铑(Ⅰ)催化的不对称硅氢化反应合成手性2-氨基-1-芳基乙醇研究

报道了以Rh(I)－手性2－（2－吡啶基）－4－羧甲基－1，3－噻唑烷为催化剂，2－氨基芳香酮的不对称硅氢化反应，在常温常压下手性2－氨基－1－芳基乙醇的产率几乎可达定量，产品光学纯度可达80％e.e以上。     

合成芳樟醇的研究进展

本文综述了合成芳樟醇的路线及关键反应的研究进展．包括乙炔－丙酮法、异戊二烯法、β－蒎烯法与α－蒎烯法．重点综述α－蒎烯法，即：蒎烯氢化、蒎烷氧化、蒎烷氢过氧化物还原与蒎烷醇的热解。     

噻唑烷类配体的手性结构及其在催化苯乙酮不对称硅氢化？…

用分级结晶或柱层析方法对２－（２－吡啶基）－４－羧甲基－１，３－噻唑烷及２－甲基－２（２－吡啶基）－４－羧甲基－１，３－噻唑烷两种手性配体进行提纯，分别考察了其与」Ｒｈ（ＣＯＤ）Ｃｌ「２制备的在位催化剂催化苯乙酮的不对称硅氢化反应，发现只有噻唑烷环上的Ｃ４位手性中心对催化反应结果有影响，其Ｃ２位手性中心在Ｒｈ（Ｉ）催化下发生了快速差向异构化反应。     

聚铝氨烷－铂络合物催化α－萘酚选择性氢化反应的研究

本文研究了二氧化硅负载的聚铝氨烷－铂络合物在α－萘酚选择性氢化反应中的催化性能。发现此催化剂在３０—５０℃和０．１ＭＰａ的温和条件下，对α－萘酚的氢化反应具有较高的催化活性和选择性。当α－萘酚的转化率达１００％时，目的产物５，６，７，８－四氢－α－萘酚的选择性高于８０％。考察了络合物中Ｎ／Ｐｔ摩尔比、反应温度、时间、溶液的ｐＨ值和溶剂等反应条件对催化活性及选择性的影响，此催化剂重复使用三次后，催化活性和选择性未见明显下降，具有良好的稳定性。     

化学简讯

有关无机化学消息七则氟铂(V)酸二氧 O_2~ [PtF_6]~-:借混合等克分子量的氧和六氟化铂在室温形成。它的化学性质和磁化率与上列结构相符。较高级的氢化锗(锗烷):将锗甲烷在产生臭氧的仪器(静放电)中循环,可获得较高级的锗烷。经气体层析可得20%锗乙烷,26%锗丙烷,10%锗丁烷,0.8%锗戊烷,9.6%锗己烷,0.6%锗庚烷,0.05%锗辛烷和少于0.01%的锗壬烷。氮化铀的熔点:在至少2.9大气压的氮气下,氮     

羊毛—过渡金属络合物的合成及其选择性催化氢化性能的研究

合成和初步表征了以天然高分子羊毛为载体的羊毛一钯单金属和羊毛－钯－铁双金属络合物催化剂；研究表明，在羊毛－钯络合物催化剂中，引入第二金属能极大地改进它的催化性能，提高其催化选择性，更有效的接近酶催化剂的特征．在常温常压下，以羊毛－钯－铁双金属络合物作催化剂，能顺利地使氯代硝基苯和氯代苯甲醛选择氢化成氯代苯胶和氯代苯甲醇．产率均为１００％，有效地抑制了氰取代基的氢解脱除，络合物催化剂中的钯／铁原子比极大地影响着该类氢化反应选择性，在氯代硝基苯和氯代苯甲醛的氢化反应中，最佳的钯／铁原子比分别为１：３和１５：１，这时反应的选择性均达到１００％，溶剂和温度对氢化反应速度均有一定的影响．     

手性噻唑烷-铑(I)配合物催化的苯乙酮不对称硅氢化反应

由L-半胱氨酸甲酯与α-吡啶甲醛缩合制备了2-(α-吡啶基)-4-羧甲基-1, 3-噻唑烷手性配体。用该手性配体与[Rh(COD)]2反应原位生成的Rh(I)配合物为催化剂进行了苯乙酮的不对称硅氢化反应。反应的化学产率达91%, 光学产率达82.1%e.e.。考察了各种反应条件对催化剂性能的影响。     

锗甲基丙酰—α—氨基酸酯系列倍半氧化物的合成与表征

锗甲基丙酰氯与α－氨基酸酯反应继而水解得到４个新的锗甲基丙酰－α－氨基酸乙酯倍半氧化物，研究了其ＩＲ，＾ＨＮＭＲ和１３ＣＮＭＲ与氨基酸代基结构效应的关系。     

手性噻唑烷-铑(I)配合物催化的苯乙酮不对称硅氢化反应

由L-半胱氨酸甲酯与α-吡啶甲醛缩合制备了2-(α-吡啶基)-4-羧甲基-1, 3-噻唑烷手性配体。用该手性配体与[Rh(COD)]2反应原位生成的Rh(I)配合物为催化剂进行了苯乙酮的不对称硅氢化反应。反应的化学产率达91%, 光学产率达82.1%e.e.。考察了各种反应条件对催化剂性能的影响。     

两种四乙酸四氮杂环烷化合物的合成

在氢氧化钾存在下，1，4，7，10-四氮杂环十二烷与溴乙酸进行N-羧甲基化反应，得到N，N′N″N-四乙酸1，4，7，10-四氛杂环十二烷（DOTA，I），经重结晶纯化，产率88．1％．在碳酸钾存在下，1，4，8，11-四氮杂环十四烷与溴乙酸卡酯进行反应，生成N－乙酸苄酯中间体．该中间体在室温和4．04×105Pa氢气压力下，用Pd／C地催化氢解脱苄基得到N，N′N″N-四乙酸1，4，8，11－四氮杂环十四烷（TETA，Ⅲ），产率56．0％。     

Effect of cathodic electrolyte on the performance of electrochemical hydride generation from graphite cathode

The classic silver diethyldithiocarbamate (SDDC) spectrophotometric procedure for arsenic determination has been used for investigation of the effect of cathodic electrolyte on the performance of electrochemical hydride generation (HG) from graphite cathode. The results of this study show that the presence of a soft metal ion such as Cd(II), Sn(II) and/or Zn(II) in the acidic cathodic electrolyte can increase effectively the efficiency of electrochemical hydride generation and decrease the effect of interferences. The possible mechanisms of these effects have been discussed in detail. The parameters related to the electrochemical hydride generation were investigated. Also the characteristic data of the electrochemical hydride generation and common hydride generation by NaBH₄ were compared. Under optimised conditions, the system is selective to As(III) and total inorganic analyses can be performed after a pre-reduction stage prior to electrochemical hydride generation. This will allow the differential determination of inorganic arsenic species. The method is appropriate to the determination of 4-40 μg of each arsenic species.     

氢化物发生-电感耦合等离子体质谱联用技术研究

运用自制的接口，实现了氢化物发生与电感耦合等离子体质谱的联用。考察了连续流动氢化物发生器、气动型断流式氢化物发生器及气动型流动注射氢化物发生器与电感耦合等离子体质谱仪的联用性能。确定了仪器的最佳参数，研究了系统的分析性能，实现了能生成氢化物的8种元素的定量测定。     

Demethylation of trimethylantimony species in aqueous solution during analysis by hydride generation/gas chromatography with AAS and ICP MS detection

The method of hydride generation for the speciation of antimony compounds was examined with respect to the problem of molecular "rearrangement'. Specifically, demethylation of trimethylstilbine during the analysis of trimethylantimony dichloride (Me₃SbCl₂) was studied. Previously published observations that enhanced demethylation takes place as a result of inadequate preconditioning of the analytical apparatus were found to be not reproducible. However, demethylation was enhanced as the pH decreased when using two different analytical methods: semi-continuous flow hydride generation–gas chromatography–atomic absorption spectrometry (HG– GC–AAS), and batch-type hydride generation– gas chromatography–inductively coupled plasma mass spectrometry (HG–GC–ICP MS). Applications of the hydride generation method to environmental samples revealed differences in analytical results at high and low pH, and enhanced demethylation taking place because of the matrix in a fungal extract sample. The authors recommend that researchers using the method of hydride generation for antimony compounds carefully test the reaction conditions with standard compounds and use the method of standard addition only. © 1998 John Wiley & Sons, Ltd.     

碱性体系在线氢化物发生—原子荧光光谱法测定痕量铋

提出了一种碱性体系在线氢化物发生－原子荧光光谱法测定痕量铋的分析方法。设计了在线氢化物发生系统流路及操作程序，研究了碱性体系氢化物发生的各项最佳条件。方法操作简便快速，能有效地消除过渡元素的严重化学干扰。应用于黄铜标样中痕量铋的直接测定，获得满意结果。     

Determination of zinc in food using atomic fluorescence spectrometry by hydride generation from organized media

A method was proposed for the determination of zinc by atomic fluorescence spectrometry with hydride generation from surfactant-based organized media. The ability of different nature micelles to improve hydride generation of zinc was investigated using an intermittent flow hydride generator and the possible mechanism was discussed. The advantages of hydride generation from the organized media of cetyltrimethylammonium bromide (CTAB) were contrasted with that from aqueous media in sensitivity and precision of the zinc determination. The micellar media of CTAB improved the hydride generation processes of zinc both thermodynamically and kinetically. In addition some transition metals, presumably metal borides, were found to catalyze the hydrogenation of zinc. The proposed method has been validated by the determination of zinc in the certified reference materials using the standard addition method with satisfactory result.     

Electrochemical hydride generation as a sample-introduction technique in atomic spectrometry: fundamentals,interferences, and applications

Electrochemical hydride generation (EC-HG) has been proposed as a valid alternative to chemical generation as a sample-introduction technique in atomic spectrometry. In this review fundamental aspects of the technique are revised, including designs of electrolytic cells, mechanisms of the generation process, and interferences caused by the presence of different species. Special attention is paid to the role of the configuration of the cathodes and their materials on the efficiency of hydride generation and on interferences from concomitant species. An overview of the application of EC-HG to the analysis of real samples is also given.     

A new continuous hydride generator for ICP-AES

With the construction of a tubular hydride generator some of the technical inconveniences of the hydride generation technique are overcome. The system allows the determination of hydride forming elements and mercury with a sample uptake rate of 1 ml/min without loss of sensitivity. Due to the small volume of the reactor and the performed neutralization of the reaction mixture in the siphon the memory effect is reduced. The sodium hydroxide used for neutralization also prevents the generation of an excess of hydrogen and therefore removes its negative influence on the plasma discharge.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

流动注射氢化物石墨炉原子吸收法的应用研究 Ⅰ.——实验装置与分析性能

氢化物石墨炉联用技术的原理是先在较低温度下将氢化物蒸气通入石墨炉并分解沉积于石墨管的内表面,然后再在高温下原子化。该法能明显提高灵敏度,消除液相和气相干扰。本文采用自制的半自动氢化物石墨炉进样系统及流动注射氢化物发生器,直接在普通石墨炉上进行氢化物石墨炉分析,研究了部分元素的测定条件,建立的方法操作方便,灵敏度高,耗样少,线性范围宽,是一种值得推广的新方法。     

Investigation of thallium hydride generation using in situ trapping in graphite tube by atomic absorption spectrometry

Thallium hydride was generated from aqueous solutions by merging sample and sodium tetrahydroborate reductant in a batch system. In situ preconcentration of volatile thallium hydride in a preheated graphite furnace coated with palladium, which was used as both the collection medium and atomizer, greatly improved the sensitivity for the determination of thallium by hydride generation atomic absorption spectrometry. The presence of tellurium can increase the generation efficiency of thallium hydride. The operating conditions were optimized. The calibration graph is linear up to 100 ng and the characteristic mass for thallium was 0.92 ng which is seventeen times lower than that obtained with the heated quartz tube atomizer.     

The analysis of inorganic and organometallic antimony,arsenic and tin compounds using an on-column hydride generation method

A novel method of analysis of inorganic and organometallic compounds is reported. Essentially this utilizes the well-documented hydride generation technique, but in the present method the hydrides are generated from their involatile precursors (e.g. chlorides) on a GC column and separated from each other and from extraneous materials on the same GC column in a single process. Using the method, a solution of butyltin chlorides can be directly injected into a GC AA system to yield the volatile hydrides for separation, detection and quantification. To date, species analysed by this method include inorganic As(III), Me₂AsOOH, inorganic Sb(III) and Sb(V), MeSnCl₃, Me₂SnCl₂, Me₃SnCl, Et₂SnCl₂, Et₃SnCl, BuSnCl₃, Bu₂SnCl₂, Bu₃SnCl and Pr₃SnCl. With the use of the internal standard Pr₃SnCl and with the almost complete hydridization afforded by the technique, the procedure is shown to eliminate errors and to reduce the time involved in the analysis. The use of on-column derivatization also allows for the possibility that, in some cases, organotin hydrides reported to be found in the natural environment may, in fact, be organotin chlorides being reported as hydrides owing to inadvertent hydride production on the column. Some reports of successful gas chromatography for organotin halides could also conceivably be due to on-column hydride generation.