1000 resultados para 13-127A


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为饱和醛酮类化合物的1 3C核磁共振波谱模拟 .根据该类化合物的特点 ,提取了分子的拓扑特征 ,几何特征及电子特征 .应用变量最优子集回归法进行了变量的选择 ,并用这些变量构造了回归模型 .交叉验证的结果表明 ,所得数学模型比较稳定 ,并得到了较好的预测结果

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Prediction of C-13-nuclear magnetic resonance chemical shifts for aliphatic amines is performed. The topological, geological and electronic descriptors are generated. To reduce the variables, the best subsets of the descriptors are obtained by using leaps-and-bounds regression analysis. The model is achieved using multiple regression with satisfactory results.

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The characterization of free base porphyrin 2,3,7,8,12,13,17,18-octakis(hexyl-thio) tetraazaporphyrin (H(2)OHTTAP) and its zinc(II) complexes [Zn(II)OHTTAP] containing eight thioether groups at the beta -pyrrole positions of the macrocycle was reported. Results obtained by cyclic voltammetry and differential pulse voltammetry indicated a five-electron reduction in five steps for each complex. They were oxidized in two single-electron-transfer steps to yield pi -cation radicals and dications and reduced in three single-electron-transfer steps to yield pi -anion radicals, dianions and trianions, respectively. The redox property of H(2)OHTTAP was unusual as compared to porphyrins (PPs) and phthalocyanines (Pcs). Each process was monitored by in situ thin-layer spectroelectrochemistry, which indicated that only the Ligand was electroactive. The existence of the eight hexylthio groups was responsible for the intrastack interactions and enhanced intracolumnar and intercolumnar electron motions, resulting in improved conductivity. Copyright (C) 2001 John Wiley & Sons, Ltd.

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对脂肪胺类化合物的1 3C核磁共振波谱进行了模拟 ,所用方法为数学模型法。为此 ,提取了共振碳原子所处化学环境的拓扑特征、几何特征及电子特征。运用变量最优子集回归法对变量进行了选择 ,用多元回归法构造了数学模型 ,得到了比较满意的预测结果。

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为了C-13NMR的自动解析,ESESOC系统从13CNMR本身的特征出发, 提出了不确定层数的子结构模型。即以共振碳原子为中心,以与之相连的完整的官能团为外围环境, 对这样的子结构, 其外围环境根据官能团的不同可以是一层、或二层乃至多层, 即环境层数是可变的。在此子结构模型的基础上, 从CIAC-13CNMR谱图数据库统计出13CNMR知识库。

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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。

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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MCu(M=Mn,Co)之间的协同作用,并且CuMn之间协同作用明显比CuCo的强。

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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.

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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.

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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。

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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

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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.

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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...

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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+.