Kinetics of the Oxidation of Tartrazine with Peroxydisulfate in the Presence and Absence of Catalysts

Summary.  The food dye tartrazine is oxidized with peroxydisulfate in the absence and in the presence of Ag(I) and Fe(III) catalysts. In the absence of these metal ions, the reaction shows second-order kinetics, first-order in each of the reacting species. With the Ag(I) ion in the medium the reaction proceeds considerably faster, but still follows second-order kinetics. The reaction rate depends on the concentration of Ag(I) and S₂O₈ ²⁻, but is independent of the concentration of the substrate. When Fe(III) acts as the catalyst, a marked enhancement in the reaction rate is observed, and the reaction proceeds through two parallel pathways, the catalyzed and the noncatalyzed. The catalyzed path follows third order kinetics, being first-order in substrate, oxidant, and catalyst concentration. Mechanisms of the noncatalyzed as well as the Ag(I) and Fe(III) catalyzed reaction systems are proposed. Received June 28, 1999. Accepted (revised) September 27, 1999     

Thermo-infrared-spectroscopy analysis of the interaction of naphthylammonium–montmorillonite with sodium nitrite

The deep blue organoclay color pigment (OCCP), naphthylazonaphthylammonium–montmorillonite, was synthesized in an aqueous suspension by treating montmorillonite with naphthylammonium chloride followed after 2 h by NaNO₂. The reddish-brown azo dye naphthylazonaphthylamine (commercial name “Solvent Brown 3”) was synthesized in an aqueous solution in the absence of clay from the same reagents. X-ray diffraction and thermo-infrared (IR) spectroscopy of organoclay prepared by treating montmorillonite with naphthylammonium chloride showed that the organoclay contained two types of tactoids with intercalated naphthylammonium cations and with naphthylammonium–naphthylamine associations. Naphthylammonium clay was obtained after thoroughly washing the latter organoclay. IR spectra of naphthylamine, naphthylammonium chloride, naphthylammonium clay, naphthylammonium–naphthylamine clay (with some naphthylammonium-clay), OCCP, and Solvent Brown 3 in KBr disks were recorded before and after thermal treatments up to 120 °C. IR spectrum of the OCCP was similar to that of Solvent Brown 3. An NH₃ ⁺ group was identified in the spectrum of the OCCP but not in that of Solvent Brown 3. In the latter spectrum, an NH₂ group was identified, suggesting that the amine group of the azo dye in the OCCP was protonated. It appears that the difference in color between OCCP and Solvent Brown 3 resulted from the protonation of the azo molecule in the interlayer space of the clay.     

偶氮类化合物在纳米TiO2表面光降解的UV-Vis光谱示踪研究(Ⅰ)--中间体的发现及动力学行为

用UV-Vis吸收光谱和差谱考察了以DBC-偶氮羧为主的5种偶氮化合物在纳米TiO2表面光降解的动力学行为和电子转移历程,载荷子的捕获经历一个中间过程,最终矿化为无机物.按误差补偿理论拟合的中间体峰形曲线和实验c～t图平行吻合,获得了相应的动力学参数.推测了电子转移的可能途径.     

Spectrofluorimetric Determination of Second Critical Micellar Concentration of SDS and SDS/Brij 30 Systems

Potentially useful stead-state fluorimetric technique was used to determine the critical micellar concentrations (CMC(1) and CMC(2)) for two micellar media, one formed by SDS and the other by SDS/Brij 30. A comparative study based on conductimetric and surfacial tension measurements suggests that the CMC(1) estimated by the fluorimetric method is lower than the value estimated by these other techniques. Equivalent values were observed for SDS micelles without Brij 30 neutral co-surfactant. The use of acridine orange as fluorescent probe permitted to determine both CMC(1) and CMC(2). Based on it an explanation on aspects of micelle formation mechanism is presented, particularly based on a spherical and a rod like structures.     

偶氮聚电解质在水性介质中的聚集行为和光响应性研究

研究了一种侧链型偶氮聚电解质(PPAPE)在水溶液和水/四氢呋喃混合溶液中的缔合及聚集行为.利用紫外光谱检测了缔合体的形成过程.通过测定不同浓度下溶液的表面张力确定PPAPE在水溶液中的临界聚集浓度,并利用透射电镜对PPAPE聚集体直接进行观察.研究表明,PPAPE的疏水性偶氮生色团在适当的条件下会发生缔合,并进一步聚集成具有纳米尺寸的微球.伴随缔合体的形成,PPAPE的紫外最大吸收峰位置明显蓝移,而且这种缔合行为使PPAPE的光色效应明显减弱.尽管溶液pH值对PPAPE的光色效应也有明显的影响,但作用机理有本质的区别.     

Synthesis,characterization and antibacterial studies of some new tellurated azo compounds

A series of tellurated azo compounds [i.e. (4-HOC₆H₄N=N-Ar)TeBr₃ and (4-HOC₆H₄N=N-Ar)₂TeBr₂, where Ar=5-BrC₆H₃, 5-CH₃C₆H₃ and 5-NO₂C₆H₃] were prepared by the reaction of the corresponding 2-(4-hydroxyphenylazo)aryl mercury chloride with tellurium tetrabromide in 1:1 and 2:1?mole ratio, respectively in dry dioxane as a solvent. The reduction of (4-HOC₆H₄N=N-Ar)TeBr₃ by hydrazine hydrate gave the corresponding ditelluride (i.e., (4-HOC₆H₄N=N-Ar)₂Te₂). Treatment of (4-HOC₆H₄N=N-Ar)₂TeBr₂ with hydrazine hydrate afforded the corresponding tellurides, (4-HOC₆H₄N=N-Ar)₂Te), in good yields. The structures of all newly synthesized compounds were assigned on the basis of their elemental and spectroscopic data. The antibacterial activity of tellurated azo compounds along with mercurated azo compounds was tested with agar diffusion method against the bacteria strains Staphylococcus aureus and Escherichia coli. The antibacterial activities of tellurated azo compounds were in some cases equal or better than those of the reference drug. The mercurated azo compounds were found to be the more antibacterial activity of than those of tellurated azo compounds.     

Photo-induced Alignment Behavior of Azobenzene-containing Polymer Films with Different Cross-linking Degree

Three series of amorphous copolymers containing azobenzene groups with various substituents and certain amounts of crosslinkable acrylic groups were prepared. The cross-linked polymer films were obtained by thermal polymerization of the acrylic groups in the copolymers, during which, by controlling the time of cross-linking reaction, the films can be made with different cross-linking degree (from 0 to 32%, which was monitored by FT-IR spectra measurement). Photo-induced alignment process of the films was performed under irradiation with linearly polarized light at 442 nm, and the effect of cross-linking degree on the photo-induced alignment rate was investigated. The dynamics of the photo-induced alignment was analyzed with biexponential curve fitting. The photo-induced alignment rate and the maximum transmittance of the films decreased because of the cross-linking. Furthermore, for the cross-linked samples, it was found that their saturated value of transmittances keep constant after repeated "writing" and "erasing" cycles. The findings reveal that the cross-linking of the film can effectively restrain the phototactic mass transport of azopolymer during irradiation by polarized light. The relationship between the cross-linking degree and the photo-induced alignment behavior of azopolymer is discussed in detail.     

Photoactive Poly(aryl ether)s Containing Azobenzene Moieties on Pendants for Fabrication of Thermal Stable Surface Relief Gratings

A series of azobenzene functionalized poly(aryl ether) copolymers(azo-PAEs) containing azo moieties on pendants was prepared by direct copolymerization. The amount of azobenzene chromophores could be controlled by the feed ratio of azo-monomer. Their chemical structures and properties were characterized by means of infrared(IR) spectrometry, UV-Vis, hydrogen nuclear magnetic resonance(¹H NMR), difference scanning calorimetry(DSC), and thermogravimetric analysis(TGA). The results suggest that azo-PAEs had high glass transition temperatures(T_gs) and good thermal stability. By exposing their spin-coated films to an interference pattern laser beam, azo-PAEs could be used for the fabrication of thermal stable surface relief gratings(SRGs).     

在N,N-二甲基甲酰胺/水混合溶剂中制备偶氮聚电解质自组装膜

利用静电吸附逐层自组装方法在有机溶剂N,N二甲基甲酰胺(DMF)和H2O的混合介质中制备非水溶性偶氮聚电解质自组装多层膜.研究了DMF和H2O的配比对自组装膜生长、结构与表面形态的影响.结果表明,DMFH2O的混合溶剂是非水溶性偶氮聚电解质自组装的理想介质,二者之间的配比对自组装膜的生长速度,膜的结构以及表面形态均有显著影响.随着混合溶液中DMF含量的升高,自组装膜的生长速度逐渐下降但线形生长关系越来越好,所得自组装膜中偶氮生色团的H聚集程度逐渐下降,而且自组装膜的表面越来越平整.     

Synthesis and Characterization of Novel Azo-containing or Azoxy-containing Schiff Bases and Their Antiproliferative and Cytotoxic Activities

A series of novel Schiff base derivatives was designed and synthesized from 3,3'-azobenzaldehyde and 3,3'-azoxybenzaldehyde. The newly synthesized compounds were characterized by FTIR, ¹H NMR, MS and elemental analysis and tested for their in vitro antiproliferative activities against HeLa cell lines. At the same time, the impact on the antitumor activity of the sulfanilamido, benzamido, phenolic hydroxyl or thiourea groups was investigated and discussed. Compounds 4, 6 and 10 were found to exhibit strong cytotoxic activity.