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Nitrogen Compounds (nitrogen + compound)
Selected AbstractsChemInform Abstract: Ruthenium Catalyzed Oxidation of Tertiary Nitrogen Compounds with Molecular Oxygen: An Easy Access to N-Oxides under Mild Conditions.CHEMINFORM, Issue 37 2002Suman L. Jain 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] Joint theoretical and experimental study of the gas-phase elimination kinetics of tert -butyl ester of carbamic, N, N -dimethylcarbamic, N -hydroxycarbamic acids and 1-(tert -butoxycarbonyl)-imidazoleJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2007Jose R Mora Abstract The gas-phase elimination kinetics of the title compounds were carried out in a static reaction system and seasoned with allyl bromide. The working temperature and pressure ranges were 200,280,°C and 22,201.5,Torr, respectively. The reactions are homogeneous, unimolecular, and follow a first-order rate law. These substrates produce isobutene and corresponding carbamic acid in the rate-determining step. The unstable carbamic acid intermediate rapidly decarboxylates through a four-membered cyclic transition state (TS) to give the corresponding organic nitrogen compound. The temperature dependence of the rate coefficients is expressed by the following Arrhenius equations: for tert -butyl carbamate logk1 (s,1),=,(13.02,±,0.46),,,(161.6,±,4.7) kJ/mol(2.303,RT),1, for tert -butyl N -hydroxycarbamate logk1 (s,1),=,(12.52,±,0.11),,,(147.8,±,1.1) kJ/mol(2.303,RT),1, and for 1-(tert -butoxycarbonyl)-imidazole logk1 (s,1),= (11.63,±,0.21),(134.9,±,2.0) kJ/mol(2.303,RT),1. Theoretical studies of these elimination were performed at Mřller,Plesset MP2/6-31G and DFT B3LYP/6-31G(d), B3LYP/6-31G(d,p) levels of theory. The calculated bond orders, NBO charges, and synchronicity (Sy) indicate that these reactions are concerted, slightly asynchronous, and proceed through a six-membered cyclic TS type. Results for estimated kinetic and thermodynamic parameters are discussed in terms of the proposed reaction mechanism and TS structure. Copyright © 2007 John Wiley & Sons, Ltd. [source] Simultaneous Determination of Quinoline and Pyridine Compounds in Gasoline and Diesel by Differential Pulse VoltammetryELECTROANALYSIS, Issue 6 2007Leonardo Abstract The presence of trace basic organonitrogen compounds such as quinoline and pyridine in derivative petroleum fuels plays an important role in maintaining the engines of vehicles. However, these substances can contaminate the environment and so must be controlled because most of them are potentially carcinogenic and mutagenic. For these reasons, a reliable and sensitive method was developed for the determination of basic nitrogen compounds in fuel samples such as gasoline and diesel. This method utilizes preconcentration on an ion,exchange resin (Amberlyte IR,120,H) followed by differential pulse voltammetry (DPV) on a glassy carbon electrode. The electrochemical behavior of quinoline and pyridine as studied by cyclic voltammetry (CV) suggests that their reduction occurs via a reversible electron transfer followed by an irreversible chemical reaction. Very well resolved diffusion-controlled voltammetric peaks were obtained in dimethylformamide (DMF) with tetrabutylammonium tetrafluoroborate (TBAF4 0.1,mol L,1) for quinoline (,1.95,V) and pyridine (,2.52,V) vs. Ag|AgCl|KClsat reference electrode. The proposed DPV method displayed a good linear response from 0.10 to 300,mg L,1 and a limit of detection (LOD) of 5.05 and 0.25,,g L,1 for quinoline and pyridine, respectively. Using the method of standard additions, the simultaneous determination of quinoline and pyridine in gasoline samples yielded 25.0±0.3 and 33.0±0.7,mg L,1 and in diesel samples yielded 80.3±0.2 and 131±0.4,mg L,1, respectively. Spike recoveries were 94.4±0.3% and 101±0.5% for quinoline and pyridine, respectively, in the fuel determinations. This proposed method was also compared with UV-vis spectrophotometric measurements. Results obtained for the two methods agreed well based on F and t student's tests. [source] New concepts of microbial treatment processes for the nitrogen removal in wastewaterFEMS MICROBIOLOGY REVIEWS, Issue 4 2003Ingo Schmidt Abstract Many countries strive to reduce the emissions of nitrogen compounds (ammonia, nitrate, NOx) to the surface waters and the atmosphere. Since mainstream domestic wastewater treatment systems are usually already overloaded with ammonia, a dedicated nitrogen removal from concentrated secondary or industrial wastewaters is often more cost-effective than the disposal of such wastes to domestic wastewater treatment. The cost-effectiveness of separate treatment has increased dramatically in the past few years, since several processes for the biological removal of ammonia from concentrated waste streams have become available. Here, we review those processes that make use of new concepts in microbiology: partial nitrification, nitrifier denitrification and anaerobic ammonia oxidation (the anammox process). These processes target the removal of ammonia from gases, and ammonium-bicarbonate from concentrated wastewaters (i.e. sludge liquor and landfill leachate). The review addresses the microbiology, its consequences for their application, the current status regarding application, and the future developments. [source] Autotrophic nitrification and denitrification characteristics of an upflow biological aerated filterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2001Dong-Woo Han Abstract Wastewater nitrification was carried out using a laboratory-scale upflow biological aerated filter (BAF) packed with a polyurethane-based porous medium. The filtration medium has macro-pores which provide a greater surface area for the development of biofilms. The macro-pores have both aerobic and anaerobic zones, depending on the depth of oxygen penetration in the medium. Wastewater ammonium was oxidized at a maximum rate of 1.8,kg NH4+m,3d,1 and showed more than 90% nitrification efficiency in the BAF. During the biological nitrification of wastewater, considerable nitrogen loss was observed in the BAF under oxygen-limited conditions when organic carbons were not provided for denitrification. Most probably, the lost nitrogen was converted to gaseous nitrogen compounds including dinitrogen by autotrophic dentrification and anaerobic ammonium oxidation. © 2001 Society of Chemical Industry [source] Nutritional factors determining sclerotial formation of Polyporus umbellatusLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2009Y.-Y. Liu Abstract Aims:, To find out which nutritional condition is the determining factor for sclerotial formation of Polyporus umbellatus. Methods and Results:, The nutritional requirements of 15 carbohydrates, ten nitrogen compounds, eight vitamins and eight mineral elements were studied for their effects on mycelial growth and sclerotial formation of Polyporus umbellatus using the one-factor-at-a-time method. Only fructose could induce sclerotial formation of P.,umbellatus. An additional test indicated that nitrogen source categories influenced sclerotial formation significantly and that peptone was found to be the best for sclerotial production. Through an orthogonal matrix test, the effects of carbon/nitrogen factors on sclerotial formation were found be in the order: fructose > interaction between fructose and peptone > peptone. The optimal concentration for sclerotial formation was determined to be 50·0 g l,1 fructose and 4·0 g l,1 peptone. Conclusions:, Carbon source is the factor determining sclerotial formation of Polyporus umbellatus. Nitrogen source can influence such a morphological transformation significantly. The categories of vitamin and mineral element do not have relationship with the sclerotial formation. Significance and Impact of the Study:, This study provides the preparatory knowledge for the completely artificial culture of Polyporus umbellatus for its sclerotium. [source] Nitrogen-assimilating enzymes in land plants and algae: phylogenic and physiological perspectivesPHYSIOLOGIA PLANTARUM, Issue 1 2002Ritsuko Inokuchi An important biochemical feature of autotrophs, land plants and algae, is their incorporation of inorganic nitrogen, nitrate and ammonium, into the carbon skeleton. Nitrate and ammonium are converted into glutamine and glutamate to produce organic nitrogen compounds, for example proteins and nucleic acids. Ammonium is not only a preferred nitrogen source but also a key metabolite, situated at the junction between carbon metabolism and nitrogen assimilation, because nitrogen compounds can choose an alternative pathway according to the stages of their growth and environmental conditions. The enzymes involved in the reactions are nitrate reductase (EC 1.6.6.1-2), nitrite reductase (EC 1.7.7.1), glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 1.4.1.13-14, 1.4.7.1), glutamate dehydrogenase (EC 1.4.1.2-4), aspartate aminotransferase (EC 2.6.1.1), asparagine synthase (EC 6.3.5.4), and phosphoenolpyruvate carboxylase (EC 4.1.1.31). Many of these enzymes exist in multiple forms in different subcellular compartments within different organs and tissues, and play sometimes overlapping and sometimes distinctive roles. Here, we summarize the biochemical characteristics and the physiological roles of these enzymes. We also analyse the molecular evolution of glutamine synthetase, glutamate synthase and glutamate dehydrogenase, and discuss the evolutionary relationships of these three enzymes. [source] A 15N-aided artificial atmosphere gas flow technique for online determination of soil N2 release using the zeolite Köstrolith SX6®RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2006Oliver Spott N2 is one of the major gaseous nitrogen compounds released by soils due to N-transformation processes. Since it is also the major constituent of the earth's atmosphere (78.08% vol.), the determination of soil N2 release is still one of the main methodological challenges with respect to a complete evaluation of the gaseous N-loss of soils. Commonly used approaches are based either on a C2H2 inhibition technique, an artificial atmosphere or a 15N-tracer technique, and are designed either as closed systems (non-steady state) or gas flow systems (steady state). The intention of this work has been to upgrade the current gas flow technique using an artificial atmosphere for a 15N-aided determination of the soil N2 release simultaneously with N2O. A 15N-aided artificial atmosphere gas flow approach has been developed, which allows a simultaneous online determination of N2 as well as N2O fluxes from an open soil system (steady state). Fluxes of both gases can be determined continuously over long incubation periods and with high sampling frequency. The N2 selective molecular sieve Köstrolith SX6® was tested successfully for the first time for dinitrogen collection. The presented paper mainly focuses on N2 flux determination. For validation purposes soil aggregates of a Haplic Phaeozem were incubated under aerobic (21 and 6 vol.% O2) and anaerobic conditions. Significant amounts of N2 were released only during anaerobic incubation (0.4 and 640.2,pmol N2 h,1,g,1 dry soil). However, some N2 formation also occurred during aerobic incubation. It was also found that, during ongoing denitrification, introduced [NO3], will be more strongly delivered to microorganisms than the original soil [NO3],. Copyright © 2006 John Wiley & Sons, Ltd. [source] Derivatisation for liquid chromatography/electrospray mass spectrometry: synthesis of pyridinium compounds and their amine and carboxylic acid derivativesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2003Samantha J. Barry A simple method has been developed for the pre-column derivatisation of low molecular weight primary and secondary amines and carboxylic acids using quaternary nitrogen compounds to enhance their detection by liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS). The synthesis of seven novel quaternary nitrogen reagents is described. The derivatives are designed to be relatively small molecules to avoid some of the steric hindrance problems that may be associated with larger derivatisation reagents. The compounds have amine and carboxylic acid functional groups with which to derivatise carboxylic acids and amines, respectively. Two of the compounds contain a bromine atom in order to assess the advantages of a bromine isotope pattern in the mass spectra. This acts as a simple marker for derivatisation and enables data processing by cluster analysis. Activation of the carboxylic acid group was achieved by the use of either 1-chloro-4-methylpyridinium iodide (CMPI) or the more reactive 1-fluoro-4-methylpyridinium p -toluenesulphonate (FMP).1 Using both of these active reagents, the degree of nucleophilic substitution was investigated for the derivatisation of a variety of small molecules. Whilst giving some increase in the ESI-MS response for the derivatised compounds, the FMP itself acted as a derivatising reagent in a competing reaction. In the light of this finding, FMP was reacted with the test compounds separately and gave positive results as a derivatising reagent. Detection of the ,pre-charged' derivatives of amines and carboxylic acids by LC/ESI-MS was investigated with respect to their ESI response and chromatography. Copyright © 2003 John Wiley & Sons, Ltd. [source] Structural investigations of phosphorus,nitrogen compounds.ACTA CRYSTALLOGRAPHICA SECTION B, Issue 3-2 2002A systematic study is presented on the products of aminolysis of N3P3Cl6 (1) and N3P3Ph2Cl4 (4) with dibenzylamine. Two series of mono- and disubstituted derivatives of compounds (1) and (4), namely N3P3Cl5[N(CH2Ph)2] (2) and N3P3Cl4[N(CH2Ph)2]2 (3) and N3P3Ph2Cl3[N(CH2Ph)2] (5) and N3P3Ph2Cl2[N(CH2Ph)2]2 (6) [where (2), (3), (5) and (6) are new structures], are investigated in order to determine whether steric or electronic effects prevail in the formation of dibenzylamino-substituted cyclophosphazenes. The influence of an electron-releasing group (i.e. phenyl) on the stereochemistry and degree of substitution of the product is analysed by comparison of the above two series. The difference in unsymmetrically substituted endocyclic P,N bond lengths, ,, is used as a measure of the degree of the electronic contribution, in combination with basicity constants, to quantify the degree of the electron-releasing capacity of the R group. In order to compare geminal versus non-geminal substitution, a difunctional secondary amine was used to form the compound N3P3Cl4[NMe(CH2)3NMe] (7) (a reinvestigation) for inclusion in this study. It is shown that electron-releasing groups have a greater effect on the lengthening of P,Cl bonds as opposed to endocyclic P,N bonds and that this effect is greater in the non-geminal PRCl case than for geminal PCl2. However, steric effects are shown to be dominant in the reactions of dibenzylamine with N3P3 derivatives, with a disposition to a trans stereochemistry in bisdibenzylamino derivatives. [source] Characteristics of Oil Sources from the Chepaizi Swell, Junggar Basin, ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2010LIU Luofu Abstract: So far there has been no common opinion on oil source of the Chepaizi swell in the Junggar Basin. Therefore, it is difficult to determine the pathway system and trend of hydrocarbon migration, and this resulted in difficulties in study of oil-gas accumulation patterns. In this paper, study of nitrogen compounds distribution in oils from Chepaizi was carried out in order to classify source rocks of oils stored in different reservoirs in the study area. Then, migration characteristics of oils from the same source were investigated by using nitrogen compounds parameters. The results of nitrogen compounds in a group of oil/oil sand samples from the same source indicate that the oils trapped in the Chepaizi swell experienced an obvious vertical migration. With increasing migration distance, amounts and indices of carbazoles have a regular changing pattern (in a fine linear relationship). By using nitrogen compounds techniques, the analyzed oil/oil sand samples of Chepaizi can be classified into two groups. One is the samples stored in reservoir beds of the Cretaceous and Tertiary, and these oils came from mainly Jurassic source rock with a small amount of Cretaceous rock; the other is those stored in the Jurassic, Permian and Carboniferous beds, and they originated from the Permian source. In addition, a sample of oil from an upper Jurassic reservoir (Well Ka 6), which was generated from Jurassic coal source rock, has a totally different nitrogen compound distribution from those of the above-mentioned two groups of samples, which were generated from mudstone sources. Because of influence from fractionation of oil migration, amounts and ratios of nitrogen compounds with different structures and polarities change regularly with increasing migrating distance, and as a result the samples with the same source follow a good linear relationship in content and ratio, while the oil samples of different sources have obviously different nitrogen compound distribution owing to different organic matter types of their source rocks. These conclusions of oil source study are identical with those obtained by other geochemical bio-markers. Therefore, nitrogen compounds are of great significance in oil type classification and oil/source correlation. [source] Studies on the Volatile Compounds of Roasted Spotted ShrimpCHEMISTRY & BIODIVERSITY, Issue 12 2004Toru Tachihara The aroma of spotted shrimp (Sergia lucence Hansen) was analyzed upon roasting to determine the components that constitute the characteristic roasted shrimp flavor. Our analyses resulted in the identification of ca.,200 volatiles, including high-impact sulfur and nitrogen compounds. In addition, we synthesized all possible stereoisomers of the pyrrolidine derivatives 1 and 4, and of the imine derivatives 16 and 18,20, which are very characteristic for the aroma. The odor evaluation of these chemicals revealed distinct differences, each possessing different aroma characteristics. [source] | |||||||||||||