Modification of polybenzimidazole: Synthesis and thermal stability of poly(N1-methylbenzimidazole) and poly(N1,N3-dimethylbenzimidazolium) salt

Poly(N₁,N₃-dimethylbenzimidazolium) (PDMBI) salt and poly(N₁-methylbenzimidazole) (PMMBI) were synthesized by methylation of commercial polybenzimidazole [poly-2,2′-(m-phenylene)-5,5′-bibenzimidazole (PBI)]. First, the N-lithium salt of polybenzimidazole was formed by treating polybenzimidazole solution of 1-methyl-2-pyrolidinone (NMP) with lithium hydride at 80°C for 18 h. Ninety percent substitution of PMMBI was obtained by treating the N-lithium salt of PBI with equimolar ratio of iodomethane at room temperature. Upon addition of excess iodomethane to the lithium salt of PBI at 80°C, a polymer was formed that showed 100% substitution on the N₁ nitrogen and about 30% substitution of the methyl group on the N₃ nitrogen in the form of N₁,N₃-dimethylbenzimidazolium iodide salt [PDMBI (30%)]. The content of the benzimidazolium iodide salt was increased to about 90% by dissolving PDMBI (30%) in dimethyl sulfoxide (DMSO) and re-treating with excess iodomethane at 80°C overnight. The modified PBI polymers were characterized by NMR and FTIR. The modified PBI differed in solubility from PBI. PMMBI could be easily dissolved in NMP and PDMBI in DMSO at room temperature. The solution of PDMBI could be mixed with water in all proportions without precipitation. PDMBI could be also dissolved directly in a mixture of DMSO and water (1 : 1). Typical polyelectrolyte behavior of viscosity was found in solution of PDMBI (30%) and PDMBI (90%) when DMSO and a mixture of DMSO and water were used as solvents. A salt effect on viscosity was also found in the mixed solvent solution. Thermogravimetric analysis (TGA) showed that the methyl group on the imidazole ring was unstable above 180°C under nitrogen. When PDMBI was heated under nitrogen, one of the methyl groups was lost with the counterion to result in a neutral PMMBI. © 1993 John Wiley & Sons, Inc.     

铀-2-(3,5-二溴-2-吡啶偶氮)-5-二乙氨基苯酚-Triton X-100析相体系的研究及应用

本文研究了铀-2-(3,5-二溴-2-吡啶偶氨)-5-二乙氨基苯酚(3,5-diBr-PADAP)-Triton X-100析相光度体系,建立了矿石中微量铀的测定方法,在pH 7.5三乙醇胺-盐酸介质中,将胶束溶液在 95±1℃加热 1h.络合物即被Triton X-100相完全富集.络合物最大吸收峰位于565nm.摩尔吸光系数为1.02×10～5L·mol～(-1)·cm～(-1),铀含量在0～12μg/5mL服从比耳定律.采用TBP萃淋树脂分离干扰离子,测定矿石中微量铀,结果满意.     

Determination of 3-sulfolene in sulfolane by reaction gas chromatography

Summary A simple gas-liquid chromatographic method has been developed for determining 3-sulfolene in sulfolane. The method involves thermal decomposition of sulfolene and determination of the 1.3-butadiene evolved, by GLC. Influence of the operating parameters on quantitative decomposition of sulfolene has been studied. The accuracy of the method as studied in the concentration range from 0.05 to 4.0 % (w/v) of 3-sulfolene in sulfolane is found to be within ±3.0%. It is rapid and sensitive down to 10 ppm and has potentialities for on-line applications also.

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Bestimmung von 3-Sulfolen in Sulfolan durch Reaktions-Gas-Chromatographie

Zusammenfassung Eine einfache gas-chromatographische Methode wurde entwickelt, die auf der thermischen Zersetzung der Probe und der Bestimmung des dabei aus 3-Sulfolen gebildeten 1,3-Butadiens beruht. Der Einfluß der einzelnen Parameter wurde untersucht. Innerhalb eines Konzentrationsbereichs von 0,05–4,0% 3-Sulfolen ergaben sich Fehler von ±3%. Das Verfahren ermöglicht bis herab zu 10 ppm eine schnelle und empfindliche Bestimmung und eignet sich auch zum on-line Betrieb.

     

Zum chemischen Transport von Molybdän mit SbBr3 – Experimente und Modellrechnungen

On the Chemical Transport of Molybdenum using SbBr₃ – Experiments and Thermochemical Calculations Mo migrates in a temperature gradient from the region of higher temperature to the lower temperature using SbBr₃ as transport agent. For various mean transport temperatures (750 ? T ? 1000°C; T = 0,5 (T₁ + T₂); T₂ ? T₁ = 100°C) we observed small transport rates (? ? 0,6 mg/h) which rise up to 16 mg/h for higher transport agent concentrations. Small amounts of MoO₂ and Sb were detected beside Mo in the sink. The observed solid phases in the sink are in agreement with thermodynamical calculations by CVTrans which also demonstrate that the formation of MoO₂ and Sb as well as the transport effect of SbBr₃ are caused by traces of H₂O from the quartz glass wall. The sequence of deposition of Mo, MoO₂ and Sb in the examined temperature range can be calculated (CVTrans) and measured with the transport balance.     

三环[5,2,1,0~(2,6)]癸-3-烯-8,9-二羧酸二甲酯的合成

通过对双环戊二烯的选择性羰基化加成，高产率地合成了三环[5、2、1、02，6]癸-3烯-8，9-二羧酸二甲酯。得到了无色透明的片状晶体，产率为90％。     

Synthesis of 2-chloro-1,1-difluoroallyl mesylates through novel rearrangement and CC bond formation by their Pd-catalyzed reaction with diethylzinc

Treatment of 2-chloro-3,3-difluoroprop-2-en-1-ol derivatives (2) with methanesulfonyl chloride in the presence of a base did not give the expected esters but 2-chloro-1,1-difluoroprop-2-enyl methanesulfonates (4) through a novel [3,3] sigmatropic rearrangement. Reaction of 4 with diethylzinc in the presence of tetrakis(triphenylphosphine) palladium gave 1-alkyl- or 1-aryl-2-chloro-3-fluoropenta-1,3-dienes in moderate to good yields through a CC bond formation followed by dehydrofluorination.     

Novel application of quantum chemical investigation in terms of substituent parameters: Statistical comparison of dual and single substituent parameter treatments

The correlation analysis of Mulliken charge (Q_M) calculated by using density functional theory (B3LYP/STO-3G) calculations of 1-(4-azido-5-hydroxymethyl-tetrahydro-selenophen-2-ylmethyl)-5-substituted-1H-pyrimidine-2,4-dione, were done by using mono substituent parameter (Hammett’s model), and dual substituent parameter (Taft’s, Reynolds’, and Swain’s models). The dual substituent parameter correlations of the Q_M data gave no significant improvement over single parameter correlations, the best correlation observed with the Taft’s Model as compared with the Swain’s and Reynolds’ Models, respectively. The correlation analysis of Mulliken charge can be used successfully to demonstrate the existence or absence of the interaction between the oxygen of the carbonyl group and selenium atom.     

载镍沸石上NH3-TPD脱附峰的非酸性探讨

NH_3-TPD技术表征固体催化剂的酸性似乎已很成熟,其实不然。如该技术表征HZSM-5沸石时,有作者观察到773K左右的高温脱氨峰,而有些作者则检测不到。诚然,各作者间所用试样及预处理条件等存在差异,但实验装置和实验操作条件不同带来的影响也不可忽视。此外,该技术在用于表征一些新的较复杂的催化剂时,其程脱谱也会呈现出新现象,这些现象有时是不能通过酸性来解释的,这是因为NH_3作为探针分子不仅具有碱性,同时还有还原性和配位性。本文对载镍沸石上NH_3-TPD谱图中出现的某些新峰进行了剖析和归属。     

稀土金属硼氢化物的研究(Ⅸ)——N,N''''-双(邻羟基苯叉)-1,3-丙二胺合稀土(Ⅲ)十氢十硼酸盐的合成

我们曾报道过含闭式氢硼駿根的二齿配体的稀土螯合物的合成及性质。为了解不同配体的稀土配合物在结构及性质上的差异,又合成了四齿(ONNO)配体N,N′-双(邻羟基苯叉)-1,3-丙二胺(salpr),并通过两种方法(模板合成法及配体合成法)合成了稀土配合物的闭式十氢十硼酸盐。化合物均为黄色粉末固体,室温下它们对光、空气、潮汽均稳定。     

Problems caused by the activity of Al2O3-PLOT columns in the capillary gas chromatographic analysis of volatile organic compounds

Summary Al₂O₃-PLOT columns are used with great advantage for the analysis of volatiles, because of the increased capacity ratio and selectivity compared to WCOT-columns. Their applicability is limited to relatively non-polar components with relatively low boiling points i. e. eluting before n-decane.In the analysis of the halocarbons in stratospheric air, the decomposition of certain compounds was observed. In this study the stability of a number of volatile organic compounds was determined in function dependence of the column temperature using a two-dimensional GC-system.A possible reaction mechanism for the decomposition is proposed and confirmed for several chlorinated ethanes.