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961.
The emission of NOx from coal-fired boilers can be limited by means of the selective catalytic reduction of NOx with ammonia. The amounts of unreacted ammonia downstream should be low to avoid processing and environmental problems. Continuous measurement of the ammonia in the flue gas is needed. The determination of ammonia and flue gas sampling techniques are discussed. Measurements of ammonia in exhausts of a laboratory reactor and of a pilot plant for the selective catalytic reduction of NOx with ammonia are presented. Ammonia was determined by mass spectrometry and chemiluminescence in the gas phase, and by spectrophotometric (Nessler and Berthollet reactions) or potentiometry in aqueous solution, in low (<5 μl l?1) and high (<1000 μl l?1) concentration ranges. 相似文献
962.
MNDO has been parametrized for bromine. Since d atomic orbitals (AOS) are not included, the calculations are restricted to BrI. Heats of formation, molecular geometries, ionization energies, and dioole moments are reproduced with useful accuracy. 相似文献
963.
P. Van Leuven 《International journal of quantum chemistry》1970,4(4):355-363
A method for the approximate calculation of matrix elements with respect to projected Hartree–Fock wave functions is proposed. The method is tested on some calculations in the many-parameter AMO method. It is found that the approximation reduces the amount of work, involved in the evaluation of the energy, by a factor of five and that it reproduces the exact values to within a few per cent. 相似文献
964.
The enantioselective synthesis of the potent, selective, cytotoxic, annonaceous acetogenin, (+)-gigantecin, has been completed. An asymmetric glycolate aldol serves to establish the stereocenters at C13,14 and at C21,22. A Carreira asymmetric acetylide addition is used to establish the C17 stereocenter. 相似文献
965.
A general method for determination of the stability constants of complexes of crown ethers and related compounds with small organic molecules in polar solvents is described, based on an indirect polarographic procedure. Computerized evaluation of the data forms an essential part of the procedure. 相似文献
966.
Michael J. Bunegar Roy Fields Robert N. Haszeldine 《Journal of fluorine chemistry》1980,15(6):497-509
Fluoroallene and 1, 3-difluoroallene are prepared in good overall yield by the addition of dichlorocarbene to vinyl fluoride and 1, 2-difluoroethylene respectively, followed by pyrolysis of the dichlorocyclopropanes and treatment of the resulting dichloropropenes with zinc. Pyrolysis of 1, 1-dichloro-2-fluorocyclopropane over zinc gives fluoroallene directly.The reaction of allene with 2, 2, 3-trifluoro-3-trifluoro- methyloxiran at 180°C as a source of difluorocarbene gives both 1, 1-difluoro-2-methylenecyclopropane and its rearrangement product 1-(difluoromethylene)cyclopropane, the latter reacting more readily with a second difluorocarbene to give 2, 2, 3, 3- tetrafluorospiropentane. In an analogous way, fluoroallene reacts with dichlorocarbene, generated from trifluoro(trichloromethyl) silane at 140°C, to give - and -1, 1-dichloro-2- (fluoromethylene)cyclopropane, 1-(dichloromethylene)-2-fluorocyclopropane, and 2, 2, 3, 3-tetrachloro-4-fluorospiropentane. 相似文献
967.
Lämmerhofer M 《Journal of chromatography. A》2005,1068(1):3-30
Enantiomer separations by CE employing nonaqueous conditions are reviewed. The general focus of this article is directed towards solvent effects on chiral recognition and the separation mechanism. After a general discussion of solvent effects on the individual processes involved in CE enantiomer separation, specifics for various selector classes are discussed together with a few applications of enantioselective nonaqueous CE. 相似文献
968.
[reaction: see text] N-Acylsulfonamides usually react with nucleophiles by acyl transfer and C-N bond fission. However, the hydrolysis of N-acyl beta-sultams is a sulfonyl transfer reaction that occurs with S-N fission and opening of the four-membered ring. Similar to other beta-sultams, the N-acyl derivatives are at least 10(6)-fold more reactive than N-acyl sulfonamides. 3-Oxo-beta-sultams are both beta-lactams and beta-sultams but also hydrolyze with preferential S-N bond fission. 相似文献
969.
Frederick MO Mulder JA Tracey MR Hsung RP Huang J Kurtz KC Shen L Douglas CJ 《Journal of the American Chemical Society》2003,125(9):2368-2369
A copper-catalyzed new C-N bond formation involving a sp-hybridized carbon is described here leading to a facile entry for syntheses of chiral ynamides. This direct N-alkynylation of amides should have a significant impact on the future development of synthetic methodologies employing ynamides. 相似文献
970.
A novel Ugi-five-centre-four-component reaction (U-5C-4CR) of aldehydes, primary amines, trimethylsilylazide and 2-isocyanoethyltosylate yielding tetrazolopiperazine building blocks is described. 相似文献