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Various N (various + n)
Selected AbstractsChemInform Abstract: Synthesis of 4-(N,N-Dimethylaminomethylene)-2-alkyl-2-oxazolin-5-ones via Vilsmeier Haack Reagent and Their Reactions with Various N- and O-Nucleophiles.CHEMINFORM, Issue 19 2001Ram S. Singh Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Phosphorus and nitrogen in a monomictic freshwater lake: employing cyanobacterial bioreporters to gain new insights into nutrient bioavailabilityFRESHWATER BIOLOGY, Issue 6 2010OSNAT GILLOR Summary 1. It is an uncontested paradigm that an adequate supply of the macronutrients nitrogen (N) and phosphorus (P) is critical for maintaining phytoplankton primary production in aquatic ecosystems; it has also been suggested that there is an optimal total N : total P ratio for this globally significant process. 2. This ratio, normally assessed by chemical determination of the major dissolved N and P species, poses a dilemma: do chemical measurements actually reflect the bioavailable fraction of these nutrient pools? Accurate determination of the various N and P species and their fluxes into phytoplankton cells is notoriously difficult. 3. To provide a possible solution to this difficulty, we engineered strains of the cyanobacterium Synechococcus sp. strain PCC 7942 that ,report' on N and P bioavailability via a bioluminescent signal. These strains were used to quantify, for the first time, bioavailable concentrations of these essential macronutrients in a freshwater lake. 4. Only a small fraction (0.01,1%) of the chemically determined P may actually be bioavailable to this unicellular cyanobacterium and, by inference, to the phytoplankton community in general. In contrast, bioavailable N comprises most of the dissolved N pool. Consequently, bioavailable N : P ratios based on these assays are higher then those based on chemical determinations, indicating that P limitation in Lake Kinneret is more extensive then previously thought. [source] Alkylzinc-Mediated Addition of Alkynes to N -Tosylaldimines: Enantioselective Synthesis of (E)-(2-En-3-ynyl)-aminesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009Chao Yin Abstract An alkylzinc-mediated simple and efficient procedure for the catalytic enantioselective synthesis of N- tosyl-(E)-(2-en-3-ynyl)-amines has been developed. The method works well with various N -tosylaldimines and alkynes. [source] A fluorescence study on swelling of hydrogels (PAAm) at various cross-linker contentsADVANCES IN POLYMER TECHNOLOGY, Issue 4 2009Demet Kaya Akta Abstract Disk-shaped acrylamide (AAm) gels were prepared from AAm with various N,N,-methylenebisacrylamide (Bis) contents as cross-linker in the presence of ammonium persulfate as an initiator by free-radical cross-linking copolymerization in water. Polyacrylamide (PAAm) gels were dried before using for swelling experiments. Steady-state fluorescence spectrometer was employed during the swelling of PAAm hydrogels in water. Pyranine was introduced as a fluorescence probe. Fluorescence intensity of pyranine from various Bis content gel samples was measured during in situ swelling process. It was observed that fluorescence intensity decreased as swelling has proceeded. Gravimetric and volumetric experiments were also performed. The Li,Tanaka equation was used to determine the swelling time constants, ,c, and cooperative diffusion coefficients, Dc, from intensity, weight, and volume variations during the swelling processes. It was observed that swelling time constants, ,c, increased and diffusion coefficients, Dc, decreased as the cross-linker content was increased. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 28:215,223, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20163 [source] Synthesis and antimicrobial activity of 2-substituted-2,3-dihydro-5-propoxy-1H -1,3,2-benzodiazaphosphole 2-OxidesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2001M. Venugopal Several 2-alkylcarbamato/thiocarbamato/aryloxy/trichloromethyl-2,3-dihydro-5-propoxy-1H -1,3,2-benzodiazaphosphole 2-oxides (4 and 6) were synthesised by reacting 4-propoxy- o -phenylenediamine (1) with various N -dichlorophosphinyl carbamates (3), aryl phosphorodichloridates (5a-f) and trichloromethyl phosphonic dichloride (5g) in the presence of triethylamine at 45-65 °C. Their ir, 1H, 13C, 31P nmr and mass spectral data are discussed. The compounds were screened for antifungal activity against Curvularia lunata and Aspergillus niger and for antibacterial activity against Bacillus subtilis and Escherichia coli. Most of these compounds exhibited moderate activity in the assays. [source] Extended application of a chiral stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid to the resolution of N -(substituted benzoyl)-,-amino acid amidesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10 2006Guanghui Tan Abstract A chiral stationary phase (CSP 1) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was applied to the resolution of N -(substituted benzoyl)-,-amino acid amides and esters. N -(Substituted benzoyl)-,-amino acid amides were well resolved using a mixture of acetic acid-triethylamine-acetonitrile (0.01 : 0.05 : 100, v/v/v) as an optimum mobile phase while N -(substituted benzoyl)-,-amino acid esters were not resolved at all. In contrast, both N -(substituted benzoyl)-,-amino acid amides and esters were not resolved at all or resolved very poorly on another CSP (CSP 2), which lacks the two N,H hydrogens of the amide tethers of CSP 1. Among the substituents on the benzoyl group of analytes, the nitro group was the best for good resolution of analytes on CSP 1. From these results, the two N,H hydrogens of the amide tethers of CSP 1, the carbonyl oxygen of the amide group of analytes, and the nitro group on the benzoyl group of analytes were concluded to play significant roles in chiral recognition. In addition, various N -(3,5-dinitrobenzoyl)leucine amides with different lengths of N -alkylamide chains were resolved on CSP 1 and N -(3,5-dinitrobenzoyl)leucine N -propylamide was found to show the best chiral recognition in terms of the separation (, = 1.30) and the resolution factor (RS = 3.17). [source] PdII -Catalyzed Asymmetric Addition Reactions of 1,3-Dicarbonyl Compounds: Mannich-Type Reactions with N -Boc Imines and Three-Component AminomethylationCHEMISTRY - AN ASIAN JOURNAL, Issue 8-9 2008Yoshitaka Hamashima Dr. Abstract This paper describes catalytic asymmetric Mannich-type reactions of ,-ketoesters and malonates using chiral palladium complexes. Although readily enolizable, carbonyl compounds are attractive substrates, the use of such compounds as nucleophiles in Mannich-type reactions has not been extensively investigated. In the presence of chiral Pd aqua complexes (2.5,mol,%), ,-ketoesters reacted with various N -Boc imines (Boc=tert -butoxycarbonyl) to afford the desired ,-aminocarbonyl compounds in good yield with high to excellent stereoselectivity (up to 96:4 d.r., 95,99,%,ee in most cases). In these reactions, construction of highly crowded vicinal quaternary and tertiary carbon centers was achieved in one step. A chiral Pd enolate is considered to be the key intermediate. To elucidate the stereoselectivity observed in the reaction, possible transition-state models are discussed, taking into account steric and stereoelectronic effects. Furthermore, this catalytic system was applied to the Mannich-type reaction of malonates with N -Boc imine as well as one-pot classical aminomethylation of ,-ketoesters using benzylamine salt and formalin. The reactions proceeded smoothly, and the corresponding Mannich products were obtained in high yield with moderate to good enantioselectivity. [source] Synthesis, spectral properties and application of novel disazo disperse dyes derived from polyester wasteCOLORATION TECHNOLOGY, Issue 2 2010V S Palekar Terephthalic dihydrazide was obtained through aminolytic depolymerisation of polyester bottle waste by using hydrazine hydrate. It was further reacted with 4-aminobenzoic acid in the presence of polyphosphoric acid to obtain a cyclic compound, 4,4,-[5,5,-(1,4)-phenylene)bis(1,3,4-oxadiazole-5,2-diyl)dianiline, having a heterocyclic moiety. Diazotisation of this compound followed by coupling with various N,N -disubstituted anilines afford a series of novel disazo disperse dyes. The structures of these synthesised dyes were confirmed by elemental analysis and Fourier Transform,infrared, proton nuclear magnetic resonance and mass spectroscopy. Ultraviolet,visible spectra of these azo dyes in different polar solvents showed considerable variation in the wavelength of maximum absorbance (,max). Application of these dyes on polyester and nylon fabrics using high-temperature dyeing methods gave brilliant yellowish red hues with fair to moderate light fastness and very good to excellent wash fastness and sublimation fastness. [source] Properties of poly(AAc- co -HPMA- cl -EGDMA) hydrogel-bound lipase of Pseudomonas aeruginosa MTCC-4713 and its use in synthesis of methyl acrylateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Shamsher Singh Kanwar Abstract Microbial lipases (E.C. 3.1.1.3) are preferred biocatalysts for the synthesis of esters in organic solvents. Various extracellular thermoalkaliphilic lipases have been reported from Pseudomonas sp. In the present study, a purified alkaline thermoalkalophilic extracellular lipase of Pseudomonas aeruginosa MTCC-4713 was efficiently immobilized onto a synthetic poly(AAc- co -HPMA- cl -EGDMA) hydrogel by adsorption and the bound lipase was evaluated for its hydrolytic potential towards various p -nitrophenyl acyl esters varying in their C-chain lengths. The bound lipase showed optimal hydrolytic activity towards p -nitrophenyl palmitate (p -NPP) at pH 8.5 and temperature 45°C. The hydrolytic activity of the hydrogel-bound lipase was markedly enhanced by the presence of Hg2+, Fe3+, and NH salt ions in that order. The hydrogel-immobilized lipase (25 mg) was used to perform esterification in various n -alkane(s) that resulted in , 84.9 mM of methyl acrylate at 45°C in n -heptane under shaking (120 rpm) after 6 h, when methanol and acrylic acid were used in a ratio of 100 mM:100 mM, respectively. Addition of a molecular sieve (3Å × 1.5 mm) to the reaction system at a concentration of 100 mg/reaction vol (1 mL) resulted in a moderate enhancement in conversion of reactants into methyl acrylate (85.6 mM). During the repetitive esterification under optimum conditions, the hydrogel-bound lipase produced 71.3 mM of ester after 10th cycle of reuse. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 183,191, 2007 [source] | ||||||||||