Characterization of Canadian coals by nuclear magnetic resonance spectroscopy

Apparent aromaticities of a series of Canadian coals of different rank were estimated by solid state nuclear magnetic resonance spectroscopy. The aromaticities varied from 0.57 for a lignite up to 0.86 for a semi-anthracite coal. The aromaticities correlated well with fixed carbon and oxygen content of the coals as well as with the mean reflectance of the coals. Correlations were also established between aromaticities and the H/C and H_aru/C_ar ratios of the coals. Uncertainties in calculation of the hypothetical H_aru/C_ar ratios, from experimental data were pointed out.Structural parameters of the chars derived from the coals by pyrolysis at 535°C were, also, estimated. The H/C and H_aru/C_ar ratios of the chars were markedly lower than those of coals. This was complemented by higher apparent aromaticities of the chars compared with the coals.     

Coconut husk lignin. II. Characterization by infrared and nuclear magnetic resonance spectroscopy

Results of the characterization of coconut husk lignin by infrared (IR) and proton nuclear magnetic resonance (H-NMR) spectroscopy are presented. Lignin was extracted with both alkaline and organosolv liquors. The IR spectra of dioxane lignin were very similar to those reported for hardwood lignins. Furthermore, these results combined with those obtained from the H-NMR studies suggest that coconut husk lignin can be classified into the Lm-type lignins. These lignins are characteristic of the monocotyledon class, of which the coconut palm is a member. The H-NMR studies showed that anthraquinone significantly inhibited the occurrence of lignin condensation during the alkaline extraction with sodium hydroxide solutions. This inhibition was more intense in the lignin extracted at 150°C than in that extracted at 100°C.     

Characterization of needle coke feedstocks by magnetic resonance spectroscopy

Decant oil is the traditional petroleum-derived feedstock for the production of needle coke. However, with the dwindling supply of high-quality decant oil and potential availability of coal-derived liquids, alternative feedstocks are receiving attention. One of these is ethylene pyrolysis tar. The new materials are less suitable needle coke precursors and may need to be upgraded by structural alterations. Therefore, the structure of these materials is examined at the molecular level. The average molecular parameters for the aromatic and asphaltene fractions of decant oil and pyrolysis tar are reported, along with a method for calculating these parameters which is slightly different from the previously available procedures. These parameters indicate that the average molecule in the aromatic and asphaltene fractions of decant oil and pyrolysis tar differ in certain structural units. This difference possibly may be responsible for their different behaviour on pyrolysis.     

Enzyme-catalyzed reactions in ionic liquids

Ionic liquids have been suggested as potential “green solvents” due to their unique properties such as non-volatility, nonflammability, and a wide temperature range for liquid phase. This review describes recent advances of biocatalyst reactions in ionic liquids. Enzyme-catalyzed reactions in ionic liquids-transesterification, synthesis, conversion, ammoniolysis, hydrolysis, epoxidation, resolution, and oxidation are presented. The use of ionic liquids for protein folding/refolding and the toxicity of ionic liquids are also discussed.     

Analysis of asphaltenes by carbon and proton nuclear magnetic resonance spectroscopy

Proton and ¹³C nuclear magnetic resonance spectroscopy has been used to derive a series of parameters of an ‘average molecule’ which characterize complex multicomponent organic mixtures such as asphaltenes. The method developed here is based on a minimum of assumptions and takes explicitly into account the effects of the oxygen atoms on the chemical shift of the adjacent ¹³C atoms. Moreover, the integrated intensities characterizing ring junction or substituted and unsubstituted carbon atoms are no longer determined on a chemical shift basis but are calculated by using parameters extracted from ¹H and ¹³C spectra. Factors influencing quantitative ¹³C measurements on asphaltenes in the Fourier transform mode are briefly discussed. The variations of parameters such as the aromaticity factor, the degree of substitution, and the number of aromatic and naphthenic cycles per structural unit are studied as functions of depth of burial for rock samples from the Toarcian Paris basin.     

Evaluation of diamond films by nuclear magnetic resonance and Raman spectroscopy

The quality of chemically vapor deposited diamond films was assessed in terms of sp²/sp³ content as determined by solid-state nuclear magnetic resonance (NMR) and Raman spectroscopy. While the results of the two techniques are in qualitative agreement, only the NMR spectra yield quantitative values for the sp²/sp³ ratio. Only sp³ carbon was observed in the NMR spectra of very high quality hot-filament, microwave plasma, and d.c. arc-jet chemically vapor deposited films. As expected, Raman spectroscopy is extremely sensitive to sp² bonded carbon, identifying small amounts below the detection limit of the NMR spectrometer. Comparison of the two techniques, however, indicates that Raman spectroscopy may be so sensitive to sp² bonded carbon that sp³ bonded carbon in films containing as much as 90% sp³ bonded material may remain undetected. NMR linewidths indicate that the sp³ carbon in such material shows more disorder than that found in high-quality polycrystalline films.     

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。     

Average molecular weight of oil fractions by nuclear magnetic resonance

Average molecular weight (AMW) is an important parameter of the ‘average molecule’ in oil fractions. Normally it is measured by vapour pressure osmometry (VPO), but it would be useful to have an alternative measurement. A simple algorithm based on data from the n.m.r. spectra for the calculation of a maximum AMW, considering molecules with fully extended aromatic nuclei (cata-condensed molecules), and of a minimum AMW, considering molecules with maximum condensation of the aromatic nuclei, is presented in this paper. The values obtained are consistent with VPO values for different fractions as distillates, residues or asphaltenes. This method completes the data for a full characterization of the average molecule using only n.m.r..     

Characterization of nonionic surfactants using supercritical fluid chromatography and carbon-13 nuclear magnetic resonance spectroscopy

Capillary supercritical fluid chromatography, using a carbon dioxide mobile phase and flame ionization detection, was employed for characterization of nonionic alcohol ethoxylate surfactants. Data from separations was used to calculate average molecular weights, degree of ethoxylation and distribution of telomers. The SFC approach was compared with carbon-13 nuclear magnetic resonance spectroscopy for evaluation of the same samples. The faster chromatographic technique permitted information to be obtained in the presence of materials which interfered with the NMR analysis, and provided a means of identifying the minor components of mixtures. The advantages and disadvantages of the methods are discussed and the complementary nature of the techniques illustrated.     

Microstructure characterization of low molecular weight polybutadiene using the chain end groups by nuclear magnetic resonance spectroscopy

Polymer Bulletin - Four laboratory types of low molecular weight polybutadiene (PBD) with different 1,2-vinyl isomer contents were selected for microstructure characterization by nuclear magnetic...     

Meningioma phospholipid profiles measured by31P nuclear magnetic resonance spectroscopy

Fourteen cases of intracranial meningioma were characterized after chloroform/methanol extraction by³¹P nuclear magnetic resonance (NMR) spectroscopy at 202.4 MHz. Each phospholipid class detected in the extracts was identified and quantitated in terms of its molar percentage relative to the total phospholipids measured. The following phospholipids were assayed by³¹P NMR: phosphatidylglycerol, phosphatidic acid, diphosphatidylglycerol, ethanolamine plasmalogen, phosphatidylethanolamine (PE), lysophosphatidylinositol, phosphatidylserine, sphingomyelin, lysophosphatidylcholine (LPC), phosphatidylinositol (PI), sphingosylphosphorylcholine and phosphatidylcholine. In addition, two unidentified phospholipids were detected with resonances at 0.13 and −0.78 ppm, respectively. Three distinct types of spectra were obtained on the extracts and grouped accordingly for comparison purposes. Type 1 tumors showed unusual³¹P NMR profiles with low levels of PE and PI and elevated levels of LPC; type 2 tumors were characterized by low levels of the ethanolamine phospholipids and near equivalent levels of PI and LPC. The spectra of type 1 and type 2 tumors were characteristic of degenerative cells that lacked membrane permeability associated with loss of ethanolamine plasmalogen in the presence of significant phospholipid turnover. Meningiomas belonging to the third spectral type showed characteristics similar to those of normal tissues with normal levels of PE and ethanolamine plasmalogen, as well as very low levels of LPC relative to PI. Type 3 tumors lacked the characteristic signs of degeneration noted in type 1 and type 2 tumors. The data corroborate and augmentin vivo spectroscopic findings reported earlier and demonstrate the value of³¹P NMR spectroscopic phospholipid analysis on lipid extracts for the characterization of meningiomas.     

离子液体在烷基化反应中的应用

本文介绍了离子液体的种类、制备方法、及其特性,论述了离子液体作为催化剂和溶剂的优点及其在烷基化反应中的应用和发展前景。     

离子液体中缩合反应研究进展

综述了离子液体中Knoevenagel、Aldol、Wittig、Pechmann、Paal-Knorr、Benzoin、Biginelli等各种缩合反应,表明离子液体作为一种新型的绿色溶剂有效地促进了缩合反应的进行,显著地提高了反应的选择性和收率。     

离子液体中烷基化反应研究进展

综述了离子液体中的C、O、N、S的烷基化反应研究,表明离子液体作为一种新型的绿色溶剂有效地促进了烷基化反应,显著地提高了反应的选择性和收率。     

Characterization of the micellar structure of a barium nonylphenolate/Barium carbonate complex by nuclear magnetic resonance spectroscopy

The micellar structure of a barium nonylphenolate/barium carbonate complex was characterized by ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. Several NMR techniques, including measurement of spin-lattice relaxation time, chemical shift variation, and line width of the ¹H NMR signal and solid-state ¹³C NMR data, were used in this study. NMR results indicate that the prepared barium nonylphenolate and barium carbonate complex formed a micelle structure with the oxygen atom of the nonylphenolate ring oriented toward the solid-state center core of barium carbonate while the highly branched aliphatic chain pointed outward to the hydrocarbon solvent.     

New directions in the nuclear magnetic resonance spectroscopy of polymers

The study of polymers by nuclear magnetic resonance spectroscopy has made tremendous advances in the last few years, not only with the development of superconducting solenoid magnets with increasing field strength, permitting the resolution of increasingly fine structural detail and greater sensitivity, but also in the development of new techniques. Among these is the use of two-dimensional (2D) NMR, permitting easier and more rigorous assignment of resonances. Another important advance has been the development of means to observe high resolution spectra in the solid state, through high-power dipolar decoupling, cross-polarization, and magic angle spinning. A third significant development is that of deuterium quad-rupole echo spectroscopy, permitting the study of chain dynamics in the solid state with unprecedented power and precision.     

Measurement of solids in triglycerides using nuclear magnetic resonance spectroscopy

A rapid and accurate method using nuclear magnetic resonance (NMR) spectroscopy is presented for determining the percentage of solids in fats and shortenings conditioned at selected temperatures or as received in the laboratory. This method provides more reliable information on the solids content of fatty materials than the empirical dilatometric solid fat index, and is applicable in the range of 50–100% solids which is beyond the limit of the official solid fat index method. The relationship between instrument response and actual solids present was determined on known mixtures of liquid and solid triglycerides. NMR and solid fat index (SFI) measurements were made on a series of commercial margarine oils of varying composition and consistency. Comparisons are presented giving the precision of the two techniques and the relationship between percentage of solids by the NMR technique and the solids fat index.