2H QUOSY 2D-NMR Experiments in Weakly Aligning Systems: From the Conventional to the Ultrafast Approach

We describe three anisotropic ultrafast (UF) QUadrupolar Ordered SpectroscopY (QUOSY) 2D-NMR experiments (referred to as ADUF 2D NMR spectroscopy) designed for recording the ²H homonuclear 2D spectra of weakly aligned (deuterated) solutes in sub-second experiment times. These new ADUF 2D experiments derive from the Q-COSY, Q-resolved and Q-DQ 2D pulse sequences (J. Am. Chem. Soc. 1999 , 121, 5249) and allow the correlation between the two components of each quadrupolar doublet, and then their assignment on the basis of ²H chemical shifts. The UF 2D pulse sequences are analyzed by using the Cartesian spin-operator formalism for spin I=1 nuclei with a small quadrupolar moment. The optimal experimental/practical conditions as well as the resolution, sensitivity and quantification issues of these ADUF 2D experiments are discussed on comparison to their conventional 2D counterparts and their analytical potentialities. Illustrative ADUF 2D experiments using deuterated achiral/prochiral/chiral solutes in poly-γ-benzyl-L-glutamate based chiral liquid crystals are presented, as well as the first examples of natural abundance deuterium (ANADUF) 2D spectrum using 14.1 T magnetic field and a basic gradient unit (53 G.cm⁻¹) in oriented solvents.     

二维核磁共振波谱和分子力学方法计算香茶菜醛溶液中的三维空间结构

采用二维核磁共振波谱完全归属了天然有机化合物香茶菜醛的~1H和~(13)C NMR化学位移,测定了部分质子的偶合常数,并用孤立自旋对近似方法定量处理香茶菜醛的相敏NOESY谱,根据1/r_(ij)~8∝A_(ij)计算出相应的质子间距离.其溶液中的三维空间结构采用以NMR结构参数为初始数据的WUPH计算程序和分子力学能量优化(MM2)完成计算.计算结果表明,得到的香茶菜醛在溶液中的三维空间结构反映了该化合物在溶液中的真实空间结构.     

Investigation of microstructure of glycidyl methacrylate/α-methyl styrene copolymers by 1D- and 2D-NMR spectroscopy

The copolymers of glycidyl methacrylate/α-methyl styrene were synthesized. The quantitative ¹³C{¹H}-NMR spectroscopy was used to determine the copolymer compositions. The distortionless enhancement by polarization transfer, ¹³C-¹H heteronuclear single quantum coherence and total correlation spectroscopy were used for the complete spectral assignment of ¹³C{¹H}- and ¹H-NMR spectra.     

烯丙基卤在五价钼体系引发丁二烯聚合反应中的链转移作用

本工作以烯丙基卤(x)为链转移剂,在非极性加氢汽油溶剂中,用MoCl_3(i-OC_5H_(11))_2—(i-Bu)_2AlO (Mo-Al)二元引发体系引发丁二烯(Bd)进行溶液聚合,探讨x对Bd聚合速度、聚合物分子量以及聚合活化能的影响,并测得了x的链转移常数。实验结果表明,烯丙基溴(Br)对聚合速度的影响甚微,烯丙基氯(Cl)和烯丙基碘(Ⅰ)却能导致聚合速度减慢;随x用量增加,分子量明显降低;在Br存在下,按Arrhenuis方程式求得的Bd聚合表现活化能为63.6千焦/摩尔,略高于不添加Br时的值。     

甲基丙烯酸羟丙酯催化链转移聚合及其催化剂链转移常数的变化

采用COBF[bis(aqua)bis((difluoroboryl)dimethylglyoximato)cobalt(II)为催化剂,AIBN为引发剂,60℃下进行甲基丙烯酸β-羟丙酯的催化链转移自由基本体聚合,得到了端基含有双键的低分子量聚合物.分别用Mayo方程法和链长分布(CLD)方程法测算反应过程中催化剂的链转移常数,发现随着反应的进行,催化剂的链转移能力逐渐下降,表观链转移常数Csapp从反应初期的2000左右下降到600左右.这主要是由于反应初期形成了部分比较稳定的碳钴键,导致Csapp在一开始迅速下降,然后趋于缓慢;反应至中后期,由于粘度效应,表观链转移常数进一步降低到300以下.研究进一步发现,由CLD方程法所得的表观链转移常数值普遍低于由Mayo方程法所得的值,且高转化率时误差更大.这是因为GPC测得的是累积产物的分子量分布,对于中、高转化率情况,有必要将其转化为瞬时产物的值.由于累积产物的数均聚合度转化为瞬时产物的数均聚合度相对容易,因而Mayo方程法较适合于测算中、高转化率时的表观链转移常数.     

2D-NMR of natural products,part V Structure elucidation and complete1H- and13C-assignment of resin acid derivatives

Application of 2D-NMR-techniques including heteronuclear 2D-J-resolved spectroscopy and¹H-¹³C-2 D-shift correlation is used to assign the¹H- and¹³C-resonances of resin acid derivatives.

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2D-NMR von Naturprodukten, 5. Mitt.: Strukturaufklärung und komplette ^1H-und ^13C-Zuordnung von Harzsäure-Derivaten

Zusammenfassung 2D-NMR-Methoden (2D-J-resolved-Spektren,¹H-¹³C-Shiftkorrelations-spektren) erlauben die Zuordnung der¹H- und¹³C-Signale von Harzsäurederivaten.

     

双甘肽稀土配合物溶液结构的~(13)C~1H NMR研究

关于双甘肽的~(13)C化学位移行为及其与稀土离子的配位作用前人有过报导。但有关水溶液中双甘肽稀土配合物的结构仍不清楚。本文测定了在重稀土离子Dy~(3+)、Ho~(3+)、Er~(3+)、Tm~(3+)和Yb~(3+)作用下双甘肽~(13)C和~1H的顺磁诱导位移,研究了水溶液中双甘肽稀土配合物的组成及结构。1 实验部分     

THEORETICAL STUDY OF CHAIN MICROSTRUCTURE OF COPOLYMERS IN ANIONIC COPOLYMERIZATION WITH CONSTANT MONOMER RATIO

In this work, the sequence distribution of copolymers generated in anionic copolymeriza-tion with a constant comonomer ratio has been theoretically investigated by means of non-steady state kinetic technique. The microstructural parameters of the copolymer, such as se-quence distribution functions, the average length of sequence and mole fractions of dyads andtriads, are derived by rigorously solving the kinetic differential equations. Furthermore, theseparameters are connected with reaction time and initial conditions and therefore become pre-dictable.     

溶胶凝胶法固定反应试剂流动注射化学发光法测定H2O2

采用溶胶凝胶技术对Luminol-Co(1)-H     

~1H和~(19)F NMR研究镍系催化丁二烯聚合中醇类对BF_3·OEt_2的增溶作用

<正> 在镍系催化丁二烯聚合中,助催化剂BF_3·OEt_2在加氢汽油中溶解性差,往往形成非均相体系,因而降低了催化剂体系的稳定性和氟的利用率。我们曾研究了A1(i-Bu)_3分别与丙醇、丁醇、戊醇,己醇、辛醇、壬醇、癸醇和十六醇按等摩尔交换,制得A1(i-Bu)_2OR作助催化剂,观察Al/B与催化活性的关系,发现以十六醇为最好,Al/B在0.25—0.95聚合活性较高,超出此限活性迅速下降。为了进一步提高Al/B,采用了向镍催化体系添加醇的方法。聚合实验证实了该法可提高氟的利用率。测定醇-硼体系的~1HNMR,证实了醇-硼分子间形成了氟-氢氢键。     

H_2O-CHCl_3-CCl_4体系中水行为的~1H NMR研究

我们以四氯化碳为稀释剂,用~1H NMR研究了水分子及其聚合物与氯仿的氢键作用.实验用氯仿.四氯化碳以及四甲基硅烷(TMS)均为北京化工厂分析纯试剂,其中氯仿经纯化后,取用60℃馏份.测试用亚沸蒸馏水.溶液在配好后平衡24小时,以TMS为内标,在日本电子FX-90Q NMR仪上测化学位移.溶液的水浓度用三菱CA-05型测水仪测定,精度为1％,实验温度24±℃.     

咪唑与单线态氧(~1O_2)1,2-环加成反应的理论研究

采用较新的半经验分子轨道方法Austin Model 1(简称AM1方法),辅以Berny梯度优化方法,对单线态氧(~1O_2)与咪唑的1,2-环加成反应,进行了理论研究。计算获得实验尚未检测到的4,5-二氧环丁烷(4,5-dioxetane)的结构,并在反应势能面上找到单重态双自由基中间体及通过该中间体的两步反应的过渡态。通过对过渡态的结构特征、虚振动方向以及对反应过程的电荷分布情况、轨道相互作用等的分析,说明该反应是经由单重态双自由基中间体的分步反应。两步反应的活化势垒分别为39.2kJ·mol~(-1)和150.5kJ·mol~(-1)。     

Site-specifically cleavage of oxidized insulin B chain with Zn（Ⅱ） ion studied by electrospray ionization mass spectrometry

The electrospray ionization mass spectrometry and tandem mass spectrometry investigation showed that the binding sites of Zn^2＋ with oxidized insulin B chain are His 5, His 10, and Arg 22, which lead to the selective cleavages of the peptide bonds at Ash 3- Gin 4, His 5-Leu 6, Gly 8-Ser 9, and Glu 21-Arg 22 of oxidized insulin B chain.     

DMF-H_2O缔合体系的~1HNMR研究

DMF水溶液是一种生物分子水溶液的简单生化模型。测量了DMF-H_2O体系不同 温度下全浓度范围的~1H NMR数据，对体系中的缔合情况进行了讨论，基于H_2O, H_2O·DMF, (H_2O)_2和(DMF)_2·H_2O的缔合平衡建立了化学缔合模型，采用最 小二乘法拟合实验数据，联合遗传算法和Levenberg-Marquardt算法对模型参数进 行全局寻优求解得不同温度的缔合平衡常数K，再根据不同温度的K求得缔合平衡的 ΔH和ΔS。为了更好地理解DMF水溶液中分子间的相互作用，还测量了298 K下DMF- CCl_4和DMF-BuOH体系全浓度范围的~1H NMR数据作为比较，结合NMR的基本原理对 各DMF溶液体系~1H NMR的实验现象进行了分析和解释，认为水溶液的特殊结构、氢 键和DMF酰胺基的共轭体系是影响DMF-H_2O体系~1H NMR的主要因素。     

二维核磁共振法研究线型聚乙二醇与树枝状聚苄醚形成的三嵌段共聚物

嵌段共聚物是由几个不同的高分子链段通过化学键相连所构成的 .在合成方法上一般是通过几类不同的活性聚合 ,调控单体的加料次序或者通过不同的大分子链段末端的反应活性点偶联而成[1～ 3 ] .所形成的化学键将嵌段共聚物中不相溶的几段相连 ,于是在特定的条件下就产生了微相分离的现象 ,继而可以在 1 0～ 1 0 0nm尺度范围内形成各种各样的微区结构[4,5] .在过去的几十年里 ,研究的重点是认定嵌段共聚物的微区结构和研究微相分离的动力学 ,已发表了大量重要的结果 ,至今仍然是高分子科学中的热门课题 .非常重要的一点是 ,正是由于不同的高分…     

Quantum chemistry study on B32 and B32H2–32

The structures of B32 and B₃₂H^2–₃₂ with I_h symmetry have been investigated by means of ab initio calculations at STO-3G level. The relationship between molecular orbitals of them has been analyzed and their bonding properties have been discussed. Then the possibility of their existence, as well as the similarity and difference between B₃₂ (B₃₂H^2–₃₂) and C₆₀ (C₆₀H₆₀) have been inferred.     

THE 31P NMR SPECTRA OF ISOMERIC DIAMINOHEXA-CHLOROCYCLOTETRAPHOSPHAZATETRAENES; EXAMPLES OF A2B2 AND AA'BB' SPIN SYSTEMS

Abstract

The ³¹P nmr spectra of 2,4- and 2,6-diamino-derivatives of octachlorocyclotetraphosphazatetraene, N₄P₄Cl₆(NR¹R²)₂ (R¹ = H, R² = Bu^t; R¹ = H, R² = CH₂Ph; R¹ = Me, R² = Ph), have been measured. The 2,4- and 2,6-isomers were analysed as AA'BB' and A₂B₂ spin systems respectively. In the 2,4-isomers the spin-spin couplings ²J(PNP) and ⁴J(PNPNP) were of opposite sign.     

Site-specifically Hydrolytic Cleavage of Oxidized Insulin B Chain With Cu(II) Ion

Selectively chemical cleavage of peptides and proteins is one of the most important reactions in both chemical and biochemical processes. Over the past decade, the interaction of palladium(II) complexes with methionine, cysteine and histidine-containing peptides and proteins and the hydrolytic cleavage of the corresponding amide bond by Pd(II) complexes have been extensively studied1-13. However, reports concerning the directly selective hydrolysis of peptides and proteins with other simple …