Ultrasonically activated reduction of substituted nitrobenzenes to corresponding N-arylhydroxylamines

Arylhydroxylamines can be obtained by reduction of the corresponding nitroaromatic compounds. We report here an efficient preparation of arylhydroxylamines by a controlled reduction of nitro compounds using zinc metal and ammonium chloride under ultrasonic activation in very short reaction times.     

Improvement of Nonlinear Modulation by Cascaded Mach-Zehnder Configuration

A two-stage cascaded Mach-Zehnder modulator is employed for the linear external modulation of a laser. The modulation electric fields are applied on the first and second stages in the Z and Y directions, respectively. Because of the inherent versatility of the adjustable modulation parameters, improved modulation perfor mances with a high modulation depth and a high linear response are demonstrated. When a modulation depth of 21 % is required, the ratios of the second and third harmonic terms to the fundamental term can be simultaneously achieved as low as 104 and 86.7 dB, respectively.     

A note on reduction of quadratic and bilinear programs with equality constraints

Reduction of some classes of global optimization programs to bilinear programs may be done in various ways, and the choice of method clearly influences the ease of solution of the resulting problem. In this note we show how linear equality constraints may be used together with graph theoretic tools to reduce a bilinear program, i.e., eliminate variables from quadratic terms to minimize the number of complicating variables. The method is illustrated on an example. Computer results are reported on known test problems.     

Normal Ideals and Expected Reduction Numbers #

We give a criterion for normality of certain strongly Cohen-Macaulay ideals, of a regular local ring, having the expected reduction number.     

DBC-偶氮胂与氯化亚锡的氧化还原反应

本文报道应用紫外光谱及化学鉴定反应,对锡(Ⅱ)与DBC-偶氮胂的褪色作用进行了研究。首次发现,在酸性介质中,SnCl_2可使DBC-偶氮胂分子中的两个发色团双偶氮基断裂,使试剂分解为小分子产物,从而导致试剂褪色,以至无色。     

New enantioselective method for hydration of alkenes using cyclodextrins as phase transfer catalyst

A new enantioselective/inverse phase transfer catalysis (IPTC) reaction for the Markovnikov hydration of double bounds by an oxymercuration-demercuration reaction with cyclodextrins as catalysts was disclosed. Moderate ee (up to 32%) and yields (14-60%) were obtained for allylic amines and protected allylic alcohols as starting materials.     

预处理条件对用于CO_2加氢的超细CuO－ZnO－SiO_2催化剂性能的影响

采用ＸＲＤ、ＢＥＴ、ＴＰＲ手段，研究了焙烧和还原温度对超细ＣｕＯ－ＺｎＯ－ＳｉＯ２催化剂的性质及其ＣＯ２加氢反应催化活性的影响．胶体在５７３－７７３Ｋ范围内焙烧生成ＣｕＯ、Ｃｕ２Ｏ、ＺｎＯ晶相，随着焙烧温度继续升高，ＣｕＯ和ＺｎＯ晶粒逐渐变大，但催化剂的比表面积和孔容变化很小．在９７３Ｋ焙烧后出现Ｚｎ２ＳｉＯ４晶相，使催化剂比表积和孔容变小，导致催化剂活性降低．焙烧温度对催化剂活性的影响大于对ＣＯ２加氢产物分布的影响．在５４８－６４８Ｋ范围内，催化剂还原温度对其催化活性影响不大．７０３Ｋ高温还原后，可能由于Ｃｕ０晶粒的出现，使得催化剂的活性下降．ＴＰＲ研究结果进一步表明，焙烧温度影响ＣｕＯ同ＺｎＯ、ＳｉＯ２之间的相互作用和催化剂的还原行为．     

Application of organolithium and related reagents in synthesis XVI: Synthetic strategies based on aromatic metallation. A concise regiospecific conversion of chlorobenzoic acids into their benzylated derivatives

Summary The reaction of benzyl bromide withbis-(N- and C-ortho)-lithiated chloroanilides4,5, and6 has been examined. It has been found that in the case where the lithiated compound was derived frommeta-methoxyanilides, pre-addition of LiBr orTMEDA was required to achieve C-benzylation. These results were accounted for by the conversion of the usually formed dimer into a mixed dimer with the LiBr orTMEDA complex in which the C-lithium bond appears to be more accessible towards electrophiles. The practical synthesis of -benzylchlorobenzoic acids10,11, and12 was accomplishedvia ionic reductive cleavage (Et₃SiH/TiCl₄) of the corresponding phthalides18,19, and20. The acids10,11b, and11c afforded the corresponding anthrones, upon treatment with trifluoroacetic anhydride which were oxidized by chromium trioxide to the new chloroantraquinones21,22, and23.

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Anwendung von Organolithium und verwandten Reagenzien in organischen Synthesen, 16. Mitt.: Synthesen mittels aromatischer Metallierung. Eine bequeme regiospezifische Umwandlung von Chlorbenzoesäuren in ihre Benzylderivate

Zusammenfassung Die Reaktion von Benzylbromid mit denbis-(N- und C-ortho)-lithiierten Chloraniliden4,5 und6 wurde untersucht. Im Falle lithiierter Verbindungen ausmeta-Methoxyaniliden ist die Zugabe von LiBr oderTMEDA während des Lithiierungsprozesses für die C-Benzylierung erforderlich. Diese Ergebnisse werden durch Umwandlung des gewöhnlich enstehenden Dimers in ein gemischtes Dimer mit dem LiBr- oderTMEDA-Komplex erklärt, in welchem die C-Li-Bindung für Elektrophile leichter zugänglich ist. Diese praktische Synthese dero-Benzylchlorbenzoesäuren10,11 und12 wird durch reduktive Spaltung der entsprechenden Phthalide18,19 und20 mit Et₃SiH/TiCl₄ ergänzt. Bei der Reaktion der Säuren10,11b und11c mit Trifluoressigsäureanhydrid entstehen die erwarteten Anthrone, die durch Oxidation mit Chromtrioxid in die neuen Chloranthrachinone21,22 und23 umgewandelt wurden.

     

还原荧光法测定水和废水中的对硝基酚

本文用乙酸丁酯萃取水和废水中的对硝基酚,用氢氧化钠溶液反萃取,然后用硼氢化钾还原对硝基酚为对氨基酚,用荧光法进行分析测定。荧光激发波长和发射波长分别为274nm和372nm。检测限为3.0μg/L。样品加标回收率为89％～96％。     

On the Reduction of Copper Oxide

The reduction of CuO with hydrogen has been studied with a temperature programmed reduction technique. According to a proposed reduction mechanism, the reduction was initiated with a interaction between hydrogen and active sites of copper oxide, the rate of the reduction was limited by the diffusion of water from the crystalline. The activation energy of this diffusion is found to be 13Kcal/mol. Reoxidation of copper powder may cause redispersion of the crystalline. The chemical interaction between copper oxide and Cabosil is found very weak.