1000 resultados para 1995_12180120 LAPS-13
Resumo:
用人工神经网和多元回归方法对含2个碳的21个卤代化合物的35个化学位移进行计算机图谱模拟,结果表明,人工神经网络方法优于多元回归方法,同时此种方法处理这类问题有明显的优势。波谱模拟技术在有机化合物结构解析中是非常有用的方法。
Resumo:
合成了一系列结构为层状ABO3的复合氧化物La4BaCu5-xMxO13(M=Mn,Co),并利用XRD、X射线能谱、氧程序升温脱附和化学分析方法对它们的结构和活性氧种进行了研究。XRD分析结果表明:它们的结构为五层的ABO3结构。活性氧种的研究表明La4BaCu5O13中掺杂Mn或Co之后,样品中明显存在的MCu(M=Mn,Co)之间的协同作用,并且CuMn之间协同作用明显比CuCo的强。
Resumo:
Amorphous samples of polyether ketone with cardo(PEK-C) have been studied in the solution state by C-13, H-1 high-resolution NMR, The H-1 and C-13 1D NMR spectra were assigned using two dimensional chemical shift correlated spectroscopy, 2D homonuclear correlated(COSY) and heteronuclear correlated (HETCOR) spectroscopy present important information. In this work, the structural units of PEK-C was determined by NMR. For some peaks, these assignments are confirmed by two dimensional long-range heteronuclear correlation experiments, A little modification is made on the original C-13 peak assignments for the main chain, The symmetry and the isotacticity of the chain structure for PEK-C are obvious on NMR data.
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The aqueous complexation of lanthanide complexes of citrate in pH 7.4 solutions has been studied by using lanthanide-induced shift and relaxation times measurement methods. These results indicate that citrate coordinate via 3-hydroxyl and 3-carboxylate groups with lanthanide ions and form 1:2 (Ln/cit) isostructural complexes through lanthanide series. We suggest a new coordination geometry which is different from that described in literature.
Resumo:
Reverse phase high performance liquid chromatography (HPLC) was used to separate and quantify aromatic diester-diacids isomers which arise from the opening selectivity of anhydride rings towards methanol. C-13 NMR spectroscopy was a supplementary tool to characterize the isomer structure. It was found that a meta-position attack is slightly preferred in pyromellitic dianhydride (PMDA), while the preferred position of an attack in bridged dianhydrides is determined by the chemical nature (donors or accepters) of the bridged group. The stronger its electron-withdrawing abilities, the lower the probability of a meta-position attack.
Resumo:
近年来,随着计算机技术的发展,C-13 NMR技术取得巨大的进步,并获得了与日俱增的广泛应用。目前,已成为化学、化工、生物、医学等领域不可缺少的分析技术。C-13 NMR波谱模拟在有机化合物结构自动解析中起着极为重要的作用,它能帮助科学家们对复杂的化合物进行结构解析,并对测定的化合物的化学位移进行验证。本论文在该领域进行了很多有意义的尝试,工作的目的是采用多元统计方法为化合物的C-13 NMR波谱模拟建立相关数学模型,并取得了一些有意义的结果。主要工作如下:1. 对饱和烷烃类化合物进行了~(13)C NMR波谱模拟,通过使用校正的分子连接性指数和几何参数,取得了比较满意的结果,其结果比Crant和Paul的烷烃模拟要好。2. 对环烷烃类化合物进行了~(13)C NMR波谱模拟,得到了具有较好预测能力的相关数学模型。3. 对饱和醇类化合物进行了~(13)C NMR波谱模拟,通过提取共振碳的拓扑指数、电荷参数和几何参数,构造了比较满意的数学模型。4. 对脂肪胺类化合物进行了~(13)C NMR波谱模拟,通过使用拓扑指数、电荷参数和几何参数,获得了比较好的相关数学模型。5. 对饱和醛酮类化合物进行了~(13)C NMR波谱模拟,通过使用拓扑指数、电荷参数和几何参数,获得了比较好的相关数学模型。
Resumo:
用固体高分辨NMR系统地研究了几种典型的均聚物,共聚物,聚合物共混物以及用接枝共聚物增容的不相容聚合物共混体系的13C自旋-晶格弛豫特性。研究结果表明:13C自旋-晶格弛豫时间(T1(C))是表征固体聚合物体系的很有用参数,它能提供有关本体聚合物微观形态结构的信息,并可望建立聚合物的微观结构与宏观性能的关系,它不仅能准确无误地反映共混体系中可能存在的各种相互作用,而且能定性地给出相互作用的大小和准确地指明相互作用产生的位置,因而为揭示共混体系的相容机理提供了最直接的证据,另外T1(C)还能给出增容剂对不相容共混体系的增容作用和增容机制的直接实验证据
Resumo:
用稀土离子诱导位移和顺磁弛豫时间测定等NMR方法研究了稀土柠檬酸配合物在pH7.4的溶液中的配位结构.结果表明稀土离子通过3-羟基和3-羧基与柠檬酸配体形成1:2的配合物,两个端羧基没有参与配位.通过计算稀土离子和柠檬酸配体中各个碳原子间的空间距离的相对比,建立了稀土离子与柠檬酸配体配位的新模式.
Resumo:
茂锆载体催化剂下的乙烯/辛烯共聚及聚合物的~(13)CNMR研究刘胜生,于广谦,黄葆同(中国科学院长春应用化学研究所长春130022)关键词茂锆载体催化剂,共聚,序列分布,~(13)CNMR由于茂锆催化剂具有高活性,单一活性中心等特点[1,2],并且能...
Resumo:
TTHA complexes with diamagnetic rare earth ions (La3+, Y3+ and LU(3+)) were studied by H-1 and C-13 NMR spectroscopy. A symmetric structural model was suggested for La(TTHA) complex and an asymmetric model for Y(TTHA) and Lu(TTHA) complexes. The complex formation was dependent on the pH value of the solution. The interactions of La(TTHA) with the additional metal ions (La3+, Y3+ and Ca2+) were relatively weak, but relatively strong for that of Lu(TTHA) with the additional Lu3+.
A new topological index for the Changchun institute of applied chemistry C-13 NMR information system
Resumo:
A method to assign a single number representation for each atom (node) in a molecular graph, Atomic IDentification (AID) number, is proposed based on the counts of weighted paths terminated on that atom. Then, a new topological index, Molecular IDentification (MID) number is developed from AID. The MID is tested systematically, over half a million of structures are examined, and MID shows high discrimination for various structural isomers. Thus it can be used for documentation in the Changchun Institute of Chemistry C-13 NMR information system.
Resumo:
采用固相反应法合成了接Ce3+、Gd3+、Tb3+的CaLaB7O13,并测定了它们的光谱.在Ce3+的光谱中发现文献中尚未报导的317nm激发峰和293nm发射峰.293发射属于不常见的5d能带中次最低能级向基态的跃迁,并随着Ce3+离子浓度增加而变弱,当掺杂浓度大于0.1mol时,293nm发射峰消失.
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用电子自旋共振(ESR)和固体 ̄(13)CNMR研究了聚丙烯腈(PAN)在不同裂解温度(T_P)下的结构变化,当T_P从250℃增加到600℃,ESR信号线形没有变化,g值与T_P无关,ΔH_(PP)减小,自旋浓度(N_S)开始增加,T_P进一步升高,N_S又减少. ̄(13)CNMR谱指出在不同T_P下谱峰发生很大变化,与另文报道的红外及X-射经衍射结果一致,随T_P升高,PAN逐渐脱去小分子形成具有环化共轭结构的产物.
Resumo:
Ethylene-propene copolymers (EPR) were synthesized at different feed compositions using a highly active and isospecific MgCl2-supported Ti-based catalyst. The thermal behavior of EPR was studied by differential scanning calorimetry, the heterogeneity by f
Resumo:
HexafluorobisA polyethersulfone-cardo polyethersulfone, random and block copolymers with different segment lengths were synthesized by a reaction of 4,4'-(hexafluoroisopropylidene)diphenol and 3,3'-bis(4-hydroxyphenyl)-1-isobenzopyrrolidone with bis(4-chl