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1.
纤维素是地球上储量最丰富的生物可再生资源,具有价格低廉、易改性、可生物降解等特点.纤维素衍生化是拓展纤维素应用的重要手段之一.纤维素碳酸酯是重要的纤维素衍生物之一,在包装材料、热塑性材料、固体电解质等领域具有重要的应用潜力.本文基于1,8-二氮杂二环十一碳-7-烯(DBU)/二甲基亚砜(DMSO)/CO_2体系溶解活化纤维素,通过原位DBU的有机功能催化作用催化纤维素与碳酸二甲酯之间的转酯化反应,合成了纤维素甲基碳酸酯.结果表明,碳酸二甲酯与纤维素脱水葡萄糖单元(AGU)摩尔比为8:1,反应温度为60℃,反应时间为12 h时,可得到取代度(DS)1.09的纤维素碳酸酯,并通过核磁共振、红外光谱、热重分析(TGA/DSC)等表征方法研究纤维素碳酸酯结构与热性能的关系.DSC/TGA结果显示,当纤维素甲基碳酸酯的取代度为1.09时,其玻璃化转变温度为62.9℃,起始降解温度为305.5℃. 相似文献
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《中国科学:化学》2016,(12)
基于1,8-二氮杂二环十一碳-7-烯(DBU)存在下,纤维素与CO_2在二甲基亚砜(DMSO)中反应生成纤维素可逆聚离子液体反应的原理,实现纤维素溶解与活化,同时实现原位DBU催化棉浆纤维素与苯甲酸甲酯的转酯化反应,成功制备了不同取代度的纤维素苯甲酸酯.探索了不同反应时间、反应温度、苯甲酸甲酯与纤维素脱水葡萄糖单元(AGU)比例对纤维素取代度的影响,并对纤维素苯甲酸酯进行核磁共振氢谱、碳谱、红外光谱、差示扫描量热法(DSC)、热重分析(TGA)及X射线衍射(XRD)表征.结果表明,转酯化反应温度为115℃,苯甲酸甲酯与AGU比例为5:1,反应24 h时取代度最高能达到0.53.和纤维素相比,纤维素苯甲酸酯有明显的玻璃化转变温度,但其热稳定性下降. 相似文献
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新型液晶材料细菌纤维素苯甲酸酯的合成与表征 总被引:1,自引:0,他引:1
以细菌纤维素(BC)为原料,通过酯化反应制备了细菌纤维素苯甲酸酯(BBC).用红外(FT-IR)表征了产物结构,并且通过DSC、POM和WAXD研究了产物的热致液晶织构及其性能.从DSC和POM研究得知,细菌纤维素苯甲酸酯在281.7℃-356.3℃之间可以形成近晶型液晶相. 相似文献
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研究了涂敷量对双选择体手性固定相分离特性的影响。分别将纤维素-三(3,5-二甲基苯基氨基甲酸酯)与纤维素-三(4-甲基苯甲酸酯),直链淀粉-三(3,5-二甲基苯基氨基甲酸酯)与直链淀粉-三(4-甲基苯甲酸酯)进行共混,得到两种共混合物。以这两种共混合物为手性选择体,制备了涂覆量分别为17%及25%的四种手性固定相。评价了这些固定相的手性分离性能,结果表明:增加手性选择体的涂覆量,直链淀粉衍生物双选择体固定相的手性分离性能得到提高,而纤维素衍生物固定相的手性分离性能则稍有降低。较高涂覆量的纤维素衍生物固定相在含叔丁醇、异丁醇和正丁醇流动相中的保留因子依次减小,而其手性识别能力依次增强。 相似文献
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总结了近年来聚(β-羟基丁酸酯)、β-羟基丁酸酶—β-羟基戊酸酯共聚物与可生物降解高分子共混物的相容性、结晶性、热性能、加工性能、力学性能和生物降解性能。通过共混。聚(β-羟基丁酸酯)与—β-羟基丁酸酶卢羟基戊酸酯共聚物的性能得到显著改善。 相似文献
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以1,6-二溴己烷、氰基联苯酚和N-甲基咪唑为主要原料,合成含有咪唑基团的联苯类液晶(CbP)。以离子液体1-烯丙基-3-甲基咪唑氯盐(AMIM·Cl)为溶剂,将木浆纤维素(WPC)与CbP共混得到铸膜液,再通过浸渍沉淀相转化技术将铸膜液制成纤维素液晶膜(WPC/CbP)。采用哈克流变仪对溶液性能进行表征,用傅里叶红外光谱(FT-IR)、X-射线光电子能谱(XPS)、差示扫描量热(DSC)等对膜结构和性能进行表征。结果表明,CbP的引入改变了纤维素分子内及分子间的氢键作用,提高了纤维素膜的热稳定性。当CbP在铸膜液中的质量分数为3%时,溶液黏度最低。与纯纤维素膜相比,此WPC/CbP膜的拉伸强度提高了27.56%,紫外光透光率降低了35%左右。 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields. 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments. 相似文献
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The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields. 相似文献
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N. A. Nedolya 《Chemistry of Heterocyclic Compounds》2008,44(10):1165-1219
The review contains a concise historical account and information on the most significant researches undertaken by the staff
at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry
of Heterocyclic Compounds.
Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008. 相似文献
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A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL. 相似文献
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Regiospecific and direct imidation of the methyl C(sp3)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products. 相似文献
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A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions. 相似文献