Diazotisation and aso=coupling reactions have been studied and the results are reported. A kinetic study of the acid catalysed diazotisation of various aniline derivatives has been made. The substrates considered were 2,4-dinitro-aniline, 4-nitroaniline, sulphanilaraide (aniline-4-sulphonamide) and sulphanilic acid (aniline-4-sulphonic acid). A new pK(_a) value of l.4 is reported for sulphanilamide. A study of the diazotisation of sulphanilic acid and sulphanilamide in the presence of Cl¯, Br¯, SCN¯, and SC(NH(_2))(_2) shows that the general catalytic trend Cl¯ < Br¯, SCN¯ < SC(NH(_2))(_2) is followed; whereas for the corresporaing nitrosating agents the general reactivity trend NOCl > NOBr >; NOSCN >NOS(^+)C(NH(_2))(_2) is followed. No catalysis was observed in the case of 2,4=dinitroaniline and this has-been interpreted in terms of a rapid reversible nitrosation in which the rate of the denitrosation step is greater than the rate of decomposition of the intermediate nitrosammonium ion. The bimolecular rate constants obtained for sulphanilic acid and sulphanilamide approach the diffusion controlled limit for this process in the case of NOCl and NOBr, Also reported is a study of the diazotisation of two heteroaromatic amines: 2-amino-5-nitrothiazole and 3-amino-l,2,4-triazoleo Catalysis by acid and the nucleophiles Cl¯ and SCN¯ has been observed. The catalytic and reactivity trends described above have been noted for reaction of these heteroaroraaticso The Pk(_a) value for 2-amino—5-nitrothiazole has-been determined and agrees well with the literature values. In addition to the above studies of diazotisation mechanisms, results are reported of a study of the leaving abilities of various electrofugal leaving groups X during ipso=coupling of 4=nitroaniline with 4-X,N- dimethylanilineso The sequence of leaving abilities has been determined by product yield studies. Rate constants for attack of ArN(^+)(_2) have also been determined. It is suggested that a substrate molecule (X-Ar-NMe(_2)) acts as a base in removing the group X from the Wheland intermediate.

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No description available.

The laser-induced holographic gratings in the azo-dye-doped liquid crystals have been investigated by changing the temperature, and the concentration of the sample, the intensity of the two writing beams, and the polarization of probe beams. The cw Nd:YAG laser has been employed as the writing beams and the cw He-Ne laser has been employed as a real-time probe beam to detect the first order diffraction singals. The gratings are the results of photo-isomerization of azo dye and the structure alignment of liquid crystals. The model has been established to explain the first order diffraction signals, the mechanism of gratings formation and the temperature dependence.

No description available.

In this research, the ability of anaerobic and aerobic biological sludges to reduce and stabilize azo dye compounds was studied. Synthetic dye solutions and an industrial textile wastewater were both treated using anaerobic and aerobic biomass, separately and in sequential step-treatment processes. The primary objective was to reduce the wastewater color to an intensity that complies with the Virginia Pollutant Discharge Elimination System (VPDES) permit level. This level is set at 300 American Dye Manufactures Institute (ADMI) units. Further objectives were to achieve reductions in the total kjehdal nitrogen (TKN) and total organic carbon (TOC) in the wastewater. Anaerobic and aerobic treatment systems were both effective in reducing the wastewater color; however, anaerobic treatment generally produced the greatest color removal. Anaerobic/aerobic (ANA/AER) sequential step-treatment provided the best reductions in ADMI color, TKN and TOC. Anaerobic/aerobic/anaerobic/aerobic (ANA/AER/ANA/AER) sequential step-treatment did not yield greater reductions in ADMI color, TKN, or TOC as compared to ANA/AER sequential step-treatment. / Master of Science

This work demonstrates the pretilt angle controllable photo-alignment effect in nanoparticles and azo-dye doped liquid crystal film. Followed by increasing the absorbed azo-dye, the vertical alignment induced by nanoparticles of polyhedral oligomeric silsesquioxanes (POSS) can be changed from high pretilt to low pretilt angle. Competition between the homogeneously aligned azo-dye and POSS-induced spontaneous vertical alignment domain generated the variable pretilt angle. The pretilt angle is a function of the pumping intensity and can be controlled continuously within the range of 0¢X~90¢X. With the sufficient absorption of photo excited azo-dye, The POSS induced vertical alignment can be switch to homogeneous alignment. The pretilt angle and surface energy are also examined to confirm the alignment effect. Both nanoparticles and azo-dye induced vertical and homogeneous alignment are non contact methods, and suitable for low temperature plastic process.

In this study, a high power Q-switch pulse laser has been used as the writing beams. The laser-induced holographic gratings in the DR1-doped liquid crystal samples and the DR1-PMMA polymer thin films were investigated by changing the temperature of samples and the angles of two writing beams. The He-Ne cw laser has been used as a real-time probe beam to detect the first order diffraction signals. Without external field, the gratings are the results of concentrations and diffusions of azo dye isomers. The diffusion model has been utilized to analyze the first order diffraction signals in order to understand the mechanics of gratings and the effect of temperature and angle.

Previous work in our group has been directed towards the synthesis of crown-ethers for use in the selective complexation of metal ions and as chiral ligands for use in asymmetric catalysis. The development of a modular approach to macrocycle assembly has enabled the synthesis of a library of pyridine-based macrocycles possessing multiple donor sites where chirality was readily introduced from simple amino acids.The nucleophilic ring opening of aziridines 181, 193 or 194, allowed the highly selective synthesis of thioether-based spacers and macrocycles. Extension of this basic approach to the synthesis of seleno-crown ethers was also investigated. The use of chiral-pool starting materials derived from D- or L-alanine, provided access to optically pure macrocycles. The use of the Sharpless-Huisgen 'click' reactions allowed the attachment of a carbohydrate residue directly to a macrocycle via a triazole unit. We hope to attach a macrocycle, carbohydrate residue and azo dye together, to be able to examine further diseases such as Alzheimer's. We have so far succeeded in attaching a macrocycle and sugar to a central scaffold by performing a one-pot double 'click' reaction. The distance between the points of attachment of the chromophore to the macrocycle metal binding site is probably, in this first generation sensor, too great to enable a metal-macrocycle binding event to be reported.

Neste trabalho foi estudada a degradação eletroquímica do azo corante Preto Ácido 210 (PA210) utilizando ânodos dimensionalmente estáveis de composição Ti/Ir0,10Sn0,90O2 e Ti/Ir0,30Sn0,70O2 preparados pelo método de decomposição térmica de precursores poliméricos. Os efeitos da presença e da concentração de cloreto, da composição eletródica, da densidade de corrente e do tempo de eletrólise sobre a oxidação eletroquímica de 100 ppm do corante PA210 foram avaliados. Em todas as condições estudadas, a remoção da absorbância em 465 nm (max) foi superior a 94% depois de 30 min de eletrólise. A redução de TOC foi proporcional à concentração de íons cloreto no eletrólito e não mostrou dependência da composição eletródica. A formação de espécies organocloradas variou na faixa de 8 a 16 ppm, sendo que as maiores concentrações de AOX foram obtidas para o eletrólito com maior concentração de cloreto. A redução máxima de TOC obtida foi de 25% depois de 90 min de eletrólise à densidade de corrente de 25 mA cm-2 para o eletrólito HCl 0,1 mol L-1. A eficiência de corrente foi calculada em relação ao TOC, sendo obtido o melhor resultado, de 9,14%, em 30 min de eletrólise com HCl 0,1 mol L-1 a 25 mA cm-2, sendo esta eficiência quatro vezes maior que para melhor eficiência em meio de H2SO4 0,1 mol L-1. O estudo da relação TOC / AOX indica que após as eletrólises houve a adição de cloreto as substâncias orgânicas gerando espécies organocloradas que apresentam uma relação de aproximadamente 1 átomo de cloro para cada 5 átomos de carbono. / The electrochemical degradation of the azo dye Acid Black 210 (AB210) using dimensionally stable anodes of composition Ti/Ir0,10Sn0,90O2 and Ti/Ir0,30Sn0,70O2 prepared by thermal decomposition of polymeric precursors was studied. The effects of the presence and concentration of chloride, electrode composition, current density, and electrolysis time on the electrochemical oxidation of 100 ppm dye PA210 were evaluated. In all the studied conditions, the removal of the absorbance at 465 nm (max) was greater than 94% after 30 min of electrolysis. The reduction of TOC was proportional to the concentration of chloride ions in the electrolyte and was not shown to be dependent on electrode composition. The formation of organochloride species varied in the range from 8 to 16 ppm, with higher concentrations of AOX being obtained for the electrolyte with high chloride concentration. The maximum reduction of TOC was 25% after 90 min of electrolysis, at a current density of 25 mA cm-2, for the electrolyte HCl 0.1 mol L-1. The current efficiency was calculated in relation to TOC, and the best result was 9.14% after 30 min of electrolysis in HCl 0.1 mol L-1 at 25 mA cm-2. This efficiency is four times higher than the best efficiency obtained by using only H2SO4 0.1 mol L-1 as electrolyte. The study of the TOC / AOX relationship indicates that there was addition of chloride to the organic substances after electrolysis, thus genetaring organochloride species with a ratio of about 1 atom of chlorine for every 5 carbon atoms.