- Design and mechanism of iron catalyzed carbon-carbon bond cleavage and N-oxidation processes of hazardous dyes for selective synthesis of nitroarenes and aminoarenecarboxylic acids
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An efficient iron catalyzed oxidative degradation process has been developed for selective conversion of environmentally hazardous azo and indigo dyes into nitroarenes and aminoarenecarboxylic acids (anthranilic acids) respectively, using polymer supported tribromide reagent at an alkaline pH. The in situ generated and the isolated (defined) chloro-iron(II)-terpyridine- pyridine carboxylate [Fe(tpy)(pic)Cl] catalyst system has been developed and its catalytic function was invented for the degradation process. The different nitrogenous and oxygen ligands have been screened out for the development of best catalyst system, and eventually we explored pyridine 2-carboxylic acid and terpyridine ligands together, were found to be the best. Notably, the in situ generated and the defined catalyst systems have found to be more effective with similar catalytic activities towards the oxidative degradation of both the dyes. As a result, the whole oxidative degradation process has been carried out with Fe(tpy)(pic)Cl catalyst system and the general process utilizes the efficient catalytic method for the selective oxidation of -NN- and -CC- bonds of azo and indigo dyes respectively. The detailed catalysis, mechanistic and kinetic investigations have been made for the reactions. Interestingly, both the dyes proceed with a common oxidative degradation mechanism under identical kinetic patters. A common oxidative degradation mechanism which operates in both the dyes has been proposed and an identical related kinetic model was designed. The main interesting aspect of the present work pertains to the catalytic conversion of environmentally hazardous compounds into useful molecules; such are anthranilic acids and nitrobenzenes. Other special aspect related to catalytic activity of iron and potentially, iron catalyst accelerates the reaction rates with 15-20-fold faster. The reactions were also carried out with different polymer supported trihalide and inter-halide reagents. Notably, trichloride and inter-halide regents were found to be more reactive. The catalytic method developed for the degradation process was found to be very efficient and the involvement of cost-effective reagents makes the reaction simple, and can be conveniently scalable to industrial/technological operations with suitable modifications.
- Jagadeesh, Rajenahally V.,Kiran,Bhagat, Pundlik R.,Kumar, S. Senthil,Nithya,Khan, F. Nawaz,Sivakumar
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experimental part
p. 92 - 104
(2011/05/05)
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- Triphendioxazine dyestuffs
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The novel triphendioxazine dyestuffs of the formula STR1 in which the substituents R, R', T1, T2, X, Y and n have the meanings given in the description are highly suitable for the dyeing and printing of cellulose-containing or amido-containing material.
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- Process for the preparation of sulfonated anthranilic acids
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A process for the preparation of 4-sulfonated anthranilic acids by sulfonation of ortho-nitrotoluenes with chlorosulfonic acid or oleum followed by oxidation of the methyl group and, finally, reduction of the nitro group.
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- Fibre-reactive dyes, containing both chloro and fluoro triazine radicals
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Fibre-reactive dyes of the formula STR1 wherein D is the radical of a benzene or naphthalene azo dye which contains sulpho groups, each of R1, R2 and R3 is a hydrogen atom, B is an arylene group and A is an amino group.
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- Process for the manufacture of symmetric 1:2 chromium complexes of azo dyes
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The present invention relates to a process for the manufacture of 1:2 chromium complexes of metallisable azo dyes, wherein the azo dyes are treated in aqueous solution at pH 7 to 9 with at least the stoichiometric amount of a chromium complex, and, in the course of the chroming, the reaction medium is acidified once or repeatedly to a pH of 6 or less and subsequently brought back again to pH 7 to 9.
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