- Kinetic studies on the thermal cis-trans isomerization of 1,3-diphenyltriazene in aqueous solution. Effects of acids and bases
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The thermal cis-to-trans isomerization of 1,3-diphenyltriazene (DPT) has been investigated in buffered aqueous solutions by means of laser-flash photolysis techniques. The cis-to-trans isomerization process is found to be catalyzed by general acids and general bases as a result of acid/base-promoted 1,3-prototropic rearrangements. Acid catalysis is attributed to rate-limiting proton transfer to the nitrogen-nitrogen double bond of cis-DPT, whereas base catalysis is attributed to rate-limiting base-promoted ionization of the amino nitrogen of cis-DPT leading to the isomerization. In addition, a process ascribed to the interconversion of cis rotamers through hindered rotation around the nitrogen-nitrogen single bond is also observed; at high pH this process becomes rate-limiting.
- Barra, Monica,Chen, Nan
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- Thermal cis-to-trans isomerisation of triazene dyes in doped polymer films
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The kinetics of the thermal conversion of the cis to the trans isomeric forms of 1,3-diphenyltriazene and 1-phenyltriazenes derived from cyclic amines were determined in both poly(methyl methacrylate) and polystyrene doped films in the glassy state, using
- Tabone, Ryan,Barra, Mónica
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experimental part
p. 180 - 186
(2011/01/12)
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- Substituent effects on the thermal cis-to-trans isomerization of 1,3-diphenyltriazenes in aqueous solution
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The thermal cis-to-trans isomerization of some symmetrically p,p′-disubstituted 1,3-diphenyltriazenes has been studied by means of laser-flash photolysis techniques. The geometric isomerization is catalyzed by general acids and general bases as a result of acid/base-promoted 1,3-prototropic rearrangements. Acid catalysis becomes more prominent as the electron-donating character of the para substituent increases, while base catalysis becomes more important as the electron-withdrawing character of the para substituent increases. In addition, the rate ascribed to the interconversion of neutral cis rotamers through hindered rotation around the nitrogen-nitrogen single bond is found to decrease as the electron-withdrawing character of the para substituent increases. Rates of interconversion of neutral cis rotamers are also found to decrease with decreasing solvent polarity, which is indicative of the involvement of a polar transition state. On the other hand, kinetic investigations of the acid-catalyzed decomposition of target triazenes are consistent with an A1 mechanism.
- Chen, Nan,Barra, Monica,Lee, Ivan,Chahal, Navjot
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p. 2271 - 2277
(2007/10/03)
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- PHOTOCHEMISTRY OF 1,3-DIPHENYLTRIAZENE IN VARIOUS MEDIA. I: PHOTOLYSIS IN LIQUID SOLUTIONS.
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1,3-Diphenyltriazene has been irradiated at 360 nm in various liquid solutions. Reversible trans-cis photoisomerization has been detected in solvents which do not form hydrogen bonds. Irreversible photolysis is observed with an appreciable amount of cage recombination products in all solvents. This reaction is well suited for a study in solid environments.
- Baro,Dudek,Luther,Troe
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p. 1155 - 1161
(2007/10/02)
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- Treatment of aromatic amines with gas mixtures derived from the oxidation of ammonia to effect diazotization/coupling
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1,3-Diaryl triazenes, e.g., 1,3-diphenyltriazene, intermediates in the synthesis of aromatic diamines, e.g., p-phenylenediamine, are prepared by catalytically oxidizing ammonia, and subsequently the resulting nitric oxide, with a gas comprising diluted molecular oxygen, e.g., air, so as to produce a gas mixture containing dilute NOx, i.e., NO2 preferably admixed with NO, x being (1 + n), wherein n is the NO2 fraction of the NOx ; and contacting the gas mixture, preferably at a temperature in the range of about from 25° to 350° C., with excess primary aromatic monoamine, e.g., aniline, so as to result in a monoamine temperature in the range of about from 25° to 90° C., preferably 40° to 60° C., during contact. Highest yields of triazene are obtained when the x in NOx is about from 1.3 to 1.7, and the amount of NOx gas mixture contacted with the monoamine and the time of contact are such that at least about 60% by weight of the monoamine remains unconsumed. A gas mixture temperature just prior to gas contact with the liquid monoamine in the range of about from 110° to 275° C. is more preferred under certain circumstances.
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