共查询到20条相似文献,搜索用时 93 毫秒
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一、引言近十几年来化学家们详尽地研究了胶束体系对某些基态有机化学反应速率的影响,发现胶束能显著地提高反应速率,并把这一效应归结为两点:1.胶束能把反应物包围起来,从而增加了反应物的区域浓度,加快了反应速率;2.胶束-水的界面具有一些特殊的性质,例如,离子型胶束表面的区域电场可高达10~6V/cm,这就能大大地影响反应的过渡态,从而影响反应速率。 相似文献
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溶解有机物对控制海洋和淡水水生系统的化学、生物和物理特性有重要的影响.光化学降解溶解有机物改变了生态体系的溶解有机碳、有机物的分子量及光学特性,并且产生复杂的反应性氧化合物、二氧化碳、一氧化碳、小分子量的有机酸、氨基酸、二硫化碳等,对生物过程有重要的影响.本文简要综述了光化学降解溶解有机物的过程机理及其对生物过程的影响. 相似文献
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一类酶反应底和的光化学荧光研究 总被引:1,自引:0,他引:1
研究了对位取代酚在酶反应底物的光化学荧光反应机理,指出光子不仅可以取代过氧化物酶,而且可以取代氧化剂(H2O2)。用于测定多处酶反应底物,结果满意。 相似文献
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从史前人走出所居住的洞穴、到阳光下起,人们就已经意识到阳光对自身的作用以及对环境的影响。地球上许多生命过程如光合作用和视觉过程都和光化学过程有关,这不仅反映了太阳辐射是地球主要的能量来源这一事实,而且也说明光化学反应对人类生存的重要意义。现代光化学的开始,如果不考虑十八世纪末Hales对光合作用的报告和十九世纪中叶卤化银照相术的出现,应当认为本世纪初意大利的Clinician和Silber对在有机光化学中的研究 相似文献
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光化学动力学法测定硝酸盐和亚硝酸盐 总被引:13,自引:1,他引:13
本文研究了甲基橙动力学法测定水、食品及蔬菜中硝酸盐和亚硝酸盐。在紫外光照射下甲基橙退色程度与硝酸盐和亚硝酸盐含量成正比。文中提出首先测定二者的总量,然后在氨基磺酸存在下测定硝酸盐的量,再差减求得亚硝酸盐的量。 相似文献
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我国的光化学研究自1978年以来取得了蓬勃的发展和长足的进步。本文扼要地介绍了研究工作发展的简况,指出,我国的光化学已从起步时那种比较侧重注意具体合成方法和具体反应的研究水平,提高到对机理、对光化学和光物理中一些基本现象和基本运动规律研究的较深入的阶段,并进而发展为有明确应用背景和与高技术研究及开发密切相关的这样一种基础和应用并重的新研究格局。文章指出我国的光化学研究将会继续以较快速度发展,并以崭新姿态进入2000年。 相似文献
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在0.2mol/LH2SO4-10%乙醇介质中及紫外光照射条件下磷钼杂多酸光还原为磷钼蓝(λmax=780nm)。据此建立了一个测定0.05~2.0μg/mL磷的光化学分析新方法,并用于试样分析。探讨了光化学反应机理。 相似文献
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Organic photochemical reactions can be understood as transformations of the electronically excited states of the reactant molecules. By considering Lewis structure or molecular orbital representations of these excited states it is possible to outline the several possible reactions available in the case of a given reactant. A number of different types of photochemical transformations are now reasonably well understood. In these cases one finds the same common controlling feature, namely the tendency for an excited state species to follow mechanistic pathways of minimum energy and the requirement for continuous electron redistribution in following these pathways. These preferred transformations can often be selected by inspection of relative bond orders for different types of bonding, by comparison of the potential energy surfaces available to the excited state molecules, and by use of correlation diagrams. The reactions derive from both singlet and triplet states, and one of the more reliable methods now available for identifying excited states reacting is termed the “fingerprint method”. Examples of the author's mechanistic approach are given both for ketone and for hydrocarbon photochemistry. 相似文献
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Heinz D. Roth 《Angewandte Chemie (International ed. in English)》1989,28(9):1193-1207
Although sunlight induced photochemistry must have occurred on the planet Earth for billions of years, the chemical changes caused by light have attracted systematic scientific scrutiny only relatively recently. How did scientists first conceive the idea that the interaction of materials with light could not only cause physical phenomena, but could also alter their chemical nature? When sunlight began to be employed as a heat source for distillation, the eventual discovery of photochemical reactions was assured. One can envision three types of changes that would have aroused the curiosity of laboratory chemists: color changes; the evolution of gas bubbles (oxygen in photosynthesis); and the precipitation of a photoproduct less soluble than its precursor. Less predictable was the observation that sunlight caused crystalline santonin to burst because it is converted into a product with a different crystal lattice. In the course of the eighteenth and nineteenth centuries a variety of photochemical reactions, some observed by chance, others uncovered in carefully planned studies, ultimately led to a major systematic investigation that established photochemistry as a viable branch of chemistry. 相似文献
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Astrid M. Müller Stefan Lochbrunner Wolfram E. Schmid Werner Fuß 《Angewandte Chemie (International ed. in English)》1998,37(4):505-507
What is the standard course of the cis – trans isomerization of nonpolar polyenes? Many results support a pathway in which only a central CH group rotates out of the plane, while the remaining parts of the molecule reorient within the plane (“hula-twist” mechanism). The intermediate structure through which the molecule passes corresponds to the geometry predicted for the conical intersection of the S1 and S0 potential energy surfaces (see picture). 相似文献
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Ewa Lipczyńska-Kochany Hiizu Iwamura Jan Kochany 《Monatshefte für Chemie / Chemical Monthly》1987,118(12):1345-1348
N-Phenylbenzenecarbohydroxamic acid undergoes a photoreaction in cyclohexane and methanol to give benzanilide as a major product.
Photochemie von N-Phenylbenzolcarbohydroxamsäure
Zusammenfassung N-Phenylbenzolcarbohydroxamsäure ergibt in einer Photoreaktion (in Cyclohexan und Methanol) Benzanilid als Hauptprodukt.相似文献
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Summary The condensed bridged isoxazolines4 are rearranged on irradiation with a low-pressure mercury lamp exclusively into condensed derivatives of tetrahydropyridine5. The selectivity of the rearrangement is due to a stabilization of the biradical8 by the overlap of the radical-electrons with -electrons of the C=C double bond and the heterocyclic ring. Quantum yields of the photorearrangement, established from the consumption of the starting materials4, were determined.
Photochemie kondensierter Isoxazoline
Zusammenfassung Die kondensierten überbrückten Isoxazoline4 werden durch Bestrahlen mit einer Niederdruckquecksilberlampe ausschließlich zu kondensierten Tetrahydropyridinderivaten (5) umgelagert. Die Selektivität der Umlagerung beruht auf der Stabilisierung des Diradikals8 durch Überlappung der ungepaarten Elektronen mit -Elektronen der C=C-Doppelbindung und des Heterocyclus. Aus dem Verbrauch an Ausgangsmaterial (4) wurden Quantenausbeuten der Photoumlagerung bestimmt.相似文献
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Herbert Meier 《Angewandte Chemie (International ed. in English)》1992,31(11):1399-1420
Stilbenes and compounds containing stilbene units in their structures form the material basis for numerous research projects in photophysics and photochemistry. Moreover, because these compounds are easy to synthesize and are thermally and chemically stable, they are taking on an increasingly prominent role in the area of materials science investigations into optical, electrical, and optoelectronic properties. In accordance with the interdisciplinary nature of such studies, this article aims to provide a bridge extending from molecular theory and photophysical measurements, through preparative applications, to material effects and their potential technical applications. 相似文献