Synthese von ungesättigten und gesättigten Aminosäurederivaten durch kathodische Reduktion von Azidozimtsäureester

Cathodic reduction of -azidocinnamic ester under aprotic conditions on Hg, Pt, or graphite electrodes can be directed to high yields of N,N-diacylated dehydroaminoacid derivates (f.i. addition of acetic anhydride) or to almost quantitative yields of -aminocinnamic ester in very pure form by careful addition of H⁺-donors. The dehydroamino compounds in turn can be further reduced to the corresponding saturated compounds by following H⁺-addition and changed electrolysis potential. Almost no dimerization occurs.

     

The cellulose system in viscin from mistletoe berries

The cellulose system of the viscous fibrous cellulosic polysaccharide (viscan) in the viscin tissue of the European mistletoe, Viscum album L., was analyzed by chemical and physicochemical techniques including sugar analysis, optical and transmission electron microscopy, X-ray and electron diffraction together with solid state CP/MAS ¹³C-NMR spectroscopy. The results confirmed that in the elongated thin viscin cells, the cellulose microfibrils (having a diameter of around 3 nm) were tightly coiled with their axes perpendicular to the long axis of the cell. Upon stretching these cells became deformed by more than a hundred fold. In such a deformation, the cellulose microfibrils became unwound to be perfectly aligned along the stretching direction. Based on solid-state CP/MAS ¹³C-NMR spectroscopic analysis of the viscin tissue, it was found that its cellulose consisted of I and I polymorphs in the ratio 1:1.     

Stability of Ibuprofen in its Inclusion Complex with β-Cyclodextrin

The ibuprofen--cyclodextrin inclusion complex was prepared by theco-precipitation method. The identity of the obtained product was verified by X-ray and thermogravimetric techniques. The effect of -cyclodextrin on the stability of ibuprofen was analysed.     

稳态双曲流场中液/液混合的粘性液滴哑铃分散模型

通过对稳态双曲流场中液／液混合体系分散相液滴所受分散作用力的分析，建立了粘性液滴的哑铃分散模型．趋于将两粘性液滴分开的分散作用力与粘度比、流场类型和强度、液滴半径、哑铃取向和尺寸有关．该模型解释了流场类型与分散作用的关系．流场类型对液滴的分散具有很大影响，在纯应变拉伸流场中分散作用力是简单剪切流场中的两倍，因而对于液滴的分散，拉伸流场较简单剪切流场更有效，这与以前的实验结论符合．当体系粘度比趋于无穷大时本模型转化为刚性哑铃分散模型     

The role of the π-bonding network for trigonal level splittings of tris-bidentate Cr(acac)3 and Cr(ox) 3 3−

The varying -bonding contributions in the title compounds caused by the different electronic and molecular structure of the chelate rings are used for explaining the large band splittings in the absorption spectra by trigonal symmetry. It is shown that usual ligand field theory and the angular overlap model are not able to account for the trigonal level splitting of Cr(acac)₃ for which the coordination sphere of oxygen atoms is nearly octahedrally arranged. The experimental finding can, however, be rationalized by an extended angular overlap model which considers the phase coupling of -orbitals in the ligands leading to non-additive contributions to the metal-ligand bond energy.On leave of absence from the Bulgarian Academy of Sciences, Sofia, Bulgaria     

同步辐射白光全反射XRF在痕量元素检测的初步应用研究

叙述了同步辐射白光全反射Ｘ射线荧光分析的实验装置，给出了几种标准物质ＴＸＲＦ实验的检出限，并对实验结果进行了讨论。     

氯铝酸室温离子液体介质中正碳十二烯选择环化反应

 在氯化1－丙基－3－甲基咪唑（PMImCl）、氯化1－丁基－3－甲\r\n基咪唑（BMImCl）、氯化1－丁基吡啶（BPCl）和溴化1－乙基吡啶（E\r\nPBr）季铵盐与AlCl3构成的室温离子液体介质中，首次发现正十二碳烯\r\n（简称十二烯）可以高选择性地发生环化反应生成环十二烷．依次在反\r\n应管中加入氯铝酸室温离子液体、乙醇和十二烯，其中AlCl3的量为0．\r\n01mol，AlCl3与季铵盐的摩尔比为2，乙醇为10ml，十二烯为2ml（9．\r\n3mmol）．当反应体系中不添加乙醇时，十二烯转化率和环十二烷选择\r\n性仅分别为4．2％和73．1％．这是由于十二烯和氯铝酸离子液体形成\r\n两相体系而不易充分接触，故十二烯转化率和环十二烷选择性较低．当\r\n反应体系中加入乙醇时，十二烯和氯铝酸离子液体体系变为单相，使得\r\n十二烯和氯铝酸离子液体可以充分接触，十二烯转化率和环十二烷选择\r\n性可分别达到12．4％和82．9％．压力对提高十二烯转化率和环十二烷\r\n选择性有很大的影响．p（N2）＝3．0～6．0MPa下反应12h，十二烯转\r\n化率和环十二烷选择性可分别达到27．2％和93．8％．反应结束后加热\r\n除去乙醇，产物自动与离子液体分层，便于分离，且离子液体介质可重\r\n复使用．     

超强酸性室温离子液体反应介质中烷烃羰化研究

在卤化1-烷基吡啶和1-甲基-3-烷基咪唑季胺盐与无水AlCl_3组成的超强酸性 氯铝酸室温离子液中，首次实现了烷烃与CO的直接羰化反应。2，2，4-甲基戊烷可 直接与CO反应，产物为酮。     

Determination of fluoride in complex liquid matrices by electrothermal atomic absorption spectrometry with in-furnace oxygen-assisted ashing

A new chemical method is reported for the determination of total fluoride in complex liquids and suspensions, such as fruit juices, urine, serum and blood. It is based on the formation of the A1F radical in a graphite furnace afterin situ oxygen-assisted ashing of the untreated sample. The absorbance of this radical is measured at 227.45 nm. The method is relatively easy to use and provides a low detection limit (14 ng/ml) and reasonable reproducibility (5–10%).     

Thermogravimetric study of polyacrylamide with evolved gas analysis

Dried samples of polyacrylamide in an He atmosphere have been subjected to thermogravimetric analysis in the 30–600°C range, and the evolved gases were monitored by FTIR. Water, ammonia, and small quantities of carbon dioxide are released in the first stages of decomposition (220–340°C), where the polymer chains remain intact and the reaction occurs on the pendant amide groups. In the second stage of decomposition (340–440°C), the majority of the weight loss occurs, and main chain breakdown occurs, releasing carbon dioxide, water, nitrile compounds, and imides. Trapping of the gases in this stage and analysis by GC–FTIR and GC–MS reveals the presence of more than 20 decomposition products, and confirms that a large proportion of these can be assigned to glutarimide and its substituted analogs. Imidization and dehydration reactions on the amide groups, as well as free radical breakdown of the main chains, with inter- and intramolecular hydrogen transfer, can account for many of the products of the decomposition. © 1993 John Wiley & Sons, Inc.