Reactive dyes acid hydrolysis

Rate constants and the products formed in the hydrolysis of Cl Reactive Red 194 (7.76) at 50 °C and pH values in the 10-12 region were determined by high-pressure liquid chromatography. In addition to the normal hydrolysis of the two reactive systems, the imino link between the triazine and benzene nuclei was also hydrolysed [67]. The heterobifunctional copper formazan dye Cl Reactive Blue 221 and two blue anthraquinone monofunctional reactive dyes of the bromamine acid type, namely the aminochlorotriazine Blue 5 and the sulphatoethylsulphone Blue 19, were compared in terms of their sensitivity to... 

In contrast to cellulosic dyeing with reactive dyes, the fibroin-dye bonds are remarkably stable in aqueous media of pH 4 to 10 [117]. Since there exists only a negligible amount of bond hydrolysis even at high temperature and in a medium of pH 2, the cleavage of the fibroin-dye bond is not a problem in reactive-dyed silk. The stability of these bonds when dyeing with difluoropyrimidine dyes is the highest in both acidic and basic media [118]. 

This problem has been confirmed recently in a study of the mechanism of covalent reaction between nylon 6.6 and the sulpha toe thylsulphone dye Cl Reactive Blue 19 (7.37). Acid hydrolysis of the dyed fibre and HPLC analysis of the hydrolysate yielded the 6-aminohexylaminoethylsulphonyl derivative of Blue 19. Even when the dyeing procedure was optimised to achieve maximal exhaustion and fixation to the fibre [128], only about 30% of the N-terminal amino groups in the nylon 6.6 were accessible because of mutual blocking effects between these bulky anionic dye molecules. 

Long-term dye stability—Low-temperature reactive dyes will slowly hydrolyze with water over long periods of time, even at room temperature. To prevent slow hydrolysis, the dye impregnation bath was kept at a slightly acid pH (- 6.0). This technique proved successful, with dye solutions maintained for several weeks without detectable degradation. 

Reaction of cyanuric chloride with amines to give reactive dyes 2. Sulfonation and nitration of naphthalene at low temperatures 3. Reaction between terephthalic acid and ethylene oxide in a solvent in the presence of dissolved catalysts 4. Manufacture of diisocyanate by reaction between phosgene and hydrochlorides of amines 5. Alkaline hydrolysis of solid esters such as di-/3-chloroelhyl oxalate and nitrobenzoic acid esters Venkatraman (1972) Groggins (1958) Hydrocarbon Proc. Petrol. Refiner (1971) Bhatia et al. (1976) Sharma and Sharma (1969, I970a,b)... 

Reduction of Methylene Violet with zinc in acetic acid gives the air-sensitive leuco 20 which is further reacted with acetic anhydride in mild conditions to yield the acetylated leuco 21. The latter being air stable can be isolated and, the ring N-H being less reactive is not affected by acetylation at room temperature. The leuco 21 is again aroylated to produce the leuco 22. Selective hydrolysis provides the desired leuco dye 12 which regenerates the true Methylene Violet (6) on oxidation.83... 

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