共查询到20条相似文献,搜索用时 46 毫秒
1.
应用NMR技术、激光拉曼光谱和硅钼酸方法研究了碱性硅铝酸盐聚合反应中铝酸根离子和硅酸根离子的存在状态及其变化.发现聚合反应是低分子量硅铝酸根离子之间或低分子量硅铝酸根离子与低分子量硅酸根离子之间的反应. 相似文献
2.
研究了在聚乙烯醇存在下,硅、磷、砷杂多酸与罗丹明6G形成离子缔合物的反应,建立了能同时测定硅、磷、砷的卡尔曼滤波分光光度法。用于钢样中微量硅、磷、砷的同时测定,操作简便快速,相对误差小于8%。 相似文献
3.
用阳极腐蚀的方法制备了多孔硅样品,用电化学方法在多孔硅中注入Er3+、In3+等金属离子,并对注入离子后多孔硅的光致荧光光谱进行了研究,结果表明:注入Er3+及In3+后的多孔硅在588nm处的发光峰强度大大增加,同时发光峰稍有展宽。随着离子注入时间的增长,强度继续增加,但当离子溶液浓度一定时,这种增强对时间具有饱和性。 相似文献
4.
5.
6.
7.
毛禹平 《理化检验(化学分册)》2003,39(11):671-672
金属铜钴镍中微量硅的光度法分析 ,由于有色离子的干扰 ,现行的方法中 ,常用萃取方法分离硅[1,2 ] ,使得分析流程长 ;使用有机溶剂污染环境 ,对操作者健康不利。本文采用铁氰化钾 亚铁氰化钾沉淀分离大量铜钴镍等离子 ,让微量硅留于溶液中 ,利用小体积 硅钼蓝吸光光度法较好地解决了大量有色离子中微量硅的分离与测定。1 试验部分1.1 仪器与试剂72 1型分光光度计 (上海第三分析仪器厂 )沉淀剂 :称取铁氰化钾、亚铁氰化钾各 3.8g于2 5 0ml烧杯中 ,加水约 5 0ml,微热溶解后 ,移入10 0ml容量瓶中 ,用水稀释至刻度 ,混匀。硅标准溶液 :以高… 相似文献
8.
比较了铂,铑,钯的氯化物对乙炔和甲基二氯硅烷的气固相硅氢加成反应的催化活性;筛选了铂催化剂中的无机载体;研究了浸渍法和制备的铂催化剂的催化反应行为。结果表明,浸渍法制备的铂催化剂中存在两类稳定性不同的活性中心,铂离子是具有催化活性的组分,甲基二氯硅烷与铂离子间的氧化还原反应是导致催化剂 相似文献
9.
基于银镜反应,在动态下用稀氨水将银氨配离子还原为纳米银颗粒,并沉积在硅颗粒表面。与常用含银复合材料之银盐直接还原法和硝酸盐高温分解法相比,配位还原法具有制备工艺简单快速、银颗粒分散度高和银盐转化率高等特点。得到的硅/银复合材料中粒径小于20 nm的银颗粒均匀分布在硅颗粒表面,无其他杂质相。与纯硅粉负极相比,硅/银复合材料(含银10wt%)能有效抑制硅负极在循环初始阶段的容量快速衰减,30次循环可逆容量大于500 mAh·g-1。交流阻抗测试显示,纳米银颗粒的存在能显著提高电子电导,进而改善硅负极的循环稳定性。 相似文献
10.
11.
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
12.
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
13.
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
14.
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
15.
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
16.
Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
17.
The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
18.
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
19.
Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular SN2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively. 相似文献
20.
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