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21.
Lidia Jasinska Cor E. Koning 《Journal of polymer science. Part A, Polymer chemistry》2010,48(24):5907-5915
A new experimental approach for preparing biobased, water‐soluble polyesters (PEs) via titanium(IV) n‐butoxide‐catalyzed bulk polycondensation is presented. In the described method polymers were obtained from isosorbide, maleic anhydride and poly(ethylene glycol) (PEG). The chemical structure of the synthesized PEs was confirmed using 2D NMR spectroscopy and by titration methods. Careful analysis of 2D NMR spectra viz. correlation spectra (COSY), heteronuclear single quantum correlation spectra (HSQC) and heteronuclear multiple‐bond correlation spectra (HMBC) allowed to accomplish the complete proton assignment of isosorbide, PEG, and unsaturated acid residues in the PEs. Moreover, by using NMR spectroscopy the transformation of maleic anhydride into fumaric acid ester and the absence of maleic acid ester units in the final polymer were proven. However, during polycondensation part of the unsaturated bonds has reacted in a Michael addition with isosorbide or PEG. Gel permeation chromatography measurements revealed that the unsaturated PEs have Mn values in the range 3000–5000 g/mol. These PEs, with a low content of carboxylic acid end groups, exhibited sufficient thermal resistance for practical applications, for example, as free radical curable coatings. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
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Lidia Angeleri-Hü gel Jan Trlifaj 《Transactions of the American Mathematical Society》2002,354(11):4345-4358
Let be a right noetherian ring and let be the class of all finitely presented modules of finite projective dimension. We prove that findim iff there is an (infinitely generated) tilting module such that pd and . If is an artin algebra, then can be taken to be finitely generated iff is contravariantly finite. We also obtain a sufficient condition for validity of the First Finitistic Dimension Conjecture that extends the well-known result of Huisgen-Zimmermann and Smalø.
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The novel alkyl N-methyl-N-polystyreneamino-2-isocyanoacrylate was used for the synthesis of 1-substituted imidazole-4-carboxylates utilizing a "catch and release" methodology. The reactions were performed under microwave irradiation, affording the title compounds in both high yields and chemical purity directly to solution, from the solid phase support. 相似文献
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The cyclization of the A-B rings of squalene to hopene is studied computationally (DFT). A transition structure is found for a concerted, asynchronous pathway for the formation of chair-chair decalin carbocation. The computationally derived conformer leading to this asynchronous transition structure is remarkably similar to the analogous region of 2-azasqualene encapsulated by squalene-hopene cyclase recently reported by Schulz. A concerted A-B ring closure is likely to occur in the cyclization of squalene to hopene. [structure--see text] 相似文献
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The effectiveness of electrochemical reactors for industrial wastewater treatment has been improved since three-dimensional electrodes have been introduced; in fact, limitations of mass transfer can arise, due to the low concentrations of pollutants which may be involved in the process. Three-dimensional electrodes offer a very high electrode area per unit electrode volume and they can act as turbulence promoters or give rise to high linear electrolyte velocity, resulting in high values of mass transport coefficient. However, careful selection of operative parameters is needed in order to obtain high performance. This paper examines the results obtained in our laboratory on the cathodic reduction of copper at RVC electrodes; in particular the interference of dissolved oxygen is studied during the removal of copper from extremely diluted solutions (C < 10 ppm). Some results are also discussed on the removal of organic pollutants by electrochemical oxidation at three-dimensional anode consisting of a fixed bed of carbon pellets. 相似文献
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Konstantinova LS Rakitin OA Rees CW Souvorova LI Golovanov DG Lyssenko KA 《Organic letters》2003,5(11):1939-1942
[reaction: see text] In a remarkable cascade reaction, triethylamine is converted into the thienopentathiepin 2a and the heptathiocane 3a by a preequilibrated solution of disulfur dichloride and DABCO in chloroform. 相似文献
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Discussion of theg-factor value of fullerene is based on the model of itinerant electrons restricted to the surface of the fullerene molecule C60. The Ag shift, i.e., the difference between the experimentalg-factor and theg-factor of free electron Δg = g ? 2.0023 for C 60 ?1 is negative as for a very small metallic conducting particle.g-factor value is proportional to the interaction between itinerant electrons in the conduction band, thus the Δg is negative for C 60 ?1 and C 60 ?3 having less than half filled conduction band, while Δg is positive for C 60 + where the conduction band is almost filled. 相似文献
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