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排序方式: 共有520条查询结果,搜索用时 4 毫秒
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2.
Edwige Jeanneau-Nicolle Claude Bosso Martine Benoit-Guyod Grard Leclerc 《Journal of mass spectrometry : JMS》1993,28(1):37-41
The electron impact mass spectra of two series of 5-oxo-tetrahydro-5H-thiazolo [3,2-a]pyrimidine-6-ethylcarboxylates and 7-oxo-tetrahydro-7H-thiazolo [3,2-a]pyrimidine-6-ethylcarboxylates were measured and fragmentation patterns examined. Structures were assigned from analysis of oxo molecular ion fragmentations. Compounds of the 5-oxo series gave an [M – CO2C2H5]+ fragmentation whereas compounds of the 7-oxo series gave three characteristic cleavages. This decomposition was confirmed for one pair of isomers by high-resolution mass spectrometry and unimolecular mass-analysed ion kinetic energy spectrometry. Electron impact mass spectrometry is a convenient method for assigning structures of 5- and 7-oxo regioisomers of tetrahydrothiazolo[3,2-a]pyrimidine-6-carboxylates. 相似文献
3.
Abdelhouad Oukhrib Laurence Bonnafoux Armen Panossian Sandrine Waifang Duc Hanh Nguyen Martine Urrutigoity Françoise Colobert Maryse Gouygou Frédéric R. Leroux 《Tetrahedron》2014
A new family of non-symmetrical disubstituted dibenzophospholes possessing different steric and electronic effects have been synthesized and characterized. Their preliminary evaluation in rhodium-catalyzed hydroformylation reactions is presented. 相似文献
4.
Jacques Bastide Eduardo Mendes Franois Bou Martine Buzier Peter Lindner 《Macromolecular Symposia》1990,40(1):81-99
In this paper, it is shown how a percolation process can be used to describe the inhomogeneities of polymer concentration, appearing in gels prepared by random crosslinking of a semi-dilute solution, and how they are modified by swelling or stretching of the network. Neutron scattering experimental data are compared to the predictions of this model in the isotropic and anisotropic cases. A good agreement is found. In particular, “abnormal” butterfly patterns in the iso-intensity curves have been detected, as expected from the model. 相似文献
5.
Shuang-Qi Tang An-Ping Wang Martine Schmitt Frédéric Bihel 《Tetrahedron letters》2018,59(15):1465-1468
Employing Triton X-100 as a surfactant, the tert-butyl hydroperoxide-mediated dioxygenation of styrene with molecular oxygen and N-hydroxyphthalimide was achieved in water at room temperature, providing the corresponding dioxygenated products in 9–93% yield. This facile method is eco-friendly, feasible on gram scale, and applicable to a wide range of styrene derivatives with a variety of functional groups. 相似文献
6.
Pierre Thuéry Martine Nierlich Jacques Vicens Bernardo Masci 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(1):70-71
The title compound, 7,13,21,27-tetra-tert-butyl-3,17-dioxapentacyclo[23.3.1.15,9.111,15.19,23]ditriaconta-1(29),5,7,9(30),11(31),12,14,19(32),20,22,25,27-dodecaene-29,30,31,32-tetraol, crystallizes as a solvate with one molecule of chloroform and one molecule of tetrahydrofuran, C46H60O6·CHCl3·C4H8O. The calixarene assumes a cone-like conformation stabilized by intramolecular hydrogen bonds involving both phenolic and ether O atoms. The two solvent molecules are located in each of the two half-cone cavities of the calixarene. 相似文献
7.
8.
Martine Tessier Ernest Marechal 《Journal of polymer science. Part A, Polymer chemistry》1989,27(2):539-553
Several di-, tri- or multiblock poly(isobutylene-b-amide-11)s are prepared by reaction of α-mono or α,ω-dianhydride oligoisobutylenes with α-mono or α,ω-diamino oligoamides, in o-dichorobenzene at 140°C. They are characterized mainly by 1H- and 13C-NMR spectroscopy and GPC, using the trifluoroacetylation technique. Their thermal differential chromatograms are reported and analyzed. 相似文献
9.
Philippe Mongondry Chantal Bonnans‐Plaisance Martine Jean Jean Franois Tassin 《Macromolecular rapid communications》2003,24(11):681-685
The hydroxyl end groups of poly(ethylene glycol) (PEG) have been transformed easily and quantitatively into amino groups via the Mitsunobu reaction. Phthalimide was alkylated with PEGs and the hydrazinolysis of the resulting phthalimido‐PEGs gave the amino compounds in high yields. Quaternization of the amino groups leads to hydrophilic polymer chains bearing a positive charge on one or two ends, depending on the chosen PEG. Such products can be used to protect sterically, negatively charged particles such as clays.
10.
Regert M 《Journal of separation science》2004,27(3):244-254
Although organic materials are very sensitive to biochemical alteration processes, they may be preserved for millennia in various archaeological contexts. Remains of adhesives made during prehistory were discovered at different sites, in the form of residues adhering to flint tools and ceramic vessels or as free lumps in sediment. To characterise the natural substances exploited for adhesive production during late prehistory, we undertook GC and GC/MS analysis of 90 samples from 8 sites dating from the Neolithic to Iron Age periods. This paper discusses our approach to the study of organic adhesives preserved in archaeological contexts, with a particular focus on the presentation of the various categories of organic adhesives that we analysed and the choice of chromatographic conditions adapted to the specificity of such samples. The results obtained show that birch bark tar, a triterpenoid adhesive made by destructive distillation of white birch bark, was predominantly used during the neolithic period even though other materials such as various barks or organic fossil substance were also used. During the Bronze and Iron ages, which follow the Neolithic period, adhesive production is evolving through the expansion of the range of the natural substances used (identification of diterpenoid pine resin) and the addition of beeswax as a plasticiser to birch bark tar. By combining chromatographic analysis and archaeological data, it was thus possible to follow the evolution of adhesive making at the end of prehistory, testifying to the inventiveness of the craftsmen whatever the period considered. 相似文献