Enzyme-catalyzed polymerization of 8-hydroxyquinoline-5-sulfonate by in situ nuclear magnetic resonance spectroscopy

In this report, we describe the use of in situ NMR spectroscopy to elucidate the mechanism of horseradish peroxidase-catalyzed oxidative free-radical coupling of phenols. We demonstrate the potential of the technique for the polymerization of 8-hydroxyquinoline-5-sulfonate (HQS). Based on the structural changes, we establish the involvement of ortho- and para-position protons (to the hydroxyl group) in the oxidative free-radical coupling polymerization with their relative preferences. For example, in HQS, we establish that the positions 2, 4, and 7 are involved in the chemical bonding with the order of preference being 7 ≥ 2 > 4. Analyses of ¹³C-NMR data suggest the formation of C—C- and C—O—C-type coupling bonds during enzymatic polymerization. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1257–1264, 1998     

Structure of initial and ultimate chain units of polydienes obtained with rare-earth catalysts as revealed by H nuclear magnetic resonance spectroscopy

The structure of initial and ultimate chain units in polybutadiene and polyisoprene was studied by means of ²H nuclear magnetic resonance spectroscopy. Polydienes were prepared with a neodymium catalyst; quenching was performed with deuteromethanol. The enrichment of quenched ultimate units by trans-1,4 structures at the expense of cis-1,4 structures at high polymer yields was observed. When using diisobutylaluminium deuteride DAl(i-Bu)₂, as chain transfer agent, it was shown that the principal site of chain transfer reaction was the Al-D bond. The initial unit of polybutadiene was predominantly of trans-1,4 structure.     

Structure of initial, ultimate and inner chain units of polybutadiene obtained with a rare-earth catalyst as revealed by C nuclear magnetic resonance spectroscopy

The structure of initial, ultimate and inner chain units in polybutadiene produced with NdCl₃. 3(i-PrOH)---HAl(i-Bu)₂was studied by means of ¹³C nuclear magnetic resonance spectroscopy. Initial units are shown to be predominantly of trans-CH₃CH=CHCH₂--- structure. Conversely, 90% of inner units have cis configuration. Ultimate units obtained by quenching with H₂O (D₂O) are predominantly of 1,2 structure. On the basis of the data obtained, the polymerization mechanism was discussed.     

红外和核磁共振法鉴定聚醚型聚酯的组成结构

利用红外吸收光谱及核磁共振波谱仪的一维和二维技术对一种未知聚合物试样进行鉴定。由核磁共振二维技术分析得出聚醚酯的序列结构及其分布。结果表明:该未知聚合物试样为聚醚酯弹性体,由对苯二甲酸、间苯二甲酸、新戊二醇、乙二醇、聚四氢呋喃醚共聚而成。     

Two-dimensional nuclear magnetic resonance of resins

A group of resins was synthesised from a series of phenols and aldehydes, and their structures comprehensively deduced from two-dimensional nuclear magnetic resonance spectroscopy (2-D NMR). Correlation spectroscopy, in particular carbon-proton heteronuclear chemical shift correlation spectroscopy, was shown to be especially incisive in assigning structural features to the NMR signals. The method has permitted fuller structural characterisation of these materials than was heretofore possible, and has identified, inter alia, methylene and methyleneoxy bridges unequivocally: complex substitution patterns in the phenol-derived aromatic rings have also been elucidated. It is demonstrably possible to apply the same techniques to similar complex resin structures, and to utilise these structural insights to determine the mechanistic processes involved in their syntheses.     

核磁共振法测定涤纶长丝含油率

采用核磁共振仪测试涤纶长丝含油率,初步探讨了其在生产过程中的应用。结果表明:与传统洗涤法相比,核磁共振法具有快速、简便、试样不需制备、不称重、不需溶剂的优点,且测试精密度和准确度高。     

定量核磁共振法研究进展

核磁共振法广泛应用于有机化合物的定性分析,但是它在化合物纯度定值、含量测定中也具有很重要的作用,分为一维谱(1H、13C、14N、15N、19F、31PNMR)、二维谱(J-分辨、1H-1H、1H-13C、DOSY)、液相色谱-核磁共振联用法(LC-NMR)、固体NMR等NMR类型。其中,1H谱最常用,其他一维谱对不同化合物各有其优势。二维核磁共振法对于在一维谱图中信号严重重叠的复杂样品的定量分析非常重要。LC-NMR联用技术将高效的分离手段与NMR联用,可以获得复杂样品的信息。介绍了各类定量核磁共振法在各领域的研究进展。     

定量核磁共振技术及其在环保型轮胎助剂开发中的应用进展

介绍了欧盟REACH法规对轮胎中多环芳烃(PAHs)含量的限制及所规定的定量核磁共振(QNMR)检测方法对我国合成橡胶工业的影响,综述了QNMR技术的特点、测定PAHs的原理及主要影响参数,提出了QNMR技术在环保轮胎助剂开发中的应用方向。     

共聚酯中间苯二甲酸含量的NMR测定

介绍了共聚酯中间苯二甲酸含量的测定方法之一———核磁共振法(NMR),表明对于间苯二甲酸含量较低的共聚酯,采用13C谱的测定结果较好。     

Investigations of polymer chains in oriented fluid phases with deuterium nuclear magnetic resonance

Deuterium nuclear magnetic resonance (D n.m.r.) is a potentially powerful technique for exploring molecular structural and dynamical properties of polymer chains in bulk fluids and concentrated solutions. A variety of systems can be investigated (the solid state, elastomeric networks, sheared polymer fluids, chain solutes in liquid crystal solvents, and polymeric liquid crystals), over a wide range of dimensions (local chain properties, rotational isomeric state parameters, behaviour between network junctions or entanglements, evolution of tube distributions, and domain sizes of homogeneous chain alignment). A coarse comparison of low molar mass liquid crystals with condensed phases of entangled polymer fluids and elastomeric networks illustrates the key features of the D n.m.r. technique and establishes a common framework for interpreting experiments.     

Applications of in situ magnetic resonance techniques in chemical reaction engineering

NMR spectroscopy is now a well‐established technique for the in situ study of surface chemistry and the chemical processes occurring during catalytic reactions. Developments in probe design are making the sample environments ever closer to the operating conditions of the catalyst in industrial use. In parallel with these advances there is an increasing interest in the application of field gradient magnetic resonance techniques, namely pulsed gradient spin echo (PGSE) NMR and magnetic resonance imaging (MRI), to in situ studies of mass transport processes in catalysts and reactors. An overview of the recent developments in in situ NMR spectroscopy, PGSE NMR and MRI studies in application to catalysis and reaction engineering is presented and the potential of these techniques in the numerical modelling of catalytic processes and reactor design is highlighted. This revised version was published online in August 2006 with corrections to the Cover Date.     

Petrophysical characterization of coals by low-field nuclear magnetic resonance (NMR)

Nuclear magnetic resonance (NMR) has been widely used in petrophysical characterization of sandstones and carbonates, but little attention has been paid in the use of this technique to study petrophysical properties of coals, which is essential for evaluating coalbed methane reservoir. In this study, two sets of NMR experiments were designed to study the pore types, pore structures, porosity and permeability of coals. Results show that NMR transverse relaxation (T₂) distributions strongly relate to the coal pore structure and coal rank. Three T₂ spectrum peaks identified by the relaxation time at 0.5-2.5 ms, 20-50 ms and >100 ms correspond to pores of <0.1 μm, >0.1 μm and cleats, respectively, which is consistent with results from computed tomography scan and mercury intrusion porosimetry. Based on calculated producible and irreducible porosities through a T₂ cutoff time method, we propose a new NMR-based permeability model that better estimates the permeability of coals. In combination with mercury intrusion porosimetry, we also propose a NMR-based pore structure model that efficiently estimates the pore size distribution of coals. The new experiments and modeling prove the applicability of NMR in petrophysical characterization of intact coal samples, which has potential applications for NMR well logging in coalbed methane exploration.     

Assessment of oxidative deterioration of salted dried fish by nuclear magnetic resonance

Nuclear magnetic resonance (NMR) was used to evaluate the oxidative deterioration of oil in salted dried fish. The ratios of olefinic proteons (Ro) and divinylmethylene protons (Rm) to aliphatic protons in the oil of salted dried fish, as determined by NMR, decreased steadily during storage. On comparing Ro and Rm with data for peroxide value (PV) and acid value, Ro was shown to serve as an index of the oxidative deterioration of the oil of salted dried fish, particularly in the case of oil whose PV had decreased.     

Study of the characterization and curing of benzoxazines using 13C solid-state nuclear magnetic resonance

Benzoxazines derived from bisphenol-A, formaldehyde, and primary amines were characterized using ¹³C solid-state NMR spectroscopy. The two 1,3-benzoxazines studied in this work are 2,2′-(3-methyl-4-dihydro-1,3,2-benzoxazine)propane, ( B-m ) and 2,2′-(3-phenyl-4-dihydro-1,3,2-benzoxazine)propane ( B-a ). Solid-state ¹³C-NMR spectra were obtained for B-m and B-a and the observed peak positions were noted. These resonances agreed well with chemical shifts calculated based on the chemical structure. Samples of B-m and B-a were cured at two different temperatures: 150 and 200°C. The polymerizations induced spectral changes including new resonances, intensity changes, and line-width broadenings. Kinetic analysis of the curing data gave different kinetic parameters for the two cure temperatures, which is expected since the first cure temperature is below the material's glass transition temperature (T_g) while the second cure temperature is above the T_g. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1413–1425, 1998     

C nuclear magnetic resonance spectral analysis of stereosequences in ethylene-propylene copolymer

A number of split peaks dependent on both comonomer sequences and stereosequences were observed in the ¹³C nuclear magnetic resonance (n.m.r.) spectrum of ethylene-propylene (E-P) copolymer. The ¹³C chemical shifts of methylene carbon in stereoisomers of the respective hexad comonomer sequences were predicted by a chemical-shift calculation using the gamma effect on ¹³C chemical shifts and Mark's rotational isomeric state model for E-P copolymer. Assignments of the split peaks that arise from different hexad stereosequences were given by comparison between the observed and calculated chemical shifts. Reference was made to the hexad assignments of comonomer-sequence-dependent peak splittings determined in our previous calculation of ¹³C n.m.r. chemical shifts of stereoregular E-P copolymers. The tacticities were estimated for successive (not separated by ethylene units) propylene units in the hexad sequences.     

Hydrogenation of low‐molar‐mass,OH‐telechelic polybutadienes. II. Nuclear magnetic resonance and infrared spectrometric determination of hydroxyl end groups before and after hydrogenation by diimide

¹H nuclear magnetic resonance (¹H‐NMR), ¹³C‐NMR, and infrared spectroscopies were used to determine concentrations (c_OH, in mmol/g) of the secondary hydroxyl end groups in the low‐molar‐mass, OH‐telechelic polybutadienes, and their hydrogenated analogs. Mean OH‐functionality (f_OH ≤ 2), that is, an average number of OH groups per one polymer chain, was calculated from c_OH for each sample and each method, and the results were compared with those obtained by a conventional acetic anhydride titration method. It has been found that with molar masses of the samples studied (2310 to 3410 g/mol), the differences between individual spectrometric methods are usually not higher than approximately 10%, which corresponds to an expected relative experimental error. Certain differences in f_OH between individual methods are discussed. No systematic change of f_OH after virtually total hydrogenation of the olefinic double bonds of the polymeric substrate by diimide was observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3214–3224, 1999     

用固体核磁技术分析PE 100管材料的抗熔垂性

用固体核磁技术分析了2种具有不同抗熔垂性能的聚乙烯管材料的凝聚态结构与流变性能。管材树脂的抗熔垂性能与其核磁迟豫特性紧密相关,好的抗熔垂性能对应更长的纵向迟豫时间。抗熔垂性能好的双峰管材料的重均分子量更高,高相对分子质量部分的含量更多。     

Theory of nuclear magnetic relaxation

A theory of nuclear magnetic relaxation centred around the rotation operator is proposed. The theory is applicable in principle to molecules of arbitrary shape, and account is taken of the effects of their inertia. Calculation of relaxation times associated with anisotropic chemical shift and spin-rotational interactions provides illustrations of how the theory may be employed.     

Monitoring a progressing transesterification reaction by fiber-optic near infrared spectroscopy with correlation to 1H nuclear magnetic resonance spectroscopy

Biodiesel is a promising alternative diesel fuel obtained from vegetable oils, animal fats, or waste oils by transesterifying the oil or fat with an alcohol such as methanol. In an extension of previous work, fiber-optic near infrared spectroscopy was used to quantitatively monitor the transesterification reaction (6-L scale) of a vegetable oil (soybean oil) to methyl soyate. The results were correlated with ¹H nuclear magnetic resonance spectroscopy. The method described here can be applied to the transesterification of other vegetable oils.     

31P nuclear magnetic resonance studies on alkyl phosphate emulsifiers in cosmetic oil-in-water emulsions

Cosmetic oil-in-water emulsions with a stearyl phosphate emulsifier are examined by means of static and dynamic ³¹P nuclear magnetic resonance (NMR) techniques to characterize the molecular properties of the emulsifier in situ. The interfacially bound emulsifier can be deteced by high-resolution NMR spectroscopy, whereas the excess emulsifier exists as a solid lipid phase not detectable by this technique. The emulsions and the emulsifier raw material, consisting of monostearyl phosphate as well as distearly phosphate, are examined by solid state cross polarization magic angle spinning NMR spectroscopy to prove the existence of solid emulsifier phases in the emulsions. By applying dynamic ³¹P NMR methods to the interfacially bound emulsifier, information about the molecular dynamics at the interface is obtained. The results of the T ₁ and T ₂ relaxation time measurements indicate a restricted motion of the molecules that is dependent on the oil droplet size in the emulsions. This is verified by ³¹P NMR pulsed gradient spin echo self-diffusion measurements on emulsions with different droplet sizes. Only about 5 wt% of the total emulsifier used is bound at the interface; the excess forms solid lipid phases. The coverage of the interface seems to be independent of the emulsifier concentration. Only the monoester of the emulsifier raw material shows interfacial activity. Its mobility indicates the two-dimensional environment of the molecules on the surface of the oil droplets.