IR spectroscopic investigation of structural hydroxyl groups in W−Si heteropolycompound supported on Al2O3

Structural hydroxyl and deuteroxyl groups within the K₄[SiW₁₂O₄₀]/Al₂O₃ and K₆[SiW₁₁PdO₃₉]/Al₂O₃ systems were studied by diffuse-reflectance FTIR spectroscopy in a spectral range of fundamental stretching vibrations, first overtones, and combination bands of stretching and bending vibrations. For hydroxyl groups, the region of combination vibrations is the most informative. The calculated frequencies of bending vibrations of hydroxyl groups (865 and 730 cm⁻¹) are characteristic of acidic OH groups. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2017–2020, October, 1999.     

典型无机含氧酸自由基的特性

碳酸自由基、硝酸自由基、磷酸自由基和硫酸自由基是化学反应的重要中间体，都具有氧化性，对污染物在自然和人为环境中的迁移转化会产生重要的影响.文中较为详细地介绍这几种自由基的电极电位、产生方式、检测方法及与有机物的反应方式.总结四种自由基的特性及与有机物的反应方式可发现，四种自由基和羟自由基电极电位不同，导致它们和有机物反应速率的不同；碳酸自由基并不是羟自由基去除剂，对于一些容易被氧化的化合物，碳酸自由基氧化效果比羟自由基好；四种自由基均可由羟自由基转化而来，并且这四种自由基和羟自由基与有机物反应方式基本一致，都通过电子转移、夺氢和加成的方式进行.可以预测四种自由基和羟自由基降解有机物的机理将非常相似，今后应研究四种自由基与羟自由基相互转化的规律，以及与代表性有机物的反应机理.     

流动注射荧光法测定羟基自由基

研究Sn2 + 催化H2 O2 产生的·OH的反应 ,·OH与Ce3+ 作用后氧化生成无荧光的Ce4 + 。通过测定Ce3+ 的荧光强度的变化可间接测定所产生的羟自由基 ,并结合流动注射技术 ,确定了体系最佳实验条件。测定抗氧化剂清除羟自由基的实验 ,证明该体系可作为在线筛选抗氧化剂的方法之一。     

煤中氢键类型的研究煤中氢键类型的研究

采用真空红外光谱技术清晰地观察到了碳含量７３～８８ｗ％（ｄａｆ）的四个煤样及其溶剂抽出物中的五种羟基的不同氢键缔合类型，并通过原位热解红外光谱技术研究了它们的热稳定性。结果表明，它们的热稳定性顺序为：ＯＨ…π＜ＯＨ…Ｎ＜ＯＨ自缔合≈环状四聚体ＯＨ＜ＯＨ…醚氧。     

~(19)F-NMR法测定聚醚多元醇中伯羟基的相对含量

<正> 聚醚多元醇是聚氨酯材料的主要原料之一.多元醇中伯羟基含量的多少对反应活性有着直接的影响,因此,准确地测定伯羟基含量已成为许多研究者关心的课题,并已报道了不少测定方法,其中主要包括化学动力学方法、~1H-核磁共振(NMR)法和~(19)F-NMR法,~1H-NMR法系利用不同的酰化剂,将聚醚多元醇酰化后测其酰化物的~1H-NMR谱,从伯、仲羟基相应的酯基氢的积分比例来计算伯羟基的相对含量,但由于体系中存在其它含氢基因,且是大量的,使测量困难或应用受到限制.~(19)F-NMR法测伯羟     

Surface Confined Synthesis of Hydroxy Functionalized Two-Dimensional Polymer: The Effect of the Position of Hydroxy Groups

We report on the on-surface synthesis of a series of two-dimensional polymers (2DPs) and macrocycles containing hydroxyl groups on a highly oriented pyrolytic graphite surface. The formed 2DPs and macrocycles were visualized through scanning tunneling microscopy. By varying the solvent and reaction temperature, structural evolution from oligomers to well-ordered 2DPs or discrete macrocycles was directly followed. In addition, we discovered that the reaction outcome can be steered from extended 2DPs to discrete macrocycles or catenular structures by exchanging the position of the hydroxyl and aldehyde group. These results indicate that the relative positions of hydroxyl and aldehyde groups on the biphenyl ring play a determining role in the control and selection of the final products of the surface-confined Schiff base coupling reaction.     

Extraction of Strontium and Cesium by Dicarbollides, Crown Ethers and Functionalized Calixarenes

The two main classes of extractantsused for the extraction of cesium and strontium aredicarbollides and crown ethers. Dicarbollides wereused on a large scale for the extraction of these twoelements from high-activity waste. The basicdicarbollides present drawbacks since they need to bediluted in polar solvent such as nitrobenzene and theirefficiency strongly decreases as the acidity of liquidwaste increases. Crown ethers enable cesium andstrontium to be extracted if the concentration ofsodium or the acidity of solutions are not too high.Recently, calixarenes blocked in the 1,3-alternateconformation were used for the selective extractionof cesium, even from high-salt waste matrices.     

Analysis of oxidation process of cholecystokinin octapeptide with reactive oxygen species by high‐performance liquid chromatography and subsequent electrospray ionization mass spectrometry

The C‐terminal octapeptide of cholecystokinin (CCK8) includes some easily oxidizable amino acids. The oxidation of CCK8 by reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂) and hydroxyl radicals (OH^?) was investigated using reversed‐phase high performance liquid chromatography (RP‐HPLC) and subsequent electrospray ionization mass spectrometry. The mechanism of oxidation of CCK8 in the H₂O₂ system differed from that of CCK8 in the Fenton system, in which OH^? are produced. In the H₂O₂ system, ²⁸Met and ³¹Met were oxidized to methionine sulfoxide, and no further oxidation or degradation/hydrolysis occurred. On the other hand, in the Fenton system, ²⁸Met and ³¹Met residues were oxidized to methionine sulfone via the formation of methionine sulfoxide. In addition, the oxidized product was observed at the Trp residue but not at the Tyr residue, and small peptide fragments from CCK8 were observed in the Fenton system. From these results, it was concluded that ²⁸Met and ³¹Met residues of CCK8 are susceptible to oxidation by ROS. Copyright © 2009 John Wiley & Sons, Ltd.