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961.
J.K. Terlouw W. Heerma P.C. Burgers G. Dijkstra A. Boon H.F. Kramer C.A. Salemink 《Tetrahedron》1974,30(23-24)
The mechanism of formation of the prominent C15H19O2 ion at m/e 231 in the mass spectra of Δ1(6)-tetrahydrocannabinol and five isomeric cannabinoids has been investigated. Except via a well-documented two step process, involving an RDA mechanism, a sizeable percentage of these ions is formed by a novel one-step route from the molecular ion. This was deduced from the spectra of deuterium-labelled compounds and measurements of the kinetic energy release of metastable ions. The latter value for the one step process varies from 25–44 meV for the six compounds investigated, attributed to two interdependent effects, different transition state geometries and common transition states differing in the time elapsing before their formation. 相似文献
962.
Kinetic studies of reactions of the MoMo bonded complex (h5-C5H5)2Mo2(CO)6 in decalin show that it undergoes reversible homolytic fission and that the activation enthalpy required to break the MoMo bond is 135.9 ± 2.2 kJ mol?1. 相似文献
963.
Chromatographia - A high-performance liquid chromatography (HPLC) method was developed for the purification of 50mg crude human chorionic gonadotropin (HCG) hormone sample in one chromatographic... 相似文献
964.
A New Synthetic Way to the Tetracyclic Skeleton of Cyclohepta (def)fluorene The synthesis of 2-Methyl-4, 5, 6, 8, 9, 10-hexahydrocyclohepta (def)fluorene 2 is described starting with the reduction of the ketone 3 by a (1:1)-mixture of LiAlH4/AlCl3 to the hydrocarbon 4 . After metallation with butyllithium 4 was allowed to react with bromoacetic acid to yield 5 . The cyclization of this compound was performed with p-toluenesulfonic acid to give the tetracyclic ketone 6 which was converted to the tetracyclic hydrocarbon 2 by reduction with LiAlH4/AlCl3. 相似文献
965.
Alfred Renner Andreas Kramer 《Journal of polymer science. Part A, Polymer chemistry》1989,27(4):1301-1323
Allyl-bicyclo-(2,2,1)hept-5-en-dicarboxylic(2,3)imides (allylnadic-imides) are prepared by heating equivalent amounts of allylnadic anhydride and amines. Mixtures of isomers (1-allyl-endo, 6-allyl-endo and exo) were obtained, separated by flash chromatography and identified by 1H- and 13C-NMR. A series of novel allylnadic-imide monomers is described. Upon heating to 250°C oligomers are obtained. Diels—Aider rearrangement and “ene” type addition reactions seem to play a major role in oligomer formation. Bis- and tris-allylnadic-imides are viscous liquids resins or low melting solids, which are soluble in common solvents. Upon heating to 250°C insoluble, high Tg solids are obtained with good thermooxidative and environmental stability and with reduced burning rate. Cured allylnadic-imide resins are excellent high temperature insulators and low permittivity dielectrics. Crosslinked copolymers with maleic-imides and epoxy resins are described. Neat resin and carbon fiber composite properties are reported. 相似文献
966.
C. T. Vijayakumar K. Lederer A. Kramer 《Journal of polymer science. Part A, Polymer chemistry》1989,27(8):2723-2748
The isomerization, polymerization, and degradation aspects of endo-N-phenylnadimide and endo-N-isobutylnadimide (NPNI-N and NIBNI-N) were investigated using infrared analysis (IR), differential thermal analysis (DTA), gel permeation chromatography (GPC), thermogravimetric analysis (TG), and capillary gas chromatography-mass spectroscopic (GC–MS) techniques. Although the endotherm related to the retro-Diels–Alder reaction is not registered in the DTA thermographs, on-line mass spectrometric studies revealed the occurrence of this process. The formation of the Diels–Alder adduct of cyclopentadiene with N-isobutylnadimide (NIBNI) during the polymerization of NIBNI-N is proved. GPC studies on NPNI-N and NIBNI-N cured at 300°C for 3.0 h showed the average degree of polymerization to be three to four. The polymers obtained by curing NPNI-N and NIBNI-N at 300°C for 3.0 h showed 109.8 kJ/mol as the activation energy for degradation. The dynamic and isothermal pyrolysis studies clearly indicated the presence of intact norbornyl units in the polymer, and the breakage of ? CH2? bridges in the strained norbornyl structural elements was found to be the point of aromatization during degradation. 相似文献
967.
968.
We evaluate theO(s) corrections to weak, charged current production of charm quarks. For perturbative subtractions and parton densities in the deep inelastic scheme the residual corrections to p and
charm production structure functionsF
2,F
3 andF
L are presented. The consequences of these corrections with respect to they dependence of the cross section is discussed.Supported by Bundesministerium für Forschung und Technologie. 05 5HH91P (8), Bonn, FRG 相似文献
969.
970.