Substituent Distribution of Cyanoethyl Cellulose

Estimation of the substitution distribution for cyanoethyl cellulose was carried out by ¹H and ¹³C NMR spectroscopic analyses after the additional acetylation. Based on the complemental function of cyanoethyl and acetyl substituents, the degree of substitution (DS) of cyanoethyl groups could be calculated from the ratios of the ¹H integrated intensities in acetyl methyl ( 1.8–2.1) and cyanoethyl methylene ( 2.6–2.9) protons, and also from the corresponding ratios for acetyl methyl carbon signals ( 19.7–21.3) and cyanoethyl methylene carbon signals ( 17.5–19.0). Good agreement was obtained between the DS values obtained from the NMR spectroscopic analyses and those determined by the conventional nitrogen content method, indicating the validity of the NMR method used. In addition, the NMR method was found to be effective in determining the positional substituent distribution by the quantitative analysis of the three cyan carbon signals ( 118–120).     

Distribution of Substituents along the Cellulose Chain on Cellulose Xanthate and Carboxymethyl Cellulose

The distribution of substituents of cellulose xanthogenate and carboxymethyl cellulose along the cellulose chains and therefore in relation to the molecular mass can be measured using size exclusion chromatography including a multi angle laser light scattering and mass detection for determining the molecular mass of the derivative assisted by an UV- detection for determining the xanthate groups and carboxymethyl groups after derivatisation, respectively. The results investigating cellulose xanthogenate show that the temperature used in dissolving xanthogenate and in ripening viscose influences the distribution of xanthate groups in a different way; but all steps processing viscose are connected with a loss in the degree of substitution in ripening the distribution of substitution additionally becomes more even. The investigated carboxymethyl cellulose revealed different distribution of carboxylic groups in dependence on the viscosity of the CMC.     

14,17-Ethano-norcodeinone

Summary A new codeinone derivative was synthesized starting with northebaine which might be of interest with regard to the question of opiate-receptor affinity in the sense of its rigidity near the anionic side of the alkaloid.

Herrn Prof. Dr. W. Wiegrebe mit den besten Wünschen zum 60. Geburtstag gewidmet.     

In situ crystallization of bacterial cellulose II. Influences of different polymeric additives on the formation of celluloses Iα and Iβ at the early stage of incubation

Effects of polymeric additives with different degrees of polymerization (DP) or substitution (DS) on the crystallization of celluloses I and I have been examined at an early stage of the incubation of Acetobactor xylinum by using newly developed FT-IR spectroscopy. It was found that the mass fraction of cellulose I is greatly decreased with increasing concentrations of carboxymethyl cellulose sodium salt (CMC) or xyloglucan (XG) in the incubation medium. Such a decrease in the mass fraction of cellulose I, which corresponds to the enhanced crystallization of cellulose I, is more prominent for CMC or XG with lower DPs, but the additives with too low DPs are not so effective probably due to higher solubility and the lower adhesion on the surface of microfibrils. Moreover, the mass fractions of celluloses I and I are highly correlated with the crystallite size of microfibrils, indicating that I is crystallized in larger-size microfibrils while I is produced in smaller-size microfibrils. On the basis of these experimental results, the mechanism of the crystallization of celluloses I and I is discussed in the Acetobactor xylinum system.     

Substituent effects of phosphonate groups electronic repartition of π-conjugated ferrocene analogues of stilbene

The synthesis of para-substituted ferrocene analogues of stilbene was performed by using the Heck reaction, starting from vinylferrocene. The variation of the electronic density of these compounds with the electronic withdrawing strength of the substituents was studied using ¹³C NMR spectroscopy, absorption spectra and cyclic voltammetry. The correlation of Hammett constants with the redox properties of the substituted compounds using Nagy's method allowed us to revisit the determination of the Hammett constants of diethyl phosphonate ester and phosphonic acid substituents. Our measurements were in agreement with the literature except for the diethyl phosphonate group.     

Noble Metal Decoration and Alignment of Carbon Nanotubes in Carboxymethyl Cellulose

A facile microwave method (MW) is described that accomplishes alignment and decoration of noble metals on carbon nanotubes (CNT) wrapped with carboxymethyl cellulose (CMC). Carbon nanotubes such as single‐ and multi‐walled, and Buckminsterfullerene (C‐60) are well dispersed using the sodium salt of CMC under sonication. Addition of respective noble metal salts then generates noble metal‐decorated CNT composites at room temperature. However, aligned nanocomposites of CNTs could only be generated by exposing the above nanocomposites to MW irradiation. The CNT composites are characterized using scanning electron microscopy, energy dispersive X‐ray analysis, X‐ray mapping, transmission electron microscopy, and UV‐visible spectroscopy. The general preparative procedure is versatile and provides a simple route to manufacturing useful metal‐coated CNT nanocomposites.

     

基于羧甲基纤维素钠制备氮掺杂多孔炭及其电容性能研究

以羧甲基纤维素钠(NaCMC)为碳源, 利用直接炭化工艺(无需进一步活化)制备多孔炭材料; 然后, 以CO(NH₂)₂为氮源, 形成了氮掺杂多孔炭材料. 氮的存在形式包括吡啶N、石墨N和吡咯N. 实验结果表明, 羧甲基纤维素钠与CO(NH₂)₂之间的配比可以有效控制氮存在形式、含量、样品的比表面积及孔的结构等. 样品的电化学性能测试表明, 氮掺杂后多孔炭材料的超电容性能得到了显著提升. 以carbon-N-1:20为例, 其比表面积可达858 m²·g^-1, 远高于未经氮掺杂carbon-blank 的463 m²·g^-1, 其质量比电容则由94.0 F·g^-1提高到了156.7F·g^-1.     

15个乙烯—乙烯基化合物共聚物的取代基参数

本文应用取代基参数（ＳＣＳ）方法处理了１５个ＥＶ共聚物的＾１３ＣＮＭＲ谱，它们是：（１）乙烯α－烯烃共聚物，即乙烯－丙烯共聚物，乙烯－丁烯－１共聚物，乙烯４－甲基－１－戊烯共聚物，乙烯－己烯－１共聚物和乙烯－辛烯－１共聚物；（２）乙烯－含氧乙烯共聚物，即乙烯－甲基丙烯酸Ｎ，Ｎ－二甲基胺乙酯共聚物，乙烯－丙烯酸甲酯共聚物，乙烯－丙烯酸共聚物，乙烯－乙酸乙烯酯，乙烯－乙烯醇，乙烯－一氧化碳共聚物（ＥＣ     

13C CPMAS NMR investigations of cellulose polymorphs in different pulps

In order to obtain information about the crystallinity and polymorphs of cellulose, and the occurrence of hemicelluloses in pulp fibers, wood cellulose, bacterial cellulose, cotton linters, viscose, and celluloses in different pulps were investigated by solid state ¹³C CPMAS NMR spectroscopy. A mixed softwood kraft pulp and a dissolving-grade pulp were treated under strongly alkaline and acidic conditions and the effect on cellulose crystallinity was studied. The presence of different crystalline polymorphs of cellulose and the amounts of hemicelluloses are considered.     

Synthesis of New Hybrid Organic-Inorganic Alumina Gels by the Sol-Gel Method

New hybrid organic-inorganic alumina gels have been prepared by reacting aluminum sec-butoxide and propane-1,2-diol, in CCl₄ as solvent. This reaction occurred without water addition and without the use of any catalyst, leading to the formation of transparent and monolithic gels. IR,²⁷Al and¹³CNMR show that an interchange reaction between OBu ^s alkoxide groups and diol groups occurred, leading to the hybrid gels. Samples heat treated at different temperatures under argon are weakly porous and have a small specific surface area. XRD indicates the presence of pure α-alumina at 1450°C.     

Fractionation of Polysaccharide Derivatives and Subsequent Analysis to Differentiate Heterogeneities on Various Hierarchical Levels

A set of methyl celluloses of DS 1.8 has been fractionated by stepwise solvent extraction. All fractions have been investigated with respect to their monomer composition and methyl distribution in the polymer chains. Deviation from the random model and differences between the four samples could be determined with higher sensitivity and more differentiated than for the unfractionated material. Structure complexity of cellulose ethers on different hierarchical levels is outlined and discussed.     

Synthesis and Stereochemistry of New N-Substituted Cytisine Derivatives

A series of new N-substituted cytisine derivatives was synthesized. The ¹ H and ¹³ C NMR spectra of certain compounds exhibit a doubled set of signals. This is explained by formation of diastereomeric pairs in compounds containing an asymmetric center in the substituents. The signal splitting in -COHC=CHCO ₂ H and HC=O (formyl) derivatives is explained by the existence of Z and E invertomers. Their stereochemical features are discussed. Amide conjugation is confirmed by temperature experiments.     

Trimethylsilylation of Cellulose in Ionic Liquids

Trimethylsilylation of cellulose in different 1,3‐dialkylimidazolium ionic liquids (IL) with hexamethyldisilazane (HMDS) as a silylating agent was investigated. Trimethylsilyl (TMSi) cellulose with a degree of substitution (DS) greater than 1 is insoluble in the IL. The maximum DS obtained depends on the nature of the anion. Carboxylate and diethylphosphate counterions gave better results than chloride or thiocyanate, which corresponds to the solubility of HMDS in the IL. Controlled silylation with stoichiometric amounts of HMDS was feasible in imidazolium carboxylates and diethylphosphate. Analysis of the substitution pattern of the silyl groups in the anhydroglucose unit (AGU) by methylation analysis gave a more homogeneous distribution under (initially) homogeneous conditions (fewer unsubstituted AGUs, fewer trisubstituted AGUs) compared to TMSi cellulose obtained in liquid ammonia.

     

硫酸耐尔蓝共振光散射法测定羧甲基纤维素钠

硫酸耐尔蓝共振光散射法测定羧甲基纤维素钠;羧甲基纤维素钠;硫酸耐尔蓝;共振瑞利散射;共振非线性散射     

Adsorption Behavior and Inhibition Corrosion Effect of Sodium Carboxymethyl Cellulose on Mild Steel in Acidic Medium

The effect of sodium carboxymethyl cellulose (Na-CMC) on the corrosion behavior of mild steel in 1.0 mol·L⁻¹ HCl solution has been investigated by using weight loss (WL) measurement, potentiodynamic polarization, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) methods. These results showed that the inhibition efficiency of Na-CMC increased with increasing the inhibitor concentration. Potentiodynamic polarization studies revealed that the Na-CMC was a mixed type inhibitor in 1.0 mol·L⁻¹ HCl. The adsorption of the inhibitor on mild steel surface has been found to obey the Langmuir isotherm. The effect of temperature on the corrosion behavior of mild steel in 1.0 mol·L⁻¹ HCl with addition of 0.04% of Na-CMC has been studied in the temperature range of 298–328 K. The associated apparent activation energy (E^*_a) of corrosion reaction has been determined. Scanning electron microscopy (SEM) has been applied to investigate the surface morphology of mild steel in the absence and presence of the inhibitor molecules.     

Adsorption Behavior and Inhibition Corrosion Effect of Sodium Carboxymethyl Cellulose on Mild Steel in Acidic Medium

The effect of sodium carboxymethyl cellulose (Na-CMC) on the corrosion behavior of mild steel in 1.0 mol·L-1 HCl solution has been investigated by using weight loss (WL) measurement, potentiodynamic polarization, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) methods. These results showed that the inhibition efficiency of Na-CMC increased with increasing the inhibitor concentration. Potentiodynamic polarization studies revealed that the Na-CMC was a mixed type inhibitor in 1.0 mol·L-1 HCl. The adsorption of the inhibitor on mild steel surface has been found to obey the Langmuir isotherm. The effect of temperature on the corrosion behavior of mild steel in 1.0 mol·L-1 HCl with addition of 0.04% of Na-CMC has been studied in the temperature range of 298-328 K. The associated apparent activation energy (E*a ) of corrosion reaction has been determined. Scanning electron microscopy (SEM) has been applied to investigate the surface morphology of mild steel in the absence and presence of the inhibitor molecules.     

A review of: “Particle-Size Distribution II: Assessment and Characterization (ACS Symposium Series 472; Provder,T”, Ed.; American Chemical Society: Washington, 1991. pp. xiii+407 $89.95.

ABSTRACT

An automated set-up is described which permits the fast determination of the composition limits of isotropic microemulsion phases of ternary (water/oil/surfactant) systems. It is especially well suited for the investigation of systems including nonionic surfactants, which are very sensitive to temperature changes.

Four systems have been tested including hydrogenated as well as fluorinated surfactants and oils. Both direct and inverse microemulsion phases have been chosen for these investigations.

The results obtained and their comparison with previously reported diagrams are used to draw some general conclusions concerning the advantages and limits of an automatic procedure. It appears that the recordings obtained with such procedures are particularly easy to interpret for certain types of systems for which very neat turbidity changes are observed (case of reverse fluorinated systems for instance). For other systems (those for which there exists a liquid-crystalline phase for instance) care must be taken when interpreting the turbidity vs temperature curve.

The method is particularly useful when dealing with expensive products for which one cannot afford to prepare a sealed ampoule for each point of interest in the phase diagram.     

A comparative study of NMR chemical shifts of sparteine thiolactams and lactams

The ¹³C and ¹H NMR spectra of the four possible thiolactams of sparteine (1) were recorded and the thiolactam group effects were determined. Most of the effects are greater than those of the lactam group in the oxo analogs. A good linear correlation between the ¹³C chemical shifts of CS and those of CO was found. The effects could help in assignment of the spectra and determination of conformation of thiolactams and related thiocarbonyl compounds.