醛酮类化合物的~(13)C核磁共振波谱模拟

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

~(13)C核磁共振波谱模拟的研究

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。

几种典型固体聚合物体系的~（13）C自旋－晶格弛豫特性

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

谷胱甘肽与稀土离子作用的~(13)C NMR研究

本文利用顺磁稀土离子的诱导化学位移变化的性质,研究了多官能团配体谷胱甘肽(GSH)与稀土的配位作用.在水溶液中GSH通过分子两端的羧基负离子与稀土形成遥爪配位结构.谷氨酸端和甘氨酸端羧基与Eu~(3+)的配位稳定常数分别为12.5±0.1L/mol和100.0±0.5L/mol.从~(13)C化学位移的pH变化曲线求得谷氨酸端和甘氨酸端羧基解离的pK_a值分别为2.20±0.02和3.50±0.04.对Dy~(3+)、Ho~(3+)、Er~(3+)、Tm~(3+)和 Yb~(3+)作用下,GSH的~(13)C位移数据分析表明,配体与这些离子形成同构的配合物,分子两端羧基均可能以双齿形式与稀土配位.

水溶液中稀土离子与甘氨酸、丝氨酸、天冬氨酸作用的~(13)C NMR研究

测定了酸性水溶液中甘氨酸、丝氨酸和天冬氨酸稀土络合物(Ln=La、Pr、Nd、Eu、Tb、Dy、Ho、Er、Tm和Yb)的~(13)C诱导位移。对位移试剂的分析指出,三种氨基酸通过α-羧基以双齿形式配位于稀土,配位键长为0.23nm～0.25nm,天冬氨酸的y-羧基也是配位基团。由本文与文献中已报道的各种氨基酸稀土络合物的~(13)C诱导位移的系统分析表明,配体~(13)C超精细偶合常数A值和结构因子G值有如下规律:(1)│A(C_0)│<│A(C_α)│;A(C_0)为正,A(C_α)为负;(2)│G(C_0)│>│G(C_α)│;配体碳核的G均为负值。

高分辨~(13)C NMR在聚合物辐射化学中的应用

综述了高分辨~(13)C核磁共振谱(~(13)C NMR)在聚合物辐射化学研究中的应用。重点介绍了用固体高分辨~(13)C NMR研究聚合物辐射交联结构途径和应用范围。

光活性聚甲基丙烯酸三苯甲酯链结构的研究——PTrMA的~(13)C液体和固体NMR谱

80年代出现的光活性高聚物—聚甲基丙烯酸三苯甲酯(PTrMA)是由非手性单体经不对称阴离子聚合得到的。近年来,PTrMA作为手性固定相在分离手性化合物方面得到了越来越多的实际应用。由于聚合物侧基上的三个苯基产生的大位阻,使它具

用~(13)C-NMR法研究酚酞/双酚T型聚芳醚砜的序列结构

利用~(13)C核磁共振法研究了酚酞/双酚T型聚芳醚砜共聚物((PP/Bis-T)PES)的序列结构,分析了将双酚T单元引入酚酞型聚芳醚砜(PES-C)聚合物分子中对其酚酞单元的核磁共振谱的影响,并证实了(PP/BiS-T)PES属于无规共聚物。

青藏高原东部高寒草甸植物δ~(13)C年间变化及其环境分析

植物有机体稳定碳同位素组成受植物生长期间气候环境因子的影响,包含了大量的环境信息。要真正理解植物体同位素组成所包含的环境信息首先要研究植物体同位素组成与环境之间的关系。文章通过分析2002年和2003年青藏高原东部青海省门源县境内隶属于19科41属51种植物叶片的δ~(13)C值,研究高寒草甸植物稳定碳同位素组成的年间变化及其与环境因子的关系,分析影响δ~(13)C值变化的关键因子。结果表明,所测植物的δ~(13)C值分布在一个很小的范围-29.2‰～-24.9‰之间,平均值为-26.9‰,说明所测植物的光合作用均通过C3途径实现,这可能与该研究区较低温度有关。研究发现一年生植物δ~(13)C值明显低于多年生植物,而且一年生和多年生植物δ~(13)C值之间的差异在2002年（t=-3.031,P〈0.01）和2003年（t=-3.567,P〈0.001）均能达到显著性水平,表明多年生植物水分利用效率显著高于一年生植物,能更好的适应该地区寒冷干燥的低温环境。两年间植物δ~(13)C值有明显不同,2003年显著低于2002年（t=6.786,P〈0.001）。通过分析两年间环境因子的变化认为植物叶片δ~(13)C值的年间变化主要是由于降水的变化引起的,随降雨量的增加而降低。不同植物种δ~(13)C值年间变化差别很大,反应了植物对环境变化的不同响应。在植被恢复中应选用植物δ~(13)C值随环境变化存在较大差异的物种,因为此类物种能够采取不同的对策适应该地区环境的变化。

吉林金川西大甸子泥炭沉积中火山物质的发现及其意义附：泥炭中胡敏酸的稳定碳同位素值（δ<'13>C）作为古气候代用指标可行性研究

泥炭以发育广泛、连续沉积好、沉积速率大（可达1mm/a甚至更大）、记录丰富等特点,正成为过去全球变化研究的良好综合地质档案.参考冰芯、黄土、深海沉积物等中矿物固体的研究思路和方法,希望能对泥炭中可能存在的火山物质和其它风粉尘进行研究.在对吉林金川西大甸子泥炭样品的处理过程中,摸索出一套泥炭样品中固体物质（如火山物质）初步的处理、分析方法;并对金川西大甸子干玛珥泥炭沉积中部一段泥砂状物质进行鉴定,首次发现火山玻璃,判断这些泥砂物为火山灰砂.目前研究表明,泥炭纤维素的δ<'13>C序列能较好地反映古气候变化,那么泥炭中胡敏酸的δ<'13>C序列可否也能反映古气候变化,该文对此作了初步研究.用碱溶酸沉淀方法从泥炭中提取出所谓的胡敏酸,用燃烧法将胡敏酸、纤维素中的碳转化为CO<,2>气体,测定它们的稳定碳同位素组成（δ<'13>C）.与能较好地反映气候变化的纤维素δ<'13>C序列相比,胡敏酸的δ<'13>C序列反映气候变化不明显.

Structure of pentacyclo[7.4.2.02,6.06,15.011,14]pentadec-4-ene-7,13-dione, a novel pentacyclic C15 quinane system

C 15H 1602 (a synthetic precursor to dodecahedrane), monoclinic, P21/n, a = 12.171 (5), b = 6.976(5), c = 13.868 (3) A, B = 102.56 (3) ° , Z = 4, D m = 1.30, D c = 1.318 g cm -3, F(000) = 488, g(Mo K¢t) = 0.92 cm- 1. Intensity data were collected on a Nonius CAD-4 diffractometer and the structure was solved by direct methods. Full-matrix least-squares refinement gave R = 0.077 (R w = 0.076) for 1337 observed reflections. All the five-membered rings are cis fused and have envelope (C s symmetry) conformations.

Peptide mimics for structural features in proteins. Crystal structures of three heptapeptide helices with a C-terminal 6-->1 hydrogen bond.

The crystal structure determination of three heptapeptides containing alpha-aminoisobutyryl (Aib) residues as a means of helix stabilization provides a high-resolution characterization of 6-->1 hydrogen-bonded conformations, reminiscent of helix-terminating structural features in proteins. The crystal parameters for the three peptides, Boc-Val-Aib-X-Aib-Ala-Aib-Y-OMe, where X and Y are Phe, Leu (I), Leu, Phe (II) and Leu, Leu (III) are: (I) space group P1, Z = 1, a = 9.903 A, b = 10.709 A, c = 11.969 A, alpha = 102.94 degrees, beta = 103.41 degrees, gamma = 92.72 degrees, R = 4.55%; (II) space group P21, Z = 2, a = 10.052 A, b = 17.653 A, c = 13.510 A, beta = 108.45 degrees, R = 4.49%; (III) space group P1, Z = 2 (two independent molecules IIIa and IIIb in the asymmetric unit), a = 10.833 A, b = 13.850 A, c = 16.928 A, alpha = 99.77 degrees, beta = 105.90 degrees, gamma = 90.64 degrees, R = 8.54%. In all cases the helices form 3(10)/alpha-helical (or 3(10)helical) structures, with helical columns formed by head-to-tail hydrogen bonding. The helices assemble in an all-parallel motif in crystals I and III and in an antiparallel motif in II. In the four crystallographically characterized molecules, I, II, IIIa and IIIb, Aib(6) adopts a left-handed helical (hL) conformation with positive phi, psi values, resulting in 6-->1 hydrogen-bond formation between Aib(2) CO and Leu(7)/Phe(7) NH groups. In addition a 4-->1 hydrogen bond is seen between Aib(3) CO and Aib(6) NH groups. This pattern of hydrogen bonding is often observed at the C-terminus of helices proteins, with the terminal pi-type turn being formed by four residues adopting the hRhRhRhL conformation.

Carbon-13 and proton relaxation study of backbone dynamics of poly(vinyl acetate) in solution

The dynamics of poly(vinyl acetate) in toluene solution has been examined by C-13 and proton relaxation. C-13 spin-lattice relaxation time and nuclear Overhauser enhancement measurements were carried out as a function of temperature at 50.3 and 100.6 MHz. The spin-lattice relaxation times for backbone protons were measured at different temperatures at 200 MHz. The relaxation data have been analyzed using the Hall-Weber-Helfand (HWH) model, which describes backbone dynamics in terms of conformational transitions and the Dejean-Laupretre-Monnerie (DLM) model, which includes bond librations in addition to conformational transitions. The parameters obtained from the analysis of C-13 relaxation data were utilized to predict the proton relaxation data. The DLM model was found to be more successful in reproducing the experimental results. To study the influence of libration further, proton relaxation data for poly(vinyl acetate) over a wider range of temperature reported in the literature were analyzed by these two models. The DLM model could reproduce the experimental data at all temperatures whereas the HWH model was found to be successful only in accounting for the experimental data at high temperatures. The results demonstrate the importance of including the librational mode in the description of the backbone dynamics in polymers.

Carbon-13 relaxation study of chain segmental motion and side-chain internal rotations of poly(isobutyl methacrylate) in solution

The dynamics of poly(isobutyl methacrylate) in toluene solution has been examined by C-13 spin-lattice relaxation time and NOE measurements as a function of temperature. The experiments were performed at 50.3 and 100.6 MHz. The backbone carbon relaxation data have been analyzed using the Dejean-Laupretre-Monnerie (DLM) model, which describes the dynamical processes in the backbone in terms of conformational transitions and bond librations. The relaxation data of the side chain nuclei have been analyzed by assuming different motional models, namely, unrestricted rotational diffusion, three site jumps, and restricted rotational diffusion. The different models have been compared for their ability to reproduce the experimental spin-lattice relaxation times and also to predict the behavior of NOE as a function of temperature. Conformational energy calculations have been carried out on a model compound by using the semiempirical quantum chemical method, AM1, and the results confirm the validity of the motional models used to describe the side-chain motion.

Preparation, Characterization And Properties Of C-60 And C-70 - Spectroscopy, Structure, Anions, Interaction With Electron-Donors And Superconductivity

Preparation and characterization of the fullerenes, C60 and C70, are described in detail, including the design of the generators fabricated locally. The characterization techniques employed are UV-visible, IR, Raman and C-13 NMR spectroscopies, scanning as well as transmission electron microscopy and mass spectrometry. The electron energy level diagram of C60 as well as the one-electron reductions of C60 and C70 leading to various anions are discussed. Electronic absorption spectra of C60- and C60(2-) are reported. Phase transitions from the plastic to the crystalline states of C60 and C70 are examined. Based on a C-13 NMR study in a mixture of nematic liquid crystals, it has been demonstrated that C60 retains its extraordinary symmetry in solution phase as well. Interaction of C60 and C70 with strong electron-donor molecules has been investigated employing cyclic voltammetry. Superconductivity of K(x)C60 has been studied by non-resonant microwave absorption; Na(x)C60 as well as K(c)C70 are shown to be non-superconducting. Doping C60 with iodine does not make it superconducting. Interaction of C60 with SbCl5 and liquid Br2 gives rise to halogenated products.