光学双稳性临界点的相变行为

本文详细地讨论了光学双稳性(OB)的临界现象。理论分析主要以忽略量子涨落的Fokker-Plank方程的静态解为基础。结果发现,OB的临界现象可以纳入Landau二级相变理论的框架,并且有关临界指数之间的关系也服从标度律。 关键词：     

Thermisches Verhalten von Caesiumchloroferraten(III) und Caesiumchloroferrat(III)-Hydraten. II. Die Rehydratation der Zersetzungsprodukte von Cs3[FeCl6] – Eine ramanspektroskopische Untersuchung unter definierter Wasserdampfatmosphäre [1]

The Thermal Behaviour of Caesiumchloroferrates(III) and Caesiumehloroferrate(III) Hydrates. II. The Rehydration of Decomposition Products of Cs₃[FeCl₆] — A Raman Spectroscopic Study under Definite Atmosphere of Water Vapour Cs₃[FeCl₆] formed by dehydration of Cs₃[FeCl₆] · H₂O at about 160°C does not change at normal atmosphere within 3 till 4 hours. Rehydration under the vapour pressure of the eliminated water yields the monohydrate in nearly the same time. In the same manner rehydration of the solid mixture of Cs[FeCl₄] and 2 CsCl formed by thermal decomposition of the metastable Cs₃[FeCl₆] (280°C) produces the intermediates Cs₃[Fe₂Cl₉] and Cs₂[Fe(H₂O)Cl₅] in mixtures with CsCl and, finally, Cs₃[FeCl₆] · H₂O. The formation of Cs₃[Fe₂Cl₉] from Cs[FeCl₄] and CsCl is accelerated by water. The reaction cycle has been studied using Raman and IR spectroscopy. The results will be discussed with respect to thermoanalytical data.     

Pyrimidine acyclo-C-nucleosides by ring transformations of 2-formyl-L-arabinal

The protected 2-formyl-L-arabinal 2 reacted with thiourea and cyanamide in the presence of sodium hydride to afford via ring transformations the 5-[1R,2S-1,2- bis(benzyloxy)-3-hydroxypropyl]-1,2-dihydropyrimidines 3 and 4, respectively. Similarly, treatment of 2 with 3-amino-2H-1,2,4-triazole yielded 6-[1R,2S-1,2- bis(benzyloxy)-3-hydroxypropyl][1,2,4]-triazolo[1,5-a]pyrimidine (5).     

Structural insights into aluminum chlorofluoride (ACF)

The structure of the very strong solid Lewis acid aluminum chlorofluoride (ACF, AlCl(x)F(3-x), x = 0.05-0.3) was studied by IR, ESR, Cl K XANES, (19)F MAS NMR, and (27)Al SATRAS NMR spectroscopic methods and compared with amorphous aluminum fluoride conventionally prepared by dehydration of alpha-AlF(3) x 3H(2)O. The thermal behavior of both compounds was investigated by DTA and XRD. In comparison to ACF, amorphous AlF(3) prepared in a conventional way is not catalytically active for the isomerization reaction of 1,2-dibromohexafluoropropane, which requires a very strong Lewis acid. Both compounds are mainly built up of corner-sharing AlF(6) octahedra forming a random network. The degree of disorder in ACF is higher than in amorphous AlF(3). Terminal fluorine atoms were detected in ACF by (19)F NMR. The chlorine in ACF does not exist as a separate, crystalline AlCl(3) phase. Additionally, chlorine-containing radicals, remaining from the synthesis, are trapped in cavities of ACF. These radicals are stable at room temperature but do not take part in the catalytic reaction.     

Synthesis of Heteroanellated Pyranosides Starting from Methyl 4,6‐O‐benzylidene‐2,3‐dideoxy‐α‐d‐erythro‐hexopyranosid‐2‐ylidenemalononitrile

The hexopyranosid‐2‐ylidenemalononitrile 1 reacted with phenyl isothiocyanate in the presence of triethylamine to furnish (2R,4aR,6S,10bS)‐8‐amino‐4a,6,10,10b‐tetrahydro‐6‐methoxy‐2‐phenyl‐10‐phenylimino‐4H‐thiopyrano[3′,4′:4,5]pyrano[3,2‐d][1,3]dioxine‐7‐carbonitrile (2). Starting from 1, cyclization with sulphur and diethylamine yielded (2R,4aR,6S,9bR)‐8‐amino‐4,4a,6,9b‐tetrahydro‐6‐methoxy‐2‐phenylthieno[2′,3′:4,5]pyrano[3,2‐d][1,3]dioxine‐7‐carbonitrile (3), which could be transformed into the corresponding aminomethylenamino derivative 4 by treatment with triethyl orthoformate and ammonia. Intramolecular cyclization of 4 to yield (2R,4aR,6S,11bR)‐4,4a,6,11b‐tetrahydro‐6‐methoxy‐2‐phenyl[1,3]dioxino[4″,5″:5′,6′]pyrano[3′,4′:4,5]thieno [2,3‐d]pyrimidin‐7‐amine (5) was achieved by using NaH as base. (2R,4aR,6S,9bS)‐8‐Amino‐4a,6,9,9b‐tetrahydro‐6‐methoxy‐9‐(4‐methylphenyl‐sulfonyl)‐2‐phenyl‐4H‐[1,3]dioxino[4′,5′:5,6]pyrano[4,3‐b]pyrrole‐7‐carbonitrile (6) was prepared by treatment of compound 1 with tosylazide and triethylamine.     

氮氧自由基研究XVII:水溶液中哌啶氮氧自由基的电化学行为和自衰变动力学研究

循环伏安法研究表明,2,2,6,6-四甲基-4-羟基哌啶-1-氧自由基和2,2,6,6-四甲基-4-氧哌啶-1-氧自由基,在水溶液中的单电子氧化电极反应的可逆性随介质酸性,扫描速度和自由基浓度增加而增加,表明电极氧化产物可进一步发生化学反应.     

指向学习体验的物质及其转化复习的教学实践——以“钠及其化合物”为例

学习体验是学生对学习内容、过程、方法、意义的自我感受和评估,对学生学习志趣、学习素养提升有积极正向作用。以钠及其化合物复习为例,将各类别物质间转化关系的构建、物质制备原理和条件的优选作为学习体验对象,依据学习体验的内在发展历程设计学习任务及活动,引导学生亲身体验学科认知方式、学科思维方法、学科应用价值,评价体验结果,激励学生自主学习发生。