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Lori A. Nock Judah M. Goldwasser Horst G. Adolph 《Journal of polymer science. Part A, Polymer chemistry》1991,29(8):1133-1149
Polyformals of fluoro-, nitramine-, and C-nitrodiols show widely differing properties with respect to glass transition temperature, melting transition, and solubility. Polymers with desirable combinations of these properties, e.g., low Tg, high nitro content, and good solubility in polar solvents, were expected to result from acid-promoted copolycondensation of appropriate mixtures of diols with formaldehyde. A series of such condensations were carried out and the polymers obtained from binary mixtures of fluoro- and nitrodiols, different nitrodiols, and fluoro- or nitrodiols and carboranediols, were characterized by GPC, 1H-NMR, and DSC analysis. 相似文献
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The complexes CoH(PF3)4?n (PPh3)n (n = 1–3) have been prepared by low from the reaction between CoH(PF3)(PPh3)3 and butadiene. The hydrido complexes are active catalysts for the isomerisation of 1-octene to 2-octene under hydrogen or nitrogen. 相似文献
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Rh(π-C3H5)(PF3)3 (I), reacts with trifluoroacetic acid to form propene and [Rh(CF3COO)(PF3)2]2 (II). I reacts with t-butyl bromide to give [RhBr(PF3)2]2 and a mixture of propene and 2-methyl-1-propene and with n-propyl bromide to give propene and [RhBr(PF3)2]2. Rh(π-C3H5)(PPh3)2 (III), and t-butyl bromide yield propene and 2-methyl-1-propene. In these reactions a mechanism involving β-hydrogen abstraction and hydrogen migration via the metal to carbon is proposed. When III reacts with Me3SnCl the Me3Sn—moiety migrates intact to the π-allyl group. I reacts with acetyl chloride to give propene, [RhCl(PF3)2]2 and the carbonyl rhodium complex Rh2Cl2(PF3)3(CO). II does not apparently undergo phosphine ligand exchange unlike the analogous halogeno-bridged dimers. 相似文献
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R. WinterP.G. Nixon R.J. TerjesonJ. Mohtasham N.R. HolcombD.W. Grainger D. GrahamD.G. Castner G.L. Gard 《Journal of fluorine chemistry》2002,115(2):107-113
A new perfluorinated acrylate monomer containing the SF5(CF2)6-perfluorinated side chain was synthesized and polymerized into films. Bulk monomer characterization is consistent with the molecular structure based on FTIR, mass spectrometry and NMR analyses. The surface properties of polymer coatings were studied with aqueous wetting (contact angle) and X-ray photoelectron spectroscopy (XPS) methods. The surface composition is shown to be highly enriched in the terminal side chain SF5-chemistry and exhibits properties consistent with a highly apolar, non-wetting perfluorinated polymer surface. Depth-dependent XPS studies using angular-resolved methods (ADXPS) confirmed a non-stoichiometric enrichment of sulfur and fluorine at the film ambient interface, consistent with a surface presence of the terminal SF5-group and possibly film structural anisotropy in the surface zone. Time-of-flight (TOF) secondary ion mass spectrometry (SIMS) analysis supplements the XPS data by showing the presence of all expected SF5-acrylate chemistry components in the outer 15 Å of the film surface. 相似文献
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Emmanuelle A. BugnetTracy D. Nixon Colin A. KilnerRobert Greatrex Terence P. Kee 《Tetrahedron letters》2003,44(29):5491-5494
Molecular clips derived from 2,4,6,8-tetraazabicyclo[3.3.1]nonane-3,7-dione promote increased regioselectivity in the SO2Cl2-mediated electrophilic aromatic chlorination of ortho-cresol leading to para/ortho ratios (Rp/o) <25; approximately six times larger than in the absence of the clip. Specific recognition events involving hydrogen-bond, π-π and dative covalent interactions are implicated. 相似文献
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Cellulose synthesis in maize: isolation and expression analysis of the cellulose synthase (CesA) gene family 总被引:7,自引:0,他引:7
Laura Appenzeller Monika Doblin Roberto Barreiro Haiyin Wang Xiaomu Niu Krishna Kollipara Lori Carrigan Dwight Tomes Mike Chapman Kanwarpal S. Dhugga 《Cellulose (London, England)》2004,11(3-4):287-299
Stalk lodging in maize results in significant yield losses. We have determined that cellulose per unit length of the stalk is the primary determinant of internodal strength. An increase in cellulose concentration in the wall might allow simultaneous improvements in stalk strength and harvest index. Cellulose formation in plants can be perturbed by mutations in the genes involved in cellulose synthesis, post-synthetic cellulose alteration or deposition, N-glycosylation, and some other genes with as yet unknown functions. We have isolated 12 members of the cellulose synthase (CesA) gene family from maize. The genes involved in primary wall formation appear to have duplicated relatively independently in dicots and monocots. The deduced amino acid sequences of three of the maize genes, ZmCesA10–12, cluster with the Arabidopsis CesA sequences that have been shown to be involved in secondary wall formation. Based on their expression patterns across multiple tissues, these three genes appear to be coordinately expressed. The remaining genes show overlapping expression to varying degrees with ZmCesA1, 7, and 8 forming one group, ZmCesA3 and 5 a second group, and ZmCesA2 and 6 exhibiting independent expression of any other gene. This suggests that the varying levels of coexpression may just be incidental except in the case of ZmCesA10–12, which may interact with each other to form a functional enzyme complex. Isolation of the expressed CesA genes from maize and their association with primary or secondary wall formation has made it possible to test their respective roles in cellulose synthesis through mutational genetics or transgenic approaches. This information would be useful in improving stalk strength. 相似文献
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