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Chemical Conversion (chemical + conversion)
Selected AbstractsSynthesis and Some Chemical Conversions of 2-([2,2]-5-Paracyclophanyl)pyrrole.CHEMINFORM, Issue 50 2004A. V. Varlamov Abstract For Abstract see ChemInform Abstract in Full Text. [source] Chemical Conversions of 8,18-Disubstituted Derivatives of 6,16-Diphenyl-1,2,3,11,12,13-hexahydrodibenzo [g,o]-4,14-dioxa-1,5,11,15-tetraazacyclohexadecine-2,12-diones.CHEMINFORM, Issue 8 2004O. V. Kulikov Abstract For Abstract see ChemInform Abstract in Full Text. [source] Thermochemical Nanolithography of Multifunctional Nanotemplates for Assembling Nano-ObjectsADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Debin Wang Abstract Nanoscale chemical patterning of different chemical species (amine, thiol, aldehyde, and biotin) in independent nanopatterns is achieved by the iterative application of thermochemical nanolithography (TCNL) to inscribe amine patterns followed by their chemical conversion to other functional groups. Due to the unique chemical stability of the patterns, the resultant substrates can be stored for weeks and subsequently be used for covalent and molecular-recognition-based attachment of nano-objects using standard chemical protocols. In particular, the ability of this method to attach proteins and DNA to the chemical nanopatterns and to create co-patterns of two distinctive bioactive proteins is demonstrated. [source] Direct Correlation of Organic Semiconductor Film Structure to Field-Effect Mobility,ADVANCED MATERIALS, Issue 19 2005M. DeLongchamp Near-edge X-ray fine structure spectroscopy is used to measure simultaneous chemical conversion, molecular ordering, and defect formation in soluble oligothiophene precursor films. Film structure is correlated to OFET performance. Molecular orientation is determined by evaluating antibonding orbital overlap with the polarized electric field vector of incident soft X-rays (see Figure and cover). Upon conversion, the molecules become vertically oriented, allowing , overlap in the plane of hole transport. [source] Hexagonal and cubic TiOF2JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2010Samuel Shian The chemical, electrochemical, optical and electro-optical properties of titanium oxyfluoride, TiOF2, have led to interest in this compound for a number of applications. Prior analyses have indicated that TiOF2 possesses a simple cubic structure (space group Pmm) at room temperature. Three-dimensional nanostructured assemblies of polycrystalline TiOF2 have recently been synthesized via chemical conversion of intricate SiO2 structures by metathetic reaction with TiF4(g). Rietveld analysis has been used to evaluate the structure of the TiOF2 product formed by such reaction at 623,K. Unlike prior reports, this TiOF2 product possessed a hexagonal structure (space group Rc) at room temperature. Upon heating through 333,338 K, the hexagonal TiOF2 polymorph converted into cubic (Pmm) TiOF2. Differential scanning calorimetry and X-ray diffraction analyses have been used to evaluate this thermally induced phase transformation. [source] Chitin production by Lactobacillus fermentation of shrimp biowaste in a drum reactor and its chemical conversion to chitosanJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2005Mukku Shrinivas Rao Abstract Chitin was produced by fermenting shrimp heads and shells with Lactobacillus plantarum 541 in a drum reactor with an internal volume of 3 dm3. The crude chitin yield from heads and shells was 4.5 and 13% respectively, comparable to the values obtained by the chemical method. For shrimp heads 83% deproteination and 88% demineralisation and for shrimp shells 66% deproteination and 63% demineralisation were achieved. The liquor obtained in both cases was of good sensory quality with a high content of essential amino acids and therefore with potential to produce protein powder for human consumption. The crude chitin was refined and converted to chitosan using 12.5 M NaOH. The chitosan obtained had a residual ash and protein content below 1%, a solubility of more than 98%, a viscosity in the range 50,400 cP and a degree of deacetylation of 81,84%. The molecular weight was in the range (0.8,1.4) × 106 Da. IR analysis indicated that the chitosan obtained through fermentation was similar to that obtained by the chemical method. Copyright © 2005 Society of Chemical Industry [source] The integration of green chemistry into future biorefineriesBIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 1 2009James H. Clark Abstract The use of biorefineries for the production of chemicals as well as materials and energy products is key to ensuring a sustainable future for the chemical and allied industries. Through the integration of green chemistry into biorefineries, and the use of low environmental impact technologies, we can establish future supply chains for genuinely green and sustainable chemical products. The first step in these future biorefineries should be the benign extraction of surface chemicals; here the use of greener solvents, such as supercritical carbon dioxide and bioethanol, should be considered. The residues will often be rich in lignocellulosics and the effective separation of the cellulose is a major challenge which may, in the future, be assisted by greener solvents, such as ionic liquids. Lignin is nature's major source of aromatics; we need new ways to produce small aromatic building blocks from lignin in order to satisfy the enormous and diverse industrial demand for aromatics. Fermentation can be used to convert biomass into a wide range of bioplatform chemicals in addition to ethanol. Their green chemical conversion to higher value chemicals is as important as their efficient production; here clean technologies such as catalysis , notably biocatalysis and heterogeneous catalysis , the use of benign solvents, and energy efficient reactors are essential. Thermochemical processes for the conversion of biomass, such as the production of pyrolysis oil, will also play an important role in future biorefineries and here again green chemistry methods should be used to go to higher value downstream chemicals. Published in 2008 by John Wiley & Sons, Ltd [source] Towards Supramolecular Fixation of NOX Gases: Encapsulated Reagents for NitrosationCHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2005Yanlong Kang Abstract The use of simple calix[4]arenes for chemical conversion of NO2/N2O4 gases is demonstrated in solution and in the solid state. Upon reacting with these gases, calixarenes 1 encapsulate nitrosonium (NO+) cations within their cavities with the formation of stable calixarene,NO+ complexes 2. These complexes act as encapsulated nitrosating reagents; cavity effects control their reactivity and selectivity. Complexes 2 were effectively used for nitrosation of secondary amides 5, including chiral derivatives. Unique size,shape selectivity was observed, allowing for exclusive nitrosation of less crowded N -Me amides 5,a,e (up to 95,% yields). Bulkier N -Alk (Alk>Me) substrates 5 did not react due to the hindered approach to the encapsulated NO+ reagents. Robust, silica gel based calixarene material 3 was prepared, which reversibly traps NO2/N2O4 with the formation of NO+ -storing silica gel 4. With material 4, similar size,shape selectivity was observed for nitrosation. The N -Me,N -nitroso derivatives 6,d,e were obtained with ,30,% yields, while bulkier amides were nitrosated with much lower yields (<8,%). Enantiomerically pure encapsulating reagent 2,d was tested for nitrosation of racemic amide 5,t, showing modest but reproducible stereoselectivity and ,15,% ee. Given high affinity to NO+ species, which can be generated by a number of NOX gases, these supramolecular reagents and materials may be useful for NOX entrapment and separation in the environment and biomedical areas. [source] Sarcodonins and Sarcoviolins, Bioactive Polyhydroxy- p -terphenyl Pyrazinediol Dioxide Conjugates from Fruiting Bodies of the Basidiomycete Sarcodon leucopusEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2004Valeria Calì Abstract Six new polyhydroxy- p -terphenyl pyrazinediol dioxide conjugates (4,9) related to sarcodonin (3) have been isolated from the EtOAc extract of the fruiting bodies of the basidiomycete Sarcodon leucopus and we established their structures by spectral analysis and chemical conversions. Three of them, named sarcodonins , (4), , (5), and , (6), afforded the same peracetate 12 upon acetylation. Compounds 7, 8, and 9 gave peracetate 13 and were characterized as the N -oxide epimers of 3,5, respectively, and are named, accordingly, episarcodonin, episarcodonin ,, and episarcodonin ,. From the EtOH extract, we obtained a mixture of two violet pigments. Chemical and spectroscopic data allowed their structures to be established as the p -terphenyl ortho -quinones related to the sarcodonins, namely sarcoviolin , (10) and episarcoviolin , (11). Compounds 3, 4, 6, and 7 and the mixture of 10 and 11 were found to be active in assays against tumor cell cultures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] A new bioactive steroidal saponin from Sansevieria cylindricaPHYTOTHERAPY RESEARCH, Issue 2 2003Alexandra da Silva Antunes Abstract A new steroidal saponin was isolated from the leaves of Sansevieria cylindrica. Its structure was established as (3,,12,,15,,25S)-26-(,- D -glucopyranosyloxy)-22-hydroxyfurost-5-en-3-yl 12- O - (6-deoxy-,- L -mannopyranosyl)-15- O -(6-deoxy-,- L -mannopyranosyl)-,- D -glucopyranoside. The structural identification was performed using detailed analyses of 1H and 13C NMR spectra including 2D NMR spectroscopic techniques (COSY, HETCOR, HMBC and HMQC) and chemical conversions. The steroidal saponin showed no haemolytic effects in the in vitro assays and demonstrated inhibition of the capillary permeability activity. Copyright © 2003 John Wiley & Sons, Ltd. [source] Platform biochemicals for a biorenewable chemical industryTHE PLANT JOURNAL, Issue 4 2008Basil J. Nikolau Summary The chemical industry is currently reliant on a historically inexpensive, petroleum-based carbon feedstock that generates a small collection of platform chemicals from which highly efficient chemical conversions lead to the manufacture of a large variety of chemical products. Recently, a number of factors have coalesced to provide the impetus to explore alternative renewable sources of carbon. Here we discuss the potential impact on the chemical industry of shifting from non-renewable carbon sources to renewable carbon sources. This change to the manufacture of chemicals from biological carbon sources will provide an opportunity for the biological research community to contribute fundamental knowledge concerning carbon metabolism and its regulation. We discuss whether fundamental biological research into metabolic processes at a holistic level, made possible by completed genome sequences and integrated with detailed structural understanding of biocatalysts, can change the chemical industry from being dependent on fossil-carbon feedstocks to using biorenewable feedstocks. We illustrate this potential by discussing the prospect of building a platform technology based upon a concept of combinatorial biosynthesis, which would explore the enzymological flexibilities of polyketide biosynthesis. [source] The early history of 32P as a radioactive tracer in biochemical research: A personal memoirBIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION, Issue 3 2005Howard Gest The concept of using radioactive isotopes as "tracers" of chemical conversions was conceived and developed by inorganic chemist Georg de Hevesy (Nobel Laureate in Chemistry 1943). In 1935, he began to apply the technique to various biological processes using 32P, and his experiments revealed the dynamic character of physiology and metabolism. Following de Hevesy's lead, Samuel Ruben (University of California, Berkeley) exploited 32P in 1937,38 for investigation of phospholipid metabolism. Between 1937 and 1940, Ruben and colleague Martin Kamen spearheaded tracer studies in various biological systems using 32P, short-lived 11C, and other radioactive isotopes. During this period, Kamen was responsible for cyclotron-produced radioactive tracers and was able to sustain de Hevesy's research by supplying him with 32P. In 1940, Ruben and Kamen discovered long-lived 14C, which later proved to be a very powerful tool for analysis of complex biochemical processes, such as the path of carbon in photosynthesis. Between 1946 and 1950, 32P was used in studies of bacteriophage replication and photosynthetic metabolism. This memoir surveys the history of these early investigations. [source] New Templating Strategies with Salen Scaffolds (Salen=N,N,-Bis(salicylidene)ethylenediamine Dianion)CHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2008Arjan Abstract Templated approaches towards selective organic synthesis is a common feature in nature in which nucleic acid templated synthesis plays a crucial role in various fundamental biological processes. The key feature that allows control over the amazing selectivity found in natural processes is evidently the effective molarity of the reaction partners that is mediated by the macromolecular templation event. An ongoing challenge within many chemical sciences is to exploit similar templating principles and make use of synthetic systems that are designed for specific chemical conversions. Here, we describe the recent developments that involve (metallo)salen scaffolds that are used for diverse templating events (salen=N,N,-bis(salicylidene)ethylenediamine dianion). [source] Cover Picture: Sequential Nucleation and Growth of Complex Nanostructured Films (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 3 2006Mater. Abstract A sequential nucleation and growth process has been developed to construct complex nanostructured films step-by-step from aqueous solutions, as reported by Liu, Voigt, and co-workers on p.,335. This method can be applied to a wide range of materials, and can be combined with top,down techniques to create spatially resolved micropatterns. The cover figure shows images of oriented nanowires, nanoneedles, nanotubes, nanoplates and stacked columns, wagon-wheels, hierarchical films based on wagon-wheels, hierarchically ordered mesophase silicate, and micropatterned flower-like structures. Nanostructured films with controlled architectures are desirable for many applications in optics, electronics, biology, medicine, and energy/chemical conversions. Low-temperature, aqueous chemical routes have been widely investigated for the synthesis of continuous films, and arrays of oriented nanorods and nanotubes. More recently, aqueous-phase routes have been used to produce films composed of more complex crystal structures. In this paper, we discuss recent progress in the synthesis of complex nanostructures through sequential nucleation and growth processes. We first review the use of multistage, seeded-growth methods to synthesize a wide range of nanostructures, including oriented nanowires, nanotubes, and nanoneedles, as well as laminated films, columns, and multilayer heterostructures. We then describe more recent work on the application of sequential nucleation and growth to the systematic assembly of large arrays of hierarchical, complex, oriented, and ordered crystal architectures. The multistage aqueous chemical route is shown to be applicable to several technologically important materials, and therefore may play a key role in advancing complex nanomaterials into applications. [source] | |||||||||||||