Fluorous reagents and scavengers versus solid-supported reagents and scavengers,a reaction rate and kinetic comparison

Summary Reactions using fluorous reagents and scavengers are compared side-by-side with their solid-supported counterparts. Fluorous triphenylphosphine is used in the bromination reaction of alcohols, fluorous thiol is used as an electrophile scavenger for α-bromoketones, fluorous isatoic anhydride is used as a nucleophile scavenger for primary and secondary amines. Reactions involving fluorous reagents and scavengers occur in homogeneous media with solution-phase reaction kinetics. Reactions with solid-supported reagents and scavengers occur in a heterogeneous media, and the reaction kinetics are greatly affected by the nature of the solid-support and reaction environment. Significantly larger amounts of reagents and more time are usually required to complete the solid-supported reaction.     

Polyborylated reagents for modern organic synthesis

Diverse kinds of gem- and vic-diborylated compounds are now readily available thanks to advances in gem-diborylation of lithium carbenoids as well as vic-diborylation of carbon-carbon multiple bonds with diboron compounds. These diborylated reagents lead to invention of polyborylated reagents and many novel and useful synthetic methods for supreme stereocontrol. This review summarizes preparative methods and synthetic reactions of di- and polyborylated reagents with the emphasis on multiple bond formation.     

Hydrophilic Labeling Reagents of Dipyrrylmethene-BF2 Dyes for Two-Photon Excited Fluorometry: Syntheses and Photophysical Characterization

Recently introduced bioaffinity assay technology, ArcDia TPX, is based on two-photon excited fluorescence (TPE) and it enables separation-free ultra-sensitive immunoassays from microvolumes. Here we present syntheses of novel two-photon excitable fluorescent labeling reagents which have been specially designed to be used as label molecules in the ArcDia TPX assay technique. The labeling reagents are based on dipyrrylmetheneboron difluoride (dipyrrylmethene-BF2) chromophore, which have been substituted with aryl, heteroaryl or arylalkenyl chemical groups to extend the pi-electron conjugation. These substitutions results in a series of dipyrrylmethene-BF2 fluorophores with different photophysical properties. Dipyrrylmethene-BF2 fluorophores have been further substituted with a dipeptide linker unit and finally activated as succinimidyl esters to enable specific coupling with primary amino groups. The dipeptide linker serves as a spacer arm between the label and a target, and enhances the solubility of the label in aqueous solutions. Study of the chemical and photophysical performance of the new labeling reagents is described. The new labeling reagents exhibit high fluorescence quantum yields, and molar absorption coefficients. The results show that the new labels with the hydrophilic dipeptide linker unit provide large two-photon excitation cross-sections, high fluorescence quantum efficiency and good solubility in aqueous solutions. The results suggest that the novel dipyrrylmethene-BF2 labels are highly applicable to bioaffinity assays based on two-photon excitation of fluorescence.     

High-loading polyglycerol supported reagents for Mitsunobu- and acylation-reactions and other useful polyglycerol derivatives

Summary In this paper we present soluble dendritic polyglycerol (PG) supported reagents PG-DEAD, PG-PPh₃, and PG-DCC as well as scavengers PG-carbonate, PG-carbazate, and PG-amine, which all have been synthesized in high overall conversions and yields using simple purification techniques. The supported reagents have been used simultaneously in Mitsunobu and acylation reactions. All polymeric reagents and scavengers can be removed by simple precipitation/filtration protocols to give chromatography-free products of high purity. In the course of the syntheses of the polymeric reagents three intermediates turned out to be precious polyglycerol derivatives: a mixed carbonate as an electrophilic derivative, polyglyceryl carbazate as a scavenger for carbonyl compounds, as well as polyglycerylamines as amino analogues of polyglycerol.     

Dissociation energy for the P2S2 ring in a family of thionation reagents and the corresponding chemical reactivity of separated species: a density functional theory analysis

In this work, 11 members of a 1,3,2,4‐dithiadiphosphetane 2,4‐disulfides family are analyzed from a theoretical point of view. These reagents are involved in thionation processes, where the first step implies the breaking bond between sulfur and phosphorus atoms to destroy the P₂S₂ ring, which is characteristic of these compounds. Thus, we estimate this breaking bond by analyzing the Gibbs energy over several temperatures, concluding that 3 of the most representative reagents of this family (Belleau, Davy, and Lawesson) are dissociated to yield 2 symmetrical species, for temperatures less than 400 K. This estimation, in gas phase, is reasonably good with respect to experimental information where these 3 reagents react at temperatures below 383 K. These 3 reagents present the lowest dissociation energies for several temperatures due to enthalpic and entropic contributions. Reagents and their monomers were analyzed by using the density functional theory framework to show that among the studied reagents, 3 of them exhibit similar behavior between themselves and correspond to the most used reagents in experimental thionation processes. For the separated species, the density functional theory chemical reactivity predictors indicate that the phosphorus atom has the biggest response when the system accepts electrons and sulfur atoms have the biggest response when the system gives electrons. This result is totally in accord with experimental suggestions for this kind of processes.     

New approach for understanding the fundamental chemistry of the oxidative sample digestion in spectrochemical analysis

The process known as “wet digestion” is widely used in analytical chemistry as the most common way of dissolving solid samples for elemental spectrochemical analysis. Wet digestion involves the use of oxidizing reagents and acids–mainly HNO₃, H₂O₂, H₂SO₄, HClO₄, and other complementary acid reagents such as HF, HCl, or their mixtures. Wet digestion has become popular and attractive to users in part owing to the application of modern equipment with new technologies such as temperature-controlled heating blocks, microwave systems, and automated digestion systems, among others. Nonetheless, the use of modern, sophisticated instruments does not change the physical and chemical foundations of the classic chemical process. Until now, simplified equations have been used to explain this process. However, fundamental chemical mechanisms and thermodynamic concepts have been commonly left aside. In this work, the acid digestion of samples has been approached based on the chemical reactions, detailing the role and the effect of main reagents and intermediaries. The reactions that can occur during the digestion process have been specified considering the fundamental thermodynamic properties of the reagents used, especially the oxidizing reagents HNO₃ and H₂O₂. This article will be a beneficial resource for students, instructors, and professionals alike.     

Deposition of silver nanoparticles on polyester fiber under ultrasound irradiations

The polyester fiber containing Ag nanoparticles was prepared through the chemical reduction under ultrasound irradiation. Influences of reduction reagents on the morphological properties of Ag nanoparticles@polyester fiber were studied. The sizes of metallic nanoparticles vary significantly with the types of reduction reagents used in the synthesis. A strong reduction reaction promotes a fast reaction rate and favors the formation of smaller nanoparticle. A weak reduction reagent induces a slow reaction rate and favors relatively larger particles. The products were investigated by means of scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD).     

Study of cluster materials obtained by selective laser photochemistry

This paper presents experimental results from the study of the characteristics of cluster materials obtained by resonance laser photochemistry. The effect of the redox reagents used in the photoprocessing on the size and shape of cluster structures of gold has been studied. The minimum size of the structures, measured by electron microscopy, is 30–50 nm. When organic acids are used as redox reagents, fractal structures formed from flat scales are synthesized. Redox reagents based on alcohols form cluster structures of fractal type consisting of spherical clusters. Fiz. Tverd. Tela (St. Petersburg) 40, 2236–2238 (December 1998)     

Effect of alkali reagents on the crystal structure of chemically deposited CoP films

The effect alkali reagents have on the crystal structure of CoP films prepared via chemical deposition is investigated. It is shown that the use of sodium hydrogen carbonate and ammonium hydroxide in low concentrations leads to growth of the hexagonal phase in the films. As the concentration of alkali reagents is increased, the formation of a cubic or amorphous phase is observed.     

Sensitive solid-state optical sensible materials for photothermal determination of trace metals

Methods of photothermal (thermal-lens) determination of iron and mercury on the basis of solid polymer matrices with immobilized reagents are developed. These methods combine selective and efficient preconcentration of trace elements to be analyzed on a transparent polymer matrix, the sensitivity of determination with the reliable and traceable photometric procedures and highly sensitive thermal-lens detection (enhanced in polymers compared to solutions). The advantage of this approach is in the use of sensitive organic reagents previously developed for spectrophotometry. In this study, transparent polymethacrylate matrices modified with copper dithizonate and 1,10-phenanthroline were applied to the determination of mercury(II) and iron(II), respectively.     

Polymer resin library and the discovery of highly efficient polymer supported reagents and scavengers

Summary This paper is focused on the preparation of a library of highly efficient, tailor made, macroporous resins as supports for reagents and scavengers. From this library a macroporous resin, prepared with 40% cross-linking and with a porogen level of 300% in toluene gave a material superior to those presently available, and was shown to be highly efficient in the preparation of novel highly reactive polymer supported reagents, including scavengers and oxidants.     

新型螯合磁性纳米Fe_3O_4的制备及其性能研究

采用共沉淀法制备了磁性四氧化三铁(Fe3O4)纳米粒子,并通过硅烷偶联剂对其表面进行改性,进一步在其表面偶联修饰氨基硫脲,制备了螯合磁性纳米Fe3O4粒子。利用广角X射线衍射仪(WAXD)、红外光谱仪(FTIR)、分光光度计等对磁性纳米粒子的结构和性能进行了表征。结果表明,纳米Fe3O4为反尖晶石结构,通过偶联修饰可以实现氨基硫脲在纳米粒子表面的化学改性。螯合磁性纳米粒子具有良好的分散性和磁响应性,且对多种金属离子(Pb2+、Hg2+、Zn2+、Cd2+)具有良好的螯合效果。     

6-NO_2-BTAMB与钴显色反应的研究与应用

研究了6-NO2-BTAMB与钴显色反应。实验表明,在pH6.2—7.4(CH2)6N4-HCl体系中,钴与试剂定量地形成稳定的蓝绿色络合物,表观摩尔吸光系数ε650=1.18×105L·mol-1.cm-1;钴浓度在0—6μg/10mL范围内符合比耳定律。用于VB12和钴分子筛中微量钴的测定,结果令人满意。     

Ultrasound promoted N-alkylation of pyrrole using potassium superoxide as base in crown ether

Ultrasound accelerates the N-alkylation of pyrrole by alkylating reagents using potassium superoxide as base in the presence of 18-crown-6. A much lower yield of N-alkylated pyrrole was realized in the absence of ultrasound. N-alkylating reagents employed for pyrrole are methyl iodide, ethyl bromide, benzyl bromide, as well as acrylonitrile allyl cyanide and methyl acrylate. In an extension of this work, we have found that ultrasound was not necessary for the N-alkylation of indole and alkyl amine, such as diphenyl amine and piperidine with alkyl halides using our reagents. In all cases we observed that the 18-crown-6 catalyzed N-alkylation reaction gives higher yields of N-alkylated products than that without crown ether, when potassium superoxide was used as base. These observations are probably due to the potassium-crown complex which can be released when the reaction goes to completion.     

A simple and cost-effective molecular diagnostic system and DNA probes synthesized by light emitting diode photolithography

This work introduces a novel chip to be used in the future as a simple and cost-effective method for creating DNA arrays using light emission diode (LED) photolithography. The DNA chip platform contains 24 independent reaction sites, which allows for the testing of a corresponding amount of patients’ samples in hospital. An array of commercial UV LEDs and lens systems was combined with a microfluidic flow system to provide patterning of 24 individual reaction sites, each with 64 independent probes. Using the LED array instead of conventional laser exposure systems or micro-mirror systems significantly reduces the cost of equipment. The microfluidic system together with microfluidic flow cells drastically reduces the amount of used reagents, which is important due to the high cost of commercial reagents. The DNA synthesis efficiency was verified by fluorescence labeling and conventional hybridization.     

Dendronization of gold and CdSe/cdS (core-shell) quantum dots with tomalia type, thiol core, functionalized poly(amidoamine) (PAMAM) dendrons

Poly(amidoamine) (PAMAM) dendrimers containing disulfide cores (i.e., cystamine) and possessing carboxylic acid or hydroxyl terminal groups were reduced with dithiothreitol (DTT) to yield single site, thiol core, functionalized PAMAM dendron reagents. These thiol functionalized dendron reagents were used to surface modify (dendronize) both gold nanoparticles, as well as CdSe/CdS (core-shell) quantum dots (QDs). Dendronization involved self-assembly of the focal point thiol functional dendrons at the metal interface of both gold and CdSe/CdS QDs by ligand exchange of protective surfactants used for their synthesis. The synthesis, characterization and preliminary luminescence studies of these new dendritic hybrids are reported.     

Development of Oxidation Sources in Preparation of High-Tc Oxide Superconductor Thin Films Using the Molecular Beam Epitaxy Method

Film preparation of oxide superconductors, mainly of the 1-2-3 (RBa₂Cu₃O_x) and Bi-containing (Bi-Sr-Ca-Cu-O) systems, by evaporation of either metals or metal compounds by low pressure is summarized, with a particular focus on the development of oxidation sources essential to the technique. Oxidizing reagents that enable the oxidation of metal evaporates to take place in high (0·1 to 10_?3 Pa) or even ultra-high (<10_?5 Pa) vacuum are summarized using the experiments of those who tried to apply the molecular beam epitaxy method to atomically controlled fabrication of thin films of the material, especially for device processing. The evaporation in various kinds of oxidizing atmosphere, including the simple method of in situ annealing of the metal layers in oxygen to the more advanced in situ preparation of the films with strong oxidizing reagents such as atomic oxygen, ozone, nitric oxide, etc. along with the thermochemistry of the oxidation of metals by low pressure with these reagents is reviewed.     

全自动水质分析仪快速定量检测地表水中硝酸盐氮和亚硝酸盐氮

利用新型的Thermo Scientific Gallery全自动水质分析仪,检测过程中自动完成加样本、读空白、加试剂、反应显色、比色检测和数据处理等步骤。检测方法来源于美国环保署标准水质检测方法。该仪器具有样品和试剂耗量少、灵敏度高、重复性好等优点,检测过程容易实现自动化、标准化和信息化,适用于水质和环境检测领域大量样品的快速检测。     

红外光谱分析技术在浮选过程中的应用研究进展

随着浮选研究的深入发展,以捕收剂为核心的浮选药剂作用机理的研究逐渐成为研究焦点。红外光谱以速度快、成本低、无损等特点成为浮选药剂作用机理研究最为重要的手段之一。首先从文献报道数量和比例说明红外光谱在该研究中的重要地位,并总结了常见浮选药剂的红外光谱特征,最后分别阐述了红外光谱在捕收剂、抑制剂、活化剂等浮选药剂作用机理中的应用研究进展。归纳出红外光谱用于判定捕收剂在矿物表面作用三种机制的判据： 如果捕收剂作用后的矿物表面有新的吸收峰,则捕收剂在矿物表面发生了化学反应;如果仅有吸收峰的位置发生移动,并超过测试设备本身误差范围的移动量,则捕收剂在矿物表面形成的是化学吸附;排除上述产生的新红外特征吸收峰和红外特征峰的移动,且通过反复水洗即可清除表面沾染的捕收剂分子,则捕收剂在矿物表面发生的是物理吸附。并指出红外光谱在浮选过程中的应用研究存在的两大问题,一是将捕收剂与矿物表面的化学反应和化学吸附机理混淆;二是忽视红外光谱仪器吸收峰位移2～4 cm-1背景误差。展望未来红外光谱在浮选过程中的应用研究应该着眼于多种药剂混合用药在矿物表面作用机理的研究,该领域内红外光谱的定量分析研究及红外光谱吸收峰位移的背景误差分析等三方面。     

II. “Spectroscopic Investigation of Charge Transfer Complexes of Osazone Intermediates Prepared From certain monosaccharides”

Monosaccharide osazones are utilized in the spectrophotometric determination of their parent compounds through charge transfer complexes (CTC) formation with three-electron acceptor reagents. These acceptors indlude iodine (as -π-acceptor) and chloranil (tetrachloro P-benzoquinone) & TCNE (tetracyano ethylene) as π-acceptors. The presence of two phenylhydrazone moieties in the osazone molecule imparts electron-donating properties toward electron-accepting reagents, yielding spectrophotometrically measurable complexes. However, the reaction of osazone intermediates with TCNE reagent gave tricyanovinyl derivative rather than CTC formation. The above complexes together with their corresponding intermediates were subjected to structure elucidation studies to confirm the results and conclusions obtained. These studies include IR, Raman spectra, H¹, C¹³-NMR, MS, ESR (electron spin resonance spectra) and microanalysis.