbenzene XAD-4. In neutral and intermediate pH solutions the polar acrylic ester copolymer XAD-7 was more effective to the retention of alachlor. The acrylic ester copolymer showed at pH 3 the lower effectiveness in alachlor removal from water. The data of the adsorption isotherms of pesticides upon the examined polymeric resins seemed to conform to both the Freundlich and the Langmuir isotherm models.

  2. Cycloaliphatic epoxide-based photocured gelled electrolytes for secondary lithium battery applications. Electrochemical kinetic studies

    NASA Astrophysics Data System (ADS)

    Nagasubramanian, G.; Surampudi, S.; Halpert, G.

    1994-06-01

    Cycloaliphatic epoxide-based thin gelled films prepared by ultraviolet photocuring were characterized electrochemically. Mixtures of ethylene carbonate and various organic liquids in different volume ratios were used as solvents. General composition of the electrolyte was cycloaliphatic epoxide (being sold under the trade name ENVIBAR by Union Carbide) 10 to 28 weight percent (w/o), polyethylene oxide (200,000 Mw) 4 to 10 w/o, LiAsF6, 6 to 22 w/o, and mixed solvents (of different volume ratios) 80 to 40 w/o. Thin gelled films were formed on lithium (Li) electrodes and subjected to electrochemical studies. Typical values of bulk electrolyte specific conductivity and interfacial resistance obtained from ac impedance and dc measurements at room temperatures are 2 x 10(exp -3) S cm(exp -1) and 3.2 Omega cm(exp 2), respectively. Charge/discharge characteristics of the cells of the Li/electrolyte/TiS2 type were evaluated. Cathode utilization was only 33% of the total capacity.

  3. MWCNTs-Reinforced Epoxidized Linseed Oil Plasticized Polylactic Acid Nanocomposite and Its Electroactive Shape Memory Behaviour

    PubMed Central

    Alam, Javed; Alam, Manawwer; Raja, Mohan; Abduljaleel, Zainularifeen; Dass, Lawrence Arockiasamy

    2014-01-01

    A novel electroactive shape memory polymer nanocomposite of epoxidized linseed oil plasticized polylactic acid and multi-walled carbon nanotubes (MWCNTs) was prepared by a combination of solution blending, solvent cast technique, and hydraulic hot press moulding. In this study, polylactic acid (PLA) was first plasticized by epoxidized linseed oil (ELO) in order to overcome the major limitations of PLA, such as high brittleness, low toughness, and low tensile elongation. Then, MWCNTs were incorporated into the ELO plasticized PLA matrix at three different loadings (2, 3 and 5 wt. %), with the aim of making the resulting nanocomposites electrically conductive. The addition of ELO decreased glass transition temperature, and increased the elongation and thermal degradability of PLA, as shown in the results of differential scanning calorimetry (DSC), tensile test, and thermo gravimetric analysis (TGA). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to observe surface morphology, topography, and the dispersion of MWCNTs in the nanocomposite. Finally, the electroactive-shape memory effect (electroactive-SME) in the resulting nanocomposite was investigated by a fold-deploy “U”-shape bending test. As per the results, the addition of both ELO and MWCNTs to PLA matrix seemed to enhance its overall properties with a great deal of potential in improved shape memory. The 3 wt. % MWCNTs-reinforced nanocomposite system, which showed 95% shape recovery within 45 s at 40 DC voltage, is expected to be used as a preferential polymeric nanocomposite material in various actuators, sensors and deployable devices. PMID:25365179

  4. Detection and characterization of human serum antibodies to polycyclic aromatic hydrocarbon diol-epoxide DNA adducts.

    PubMed Central

    Newman, M J; Light, B A; Weston, A; Tollurud, D; Clark, J L; Mann, D L; Blackmon, J P; Harris, C C

    1988-01-01

    The presence of serum antibodies to the diol-epoxide DNA adducts of representative polycyclic aromatic hydrocarbons (PAH), chrysene, benz[a]anthracene and benzo[a]pyrene, was determined by ELISA using serum samples obtained from normal healthy individuals. Antibodies that reacted against PAH adducted-DNA, but not against PAH-adducted protein, were found in the serum of approximately 40% of the test individuals. Specificity analysis of the antibodies demonstrated that serological cross-reactions between the benzo[a]pyrene and the chrysene diol-epoxide adducts were present. Similar cross-reactivity between the benz[a]anthracene and the chrysene adducts was observed. Sera containing antibodies that were apparently specific for each of the three PAH-DNA adducts were also identified. The presence of antibodies to PAH-DNA adducts indicates both past exposure to these carcinogenic PAH and their metabolic activation to the DNA damaging metabolites. These antibodies may prove to be useful in both retrospective and prospective epidemiological studies of various diseases associated with PAH exposure. PMID:3392204

  5. MWCNTs-reinforced epoxidized linseed oil plasticized polylactic acid nanocomposite and its electroactive shape memory behaviour.

    PubMed

    Alam, Javed; Alam, Manawwer; Raja, Mohan; Abduljaleel, Zainularifeen; Dass, Lawrence Arockiasamy

    2014-10-31

    A novel electroactive shape memory polymer nanocomposite of epoxidized linseed oil plasticized polylactic acid and multi-walled carbon nanotubes (MWCNTs) was prepared by a combination of solution blending, solvent cast technique, and hydraulic hot press moulding. In this study, polylactic acid (PLA) was first plasticized by epoxidized linseed oil (ELO) in order to overcome the major limitations of PLA, such as high brittleness, low toughness, and low tensile elongation. Then, MWCNTs were incorporated into the ELO plasticized PLA matrix at three different loadings (2, 3 and 5 wt. %), with the aim of making the resulting nanocomposites electrically conductive. The addition of ELO decreased glass transition temperature, and increased the elongation and thermal degradability of PLA, as shown in the results of differential scanning calorimetry (DSC), tensile test, and thermo gravimetric analysis (TGA). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to observe surface morphology, topography, and the dispersion of MWCNTs in the nanocomposite. Finally, the electroactive-shape memory effect (electroactive-SME) in the resulting nanocomposite was investigated by a fold-deploy "U"-shape bending test. As per the results, the addition of both ELO and MWCNTs to PLA matrix seemed to enhance its overall properties with a great deal of potential in improved shape memory. The 3 wt. % MWCNTs-reinforced nanocomposite system, which showed 95% shape recovery within 45 s at 40 DC voltage, is expected to be used as a preferential polymeric nanocomposite material in various actuators, sensors and deployable devices.

  6. The role of human glutathione transferases and epoxide hydrolases in the metabolism of xenobiotics.

    PubMed Central

    Seidegård, J; Ekström, G

    1997-01-01

    Human glutathione transferases (GSTs) are a multigene family of enzymes that are involved in the metabolism of a wide range of electrophilic compounds of both exogenous and endogenous origin. GSTs are generally recognized as detoxifying enzymes by catalyzing the conjugation of these compounds with glutathione, but they may also be involved in activation of some carcinogens. The memmalian GSTs can be differentiated into four classes of cytosolic enzymes and two membrane bound enzymes. Human epoxide hydrolases (EHs) catalyze the addition of water to epoxides to form the corresponding dihydrodiol. The enzymatic hydration is essentially irreversible and produces mainly metabolites of lower reactivity that can be conjugated and excreted. The reaction of EHs is therefore generally regarded as detoxifying. The mammalian EHs can be distinguished by their physical and enzymatic properties. Microsomal EH (mEH) exhibits a broad substrate specificity, while the soluble EH (sEH) is an enzyme with a "complementary" substrate specificity to mEH. Cholesterol EH and leukotriene A4 hydrolase are two EHs with very limited substrate specificity. The activities of either GSTs or EHs expressed in vivo exhibit a relatively large interindividual variation, which might be explained by induction, inhibition, or genetic factors. These variations in levels or activities of individual isoenzymes are of importance with respect to an individual's susceptibility to genotoxic effects. This article gives a general overview of GSTs and EHs, discussing the modulation of activities, determination of these enzymes ex vivo, and the polymorphic expression of some isoenzymes. PMID:9255563

  7. Cytochrome P450 epoxygenases, soluble epoxide hydrolase, and the regulation of cardiovascular inflammation.

    PubMed

    Deng, Yangmei; Theken, Katherine N; Lee, Craig R

    2010-02-01

    The cytochrome P450 (CYP) epoxygenase enzymes CYP2J and CYP2C catalyze the epoxidation of arachidonic acid to epoxyeicosatrienoic acids (EETs), which are rapidly hydrolyzed to dihydroxyeicosatrienoic acids (DHETs) by soluble epoxide hydrolase (sEH). It is well-established that CYP epoxygenase-derived EETs possess potent vasodilatory effects; however, the cellular effects of EETs and their regulation of various inflammatory processes have become increasingly appreciated in recent years, suggesting that the role of this pathway in the cardiovascular system extends beyond the maintenance of vascular tone. In particular, CYP epoxygenase-derived EETs inhibit endothelial activation and leukocyte adhesion via attenuation of nuclear factor-kappaB activation, inhibit hemostasis, protect against myocardial ischemia-reperfusion injury, and promote endothelial cell survival via modulation of multiple cell signaling pathways. Thus, the CYP epoxygenase pathway is an emerging target for pharmacological manipulation to enhance the cardiovascular protective effects of EETs. This review will focus on the role of the CYP epoxygenase pathway in the regulation of cardiovascular inflammation and (1) describe the functional impact of CYP epoxygenase-derived EET biosynthesis and sEH-mediated EET hydrolysis on key inflammatory process in the cardiovascular system, (2) discuss the potential relevance of this pathway to pathogenesis and treatment of cardiovascular disease, and (3) identify areas for future research.

  8. LDRD final report on new homogeneous catalysts for direct olefin epoxidation (LDRD 52591).

    SciTech Connect

    Goldberg, Karen; Smythe, Nicole A.; Moore, Joshua T.; Stewart, Constantine A.; Kemp, Richard Alan; Miller, James Edward; Kornienko, Alexander (New Mexico Institute of Mining and Technology); Denney, Melanie C. (University of Washington); Cetto, Kara L.

    2006-02-01

    This report summarizes our findings during the study of a novel homogeneous epoxidation catalyst system that uses molecular oxygen as the oxidant, a ''Holy Grail'' in catalysis. While olefins (alkenes) that do not contain allylic hydrogens can be epoxidized directly using heterogeneous catalysts, most olefins cannot, and so a general, atom-efficient route is desired. While most of the work performed on this LDRD has been on pincer complexes of late transition metals, we also scouted out metal/ligand combinations that were significantly different, and unfortunately, less successful. Most of the work reported here deals with phosphorus-ligated Pd hydrides [(PCP)Pd-H]. We have demonstrated that molecular oxygen gas can insert into the Pd-H bond, giving a structurally characterized Pd-OOH species. This species reacts with oxygen acceptors such as olefins to donate an oxygen atom, although in various levels of selectivity, and to generate a [(PCP)Pd-OH] molecule. We discovered that the active [(PCP)Pd-H] active catalyst can be regenerated by addition of either CO or hydrogen. The demonstration of each step of the catalytic cycle is quite significant. Extensions to the pincer-Pd chemistry by attaching a fluorinated tail to the pincer designed to be used in solvents with higher oxygen solubilities are also presented.

  9. [Determination of epoxidized soybean oil and linseed oil in wrapping film and cap sealing].

    PubMed

    Kanno, Shinji; Kawamura, Yoko; Mutsuga, Motoh; Tanamoto, Kenichi

    2006-06-01

    A determination method was developed for epoxidized soybean oil (ESBO) and epoxidized linseed oil (ELO), which are used as plasticizers and/or stabilizers, in wrapping film and cap sealings. The ESBO method reported by Castle et al. was improved. Samples were extracted with acetone-hexane (3: 7), transmethylated under alkaline conditions, then derivatized to the 1,3-dioxolanes and analyzed by GC/MS. The recoveries of spiked ESBO and ELO were between 92.6% and 104.4%. The determination limits were 0.01 mg/g for ESBO and 0.02 mg/g for ELO in the wrapping film, and 0.04 mg/g and 0.08 mg/g in the cap sealing. ESBO and ELO were surveyed in 10 samples each of wrapping film and cap sealings currently available on the Japanese market. ESBO was found at 34.7-82.8 mg/g in polyvinyl chloride (PVC) wrapping films and at 5.47-399 mg/g in cap sealings. ELO was detected at 8.6-11.4 mg/g in polyvinylidene chloride (PVDC) wrapping films, and at 46.4 mg/g in a PVC wrapping film.

  10. Ascorbate-independent carotenoid de-epoxidation in intact spinach chloroplasts.

    PubMed

    Sokolove, P M; Marsho, T V

    1976-05-14

    Slow (greater 1 s) light-induced absorbance changes in the 475-5300 nm spectral region were examined in Type A chloroplasts from spinach. The most prominent absorption change occurred at 505 nm. The difference spectrum for this light-induced increase, its absence in osmotically shocked chloroplasts and restoration by ascorbate, and its sensitivity to dithiothreitol indicate that the absorption change is due to carotenoid de-epoxidatiion. The reaction in intact chloroplasts is characterized by its independence of exogenous ascorbate and a rate constant 3- to 8-fold higher than that reported previously for chloroplasts supplemented with ascorbate. The relevance of carotenoid de-epoxidation to other photosynthetic processes was examined by comparing their sensitivities to dithiothreitol. Levels of dithiothreitol that eliminate the 505 nm shift are without effect on saturated rates of CO2 fixation and do not appreciably inhibit fluorescence quenching. We conclude that carotenoid de-epoxidation is not directly involved in the reactions of photosynthesis or in the regulation of excitation allocation between the photosystems.

  11. Chloroperoxidase-Catalyzed Epoxidation of Cis-β-Methylstyrene:Distal Pocket Flexibility Tunes Catalytic Reactivity

    PubMed Central

    Morozov, Alexander N.; Chatfield, David C.

    2012-01-01

    Chloroperoxidase, the most versatile heme protein, has a hybrid active site pocket that shares structural features with peroxidases and cytochrome P450s. The simulation studies presented here show that the enzyme possesses a remarkable ability to efficiently utilize its hybrid structure, assuming structurally different peroxidase-like and P450-like distal pocket faces and thereby enhancing the inherent catalytic capability of the active center. We find that during epoxidation of cis-β-methylstyrene (CBMS), the native peroxidase-like aspect of the distal pocket is diminished as the polar Glu183 side chain is displaced away from the active center and the distal pocket takes on a more hydrophobic, P450-like, aspect. The P450-like distal pocket provides a significant enthalpic stabilization of ~4 kcal/mol of the 14 kcal/mol reaction barrier for gas-phase epoxidation of CMBS by an oxyferryl heme-thiolate species. This stabilization comes from breathing of the distal pocket. As until recently the active site of chloroperoxidase was postulated to be inflexible, these results suggest a new conceptual understanding of the enzyme’s versatility: catalytic reactivity is tuned by flexibility of the distal pocket. PMID:23020548

  12. Epoxidation of 1-butene-3-ol over titanium silicalite TS-2 catalyst under autogenic pressure.

    PubMed

    Wróblewska, Agnieszka; Wajzberg, Joanna; Fajdek, Anna; Milchert, Eugeniusz

    2009-04-30

    Epoxidation of 1-butene-3-ol (1B3O) with 30 wt% hydrogen peroxide over TS-2 catalyst has been studied with methanol as a solvent and at elevated pressure (autogenic). The influence of temperature in the range of 20-120 degrees C, the molar ratio of 1B3O/H(2)O(2) 1:1-5:1, methanol concentration 5-90 wt%, TS-2 catalyst concentration 0.1-5.0 wt% and the reaction time 0.5-5.0 h have been investigated. The process was described by the following functions: the selectivity of transformation to 1,2-epoxybutane-3-ol (1,2EB3) in relation to 1B3O consumed, the selectivity of transformation to organic compounds in relation to H(2)O(2) consumed and the conversions of 1B3O and hydrogen peroxide. The major product of epoxidation is 1,2EB3, a compound with many applications.

  13. Heavy Chain Single Domain Antibodies to Detect Native Human Soluble Epoxide Hydrolase

    PubMed Central

    Cui, Yongliang; Li, Dongyang; Morisseau, Christophe; Yang, Jun; Wan, Debin; Rossotti, Martín A.; Gee, Shirley J.; González-Sapienza, Gualberto G.; Hammock, Bruce D.

    2015-01-01

    The soluble epoxide hydrolase (sEH) is a potential pharmacological target for treating hypertension, vascular inflammation, pain, cancer and other diseases. However, there is not a simple, inexpensive and reliable method to estimate levels of active sEH in tissues. Toward developing such an assay, a polyclonal-variable domain of heavy chain antibody (VHH) sandwich immunoassay was developed. Ten VHHs, which are highly selective for native human sEH, were isolated from a phage displayed library. The ten VHHs have no significant cross-reactivity with human microsomal epoxide hydrolase, rat and mouse sEH, and denatured human sEH. There is a high correlation between protein levels of the sEH determined by the ELISA and the catalytic activity of the enzyme in S9 fractions of human tissues (liver, kidney and lung). The VHH based ELISA appears to be a new reliable method for monitoring the sEH, and may be useful as a diagnostic tool for diseases influenced by sEH. This study also demonstrates the broad utility of VHH in biochemical and pharmacological research. PMID:26229025

  14. Polypyrrole-functionalized ruthenium carbene catalysts as efficient heterogeneous systems for olefin epoxidation.

    PubMed

    Dakkach, Mohamed; Fontrodona, Xavier; Parella, Teodor; Atlamsani, Ahmed; Romero, Isabel; Rodríguez, Montserrat

    2014-07-14

    New Ru complexes containing the bpea-pyr ligand (bpea-pyr stands for N,N-bis(pyridin-2-ylmethyl)-3-(1H-pyrrol-1-yl)propan-1-amine), with the formula [RuCl2(bpea-pyr)(dmso)] (isomeric complexes 2a and 2b) or [Ru(CN-Me)(bpea-pyr)X)](n+) (CN-Me = 3-methyl-1-(pyridin-2-yl)-1H-imidazol-3-ium-2-ide; X = Cl, 3, or X = H2O, 4), have been prepared and fully characterized. Complexes 3 and 4 have been anchored onto an electrode surface through electropolymerization of the attached pyrrole group, yielding stable polypyrrole films. The electrochemical behaviour of 4, which displays a bielectronic Ru(IV/II) redox pair in solution, is dramatically affected by the electropolymerization process leading to the occurrence of two monoelectronic Ru(IV/III) and Ru(III/II) redox pairs in the heterogeneous system. A carbon felt modified electrode containing complex 4 (C-felt/poly-4) has been evaluated as a heterogeneous catalyst in the epoxidation of various olefin substrates using PhI(OAc)2 as an oxidant, displaying TON values of several thousands in all cases and good selectivity for the epoxide product.

  15. Epoxidized soybean oil/ZnO biocomposites for soft tissue applications: preparation and characterization.

    PubMed

    Díez-Pascual, Ana M; Díez-Vicente, Angel L

    2014-10-08

    Biocompatible and biodegradable nanocomposites comprising epoxidized soybean oil (ESO) as matrix, zinc oxide (ZnO) nanoparticles as reinforcements, and 4-dimethylaminopyridine (DMAP) as a catalyst have been successfully prepared via epoxidization of the double bonds of the vegetable oil, ultrasonication, and curing without the need for interfacial modifiers. Their morphology, water uptake, thermal, mechanical, barrier, tribological, and antibacterial properties have been investigated. FT-IR analysis revealed the existence of strong ESO-ZnO hydrogen-bonding interactions. The nanoparticles acted as mass transport barriers, hindering the diffusion of volatiles generated during the decomposition process and leading to higher thermal stability, and also reduced the water absorption and gas permeability of the bioresin. Significant improvements in the static and dynamic mechanical properties, such as storage and Young's moduli, tensile strength, toughness, hardness, glass transition, and heat distortion temperature, were attained on reinforcement. A small drop in the nanocomposite stiffness and strength was found after exposure to several cycles of steam sterilization or to simulated body fluid (SBF) at physiological temperature. Extraordinary reductions in the coefficient of friction and wear rate were detected under both dry and SBF conditions, confirming the potential of these nanoparticles for improving the tribological performance of ESO. The nanocomposites displayed antimicrobial action against human pathogen bacteria with and without UV illumination, which increased progressively with the ZnO content. These sustainable, ecofriendly, and low-cost biomaterials are very promising for use in biomedical applications, like structural tissue engineering scaffolds.

  16. Structure Property Relationships of Biobased Epoxy Resins

    NASA Astrophysics Data System (ADS)

    Maiorana, Anthony Surraht

    The thesis is about the synthesis, characterization, development, and application of epoxy resins derived from sustainable feedstocks such as lingo-cellulose, plant oils, and other non-food feedstocks. The thesis can be divided into two main topics 1) the synthesis and structure property relationship investigation of new biobased epoxy resin families and 2) mixing epoxy resins with reactive diluents, nanoparticles, toughening agents, and understanding co-curing reactions, filler/matrix interactions, and cured epoxy resin thermomechanical, viscoelastic, and dielectric properties. The thesis seeks to bridge the gap between new epoxy resin development, application for composites and advanced materials, processing and manufacturing, and end of life of thermoset polymers. The structures of uncured epoxy resins are characterized through traditional small molecule techniques such as nuclear magnetic resonance, high resolution mass spectrometry, and infrared spectroscopy. The structure of epoxy resin monomers are further understood through the process of curing the resins and cured resins' properties through rheology, chemorheology, dynamic mechanical analysis, tensile testing, fracture toughness, differential scanning calorimetry, scanning electron microscopy, thermogravimetric analysis, and notched izod impact testing. It was found that diphenolate esters are viable alternatives to bisphenol A and that the structure of the ester side chain can have signifi-cant effects on monomer viscosity. The structure of the cured diphenolate based epoxy resins also influence glass transition temperature and dielectric properties. Incorporation of reactive diluents and flexible resins can lower viscosity, extend gel time, and enable processing of high filler content composites and increase fracture toughness. Incorpora-tion of high elastic modulus nanoparticles such as graphene can provide increases in physical properties such as elastic modulus and fracture toughness. The synthesis

  17. ULTRASOUND-ASSISTED EPOXIDATION OF OLEFINS AND A,B-UNSATURATED KETONES OVER HYDROTALCITES USING HYDROGEN PEROXIDE

    EPA Science Inventory

    An efficient ultrasound-assisted epoxidation of olefins and a,B-unsaturated ketones over hydrotacite catalysts in the presence of hydrogen peroxide and acetonitrile is described. This general and selective protocol is relatively fast and is applicable to a wide variety of substra...

  18. SYNTHESIS OF TETRAHYDROPYRAN DERIVATIVES VIA A NOVEL INDIUM TRICHLORIDE MEDIATED CROSS-CYCLIZATION BETWEEN EPOXIDES AND HOMOALLYL ALCOHOLS. (R822668)

    EPA Science Inventory

    Abstract

    A cross-cyclization between epoxides and homoallyl alcohols catalyzed by indium chloride generates tetrahydropyran derivatives in high yields.

    Graphical Abstract


    Contribution of hydrolase and phosphatase domains in soluble epoxide hydrolase to vascular endothelial growth factor expression and cell growth.

    PubMed

    Oguro, Ami; Sakamoto, Koichi; Suzuki, Sachiko; Imaoka, Susumu

    2009-12-01

    Soluble epoxide hydrolase (sEH) is an important pharmacological target because it metabolizes potent bioactive substrates, epoxyeicosatrienoinc acids (EETs) and other lipid epoxide. EETs have a variety of biological functions including angiogenesis and cancer metastasis. However, the regulation and physiological function of sEH is not well understood. In this study, we found that hypoxia significantly suppressed the expression of sEH in mouse liver and a human hepatoma cell line, Hep3B. Hypoxia promotes the proliferation of vascular endothelial cells or carcinoma cells. Knockdown of sEH in Hep3B cells induced vascular endothelial growth factor (VEGF) mRNA and cell growth, both of which were suppressed by overexpression of sEH. sEH has phosphatase activity as well as epoxide hydrolase (EH) activity. We prepared mutant clones which lacking EH or phosphatase activity using the amino acid change Asp335Ser or Asp9Ala, respectively. The effects of WT sEH on cell growth were lost by mutation of either the EH domain or phosphatase domain. However, mutation of the phosphatase domain but not EH domain did not influence the expression of VEGF. These results suggest that sEH plays an important role in the physiology of cells including proliferation and that the epoxide hydrolase and phosphatase domains of sEH have different biological functions.

  19. Epoxidation of alkenes and oxidation of alcohols with hydrogen peroxide catalyzed by a manganese(V) nitrido complex.

    PubMed

    Kwong, Hoi-Ki; Lo, Po-Kam; Lau, Kai-Chung; Lau, Tai-Chu

    2011-04-14

    The manganese(V) nitrido complex (PPh(4))(2)[Mn(N)(CN)(4)] is an active catalyst for alkene epoxidation and alcohol oxidation using H(2)O(2) as an oxidant. The catalytic oxidation is greatly enhanced by the addition of just one equivalent of acetic acid. The oxidation of ethene by this system has been studied computationally by the DFT method.

  1. Ultrasound assisted, ruthenium-exchanged FAU-Y zeolite catalyzed alkylation of indoles with epoxides under solvent free conditions.

    PubMed

    Khorshidi, Alireza

    2012-05-01

    Ruthenium-exchanged FAU-Y zeolite (RuY) was used as a recyclable catalyst for regioselective ring-opening of epoxides with indoles under irradiation of sonic waves. It was found that a solvent free process, under the above mentioned conditions provides good yields of the desired 3-alkylated indole derivatives.

  2. Efficient alkene epoxidation catalyzed by molybdenyl acetylacetonate supported on aminated UiO-66 metal−organic framework

    SciTech Connect

    Kardanpour, Reihaneh; Tangestaninejad, Shahram; Mirkhani, Valiollah; Moghadam, Majid; Mohammadpoor-Baltork, Iraj; Zadehahmadi, Farnaz

    2015-03-15

    Metal–organic frameworks (MOFs) containing Mo Schiff base complexes were prepared by post-synthesis method and applied as efficient catalysts in the epoxidation of alkenes with tert-BuOOH. In this manner, UiO-66-NH{sub 2} (UiO=University of Oslo) MOF was reacted with salicylaldehyde and thiophene-2-carbaldehyde to produce bidentate Schiff bases. Then, the Schiff base ligands were used for immobilization of molybdenyl acetylacetonate. These new catalysts were characterized by FT-IR, UV–vis spectroscopic techniques, X-ray diffraction (XRD), BET, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and field emission scanning electron microscopy (FE-SEM). These catalytic systems showed excellent activity in the epoxidation of alkenes such as cyclic and linear ones with tert-butyl hydroperoxide (TBHP) in 1,2-dichloroethane, and reused several times without any appreciable loss of their activity. - Graphical abstract: Efficient alkene epoxidation with TBHP catalyzed by heterogeneous and reusable molybdenum base catalysts is reported. - Highlights: • UiO-66-NH{sub 2} was modified with salicylaldehyde and thiophene-2-carbaldehyde. • The Schiff base groups were used for immobilization of MoO{sub 2}(acac){sub 2}. • The heterogeneous catalysts were prepared. • The prepared catalysts were used for epoxidation of alkenes. • Compared to other catalyst, our catalysts were more efficient and forceful.

  3. 3-D QSAR ANALYSIS OF INHIBITION OF MURINE SOLUBLE EPOXIDE HYDROLASE (MSEH) BY BENZOYLUREAS, ARYLUREAS, AND THEIR ANALOGUES. (R825433)

    EPA Science Inventory

    Two hundred and seventy-one compounds including benzoylureas, arylureas and related compounds were assayed using recombinant murine soluble epoxide hydrolase (MsEH) produced from a baculovirus expression system. Among all the insect growth regulators assayed, 18 benzoylphenylu...

  4. Mechanistic basis for high reactivity of (salen)Co-OTs in the hydrolytic kinetic resolution of terminal epoxides.

    PubMed

    Nielsen, Lars P C; Zuend, Stephan J; Ford, David D; Jacobsen, Eric N

    2012-03-02

    The (salen)Co(III)-catalyzed hydrolytic kinetic resolution (HKR) of terminal epoxides is a bimetallic process with a rate controlled by partitioning between a nucleophilic (salen)Co-OH catalyst and a Lewis acidic (salen)Co-X catalyst. The commonly used (salen)Co-OAc and (salen)Co-Cl precatalysts undergo complete and irreversible counterion addition to epoxide during the course of the epoxide hydrolysis reaction, resulting in quantitative formation of weakly Lewis acidic (salen)Co-OH and severely diminished reaction rates in the late stages of HKR reactions. In contrast, (salen)Co-OTs maintains high reactivity over the entire course of HKR reactions. We describe here an investigation of catalyst partitioning with different (salen)Co-X precatalysts and demonstrate that counterion addition to epoxide is reversible in the case of the (salen)Co-OTs. This reversible counterion addition results in stable partitioning between nucleophilic and Lewis acidic catalyst species, allowing highly efficient catalysis throughout the course of the HKR reaction.

  5. Mechanistic aspects of metal valence change in SalenCo(III)OAc-catalyzed hydrolytic kinetic resolution of racemic epoxides.

    PubMed

    Ren, Wei-Min; Wang, Yi-Ming; Zhang, Rong; Jiang, Jing-Yang; Lu, Xiao-Bing

    2013-05-17

    The chiral SalenCo(III)OAc-catalyzed hydrolytic kinetic resolution (HKR) of racemic terminal epoxides to afford both enantioenriched epoxides and diols presents one of the most important achievements in asymmetric synthesis chemistry. Previous studies mainly focused on the development of highly efficient catalysts, while rare reports concerned the mechanistic understanding of metal valence change, associated with the formation of inactive Co(II)-Salen complex. Herein, we report the mechanistic aspects of catalyst deactivation regarding the transformation of Co(III) to Co(II) derivative in the HKR of racemic epoxides catalyzed by SalenCo(III)OAc complexes with an appended 1,5,7-triazabicyclo[4.4.0]dec-5-ene on the ligand framework by means of electrospray ionization mass spectrometry (ESI-MS). Continuous determination of transient cationic species in ESI-MS positive mode in conjunction with UV-vis spectroscopic studies at various time points provides evidence that a certain amount of SalenCo(III)OAc molecules were reduced to the corresponding Co(II) derivatives in the HKR of racemic propylene oxide or styrene oxide. To be accompanied by the reduction of Co(III) to Co(II), the resultant diols were oxidized to α-hydroxy ketones. These analyses along with some control experiments gave a mechanistic understanding of catalyst deactivation of SalenCo(III)OAc-catalyzed HKR of racemic epoxides regarding an unveiled redox reaction between Co(III)-Salen and diol, the hydrolyzed product.

  6. Alternating copolymerization of dihydrocoumarin and epoxides catalyzed by chromium salen complexes: a new route to functional polyesters.

    PubMed

    Van Zee, Nathan J; Coates, Geoffrey W

    2014-06-18

    We report the alternating ring-opening copolymerization of dihydrocoumarin with epoxides catalyzed by chromium(III) salen complexes. This process provides access to a range of perfectly alternating polyesters with high molecular weights and narrow molecular weight distributions. Atactic poly(cyclohexene dihydrocoumarate) and poly(cyclopentene dihydrocoumarate) were found to be semi-crystalline by differential scanning calorimetry.

  7. Mechanistic Basis for High Reactivity of (salen)Co–OTs in the Hydrolytic Kinetic Resolution of Terminal Epoxides

    PubMed Central

    Nielsen, Lars P. C.; Zuend, Stephan J.; Ford, David D.; Jacobsen, Eric N.

    2012-01-01

    The (salen)Co(III)-catalyzed hydrolytic kinetic resolution (HKR) of terminal epoxides is a bimetallic process with a rate controlled by partitioning between a nucleophilic (salen)Co–OH catalyst and a Lewis acidic (salen)Co–X catalyst. The commonly used (salen)Co–OAc and (salen)Co–Cl precatalysts undergo complete and irreversible counterion addition to epoxide during the course of the epoxide hydrolysis reaction, resulting in quantitative formation of weakly Lewis acidic (salen)Co–OH, and severely diminished reaction rates in the late stages of HKR reactions. In contrast, (salen)Co–OTs maintains high reactivity over the entire course of HKR reactions. We describe here an investigation of catalyst partitioning with different (salen)Co–X precatalysts, and demonstrate that counterion addition to epoxide is reversible in the case of the (salen)Co–OTs. This reversible counterion addition results in stable partitioning between nucleophilic and Lewis acidic catalyst species, allowing highly efficient catalysis throughout the course of the HKR reaction. PMID:22292515

  8. 40 CFR 63.1427 - Process vent requirements for processes using extended cookout as an epoxide emission reduction...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... process knowledge, reaction kinetics, and engineering knowledge, in accordance with paragraph (a)(2)(i) of... accordance with paragraph (f)(1)(i) of this section, or reaction kinetics in accordance with paragraph (f)(1... epoxide in the reactor liquid at the beginning of the time period, weight percent. k = Reaction...

  9. Enantiospecificity of Chloroperoxidase-Catalyzed Epoxidation: Biased Molecular Dynamics Study of a Cis-β-Methylstyrene/Chloroperoxidase-Compound I Complex

    PubMed Central

    Morozov, Alexander N.; D'Cunha, Cassian; Alvarez, Carlos A.; Chatfield, David C.

    2011-01-01

    Molecular dynamics simulations of an explicitly solvated cis-β-methylstyrene/chloroperoxidase-Compound I complex are performed to determine the cause of the high enantiospecificity of epoxidation. From the simulations, a two-dimensional free energy potential is calculated to distinguish binding potential wells from which reaction to 1S2R and 1R2S epoxide products may occur. Convergence of the free energy potential is accelerated with an adaptive biasing potential. Analysis of binding is followed by analysis of 1S2R and 1R2S reaction precursor structures in which the substrate, having left the binding wells, places its reactive double bond in steric proximity to the oxyferryl heme center. Structural analysis of binding and reaction precursor conformations is presented. We find that 1), a distortion of Glu183 is important for CPO-catalyzed epoxidation as was postulated previously based on experimental results; 2), the free energy of binding does not provide significant differentiation between structures leading to the respective epoxide enantiomers; and 3), CPO's enantiospecificity toward cis-β-methylstyrene is likely to be caused by a specific group of residues which form a hydrophobic core surrounding the oxyferryl heme center. PMID:21320452

  10. 40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane,...

  11. 40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane,...

  12. 40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane,...

  13. 40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane,...

  14. 40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane,...

  15. INVESTIGATION OF THE SURFACE PROPERTIES OF POLYMERIC SOAPS OBTAINED BY RING-OPENING POLYMERIZATION OF EPOXIDIZED SOYBEAN OIL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Epoxidized soybean oil (ESO) was converted to a polysoap via a two-step synthetic procedure of catalytic ring-opening polymerization (PESO), followed by hydrolysis with a base (HPESO). Various molecular weights of PESO and HPESO were prepared by varying the reaction temperature and/or catalyst conc...

  16. Ingestion of the epoxide hydrolase inhibitor AUDA modulates immune responses of the mosquito, Culex quinquefasciatus during blood feeding.

    PubMed

    Xu, Jiawen; Morisseau, Christophe; Yang, Jun; Lee, Kin Sing Stephen; Kamita, Shizuo G; Hammock, Bruce D

    2016-09-01

    Epoxide hydrolases (EHs) are enzymes that play roles in metabolizing xenobiotic epoxides from the environment, and in regulating lipid signaling molecules, such as juvenile hormones in insects and epoxy fatty acids in mammals. In this study we fed mosquitoes with an epoxide hydrolase inhibitor AUDA during artificial blood feeding, and we found the inhibitor increased the concentration of epoxy fatty acids in the midgut of female mosquitoes. We also observed ingestion of AUDA triggered early expression of defensin A, cecropin A and cecropin B2 at 6 h after blood feeding. The expression of cecropin B1 and gambicin were not changed more than two fold compared to controls. The changes in gene expression were transient possibly because more than 99% of the inhibitor was metabolized or excreted at 42 h after being ingested. The ingestion of AUDA also affected the growth of bacteria colonizing in the midgut, but did not affect mosquito longevity, fecundity and fertility in our laboratory conditions. When spiked into the blood, EpOMEs and DiHOMEs were as effective as the inhibitor AUDA in reducing the bacterial load in the midgut, while EETs rescued the effects of AUDA. Our data suggest that epoxy fatty acids from host blood are immune response regulators metabolized by epoxide hydrolases in the midgut of female mosquitoes, inhibition of which causes transient changes in immune responses, and affects growth of microbes in the midgut.

  17. 21 CFR 176.110 - Acrylamide-acrylic acid resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Acrylamide-acrylic acid resins. 176.110 Section... Paper and Paperboard § 176.110 Acrylamide-acrylic acid resins. Acrylamide-acrylic acid resins may be...) Acrylamide-acrylic acid resins are produced by the polymerization of acrylamide with partial hydrolysis or...

  18. Experimental Investigation of the Primary and Secondary Deuterium Kinetic Isotope Effects for Epoxidation of Alkenes and Ethylene with m-Chloroperoxybenzoic Acid.

    PubMed

    Koerner, Terry; Slebocka-Tilk, H.; Brown, R. S.

    1999-01-08

    The secondary deuterium kinetic isotope effect (DKIE) for the epoxidation of ethylene and d(4)-ethylene by m-chloroperoxybenzoic acid (MCPBA) is determined to be 0.83, or 0.95/alpha-H. The second-order rate constants for MCPBA and MCPBA-O-D epoxidation of a variety of alkenes that differ in the steric access to the double bond (anti-sesquinorbornene (2), tetramethylethylene (3), adamantylideneadamantane (4), 7-norbornylidene-7'-norbornane (5), bis(bicyclo[3.3.1.]non-9-ylidene) (6), bis(homoadamantane) (7), cyclohexene (8), 1-octene (9), trans-5-decene (10) and 2-methyl-1-pentene (11)) have been determined in dichloroethane at 25 degrees C using UV kinetics, and the primary DKIE, k(OH)/k(OD), is 1.05 +/- 0.05 in all cases. By comparison of the rates of epoxidation of sterically encumbered alkenes, it is suggested that the spiro epoxidation transition state is favored over a planar one. The products of the epoxidation of anti-sesquinorbornene are determined to be the epoxide and a cis-hydroxy ester, the latter most probably being formed by acid-catalyzed ring opening of the epoxide by in situ-produced m-chlorobenzoic acid produced in situ to form a beta-hydroxy carbocation and carboxylate ion pair that collapses to product.

  19. The effects of modulation of microsomal epoxide hydrolase activity on microsome-catalyzed activation of benzo[alpha]pyrene and its covalent binding to DNA.

    PubMed

    Guenthner, T M; Oesch, F

    1981-01-01

    The effects of modulation of microsomal epoxide hydrolase activity on the binding of calf thymus DNA of benzo[alpha]pyrene metabolically activated by rat liver microsomes were investigated. In systems where microsomal epoxide hydrolase levels were not manipulated, 2 major bound species, one derived from 9-hydroxybenzo[alpha]pyrene and the other derived from benzo[alpha]pyrene 7,8-dihydrodiol, were found in approximately equivalent amounts. When epoxide hydrolase levels were increased, either by addition in vitro of purified enzyme or by induction in vivo by trans-stilbene oxide, the binding of the benzo[alpha]pyrene 7,8-dihydrodiol product was increased, while the binding of the 9-hydroxybenzo[alpha]pyrene product was practically eliminated. When microsomal epoxide hydrolase activity was decreased by selective inhibition with low concentrations of 1,1,1-trichloropropene 2,3-oxide, the binding of the species derived from 9-hydroxybenzo[alpha]pyrene was increased several-fold, while that of the species derived from benzo[alpha]pyrene 7,8-dihydrodiol was greatly decreased. The results indicate that the binding species derived from 9-hydroxybenzo[alpha]pyrene is formed through a metabolic pathway leading to an epoxide which is a substrate of microsomal epoxide hydrolase and that microsomal epoxide hydrolase is important in regulating the pattern of binding of individual microsomally-formed benzo[alpha]pyrene metabolites to DNA.

  20. Co-purification of microsomal epoxide hydrolase with the warfarin-sensitive vitamin K1 oxide reductase of the vitamin K cycle.

    PubMed

    Guenthner, T M; Cai, D; Wallin, R

    1998-01-15

    Vitamin K1 oxide reductase activity has been partially purified from rat liver microsomes. A three-step procedure produced a preparation in which warfarin-sensitive vitamin K1 oxide reductase activity was 118-fold enriched over the activity in intact rat liver microsomes. A major component of the multi-protein mixture was identified as a 50 kDa protein that strongly cross-reacts with antiserum prepared against homogeneous rat liver microsomal epoxide hydrolase. The reductase preparation also had a high level or epoxide hydrolase activity against two xenobiotic epoxide substrates. The K(m) values for hydrolysis by the reductase preparation were similar to those for homogeneous microsomal epoxide hydrolase itself, and the specific hydrolase activities of the reductase preparation were 25-35% of the specific activities measured for the homogeneous hydrolase preparation. Antibodies prepared against homogeneous microsomal epoxide hydrolase inhibited up to 80% of reductase activity of the reductase preparation. Homogeneous microsomal epoxide hydrolase had no vitamin K1 oxide reductase activity. This evidence suggests that microsomal epoxide hydrolase, or a protein that is very similar to it, is a major functional component of a multi-protein complex that is responsible for vitamin K1 oxide reduction in rat liver microsomes.

  1. Distinct rat hepatic microsomal epoxide hydrolases catalyze the hydration of cholesterol 5,6 alpha-oxide and certain xenobiotic alkene and arene oxides.

    PubMed

    Levin, W; Michaud, D P; Thomas, P E; Jerina, D M

    1983-02-01

    Metabolism of cholesterol 5,6 alpha-oxide to the 5,6-glycol is catalyzed by a rat liver microsomal epoxide hydrolase that is distinct from the microsomal epoxide hydrolase that metabolizes a wide range of xenobiotic alkene and arene oxides. The two enzymes are antigenically distinct, and the purified microsomal epoxide hydrolase that metabolizes xenobiotic oxides does not catalyze the hydration of cholesterol 5,6 alpha-oxide. In vivo treatment of rats with inducers of microsomal epoxide hydrolase does not enhance the activity of cholesterol 5,6 alpha-oxide hydrolase and, in some cases, actually depresses enzyme activity in the resultant microsomal preparations. Octene 1,2-oxide and benz[a]anthracene 5,6-oxide, both good substrates for xenobiotic epoxide hydrolase, are not competitive inhibitors of cholesterol oxide hydration by rat liver microsomes. The above results establish the existence of a liver microsomal epoxide hydrolase that is under different regulatory control and that appears to have a different substrate specificity than the well-characterized microsomal epoxide hydrolase involved in the metabolism of a widely diverse group of alkene and arene oxides.

  2. Restorative resins: abrasion vs. mechanical properties.

    PubMed

    Jørgensen, K D

    1980-12-01

    The purpose of the present work was to examine whether it is possible by simple and reliable laboratory tests to evaluate the abrasion by food of Class 1 restorative resins. The results point to the following main conclusions: for the smooth-surface resins, i.e. the micro-filled composite and the unfilled resins, the Wallace hardness test appears to be a valid parameter for abrasion; the greater the depth of penetration of the Vickers diamond of this apparatus, the more severe abrasion is to be expected. The mode of abrasion in this type of resin is scratching. Porosity in the resins strongly enhances the abrasion. For the rough-surface resins, i.e. the conventional composites, a dual effect of the filler particles was concluded. The filler particles on the one hand protect the matrix against abrasion, but cause, on the other hand, in time an increase of the surface roughness of the composite and thereby via increased friction an increase of the abrasion. Considerations on possible ways to improve the present-day restorative resins are presented. It is stressed that the results obtained refer only to abrasion of Class 1 fillings by food.

  3. Cobalt Ions Improve the Strength of Epoxy Resins

    NASA Technical Reports Server (NTRS)

    Stoakley, D. M.; St. Clair, A. K.

    1986-01-01

    Technique developed for improving mechanical strength of epoxy resins by adding cobalt ions in form of tris(acetylacetonato)cobalt (III) complex. Solid cast disks prepared from cobalt ion-containing epoxy resins tested for flexural strength and stiffness. Incorporation of cobalt ions into epoxies increased flexural strength of resins by 10 to 95 percent. Suitable resins for this technique include any liquid or solid TGMDA resins. Improved epoxy formulation proves useful as composite matrix resin, adhesive, or casting resin for applications on commercial and advanced aircraft.

  4. Role of diaxial versus diequatorial hydroxyl groups in the tumorigenic activity of a benzo[a]pyrene bay-region diol epoxide.

    PubMed Central

    Chang, R L; Wood, A W; Conney, A H; Yagi, H; Sayer, J M; Thakker, D R; Jerina, D M; Levin, W

    1987-01-01

    Tumorigenic activities of the (7R,8S,9S,10R)-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydro derivatives of benzo[a]pyrene [(+)-B[a]P diol epoxide-2] and 6-fluorobenzo[a]pyrene (6-FB[a]P diol epoxide-2) were evaluated in newborn CD-1 mice. A total dose of 14 nmol of either diol epoxide was administered to preweanling mice, and tumorigenic activity was determined when the mice were 32 to 36 weeks old. At the termination of the study, 13% of solvent-treated control mice had developed lung tumors with an average of 0.19 tumor per mouse. No other tumors were observed in control animals. (+)-B[a]P diol epoxide-2 induced pulmonary tumors in 60% of the mice with an average of 1.9 tumors per mouse, and 14% of the male mice developed hepatic tumors with an average of 0.18 tumor per mouse. In contrast, 6-FB[a]P diol epoxide-2 had no significant tumorigenic activity at the 14-nmol dose. Although both bay-region diol epoxides have the same absolute configuration, (7R,8S,9S,10R), the hydroxyl groups of (+)-B[a]P diol epoxide-2 prefer the pseudoequatorial conformation whereas the hydroxyl groups of 6-FB[a]P diol epoxide-2 prefer the pseudoaxial conformation. The tumorigenicity results reported here are the first direct demonstration that conformation of the hydroxyl groups in a bay-region diol epoxide, in addition to the documented effect of absolute configuration, is an important determinant in the tumorigenic activity of these ultimate carcinogens. PMID:3479808

  5. Modeling of Toxicity-Relevant Electrophilic Reactivity for Guanine with Epoxides: Estimating the Hard and Soft Acids and Bases (HSAB) Parameter as a Predictor.

    PubMed

    Zhang, Jing; Wang, Chenchen; Ji, Li; Liu, Weiping

    2016-05-16

    According to the electrophilic theory in toxicology, many chemical carcinogens in the environment and/or their active metabolites are electrophiles that exert their effects by forming covalent bonds with nucleophilic DNA centers. The theory of hard and soft acids and bases (HSAB), which states that a toxic electrophile reacts preferentially with a biological macromolecule that has a similar hardness or softness, clarifies the underlying chemistry involved in this critical event. Epoxides are hard electrophiles that are produced endogenously by the enzymatic oxidation of parent chemicals (e.g., alkenes and PAHs). Epoxide ring opening proceeds through a SN2-type mechanism with hard nucleophile DNA sites as the major facilitators of toxic effects. Thus, the quantitative prediction of chemical reactivity would enable a predictive assessment of the molecular potential to exert electrophile-mediated toxicity. In this study, we calculated the activation energies for reactions between epoxides and the guanine N7 site for a diverse set of epoxides, including aliphatic epoxides, substituted styrene oxides, and PAH epoxides, using a state-of-the-art density functional theory (DFT) method. It is worth noting that these activation energies for diverse epoxides can be further predicted by quantum chemically calculated nucleophilic indices from HSAB theory, which is a less computationally demanding method than the exacting procedure for locating the transition state. More importantly, the good qualitative/quantitative correlations between the chemical reactivity of epoxides and their bioactivity suggest that the developed model based on HSAB theory may aid in the predictive hazard evaluation of epoxides, enabling the early identification of mutagenicity/carcinogenicity-relevant SN2 reactivity.

  6. Resin/graphite fiber composites

    NASA Technical Reports Server (NTRS)

    Cavano, P. J.

    1974-01-01

    Processing techniques were developed for the fabrication of both polyphenylquinoxaline and polyimide composites by the in situ polymerization of monomeric reactants directly on the graphite reinforcing fibers, rather than using previously prepared prepolymer varnishes. Void-free polyphenylquinoxaline composites were fabricated and evaluated for room and elevated flexure and shear properties. The technology of the polyimide system was advanced to the point where the material is ready for commercial exploitation. A reproducible processing cycle free of operator judgment factors was developed for fabrication of void-free composites exhibiting excellent mechanical properties and a long time isothermal life in the range of 288 C to 316 C. The effects of monomer reactant stoichiometry and process modification on resin flow were investigated. Demonstration of the utility and quality of this polyimide system was provided through the successful fabrication and evaluation of four complex high tip speed fan blades.

  7. Chemical Characterization of Phenol/Formaldehyde Resins

    NASA Technical Reports Server (NTRS)

    Brayden, T. H.

    1986-01-01

    Report discusses tests of commercial phenol/formaldehyde resins to establish relationships among composition before use, behavior during curing, and strength after curing. Resin used in carbon/carbon laminates. In curing process, two molecules of phenol joined together in sequence of reactions involving molecule of formaldehyde. Last step of sequence, molecule of water released. Sequence repeats until one of ingredients used up, leaving solidified thermoset plastic. Issues to be resolved: number and relative abundances of ingredients, presence of certain chemical groups, heat-producing ability of resin, and range of molecular weights present.

  8. Improved microbial-check-valve resins

    NASA Technical Reports Server (NTRS)

    Colombo, G. V.; Putnam, D. F.

    1980-01-01

    Improved microbial-check-valve resins have been tested for their microbicidal effectiveness and long-term stability. Resins give more-stable iodine concentrations than previous preparations and do not impart objectionable odor or taste to treated water. Microbial check valve is small cylindrical device, packed with iodide-saturated resin, that is installed in water line where contamination by micro-organisms is to be prevented. Prototype microbial check valve was tested for stability and performance under harsh environmental conditions. Effectiveness was 100 percent at 35 deg, 70 deg, and 160 deg F (2 deg, 21 deg, and 71 deg C).

  9. Hydraulic Permeability of Resorcinol-Formaldehyde Resin

    SciTech Connect

    Taylor, Paul Allen

    2010-01-01

    An ion exchange process using spherical resorcinol-formaldehyde (RF) resin is the baseline process for removing cesium from the dissolved salt solution in the high-level waste tanks at the Hanford Site, using large scale columns as part of the Waste Treatment Plant (WTP). The RF resin is also being evaluated for use in the proposed small column ion exchange (SCIX) system, which is an alternative treatment option at Hanford and at the Savannah River Site (SRS). A recirculating test loop with a small ion exchange column was used to measure the effect of oxygen uptake and radiation exposure on the permeability of a packed bed of the RF resin. The lab-scale column was designed to be prototypic of the proposed Hanford columns at the WTP. Although the test equipment was designed to model the Hanford ion exchange columns, the data on changes in the hydraulic permeability of the resin will also be valuable for determining potential pressure drops through the proposed SCIX system. The superficial fluid velocity in the lab-scale test (3.4-5.7 cm/s) was much higher than is planned for the full-scale Hanford columns to generate the maximum pressure drop expected in those columns (9.7 psig). The frictional drag from this high velocity produced forces on the resin in the lab-scale tests that matched the design basis of the full-scale Hanford column. Any changes in the resin caused by the radiation exposure and oxygen uptake were monitored by measuring the pressure drop through the lab-scale column and the physical properties of the resin. Three hydraulic test runs were completed, the first using fresh RF resin at 25 C, the second using irradiated resin at 25 C, and the third using irradiated resin at 45 C. A Hanford AP-101 simulant solution was recirculated through a test column containing 500 mL of Na-form RF resin. Known amounts of oxygen were introduced into the primary recirculation loop by saturating measured volumes of the simulant solution with oxygen and reintroducing

  10. SEM and elemental analysis of composite resins

    SciTech Connect

    Hosoda, H.; Yamada, T.; Inokoshi, S. )

    1990-12-01

    Twenty-four chemically cured, 21 light-cured anterior, three light-cured anterior/posterior, and 18 light-cured posterior composite resins were examined using scanning electron microscopy, and the elemental composition of their filler particles was analyzed with an energy dispersive electron probe microanalyzer. According to the results obtained, the composite resins were divided into five groups (traditional, microfilled type, submicrofilled type, hybrid type, and semihybrid), with two additional hypothetical categories (microfilled and hybrid). Characteristics of each type were described with clinical indications for selective guidance of respective composite resins for clinical use.

  11. Properties of a nanodielectric cryogenic resin

    SciTech Connect

    Polyzos, Georgios; Tuncer, Enis; Sauers, Isidor; More, Karren Leslie

    2010-01-01

    Physical properties of a nanodielectric composed of in situ synthesized titanium dioxide (TiO{sub 2}) nanoparticles ({le} 5 nm in diameter) and a cryogenic resin are reported. The dielectric losses were reduced by a factor of 2 in the nanocomposite, indicating that the presence of small TiO{sub 2} nanoparticles restricted the mobility of the polymer chains. Dielectric breakdown data of the nanodielectric was distributed over a narrower range than that of the unfilled resin. The nanodielectric had 1.56 times higher 1% breakdown probability than the resin, yielding 0.64 times thinner insulation thickness for the same voltage level, which is beneficial in high voltage engineering.

  12. Class II Resin Composites: Restorative Options.

    PubMed

    Patel, Minesh; Mehta, Shamir B; Banerji, Subir

    2015-10-01

    Tooth-coloured, resin composite restorations are amongst the most frequently prescribed forms of dental restoration to manage defects in posterior teeth. The attainment of a desirable outcome when placing posterior resin composite restorations requires the clinician to have a good understanding of the benefits (as well as the limitations) posed by this material, together with a sound knowledge of placement technique. Numerous protocols and materials have evolved to assist the dental operator with this type of demanding posterior restoration. With the use of case examples, four techniques available are reported here. CPD/Clinical Relevance: This article explores varying techniques for the restoration of Class II cavities using resin composite.

  13. 21 CFR 175.380 - Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...-isopropylidenediphenol-epichlorohydrin epoxy resins. 175.380 Section 175.380 Food and Drugs FOOD AND DRUG ADMINISTRATION... Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins. The...′-isopropylidenediphenol-epichlorohydrin epoxy resins, to which may have been added certain optional adjuvant...

  14. 21 CFR 175.380 - Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...-isopropylidenediphenol-epichlorohydrin epoxy resins. 175.380 Section 175.380 Food and Drugs FOOD AND DRUG ADMINISTRATION... Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins. The...′-isopropylidenediphenol-epichlorohydrin epoxy resins, to which may have been added certain optional adjuvant...

  15. 21 CFR 175.380 - Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...-isopropylidenediphenol-epichlorohydrin epoxy resins. 175.380 Section 175.380 Food and Drugs FOOD AND DRUG ADMINISTRATION... Xylene-formaldehyde resins condensed with 4,4′-isopropylidenediphenol-epichlorohydrin epoxy resins. The...′-isopropylidenediphenol-epichlorohydrin epoxy resins, to which may have been added certain optional adjuvant...

  16. Tuning the olefin epoxidation by manganese(III) complexes of bisphenolate ligands: effect of Lewis basicity of ligands on reactivity.

    PubMed

    Sankaralingam, Muniyandi; Palaniandavar, Mallayan

    2014-01-14

    A new family of manganese(iii) complexes of the type [Mn(L)Cl], where H2L is 1,4-bis(2-hydroxy-benzyl)-1,4-diazepane (), 1,4-bis(2-hydroxy-4-methylbenzyl)-1,4-diazepane (), 1,4-bis(2-hydroxy-3,5-dimethylbenzyl)-1,4-diazepane () and 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)-1,4-diazepane (), has been isolated and studied as a catalyst for epoxidation reaction. Complexes have been characterized using elemental analysis, electronic spectral and electrochemical methods and ESI-MS. The single crystal X-ray structures of and contain the MnN2O2Cl chromophore with a novel square pyramidal coordination geometry (τ: , 0.11; , 0.00). All the complexes possess a distorted square pyramidal coordination geometry in solution, as revealed by the characteristic bands observed in the electronic spectra. A time dependent density functional theory (TD-DFT) calculation has been performed to assist in the assignment of the electronic absorption spectral bands of the complexes. The Mn(iii)/Mn(ii) redox potentials (E1/2) of fall within the narrow range of 0.279-0.320 V. The catalytic ability of the complexes towards olefin epoxidation has been investigated using PhIO as the oxygen source at room temperature under an N2 atmosphere. Addition of N-methylimidazole to the reaction mixture leads to an increase in the epoxide yield. A correlation between the Lewis acidity of the Mn(iii) center as tuned by the substituents on the phenolate ligand, and the epoxide yield and product selectivity has been observed. The present complexes act as better chemoselective catalysts for epoxidation of cyclohexene and styrene rather than cyclooctene.

  17. Effects of short-term walnut consumption on human microvascular function and its relationship to plasma epoxide content.

    PubMed

    Holt, Roberta R; Yim, Sun J; Shearer, Gregory C; Hackman, Robert M; Djurica, Dragana; Newman, John W; Shindel, Alan W; Keen, Carl L

    2015-12-01

    Improved vascular function after the incorporation of walnuts into controlled or high-fat diets has been reported; however, the mechanism(s) underlying this effect of walnuts is(are) poorly defined. The objective of the current study was to evaluate the acute and short-term effects of walnut intake on changes in microvascular function and the relationship of these effects to plasma epoxides, the cytochrome-P450-derived metabolites of fatty acids. Thirty-eight hypercholesterolemic postmenopausal women were randomized to 4 weeks of 5 g or 40 g of daily walnut intake. All outcomes were measured after an overnight fast and 4 h after walnut intake. Microvascular function, assessed as the reactive hyperemia index (RHI), was the primary outcome measure, with serum lipids and plasma epoxides as secondary measures. Compared to 5 g of daily walnut intake, consuming 40 g/d of walnuts for 4 weeks increased the RHI and Framingham RHI. Total cholesterol and low- and high-density cholesterol did not significantly change after walnut intake. The change in RHI after 4 weeks of walnut intake was associated with the change in the sum of plasma epoxides (r=0.65, P=.002) but not with the change in the sum of plasma hydroxyeicosatetraenoic acids. Of the individual plasma epoxides, arachidonic-acid-derived 14(15)-epoxyeicosatrienoic acid was most strongly associated with the change in microvascular function (r=0.72, P<.001). These data support the concept that the intake of walnut-derived fatty acids can favorably affect plasma epoxide production, resulting in improved microvascular function.

  18. Reaction Mechanism for Direct Propylene Epoxidation by Alumina-Supported Silver Aggregates. The Role of the Particle / Support Interface

    SciTech Connect

    Cheng, Lei; Yin, Chunrong; Mehmood, Faisal; Liu, Bin; Greeley, Jeffrey P.; Lee, Sungsik; Lee, Byeongdu; Seifert, Soenke; Winans, R. E.; Teschner, D.; Schlogl, Robert; Vajda, S.; Curtiss, Larry A.

    2013-11-21

    Sub-nanometer Ag aggregates on alumina supports have been found to be active toward direct propylene epoxidation to propylene oxide by molecular oxygen at low temperatures, with a negligible amount of carbon dioxide formation (Science 328, p. 224, 2010). In this work, we computationally and experimentally investigate the origin of the high reactivity of the sub-nanometer Ag aggregates. Computationally, we study O2 dissociation and propylene epoxidation on unsupported Ag19 and Ag20 clusters, as well as alumina-supported Ag19. The O2 dissociation and propylene epoxidation apparent barriers at the interface between the Ag aggregate and the alumina support are calculated to be 0.2 and 0.2~0.4 eV, respectively. These barriers are somewhat lower than those on sites away from the interface. The mechanism at the interface is similar to what was previously found for the silver trimer on alumina and can account for the high activity observed for the direct oxidation of propylene on the Ag aggregates. The barriers for oxygen dissociation on these model systems both at the interface and on the surfaces are small compared to crystalline surfaces, indicating that availability of oxygen will not be a rate limiting step for the aggregates, as in the case of the crystalline surfaces. Experimentally, we investigate Ultrananocrystalline Diamond (UNCD)-supported silver aggregates under reactive conditions of propylene partial oxidation. The UNCD-supported Ag clusters are found to be not measurably active toward propylene oxidation, in contrast to the alumina supported Ag clusters. This suggests that the lack of metal-oxide interfacial sites of the Ag-UNCD catalyst, limits the epoxidation catalytic activity. This combined computational and experimental study shows the importance of the metal-oxide interface as well as the non-crystalline nature of the alumina-supported sub-nanometer Ag aggregate catalysts for propylene epoxidation.

  19. Mutagenicity and tumorigenicity of the four enantiopure bay-region 3,4-diol-1,2-epoxide isomers of dibenz[a,h]anthracene.

    PubMed

    Chang, Richard L; Wood, Alexander W; Huang, Mou Tuan; Xie, Jian Guo; Cui, Xiao Xing; Reuhl, Kenneth R; Boyd, D R; Lin, Yong; Shih, Weichung Joe; Balani, Suresh K; Yagi, Haruhiko; Jerina, Donald M; Conney, Allan H

    2013-09-01

    Each enantiomer of the diastereomeric pair of bay-region dibenz[a,h]anthracene 3,4-diol-1,2-epoxides in which the benzylic 4-hydroxyl group and epoxide oxygen are either cis (isomer 1) or trans (isomer 2) were evaluated for mutagenic activity. In strains TA 98 and TA 100 of Salmonella typhimurium, the diol epoxide with (1S,2R,3S,4R) absolute configuration [(-)-diol epoxide-1] had the highest mutagenic activity. In Chinese hamster V-79 cells, the diol epoxide with (1R,2S,3S,4R) absolute configuration [(+)-diol epoxide-2] had the highest mutagenic activity. The (1R,2S,3R,4S) diol epoxide [(+)-diol epoxide-1] also had appreciable activity, whereas the other two bay-region diol epoxide enantiomers had very low activity. In tumor studies, the (1R,2S,3S,4R) enantiomer was the only diol epoxide isomer tested that had strong activity as a tumor initiator on mouse skin and in causing lung and liver tumors when injected into newborn mice. This stereoisomer was about one-third as active as the parent hydrocarbon, dibenz[a,h]anthracene as a tumor initiator on mouse skin; it was several-fold more active than dibenz[a,h]anthracene as a lung and liver carcinogen when injected into newborn mice. (-)-(3R,4R)-3β,4α-dihydroxy-3,4-dihydro-dibenz[a,h]anthracene [(-)-3,4-dihydrodiol] was slightly more active than dibenz[a,h]anthracene as a tumor initiator on mouse skin, whereas (+)-(3S,4S)-3α,4β-dihydroxy-3,4-dihydro-dibenz[a,h]anthracene [(+)-3,4-dihydrodiol] had only very weak activity. The present investigation and previous studies with the corresponding four possible enantiopure bay-region diol epoxide enantiomers/diastereomers of benzo[a]pyrene, benz[a]anthracene, chrysene, benzo[c]phenanthrene, dibenz[c,h]acridine, dibenz[a,h]acridine and dibenz[a,h]anthracene indicate that the bay-region diol epoxide enantiomer with [R,S,S,R] absolute stereochemistry has high tumorigenic activity on mouse skin and in newborn mice.

  20. Total Synthesis of Pumiliotoxins 209F and 251D via Late-Stage, Nickel-Catalyzed Epoxide-Alkyne Reductive Cyclization

    PubMed Central

    Woodin, Katrina S.; Jamison, Timothy F.

    2011-01-01

    Pumiliotoxins 209F and 251D were synthesized using highly selective nickel-catalyzed epoxide-alkyne reductive cyclizations as the final step. The exocyclic (Z)-alkene found in the majority of the pumiliotoxins was formed stereospecifically and regioselectively, without the use of a directing group on the alkyne, and the epoxide underwent ring opening exclusively at the less hindered carbon to provide the requisite tertiary alcohol. The epoxides were prepared using diastereoselective addition of a sulfoxonium anion to a proline-derived methyl ketone. PMID:17696401

  1. Development of Highly Active and Regioselective Catalysts for the Copolymerization of Epoxides with Cyclic Anhydrides: An Unanticipated Effect of Electronic Variation.

    PubMed

    DiCiccio, Angela M; Longo, Julie M; Rodríguez-Calero, Gabriel G; Coates, Geoffrey W

    2016-06-08

    Recent developments in polyester synthesis have established several systems based on zinc, chromium, cobalt, and aluminum catalysts for the ring-opening alternating copolymerization of epoxides with cyclic anhydrides. However, to date, regioselective processes for this copolymerization have remained relatively unexplored. Herein we report the development of a highly active, regioselective system for the copolymerization of a variety of terminal epoxides and cyclic anhydrides. Unexpectedly, electron withdrawing substituents on the salen framework resulted in a more redox stable Co(III) species and longer catalyst lifetime. Using enantiopure propylene oxide, we synthesized semicrystalline polyesters via the copolymerization of a range of epoxide/anhydride monomer pairs.

  2. Method for regenerating magnetic polyamine-epichlorohydrin resin

    DOEpatents

    Kochen, R.L.; Navratil, J.D.

    1997-07-29

    Magnetic polymer resins capable of efficient removal of actinides and heavy metals from contaminated water are disclosed together with methods for making, using, and regenerating them. The resins comprise polyamine-epichlorohydrin resin beads with ferrites attached to the surfaces of the beads. Markedly improved water decontamination is demonstrated using these magnetic polymer resins of the invention in the presence of a magnetic field, as compared with water decontamination methods employing ordinary ion exchange resins or ferrites taken separately. 9 figs.

  3. Method for regenerating magnetic polyamine-epichlorohydrin resin

    DOEpatents

    Kochen, Robert L.; Navratil, James D.

    1997-07-29

    Magnetic polymer resins capable of efficient removal of actinides and heavy metals from contaminated water are disclosed together with methods for making, using, and regenerating them. The resins comprise polyamine-epichlorohydrin resin beads with ferrites attached to the surfaces of the beads. Markedly improved water decontamination is demonstrated using these magnetic polymer resins of the invention in the presence of a magnetic field, as compared with water decontamination methods employing ordinary ion exchange resins or ferrites taken separately.

  4. Further characterization of benzo[a]pyrene diol-epoxide (BPDE)-induced comet assay effects.

    PubMed

    Bausinger, Julia; Schütz, Petra; Piberger, Ann Liza; Speit, Günter

    2016-03-01

    The present study aims to further characterize benzo[a]pyrene diol-epoxide (BPDE)-induced comet assay effects. Therefore, we measured DNA effects by the comet assay and adduct levels by high-performance liquid chromatography (HPLC) in human lymphocytes and A549 cells exposed to (±)-anti-benzo[a]pyrene-7,8-diol 9,10-epoxide [(±)-anti-BPDE] or (+)-anti-benzo[a]pyrene-7,8-diol 9,10-epoxide [(+)-anti-BPDE]. Both, the racemic form and (+)-anti-BPDE, which is the most relevant metabolite with regard to mutagenicity and carcinogenicity, induced DNA migration in cultured lymphocytes in the same range of concentrations to a similar extent in the alkaline comet assay after exposure for 2h. Nevertheless, (+)-anti-BPDE induced significantly enhanced DNA migration after 16 and 18h post-cultivation which was not seen in response to (±)-anti-BPDE. Combination of the comet assay with the Fpg (formamidopyrimidine-DNA glycosylase) protein did not enhance BPDE-induced effects and thus indicated the absence of Fpg-sensitive sites (oxidized purines, N7-guanine adducts, AP-sites). The aphidicolin (APC)-modified comet assay suggested significant excision repair activity of cultured lymphocytes during the first 18h of culture after a 2 h-exposure to BPDE. In contrast to these repair-related effects measured by the comet assay, HPLC analysis of stable adducts did not reveal any significant removal of (+)-anti-BPDE-induced adducts from lymphocytes during the first 22h of culture. On the other hand, HPLC measurements indicated that A549 cells repaired about 70% of (+)-anti-BPDE-induced DNA-adducts within 22h of release. However, various experiments with the APC-modified comet assay did not indicate significant repair activity during this period in A549 cells. The conflicting results obtained with the comet assay and the HPLC-based adduct analysis question the real cause for BPDE-induced DNA migration in the comet assay and the reliability of the APC-modified comet assay for the

  5. Combination of natural fiber Boehmeria nivea (ramie) with matrix epoxide for bullet proof vest body armor

    SciTech Connect

    Anggoro, Didi Dwi Kristiana, Nunung

    2015-12-29

    Ballistic protection equipment, such as a bulletproof vest, is a soldier’s most important means of preserving life and survivability in extreme combat conditions. The bulletproof vests are designed to protect the user’s chest from injury without disturbing the ability to perform his duties. Aromatic polyamide or aramid fibers known under the trade name Kevlar, Trawon and so is synthetic fiber materials commonly used in the manufacture of bulletproof vests. This synthetic fibers have high tensile strength and ductility. Kevlar is expensive and imported material. In this study, will introduce local natural raw materials, ramie fiber (Boehmeria nivea) which is cheaper and environmentally friendly. It has enough tenacity and tensile strength as a bulletproof vest. This experiment uses two panels, there are Panel A as front surface of Panel B. Panel A is a combination of ramie and epoxide matrix, while panel B is only ramie. From several variations of experimental combinations between Panel A and Panel B, optimal combination obtained with 16 layers of panel A and 31-34 layers of panel B which is able to protect againts cal. 7.65 mm × 17 mm (.32 ACP) bullet fired through pistol .32 Pindad from a distance of 20 meters. Panel with a size of 20 cm × 20 cm has a total thickness between 12,922 to13,745 mm and a total weight between 506,26 to 520,926gram. Scanning electron microscopy (SEM) observations indicated that the porosity and surface area of the ramie fiber is smooth, fiber surfaces showed topography with micropores. SEM also showed well-arranged structure of fibers bonding. Energy Dispersive X-ray (EDX) analysis indicated 100 % carbon contents in ramie fiber. Test result indicates that panel from composite ramie-epoxide can reach the level 1of International Standard of NIJ - 010104. Compared to panel from polyester fiber, the panel from composite ramie-epoxide (0,50-0,52 kg) is lighter weight than panel polyester fiber (1,642 kg)

  6. Combination of natural fiber Boehmeria nivea (ramie) with matrix epoxide for bullet proof vest body armor

    NASA Astrophysics Data System (ADS)

    Anggoro, Didi Dwi; Kristiana, Nunung

    2015-12-01

    Ballistic protection equipment, such as a bulletproof vest, is a soldier's most important means of preserving life and survivability in extreme combat conditions. The bulletproof vests are designed to protect the user's chest from injury without disturbing the ability to perform his duties. Aromatic polyamide or aramid fibers known under the trade name Kevlar, Trawon and so is synthetic fiber materials commonly used in the manufacture of bulletproof vests. This synthetic fibers have high tensile strength and ductility. Kevlar is expensive and imported material. In this study, will introduce local natural raw materials, ramie fiber (Boehmeria nivea) which is cheaper and environmentally friendly. It has enough tenacity and tensile strength as a bulletproof vest. This experiment uses two panels, there are Panel A as front surface of Panel B. Panel A is a combination of ramie and epoxide matrix, while panel B is only ramie. From several variations of experimental combinations between Panel A and Panel B, optimal combination obtained with 16 layers of panel A and 31-34 layers of panel B which is able to protect againts cal. 7.65 mm × 17 mm (.32 ACP) bullet fired through pistol .32 Pindad from a distance of 20 meters. Panel with a size of 20 cm × 20 cm has a total thickness between 12,922 to13,745 mm and a total weight between 506,26 to 520,926gram. Scanning electron microscopy (SEM) observations indicated that the porosity and surface area of the ramie fiber is smooth, fiber surfaces showed topography with micropores. SEM also showed well-arranged structure of fibers bonding. Energy Dispersive X-ray (EDX) analysis indicated 100 % carbon contents in ramie fiber. Test result indicates that panel from composite ramie-epoxide can reach the level 1of International Standard of NIJ - 010104. Compared to panel from polyester fiber, the panel from composite ramie-epoxide (0,50-0,52 kg) is lighter weight than panel polyester fiber (1,642 kg).

  7. Resin Flow Analysis in the Injection Cycle of a Resin Transfer Molded Radome

    NASA Astrophysics Data System (ADS)

    Golestanian, Hossein; Poursina, Mehrdad

    2007-04-01

    Resin flow analysis in the injection cycle of an RTM process was investigated. Fiberglass and carbon fiber mats were used as reinforcements with EPON 826 epoxy resin. Numerical models were developed in ANSYS finite element software to simulate resin flow behavior into a mold of conical shape. Resin flow into the woven fiber mats is modeled as flow through porous media. The injection time for fiberglass/epoxy composite is found to be 4407 seconds. Required injection time for the carbon/epoxy composite is 27022 seconds. Higher injection time for carbon/epoxy part is due to lower permeability value of the carbon fibers compared to glass fiber mat.

  8. Phenoxy resins containing pendent ethynyl groups and cured resins obtained therefrom

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M. (Inventor)

    1985-01-01

    Phenoxy resins containing pendent ethynyl groups, the process for preparing the same, and the cured resin products obtained therefrom are disclosed. Upon the application of heat, the ethynyl groups react to provide branching and crosslinking with the cure temperature being lowered by using a catalyst if desired but not required. The cured phenoxy resins containing pendent ethynyl groups have improved solvent resistance and higher use temperature than linear uncrosslinked phenoxy resins and are applicable for use as coatings, films, adhesives, composited matrices and molding compounds.

  9. Dental repair material: a resin-modified glass-ionomer bioactive ionic resin-based composite.

    PubMed

    Croll, Theodore P; Berg, Joel H; Donly, Kevin J

    2015-01-01

    This report documents treatment and repair of three carious teeth that were restored with a new dental repair material that features the characteristics of both resin-modified glass-ionomer restorative cement (RMGI) and resin-based composite (RBC). The restorative products presented are reported by the manufacturer to be the first bioactive dental materials with an ionic resin matrix, a shock-absorbing resin component, and bioactive fillers that mimic the physical and chemical properties of natural teeth. The restorative material and base/liner, which feature three hardening mechanisms, could prove to be a notable advancement in the adhesive dentistry restorative materials continuum.

  10. An update on resin-bonded bridges.

    PubMed

    Barber, M W; Preston, A J

    2008-03-01

    Since the introduction of the 'Rochette' bridge in the 1970s the resin-bonded bridge has undergone a number of developments to become a commonly used technique for replacement of a missing tooth, especially in a minimally restored dentition. One of the major advantages of the resin-bonded bridge is that it requires less tooth preparation than conventional bridgework, with some authorities advising no preparation at all. Some reports have suggested poor long-term success rates, however, if used in appropriate clinical situations, this treatment modality can be extremely successful. The aim of this paper is to review the literature relating to resin-bonded bridges and suggest recommendations for clinicalpractice concerning the provision of resin-bonded bridges.

  11. Determining resin/fiber content of laminates

    NASA Technical Reports Server (NTRS)

    Garrard, G. G.; Houston, D. W.

    1979-01-01

    Article discusses procedure where hydrazine is used to extract graphite fibers from cured polyimide resin. Method does not attack graphite fibers and is faster than hot-concentrated-acid digestion process.

  12. Silicone modified resins for graphite fiber laminates

    NASA Technical Reports Server (NTRS)

    Frost, L. W.; Bower, G. M.

    1979-01-01

    The development of silicon modified resins for graphite fiber laminates which will prevent the dispersal of graphite fibers when the composites are burned is discussed. Eighty-five silicone modified resins were synthesized and evaluated including unsaturated polyesters, thermosetting methacrylates, epoxies, polyimides, and phenolics. Neat resins were judged in terms of Si content, homogeneity, hardness, Char formation, and thermal stability. Char formation was estimated by thermogravimetry to 1,000 C in air and in N2. Thermal stability was evaluated by isothermal weight loss measurements for 200 hrs in air at three temperatures. Four silicone modified epoxies were selected for evaluation in unidirectional filament wound graphite laminates. Neat samples of these resins had 1,000 C char residues of 25 to 50%. The highest flexural values measured for the laminates were a strength of 140 kpsi and a modulus of 10 Mpsi. The highest interlaminar shear strength was 5.3 kpsi.

  13. 21 CFR 872.3140 - Resin applicator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... applicator is a brushlike device intended for use in spreading dental resin on a tooth during application of tooth shade material. (b) Classification. Class I (general controls). The device is exempt from...

  14. 21 CFR 872.3140 - Resin applicator.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... applicator is a brushlike device intended for use in spreading dental resin on a tooth during application of tooth shade material. (b) Classification. Class I (general controls). The device is exempt from...

  15. 21 CFR 872.3140 - Resin applicator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... applicator is a brushlike device intended for use in spreading dental resin on a tooth during application of tooth shade material. (b) Classification. Class I (general controls). The device is exempt from...

  16. 21 CFR 872.3140 - Resin applicator.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... applicator is a brushlike device intended for use in spreading dental resin on a tooth during application of tooth shade material. (b) Classification. Class I (general controls). The device is exempt from...

  17. 21 CFR 872.3140 - Resin applicator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... applicator is a brushlike device intended for use in spreading dental resin on a tooth during application of tooth shade material. (b) Classification. Class I (general controls). The device is exempt from...

  18. Resins for Advanced Reentry Systems Applications.

    DTIC Science & Technology

    strengths of 3,000 to 6,000 psi. The strength values increased to 7,000 to 10,000 psi after the samples were reimpregnated with a furfuryl alcohol resin and repyrolyzed. The pyrolysis results are discussed.

  19. Improved high-temperature resistant matrix resins

    NASA Technical Reports Server (NTRS)

    Green, H. E.; Chang, G. E.; Wright, W. F.; Ueda, K.; Orell, M. K.

    1989-01-01

    A study was performed with the objective of developing matrix resins that exhibit improved thermo-oxidative stability over state-of-the-art high temperature resins for use at temperatures up to 644 K (700 F) and air pressures up to 0.7 MPa (100 psia). The work was based upon a TRW discovered family of polyimides currently licensed to and marketed by Ethyl Corporation as EYMYD(R) resins. The approach investigated to provide improved thermo-oxidative properties was to use halogenated derivatives of the diamine, 2, 2-bis (4-(4-aminophenoxy)phenyl) hexafluoropropane (4-BDAF). Polyimide neat resins and Celion(R) 12,000 composites prepared from fluorine substituted 4-BDAF demonstrated unexpectedly lower glass transition temperatures (Tg) and thermo-oxidative stabilities than the baseline 4-BDAF/PMDA polymer.

  20. Physicochemical characterization of three fiber-reinforced epoxide-based composites for dental applications.

    PubMed

    Bonon, Anderson J; Weck, Marcus; Bonfante, Estevam A; Coelho, Paulo G

    2016-12-01

    Fiber-reinforced composite (FRC) biomedical materials are in contact with living tissues arising biocompatibility questions regarding their chemical composition. The hazards of materials such as Bisphenol A (BPA), phthalate and other monomers and composites present in FRC have been rationalized due to its potential toxicity since its detection in food, blood, and saliva. This study characterized the physicochemical properties and degradation profiles of three different epoxide-based materials intended for restorative dental applications. Characterization was accomplished by several methods including FTIR, Raman, Brunauer-Emmett-Teller (BET) Analysis, X-ray fluorescence spectroscopy, and degradation experiments. Physicochemical characterization revealed that although materials presented similar chemical composition, variations between them were more largely accounted by the different phase distribution than chemical composition.

  1. Soluble Epoxide Hydrolase Inhibitory Activity of Selaginellin Derivatives from Selaginella tamariscina.

    PubMed

    Kim, Jang Hoon; Cho, Chong Woon; Tai, Bui Huu; Yang, Seo Young; Choi, Gug-Seoun; Kang, Jong Seong; Kim, Young Ho

    2015-12-02

    Selaginellin derivatives 1-3 isolated from Selaginella tamariscina were evaluated for their inhibition of soluble epoxide hydrolase (sEH) to demonstrate their potential for the treatment of cardiovascular disease. All selaginellin derivatives (1-3) inhibited sEH enzymatic activity and PHOME hydrolysis, in a dose-dependent manner, with IC50 values of 3.1 ± 0.1, 8.2 ± 2.2, and 4.2 ± 0.2 μM, respectively. We further determined that the derivatives function as non-competitive inhibitors. Moreover, the predicted that binding sites and interaction between 1-3 and sEH were solved by docking simulations. According to quantitative analysis, 1-3 were confirmed to have high content in the roots of S. tamariscina; among them, selaginellin 3 exhibited the highest content of 189.3 ± 0.0 μg/g.

  2. Synthesis of cyclic carbonates from epoxides and carbon dioxide by using organocatalysts.

    PubMed

    Cokoja, Mirza; Wilhelm, Michael E; Anthofer, Michael H; Herrmann, Wolfgang A; Kühn, Fritz E

    2015-08-10

    The synthesis of cyclic carbonates through coupling of carbon dioxide with epoxides is 100 % atom economical and is already performed on an industrial scale. Its impact regarding the use of carbon dioxide as a renewable carbon source is expected to grow significantly in the near future, so that the development of efficient catalysts is of high interest in academia and industry. To improve the carbon footprint and sustainability of the cycloaddition reaction, the use of organocatalytic methods is a promising approach. Herein, available metal-free catalysts for the preparation of cyclic carbonates are described and elaborated concerning the overall sustainability of the process. Therefore, the required reaction conditions, as well as the activity of the catalysts and their reusability, are compared and evaluated. In addition to ammonium-, phosphonium-, or imidazolium-based single-component catalysts and their supported analogues, the growing field of research concerning dual catalysts are also discussed in detail.

  3. Effect of epoxidation on 30% poly(methyl methacrylate)-grafted natural rubber polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Nazir, Khuzaimah; Aziz, Ahmad Fairoz; Adam, Nurul Ilham; Yahya, Muhd Zu Azhan; Ali, Ab Malik Marwan

    2015-08-01

    Epoxidized 30% poly(methyl methacrylate)-grafted natural rubber (EMG 30) as a polymer host in solid polymer electrolytes (SPEs) has been investigated. EMG30 was synthesized via performicepoxidation method onto 30% poly(methyl methacrylate)-grafted natural rubber (MG30) and the formations of epoxy group were discussed. The EMG30 were characterized by proton nuclear magnetic resonance (1HNMR) to investigate their chemical structure and differential scanning calorimeter to determine their crystallinity. A new peak in 1HNMR spectra (2.71 ppm) confirmed the appearance of epoxy group. SPE based on EMG30 doped with 40 wt% LiCF3SO3 show the highest conductivity. The complexation between EMG30 and LiCF3SO3 were confirmed by attenuated total reflection Fourier transform infrared (ATR-FTIR).

  4. Structures of an intramembrane vitamin K epoxide reductase homolog reveal control mechanisms for electron transfer.

    PubMed

    Liu, Shixuan; Cheng, Wei; Fowle Grider, Ronald; Shen, Guomin; Li, Weikai

    2014-01-01

    The intramembrane vitamin K epoxide reductase (VKOR) supports blood coagulation in humans and is the target of the anticoagulant warfarin. VKOR and its homologues generate disulphide bonds in organisms ranging from bacteria to humans. Here, to better understand the mechanism of VKOR catalysis, we report two crystal structures of a bacterial VKOR captured in different reaction states. These structures reveal a short helix at the hydrophobic active site of VKOR that alters between wound and unwound conformations. Motions of this 'horizontal helix' promote electron transfer by regulating the positions of two cysteines in an adjacent loop. Winding of the helix separates these 'loop cysteines' to prevent backward electron flow. Despite these motions, hydrophobicity at the active site is maintained to facilitate VKOR catalysis. Biochemical experiments suggest that several warfarin-resistant mutations act by changing the conformation of the horizontal helix. Taken together, these studies provide a comprehensive understanding of VKOR function.

  5. Production of monospecific antiserum to a cytosolic epoxide hydrolase from human liver.

    PubMed

    Qato, M K; Reinmund, S G; Guenthner, T M

    1990-01-15

    A method for the purification to apparent homogeneity of cytosolic trans-stilbene oxide hydrolase from human liver is presented. The method employed ion exchange and gel filtration chromatography. From 50 g of human liver, 4.9 mg of homogenous enzyme protein was obtained. Although the enzyme had lost much of its catalytic activity during purification, it was nevertheless suitable for the preparation of antibodies to the enzyme. Only one immunogenic species was present in the antigen preparation, but some antibodies that were cross-reactive to sites on catalase were present in the antiserum. These catalase-specific antibodies were removed by immunoaffinity chromatography, and an IgG fraction that is monospecific to the cytosolic epoxide hydrolase was obtained. The usefulness of antibodies to this enzyme in immunoblotting experiments, following either sodium dodecyl sulfate-polyacrylamide gel electrophoresis or isoelectric focussing, as well as in enzyme-linked immunosorbent assays, is demonstrated.

  6. "Green" films from renewable resources: properties of epoxidized soybean oil plasticized ethyl cellulose films.

    PubMed

    Yang, Dong; Peng, Xinwen; Zhong, Linxin; Cao, Xuefei; Chen, Wei; Zhang, Xueming; Liu, Shijie; Sun, Runcang

    2014-03-15

    Epoxidized soybean oil (ESO), which is a biomass-derived resource, was first used as a novel plasticizer for ethyl cellulose (EC) film preparation. Surface morphologies, mechanical performances, thermal properties, oxygen and water vapor permeabilities of plasticized EC films were detected in detail to evaluate the plasticizing effect of ESO and explore the plastication mechanisms. Results showed that ESO was an effective plasticizer that outstripped conventional plasticizers, i.e. dibutyl phthalate (DBP) and triethyl citrate (TEC) in producing high-quality films. Especially, at plasticizer concentrations of 15-25%, ESO-EC films had preferable mechanical properties and better thermal stability, as well as non-flammability. In addition, the water vapor permeability of ESO-EC films was lower than that of traditional plasticized films. Their oxygen permeability was also remained in a low level. These outstanding performances were related to the relatively high molecular weight, hydrophobicity, chemical structure of ESO, and the intermolecular interactions between ESO and EC chains.

  7. Specificity of chemiluminescence in the metabolism of benzo[a]pyrene to its carcinogenic diol epoxide.

    PubMed Central

    Hamman, J P; Seliger, H H; Posner, G H

    1981-01-01

    The metabolism of 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene results primarily in the ultimate carcinogenic metabolite of benzo[a]pyrene, 7,8-dihydroxy-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene and to a lesser extent 7,8-dihydroxy-9,10-dioxetane-7,8,9,10-tetrahydrobenzo[a]pyrene, from which chemiluminescence is observed. This specific microsomal chemiluminescence has been used to establish that the rate-limiting reaction in the metabolism of benzo[a]pyrene to the bay region diol epoxide is the production of the 7,8-diol. The microsome-mediated chemiluminescence of the parent benzo[a]pyrene is therefore an indicator of the activity of the specific sequence of metabolic reactions leading to the ultimate carcinogenic metabolite. PMID:6785756

  8. Effect of epoxidation on 30% poly(methyl methacrylate)-grafted natural rubber polymer electrolytes

    SciTech Connect

    Nazir, Khuzaimah; Aziz, Ahmad Fairoz; Adam, Nurul Ilham; Yahya, Muhd Zu Azhan; Ali, Ab Malik Marwan

    2015-08-28

    Epoxidized 30% poly(methyl methacrylate)-grafted natural rubber (EMG 30) as a polymer host in solid polymer electrolytes (SPEs) has been investigated. EMG30 was synthesized via performicepoxidation method onto 30% poly(methyl methacrylate)-grafted natural rubber (MG30) and the formations of epoxy group were discussed. The EMG30 were characterized by proton nuclear magnetic resonance ({sup 1}HNMR) to investigate their chemical structure and differential scanning calorimeter to determine their crystallinity. A new peak in {sup 1}HNMR spectra (2.71 ppm) confirmed the appearance of epoxy group. SPE based on EMG30 doped with 40 wt% LiCF{sub 3}SO{sub 3} show the highest conductivity. The complexation between EMG30 and LiCF{sub 3}SO{sub 3} were confirmed by attenuated total reflection Fourier transform infrared (ATR-FTIR)

  9. Synthesis of new macrocyclic chiral manganese(III) Schiff bases as catalysts for asymmetric epoxidation.

    PubMed

    Martinez, Alexandre; Hemmert, Catherine; Loup, Christophe; Barré, Guillaume; Meunier, Bernard

    2006-02-17

    We describe a general synthetic strategy for the preparation of a series of macrocyclic chiral manganese(III) salen complexes. The developed reaction pathway allows the modulation of the different key groups, namely, the chiral diimine, the bulky substituents in positions 3 and 3', and the linker used in the macrocyclization of the Schiff base. The different complexes presented here illustrate these readily available structural variations. The catalytic properties of the catalysts (5 mol %) were improved for the asymmetric epoxidation of 2,2'-dimethylchromene with NaOCl or H2O2 as oxygen atom donor. A large range of enantiomeric excesses was obtained (ee values from 30% to 96%), depending on the features and the stability of the complexes. The most efficient catalyst, in terms of stereoinduction (ee value = 96%), contains a diiminocyclohexyl moiety, ethyl groups in positions 3 and 3', and a short polyether junction arm.

  10. Fighting Fenton Chemistry: A Highly Active Iron(III) Tetracarbene Complex in Epoxidation Catalysis.

    PubMed

    Kück, Jens W; Anneser, Markus R; Hofmann, Benjamin; Pöthig, Alexander; Cokoja, Mirza; Kühn, Fritz E

    2015-12-07

    Organometallic Fe complexes with exceptionally high activities in homogeneous epoxidation catalysis are reported. The compounds display Fe(II) and Fe(III) oxidation states and bear a tetracarbene ligand. The more active catalyst exhibits activities up to 183 000 turnovers per hour at room temperature and turnover numbers of up to 4300 at -30 °C. For the Fe(III) complex, a decreased Fenton-type reactivity is observed compared with Fe(II) catalysts reported previously as indicated by a substantially lower H2 O2 decomposition and higher (initial) turnover frequencies. The dependence of the catalyst performance on the catalyst loading, substrate, water addition, and the oxidant is investigated. Under all applied conditions, the advantageous nature of the use of the Fe(III) complex is evident.

  11. Investigation on magnetic field dependent modulus of epoxidized natural rubber based magnetorheological elastomer

    NASA Astrophysics Data System (ADS)

    Yunus, N. A.; Mazlan, S. A.; Ubaidillah; Aziz, S. A. A.; Khairi, M. H. Ahmad; Wahab, N. A. A.; Shilan, S. T.

    2016-11-01

    This paper presents an investigation on the use of epoxidized natural rubber (ENR) as a matrix of magnetorheological elastomers (MREs). Isotropic ENR-based MRE samples were synthesized by homogeneously mixed the ENR compound with carbonyl iron particles (CIPs). The microstructure of the sample was observed, and the magnetic field-dependent moduli were analyzed using rheometer. The influences of excitation frequency, CIPs content and magnetic field on the field-dependent moduli of ENR-based MREs were evaluated through dynamic shear test. The microstructure of MRE samples demonstrated the dispersed CIPs in the ENR matrix. The remarkable increment of storage and loss moduli of the ENR-based MREs has exhibited the magnetically controllable storage and loss moduli of the samples when exposed to the magnetic field. Consequently, the CIPs content, frequency and magnetic field were significantly influenced the dynamic moduli of the ENR-based MREs.

  12. Tuning graphitic oxide for initiator- and metal-free aerobic epoxidation of linear alkenes

    PubMed Central

    Pattisson, Samuel; Nowicka, Ewa; Gupta, Upendra N.; Shaw, Greg; Jenkins, Robert L.; Morgan, David J.; Knight, David W.; Hutchings, Graham J.

    2016-01-01

    Graphitic oxide has potential as a carbocatalyst for a wide range of reactions. Interest in this material has risen enormously due to it being a precursor to graphene via the chemical oxidation of graphite. Despite some studies suggesting that the chosen method of graphite oxidation can influence the physical properties of the graphitic oxide, the preparation method and extent of oxidation remain unresolved for catalytic applications. Here we show that tuning the graphitic oxide surface can be achieved by varying the amount and type of oxidant. The resulting materials differ in level of oxidation, surface oxygen content and functionality. Most importantly, we show that these graphitic oxide materials are active as unique carbocatalysts for low-temperature aerobic epoxidation of linear alkenes in the absence of initiator or metal. An optimum level of oxidation is necessary and materials produced via conventional permanganate-based methods are far from optimal. PMID:27687877

  13. Long-term persistence of dieldrin, DDT, and heptachlor epoxide in earthworms

    USGS Publications Warehouse

    Beyer, W.N.; Krynitsky, A.J.

    1989-01-01

    Earthworms can accumulate persistent soilborne insecticides and are an important source of contamination of terrestrail wildlife. We treated experimental plots once with dieldrin, DDT, or heptachlor, and measured changes in insecticide concentrations in earthworms over a 20-year period. We estimated 'half-times,' defined as the time for a concentration in earthworms to be reduced by half. Deldrin had a half-time of 5.4 years. DDE, the metabolite of DDT most important to wildlife, increased until the third year and then decreased with a half-time of 5.7 years. Heptachlor epoxide, the metabolite of hepatachlor most important to wildlife, increased until the second year and then decreased with a half-time of 4.3 years. The declining parts of the curves of all three compounds fit exponential decay equations reasonably well. The estimates persistence are relevant to insecticides at low or moderate concentrations in relatively undistrubed soils in temperate climates.

  14. CO2-Mediated Formation of Chiral Carbamates from meso-Epoxides via Polycarbonate Intermediates.

    PubMed

    Liu, Ye; Ren, Wei-Min; He, Ke-Ke; Zhang, Wen-Zhen; Li, Wen-Bing; Wang, Meng; Lu, Xiao-Bing

    2016-10-07

    Carbon dioxide has attracted broad interest as a renewable C1 feedstock for efficient transformation into value-added organic chemicals; nevertheless, far less attention was paid to its stereochemically controlled catalytic fixation/conversion processes. Here, we report a new strategy for the selective synthesis of chiral carbamates from carbon dioxide via polycarbonate intermediates, which are formed by the desymmetric copolymerization of meso-epoxides using enantiopure dinuclear Co(III) catalyst systems with 99% enantioselectivity. Subsequent degradation reaction of the resultant polycarbonates with various primary or secondary amine nucleophiles can afford optically active carbamates, with the complete configuration retention of the two chiral carbon centers. Our accomplishment reported here opens up a new route to prepare a wide range of CO2-based carbamate scaffolds with excellent yields and 99% enantiomeric excess.

  15. A density functional theory study of propylene epoxidation on RuO2(110) surface

    NASA Astrophysics Data System (ADS)

    Atmaca, Deniz Onay; Düzenli, Derya; Ozbek, M. Olus; Onal, Isik

    2016-11-01

    Propylene epoxidation is investigated on RuO2(110) and oxygen added RuO2-Oot(110) surfaces by periodic DFT computational method. The desired product propylene oxide (PO) as well as the undesired products acetone (AC) or propionaldehyde (PA) form on both surfaces through either surface intermediate oxometallopropylene (OMMP) or direct oxygen insertion mechanisms. On RuO2(110) surface, nucleophilic lattice oxygen at bridge position (Obr) favors the stable surface intermediate mechanism where high energy requirements for forward reactions are demonstrated in our calculations. On RuO2-Oot(110) surface, however, higher reactivity of the electrophilic oxygen (Oot) species lowers the reaction barriers and enables an exothermic reaction path to the direct oxygen insertion for PO production. Therefore, RuO2-Oot surface is expected to show a higher PO rate.

  16. Clinical applications of preheated hybrid resin composite.

    PubMed

    Rickman, L J; Padipatvuthikul, P; Chee, B

    2011-07-22

    This clinical article describes and discusses the use of preheated nanohybrid resin composite for the placement of direct restorations and luting of porcelain laminate veneers. Two clinical cases are presented. Preheating hybrid composite decreases its viscosity and film thickness offering the clinician improved handling. Preheating also facilitates the use of nanohybrid composite as a veneer luting material with relatively low polymerisation shrinkage and coefficient of thermal expansion compared to currently available resin luting cements.

  17. Cesium-specific phenolic ion exchange resin

    DOEpatents

    Bibler, J.P.; Wallace, R.M.

    1995-08-15

    A phenolic, cesium-specific, cation exchange resin is prepared by neutralizing resorcinol with potassium hydroxide, condensing/polymerizing the resulting intermediate with formaldehyde, heat-curing the resulting polymer to effect cross-linking and grinding it to desired particle size for use. This resin will selectively and efficiently adsorb cesium ions in the presence of a high concentration of sodium ions with a low carbon to cesium ratio. 2 figs.

  18. Cesium-specific phenolic ion exchange resin

    DOEpatents

    Bibler, Jane P.; Wallace, Richard M.

    1995-01-01

    A phenolic, cesium-specific, cation exchange resin is prepared by neutralizing resorcinol with potassium hydroxide, condensing/polymerizing the resulting intermediate with formaldehyde, heat-curing the resulting polymer to effect cross-linking and grinding it to desired particle size for use. This resin will selectively and efficiently adsorb cesium ions in the presence of a high concentration of sodium ions with a low carbon to cesium ratio.

  19. Liquid Resins With Low VOC Emissions

    DTIC Science & Technology

    2004-12-01

    titrated with the perchloric acid / peracetic acid solution (Aldrich) until the indicator, 0.1% crystal violet in acetic acid (Aldrich), changed color from...method of reducing styrene emissions from vinyl ester (VE) resins is to replace some or all of the styrene with fatty acid -based monomers. Fatty acid ...renewable resources. VE resins with no more than 20 wt% styrene were prepared using methacrylate terminated lauric acid . The viscosities of these

  20. An Iminohydantoin Lesion Induced in DNA by Peracids and Other Epoxidizing Oxidants

    PubMed Central

    Ye, Wenjie; Sangaiah, R.; Degen, Diana E.; Gold, Avram; Jayaraj, K.; Koshlap, Karl M.; Boysen, Gunnar; Williams, Jason; Tomer, Kenneth B.; Mocanu, Viorel; Dicheva, Nedyalka; Parker, Carol E.; Schaaper, Roel M.; Ball, Louise M.

    2009-01-01

    The oxidation of guanine to 5-carboxamido-5-formamido-2-iminohydantoin (2-Ih) is shown to be a major transformation in the oxidation of the single-stranded DNA 5-mer d(TTGTT) by m-CPBA and DMDO as a model for peracid oxidants and in the oxidation of the 5-base pair duplex d[(TTGTT)·(AACAA)] with DMDO. 2-Ih has not been reported as an oxidative lesion at the level of single/double-stranded DNA or at the nucleoside/nucleotide level. The lesion is stable to DNA digestion and chromatographic purification suggesting that 2-Ih may be a stable biomarker in vivo. The oxidation products have been structurally characterized and the reaction mechanism probed by oxidation of the monomeric species dGuo, dGMP and dGTP. DMDO selectively oxidizes the guanine moiety of dGuo, dGMP and dGTP to 2-Ih, and both peracetic and m-chloroperbenzoic acids exhibit the same selectivity. The presence of the glycosidic bond results in the stereoselective induction of an asymmetric center at the spiro carbon to give a mixture of diastereomers, with each diastereomer in equilibrium with a minor conformer through rotation about the formamido C-N bond. Labeling studies with 18O2-m-CPBA and H218O to determine the source of the added oxygen atoms have established initial epoxidation of the guanine 4-5 bond with pyrimidine ring contraction by an acyl 1,2-migration of guanine carbonyl C6 to form a transient dehydrodeoxyspiroiminodihydantoin followed by hydrolytic ring opening of the imidazolone ring. Consistent with the proposed mechanism, no 8-oxoguanine was detected as a product of the oxidations of the oligonucleotides or monomeric species mediated by DMDO or the peracids. The 2-Ih base thus appears to be a pathway-specific lesion generated by peracids and possibly other epoxidizing agents and holds promise as a potential biomarker. PMID:19354244

  1. Manganese(III) Schiff base complexes: chemistry relevant to the copolymerization of epoxides and carbon dioxide.

    PubMed

    Darensbourg, Donald J; Frantz, Eric B

    2007-07-23

    Schiff base complexes of the form (acacen)Mn(III)X (acacen = N,N'-bis(acetylacetone)-1,2-ethylenediimine), where X = OAc, Cl, or N(3), have been evaluated for their ability to couple CO(2) and cyclohexene oxide in the presence of a variety of cocatalysts to provide cyclic or polycarbonates. These complexes proved to be ineffective at catalyzing this process; however, valuable information related to the coordination chemistry of these manganese Schiff bases was elucidated. Of importance, mechanistic findings as revealed by comprehensive studies involving structurally related (salen)CrX and (salen)CoX complexes strongly support the requirement of six-coordinate metal species for the effective copolymerization of CO(2) and epoxides. In the case of these Mn(III) complexes, it was determined that in chloroform or toluene solution a five-coordinate species was greatly favored over a six-coordinate species even in the presence of 20 equiv or more of various Lewis bases. Significantly epoxide monomers such as propylene oxide and cyclohexene oxide displayed no tendency to bind to these (acacen)MnX derivatives, even when used as solvents. Only in the case of excessive quantities of heterocyclic amines such as pyridine, DMAP, and DBU was spectral evidence of a six-coordinate Mn derivative observed in solution. X-ray crystal structures are provided for many of the complexes involved in this study, including the one-dimensional polymeric structures of [(acacen)MnOAc x 2H(2)O](n), [(acacen)MnN(3)](n) (mu(1,3)-N(3)), and a rare mixed bridging species [(acacen)MnN(3)](n) (mu(1,3)-N(3)/mu(1,1)-N(3)). In addition, a structure was obtained in which the unit cell contains both a (acacen)MnN(3)(DMAP) and a (acacen)MnN(3) species.

  2. Soluble Epoxide Hydrolase Null Mice Exhibit Female and Male Differences In Regulation of Vascular Homeostasis

    PubMed Central

    Vanella, Luca; Canestraro, Martina; Lee, Craig R.; Cao, Jian; Zeldin, Darryl C.; Schwartzman, Michal L.; Abraham, Nader G.

    2015-01-01

    Increased CYP epoxygenase activity and consequently up regulation of epoxyeicosatrienoic acids (EETs) levels provides protection against metabolic syndrome and cardiovascular diseases. Conversion of arachidonic acid epoxides to diols by soluble epoxide hydrolase (sEH) diminishes the beneficial cardiovascular properties of these epoxyeicosanoids. We therefore examined the possible biochemical consequences of sEH deletion on vascular responses in male and female mice. Through the use of the sEH KO mouse, we provide evidence of differences in the compensatory response in the balance between nitric oxide (NO), carbon monoxide (CO), EETs and the vasoconstrictor 20-HETE in male and female KO mice. Serum levels of adiponectin, TNFα, IL-1b and MCP1 and protein expression in vascular tissue of p-AMPK, p-AKT and p-eNOS were measured. Deletion of sEH caused a significant (p<0,05) decrease in body weight, and an increase in adiponectin, pAMPK and pAKT levels in female KO mice compared to male KO mice. Gene deletion resulted in a higher production of renal EETs in female KO compared to male KO mice and, concomitantly, we observed an increase in renal 20-HETEs levels and superoxide anion production only in male KO mice. sEH deletion increased p-AKT and p-eNOS protein expression but decreased p-AMPK levels in female KO mice. Increased levels of p-eNOS at Thr-495 were observed only in KO male mice. While p-eNOS at 1177 were not significantly different between male and female. Nitric oxide production was unaltered in male KO mice. These results provide evidence of gender differences in the preservation of vascular homeostasis in response to sEH deletion which involves regulation of phosphorylation of eNOS at the 495 site. PMID:25908301

  3. Cleanup of TMI-2 demineralizer resins

    SciTech Connect

    Bond, W.D.; King, L.J.; Knauer, J.B.; Hofstetter, K.J.; Thompson, J.D.

    1985-01-01

    Radiocesium is being removed from Demineralizers A and B (DA and DB by a process that was developed from laboratory tests on small samples of resin from the demineralizers. The process was designed to elute the radiocesium from the demineralizer resins and then to resorb it onto the zeolite ion exchangers contained in the Submerged Demineralizer System (SDS). The process was also required to limit the maximum cesium activities in the resin eluates (SDS feeds) so that the radiation field surrounding the pipelines would not be excessive. The process consists of 17 stages of batch elution. In the initial stage, the resin is contacted with 0.18 M boric acid. Subsequent stages subject the resin to increasing concentrations of sodium in NaH/sub 2/BO/sub 3/-H/sub 3/BO/sub 3/ solution (total B = 0.35 M) and then 1 M sodium hydroxide in the final stages. Results on the performance of the process in the cleanup of the demineralizers at TMI-2 are compared to those obtained from laboratory tests with small samples of the DA and DB resins. To date, 15 stages of batch elution have been completed on the demineralizers at TMI-2 which resulted in the removal of about 750 Ci of radiocesium from DA and about 3300 Ci from DB.

  4. Resin characterization by electro-acoustic measurements.

    PubMed

    Müller, Egbert; Mann, Christian

    2007-03-09

    The electro-acoustic effects, namely the ion vibration potential (IVP) and the colloidal vibration current (CVI), colloidal vibration potential (CVP) first described by P. Debye [P. Debye, J. Chem. Phys. 1 (1933) 13], are a result of charge separation of bound or free ions at different degrees by ultrasonic waves. Today commercial instruments are available to investigate liquid homogeneous and heterogeneous systems. In the present paper the application of this technique for the characterization of salts, protein solutions and resins for biochromatography is shown and valuable information about resins can be derived in a short time. Various resins were investigated with the following results: (1) the CVI magnitude is dependent of several parameters (such as particle size distribution, volume fraction, density difference); (2) the CVI is influenced by the surface modification of the resins. Polymeric modifications decrease the value of CVI. The CVI is generally lower for high capacity resins; (3) the measurement of the electro-acoustic effects can be used to detect small changes in resins. The CVI is dependent of the amount of adsorbed protein in "native" and denatured state.

  5. Mutagenic activity of the 4,5- and 9,10-dihydrodiols of benzo[i]fluoranthene and their syn- and anti-dihydrodiol epoxides in Salmonella typhimurium

    SciTech Connect

    Marshall, M.V. ); He, Z.M.; Weyand, E.H.; Rice, J.E.; LaVoie, E.J. )

    1993-01-01

    The objective of this study was to determine the relative mutagenic activities of the major dihydrodiol metabolites of benzo[i]fluoranthene (B[i]F) and their corresponding syn- and anti-dihydrodiol epoxides. Salmonella typhimurium tester strains TA97a, TA98, and TA100 were used to evaluate the mutagenic potencies of the parent hydrocarbon and these suspect proximate and ultimate mutagenic metabolites. B[i]F and the trans-dihydrodiol metabolites were active only in the presence of an external metabolic activation system (S9) with the exception of the B[i]F-4,5-diol, which was weakly active in TA98 and TA100 in the absence of S9. The B[i]F-4,5-diol was more mutagenic than the B[i]F-9,10-diol in tester strains TA98 and TA100, whereas the opposite effect was observed in TA97a. In the absence of S9, the anti-B[i]F-4,5-diol epoxide was more mutagenic than the syn-B[i]F-4,5-diol epoxide and the syn- and anti-B[i]F-9,10-diol epoxides in tester strains TA97a and TA100. The exceptional mutagenic potency of the anti-B[i]F-4,5-diol epoxide in TA100 resembles that observed by epoxides located within a fjord, or by the anti-diol epoxides of bay region methylated polycyclic aromatic hydrocarbons. In contrast, the mutagenicity of the pseudo bay region dihydrodiol epoxides arising from the B[i]F-9,10-diol more closely resembles that observed with the classical bay region dihydrodiol epoxides of chrysene. In summary, both dihydrodiol metabolites of B[i]F are mutagenic in S. typhimurium, and the relative potency varies among the tester strains. The highest mutagenic response was achieved in tester strain TA100, which detects base-pair substitutions. The most potent direct-acting dihydrodiol epoxide in this tester strain was the anti-B[i]F-4,5-diol epoxide, which agrees with the results of mouse skin painting studies that indicate that the B[i]F-4,5-diol is more tumorigenic than the parent hydrocarbon or the B[i]F-9,10-diol. 34 refs., 7 figs., 2 tabs.

  6. Synergistic interplay of a non-heme iron catalyst and amino acid coligands in H2 O2 activation for asymmetric epoxidation of α-alkyl-substituted styrenes.

    PubMed

    Cussó, Olaf; Ribas, Xavi; Lloret-Fillol, Julio; Costas, Miquel

    2015-02-23

    Highly enantioselective epoxidation of α-substituted styrenes with aqueous H2 O2 is described by using a chiral iron complex as the catalyst and N-protected amino acids (AAs) as coligands. The amino acids synergistically cooperate with the iron center in promoting an efficient activation of H2 O2 to catalyze epoxidation of this challenging class of substrates with good yields and stereoselectivities (up to 97%ee) in short reaction times.

  7. Role of keto-enol tautomerization in a chiral phosphoric acid catalyzed asymmetric thiocarboxylysis of meso-epoxide: a DFT study.

    PubMed

    Ajitha, Manjaly J; Huang, Kuo-Wei

    2015-12-07

    The mechanism of a chiral phosphoric acid catalyzed thiocarboxylysis of meso-epoxide was investigated by density functional theory (DFT) calculations (M06-2X). The nucleophilic ring opening of epoxide by thiobenzoic acid was found to proceed via a concerted termolecular transition state with a simultaneous dual proton transfer to yield the β-hydroxy thioester product. Electrostatic interactions together with the steric environment inside the chiral catalyst play an important role in determining the enantioselectivity of the reaction.

  8. The ω-3 epoxide of eicosapentaenoic acid inhibits endothelial cell proliferation by p38 MAP kinase activation and cyclin D1/CDK4 down-regulation

    PubMed Central

    Cui, Pei H; Petrovic, Nenad; Murray, Michael

    2011-01-01

    BACKGROUND AND PURPOSE Dietary intake of ω-3 polyunsaturated fatty acids (ω-3 PUFAs) like eicosapentaenoic acid (EPA) decreases cancer risk, while arachidonic acid and other ω-6 PUFAs increase risk, but the underlying mechanisms are unclear. Cytochrome P450 (CYP)-derived epoxides contribute to enhanced tumourigenesis due to ω-6 PUFA intake. Thus, ω-6 arachidonic acid epoxides (EETs) inhibit apoptosis and stimulate proliferation by up-regulating cyclin D1 expression in cells. The present study evaluated the corresponding ω-3 PUFA epoxides and assessed their role in the regulation of cell proliferation. EXPERIMENTAL APPROACH Four chemically stable EPA epoxides (formed at the 8,9-, 11,12-, 14,15- and 17,18-olefinic bonds) were synthesized and tested against growth-related signalling pathways in brain microvascular endothelial bEND.3 cells. Cell cycle distribution was determined by flow cytometry and cyclin gene expression by immunoblotting and real-time PCR. The role of the p38 mitogen-activated protein (MAP) kinase in cyclin D1 dysregulation was assessed using specific inhibitors and dominant-negative expression plasmids. KEY RESULTS The ω-3 17,18-epoxide of EPA decreased cell proliferation, interrupted the cell cycle in S-phase and down-regulated the cyclin D1/cyclin-dependent kinase (CDK)-4 complex, whereas the 8,9-, 11,12- and 14,15-epoxides were either inactive or enhanced proliferation. Cyclin D1 down-regulation by 17,18-epoxy-EPA was mediated by activation of the growth-suppressing p38 MAP kinase, but the alternate EPA-epoxides were inactive. CONCLUSIONS AND IMPLICATIONS The present findings suggest that the epoxide formed by CYP enzymes at the ω-3 olefinic bond may contribute to the beneficial effects of ω-3 PUFA by down-regulating cyclin D1 and suppressing cell proliferation. PMID:21077851

  9. Synthesis, Characterization, and Cross-Linking Strategy of a Quercetin-Based Epoxidized Monomer as a Naturally-Derived Replacement for BPA in Epoxy Resins.

    PubMed

    Kristufek, Samantha L; Yang, Guozhen; Link, Lauren A; Rohde, Brian J; Robertson, Megan L; Wooley, Karen L

    2016-08-23

    The natural polyphenolic compound quercetin was functionalized and cross-linked to afford a robust epoxy network. Quercetin was selectively methylated and functionalized with glycidyl ether moieties using a microwave-assisted reaction on a gram scale to afford the desired monomer (Q). This quercetin-derived monomer was treated with nadic methyl anhydride (NMA) to obtain a cross-linked network (Q-NMA). The thermal and mechanical properties of this naturally derived network were compared to those of a conventional diglycidyl ether bisphenol A-derived counterpart (DGEBA-NMA). Q-NMA had similar thermal properties [i.e., glass transition (Tg ) and decomposition (Td ) temperatures] and comparable mechanical properties (i.e., Young's Modulus, storage modulus) to that of DGEBA-NMA. However, it had a lower tensile strength and higher flexural modulus at elevated temperatures. The application of naturally derived, sustainable compounds for the replacement of commercially available petrochemical-based epoxies is of great interest to reduce the environmental impact of these materials. Q-NMA is an attractive candidate for the replacement of bisphenol A-based epoxies in various specialty engineering applications.

  10. Transformation Kinetics of Chlorinated Ethenes by Methylosinus trichosporium OB3b and Detection of Unstable Epoxides by On-Line Gas Chromatography

    PubMed Central

    van Hylckama, Vlie... J.; de Koning, W.; Janssen, D. B.

    1996-01-01

    A rapid and accurate method for the determination of transformation kinetics of volatile organic substrates was developed. Concentrations were monitored by on-line gas chromatographic analysis of the headspace of well-mixed incubation mixtures. With this method, the kinetics of transformation of a number of C(inf1) and C(inf2) halogenated alkanes and alkenes by Methylosinus trichosporium OB3b expressing particulate methane monooxygenase or soluble methane monooxygenase (sMMO) were studied. Apparent specific first-order rate constants for cells expressing sMMO decreased in the order of dichloromethane, vinyl chloride, cis-1,2-dichloroethene, trans-1,2-dichloroethene, 1,1-dichloroethene, trichloroethene, chloroform, and 1,2-dichloroethane. During the degradation of trichloroethene, cis-1,2-dichloroethene, trans-1,2-dichloroethene, and vinyl chloride, the formation of the corresponding epoxides was observed. The epoxide of vinyl chloride and the epoxide of trichloroethene, which temporarily accumulated in the medium, were chemically degraded according to first-order kinetics, with half-lives of 78 and 21 s, respectively. Cells expressing sMMO actively degraded the epoxide of cis-1,2-dichloroethene but not the epoxide of trans-1,2-dichloroethene. Methane and acetylene inhibited degradation of the epoxide of cis-1,2-dichloroethene, indicating that sMMO was involved. PMID:16535402

  11. Thermal rearrangement of novolak resins used in microlithography

    NASA Astrophysics Data System (ADS)

    Hardy, Ricky; Zampini, Anthony; Monaghan, Michael J.; O'Leary, Michael J.; Cardin, William J.; Eugster, Timothy J.

    1995-06-01

    Changes in phenolic-formaldehyde resin properties are described in terms of thermal exposure. At high temperature, resin molecular weight, dissolution properties and chemical composition change depending on the presence or absence of monomers. Without monomer in the resin melt at 220 degree(s)C, resin molecular weight increases with a corresponding decrease in dissolution rate. In the presence of monomer, molecular weight generally decreases. Dissolution rate may fluctuate depending on the monomer mixture. Three,five- Xylenol and 2,3,5-trimethylphenol co-monomers induced the most extreme changes in resin properties with thermal treatment. Resin degradation-recombination processes suggest a classical Friedel-Craft rearrangement mechanism.

  12. Tc-99 Ion Exchange Resin Testing

    SciTech Connect

    Valenta, Michelle M.; Parker, Kent E.; Pierce, Eric M.

    2010-08-01

    Pacific Northwest National Laboratory was contracted by CHPRC to evaluate the release of 99Tc from spent resin used to treat water from well 299-W15-765 and stored for several years. The key questions to be answered are: 1) does 99Tc readily release from the spent ion exchange resin after being in storage for several years; 2) if hot water stripping is used to remove the co-contaminant carbon tetrachloride, will 99Tc that has been sequestered by the resin be released; and 3) can spent resin be encapsulated into a cementitious waste form; if so, how much 99Tc would be released from the weathering of the monolith waste form? The results from the long term stability leach test results confirm that the resin is not releasing a significant amount of the sequestered 99Tc, evident by the less than 0.02% of the total 99Tc loaded being identified in the solution. Furthermore, it is possible that the measured 99Tc concentration is the result of 99Tc contained in the pore spaces of the resin. In addition to these results, analyses conducted to examine the impact of hot water on the release of 99Tc suggest that only a small percentage of the total is being released. This suggest that hot water stripping to remove carbon tetrachloride will not have a significant affect on the resin’s ability to hold-on to sequestered 99Tc. Finally, encapsulation of spent resin in a cementitious material may be a viable disposal option, but additional tests are needed to examine the extent of physical degradation caused by moisture loss and the effect this degradation process can have on the release of 99Tc.

  13. Resin flow monitoring in vacuum-assisted resin transfer molding using optical fiber distributed sensor

    NASA Astrophysics Data System (ADS)

    Eum, Soohyun; Kageyama, Kazuro; Murayama, Hideaki; Ohsawa, Isamu; Uzawa, Kiyoshi; Kanai, Makoto; Igawa, Hirotaka

    2007-04-01

    In this study, we implemented resin flow monitoring by using an optical fiber sensor during vacuum assisted resin transfer molding (VaRTM).We employed optical frequency domain reflectometry (OFDR) and fiber Bragg grating (FBG) sensor for distributed sensing. Especially, long gauge FBGs (about 100mm) which are 10 times longer than an ordinary FBG were employed for more effective distributed sensing. A long gauge FBG was embedded in GFRP laminates, and other two ones were located out of laminate for wavelength reference and temperature compensation, respectively. During VaRTM, the embedded FBG could measure how the preform affected the sensor with vacuum pressure and resin was flowed into the preform. In this study, we intended to detect the gradient of compressive strain between impregnated part and umimpregnated one within long gauge FBG. If resin is infused to preform, compressive strain which is generated on FBG is released by volume of resin. We could get the wavelength shift due to the change of compressive strain along gauge length of FBG by using short-time Fourier transformation for signal acquired from FBG. Therefore, we could know the resin flow front with the gradient of compressive strain of FBG. In this study, we used silicon oil which has same viscosity with resin substitute for resin in order to reuse FBG. In order to monitor resin flow, the silicon oil was infused from one edge of preform, the silicon oil was flowed from right to left. Then, we made dry spot within gauge length by infusing silicon oil to both sides of preform to prove the ability of dry spot monitoring with FBG. We could monitor resin flow condition and dry spot formation successfully using by FBG based on OFDR.

  14. Na@SiO2-Mediated Addition of Organohalides to Carbonyl Compounds for the Formation of Alcohols and Epoxides

    NASA Astrophysics Data System (ADS)

    Kapoor, Mohit; Hwu, Jih Ru

    2016-11-01

    Alcohols and epoxides were generated by the addition of organohalides to carbonyl compounds in the presence of sodium metal impregnated with silica gel (Na@SiO2) in THF at 25 °C through a radical pathway. Under the same conditions, Schiff bases were also successfully converted to the corresponding amines. Furthermore, the reaction of aldehydes with α-haloesters or 4-(chloromethyl)-coumarin with the aid of Na@SiO2 generated trans epoxides. An unprecedented mechanism is proposed for their formation. The advantages associated with these new reactions include: (1) products are obtained in good-to-excellent yields, (2) reactions are completed at room temperatures in a short period of time (<2.0 h), (3) it is unnecessary to perform the reactions under anhydrous conditions, and (4) the entire process requires only simple manipulations.

  15. Asymmetric epoxidation of unsaturated ketones catalyzed by heterobimetallic rare earth-lithium complexes bearing phenoxy-functionalized chiral diphenylprolinolate ligand.

    PubMed

    Qian, Qinqin; Tan, Yufang; Zhao, Bei; Feng, Tao; Shen, Qi; Yao, Yingming

    2014-09-05

    Four novel heterobimetallic complexes [REL2]{[(THF)3Li]2(μ-Cl)} stabilized by chiral phenoxy-functionalized prolinolate (RE = Yb (1), Y (2), Sm (3), Nd (4), H2L = (S)-2,4-di-tert-butyl-6-[[2-(hydroxydiphenylmethyl)pyrrolidin-1-yl]methyl]phenol have been synthesized and characterized. These readily available complexes are highly active in catalyzing the epoxidation of α,β-unsaturated ketones, while the enantioselectivity varies according to the ionic radii of the rare earth center. A series of chalcone derivatives were converted to chiral epoxides in 80 → 99% ee at 0 °C using TBHP as the oxidant in the presence of 10 mol % of 1.

  16. Epoxide Activated Anionic Polymerization: Application to the Synthesis of (Co)Polyethers with Controlled Structure and Tuned Properties

    NASA Astrophysics Data System (ADS)

    Labbe, Amelie; Rejsek, Virginie; Carlotti, Stephane; Deffieux, Alain

    A ring opening polymerization process allowing the fast and controlled anionic polymerization of epoxide monomers is described and applied to the synthesis of (co)polyethers with novel structure and composition. The approach is based on the simultaneous formation of complexes between an organometallic Lewis acid additive with both the anionic initiator and the monomer. In conjunction with the use of tetraalkylammonium or phosphonium salts as initiators, the addition of such additive allows the synthesis of polyethers and block copolyethers with controlled molar masses and narrow polydispersities, in hydrocarbon media, at low temperature, and in short reaction times. The low nucleophilic character of the propagating species involved in the polymerization avoids transfer to monomer, a side reaction which is often predominant in conventional anionic polymerizations. This also allows the controlled polymerization of functional epoxides such as glycidyl methacrylate and epichlorohydrin. Properties and potential applications of these new polyethers and copolyethers are also reported.

  17. Allenes in Asymmetric Catalysis. Asymmetric Ring-Opening of Meso-Epoxides Catalyzed by Allene-Containing Phosphine Oxides

    PubMed Central

    Pu, Xiaotao; Qi, Xiangbing; Ready, Joseph M.

    2009-01-01

    Unsymmetrically substituted allenes (1,2 dienes) are inherently chiral and can be prepared in optically pure form. Nonetheless, to date the allene framework has not been incorporated into ligands for asymmetric catalysis. Since allenes project functionality differently than either tetrahedral carbon or chiral biaryls, they may create complementary chiral environments. This study demonstrates that optically active C2 symmetric allene-containing bisphosphine oxides can catalyze the addition of SiCl4 to meso epoxides with high enantioselectivity. The epoxide-opening likely involves generation of a Lewis acidic, cationic (bisphosphine oxide)SiCl3 complex. The fact that high asymmetric induction is observed suggests that allenes may represent a new platform for the development of ligands and catalysts for asymmetric synthesis. PMID:19722613

  18. Asymmetric epoxidation of unfunctionalized alkenes catalyzed by sugar moiety-modified chiral salen-Mn(III) complexes.

    PubMed

    Zhao, Jiquan; Zhang, Yuecheng; Han, Furong; Zhao, Shanshan

    2009-01-05

    Several chiral Schiff-base ligands with sugar moieties at C-3 (3') or C-5 (5') of salicylaldehyde were synthesized from reaction of salicylaldehyde derivatives with diamine. These ligands coordinated with Mn(III) to afford the corresponding chiral salen-Mn(III) complexes characterized by FT-IR, MS, and elementary analysis. These complexes were used as catalysts for the asymmetric epoxidation of unfunctionalized alkenes. Only weak enantioselectivity is induced by the chiral sugar moieties at C-3 (3') or C-5 (5') in the case of absence of chirality in the diimine bridge moiety. It was also shown that the sugars at C-5 (5') having the same rotation direction of polarized light as the diimine bridge in the catalyst could enhance the chiral induction in the asymmetric epoxidation, but the sugars with the opposite rotation direction would reduce the chiral induction.

  19. Experimental verification, and domain definition, of structural alerts for protein binding: epoxides, lactones, nitroso, nitros, aldehydes and ketones.

    PubMed

    Nelms, M D; Cronin, M T D; Schultz, T W; Enoch, S J

    2013-01-01

    This study outlines how a combination of in chemico and Tetrahymena pyriformis data can be used to define the applicability domain of selected structural alerts within the profilers of the OECD QSAR Toolbox. Thirty-three chemicals were profiled using the OECD and OASIS profilers, enabling the applicability domain of six structural alerts to be defined, the alerts being: epoxides, lactones, nitrosos, nitros, aldehydes and ketones. Analysis of the experimental data showed the applicability domains for the epoxide, nitroso, aldehyde and ketone structural alerts to be well defined. In contrast, the data showed the applicability domains for the lactone and nitro structural alerts needed modifying. The accurate definition of the applicability domain for structural alerts within in silico profilers is important due to their use in the chemical category in predictive and regulatory toxicology. This study highlights the importance of utilizing multiple profilers in category formation.

  20. HPLC analysis of geometrical isomers of lutein epoxide isolated from dandelion (Taraxacum officinale F. Weber ex Wiggers).

    PubMed

    Meléndez-Martínez, Antonio J; Britton, George; Vicario, Isabel M; Heredia, Francisco J

    2006-04-01

    Lutein epoxide has been isolated from petals of dandelion (Taraxacum officinale F. Weber ex Wiggers) by thin-layer chromatography (TLC) on silica to be used for the accurate identification of this carotenoid in other sources. The extract was analyzed by high-performance liquid chromatography (HPLC) using a C(30) column, as a result of which six geometrical isomers were separated. The identification of these isomers was performed on the basis of their UV/vis spectroscopic features in the mobile phase. In quantitative terms, it was observed that all-E-lutein epoxide was the major carotenoid and that there were also high amounts of the (9Z)- and (9'Z)-isomers, although the latter may be an artifact.