Ru(II)催化有机叠氮与炔反应机理的理论研究

采用密度泛函理论, 对在Ru(II)催化剂存在下, 有机叠氮化合物和末端炔的反应机理作了深入理论研究. 在B3LYP/LANL2DZ水平上, 对该反应体系中势能面各驻点的几何构型进行了全优化计算, 并经振动频率分析确定了过渡态和中间体, 通过内禀反应坐标(IRC)的计算, 确认了反应物、中间体、过渡态和产物的相关性. 对多个反应通道的协同反应以及分步反应进行了研究. 结果表明: 协同反应通道Ic和分步反应通道IIc是反应能垒较低的反应通道, 活化自由能较其它反应通道低, 有利于1,5-二取代1,2,3-三唑的生成, 具有特定的区域选择性, 与实验结果吻合.     

The spectrophotometric determination of nitrate in natural waters,with particular reference to sea-water

Nitrate can be reduced to nitrite in good yield by means of hydrazine in alkaline solution; the reaction is promoted by catalytic quantities of copper. The authors have established the optimum conditions for tlie reduction and applied the method to the determination of nitrate in fresh waters and in sea-waters. The nitrite formed is determined by Mellon and Rider's modification of the Griess-Ilosvay procedure. The reduction with hydrazine is carried out in the presence of 0.25 p.p.m. of copper at pH 9.6 in a solution buffered with sodium phenate. It is complete within 24 hours at room temperature. The method will detect ca. 0.3 μg NO₃$\text{N}\text{l}$ and gives a standard deviation of ca. 2% in the range 20-600 μg NO₃-$\text{N}\text{l}$. Up to 60 determinations can be made per 6 hour working period. The interference of nitrite has been investigated. Ammonium salts, urea, and amino acids do not interfere, at the concentrations at which they occur in sea-water.It is preferable to analyse samples immediately after collection, but if this is not possible, they should be filtered, sterilized with 2 p.p.m. of mercuric chloride and stored in glass containers.     

Determination of boron in glass by the nuclear track technique

Summary Determination of Boron in Glass by the Nuclear Track Technique The nuclear track technique using the¹⁰B(n)⁷Li reaction, has been applied to determine boron in concentration ranges (1.59 to 7.75%) ordinarily considered high for nuclear determinations. Factors limiting the overall precision of the method and restricting the linear dependence of track density on boron concentration are examined. Boron alpha track densities are used to construct planar profiles of boron distribution within the surface region of bulk glass and CVD films. Calibration curves for quantitative lateral profiling of surfaces are constructed and show the selective corrosion of borosilicate glass surface resulting in boron depletion.     

The determination of aluminium in seawater and freshwater by cathodic stripping voltammetry

Dissolved aluminium in seawater and freshwater is determined by cathodic stripping voltammetry (c.s.v.) preceded by adsorptive collection of complex ions with 1,2-dihydroxyanthraquinone-3-sulphonic acid (DASA) on the hanging mercury drop electrode. Complexation of aluminium by DASA is rapid and no waiting period or heating of the sample is required. Optimal conditions are a DASA concentration of 10^?5 M, a solution pH of 7.1–7.3 and an adsorption potential of ?0.9 V; the c.s.v. scan is done in the differential-pulse mode. The limit of detection is 1 nM aluminium for an adsorption time of 45 s. The total time needed, including 50min deaeration and a standard addition, is 10–15 min per sample. No serious interferences were found; u.v. irradiation is recommended for samples containing high levels of organic materials.