Azo dyes Methyl Orange

The photoelectrochemical reduction of the N = N double bond of the diaryl azo dye methyl orange can be similarly sensitized by colloidal titanium dioxide les, isoj The reaction was sensitive to pH and the identity of the organic redox reaction could be shifted by conducting the photoreaction in the presence of surfactants. Cationic surfactants increased the efficiency of oxidative cleavage by inhibiting charge recombination. Polyvinyl alcohol instead favored reduction. The ambident photoactivity of methyl orange thus makes it an attractive probe for activity of irradiated semiconductor suspensions. 

Recently, Zhang et al. investigated the degradation of azo dye, methyl orange in aqueous solution with sonophotoelectrocatalytic process [65], where TiCb nanotubes were used as electrode in photoelectrocatalytic (PEC), sonophotoelectrocatalytic (SPEC) processes or as photocatalyst in photocatalytic (PC), sonophotocatalytic (SPC) processes. Experimental results showed that under the optimized experimental conditions, the rate constants of decolorization of dye were 0.0732 min 1 for SPEC process 0.0523 min-1 for PEC process, 0.0073 min 1 for SPC process and 0.0035 min 1 for PC process, respectively. The rate constants indicate that there exist a synergistic effect in the ultrasonic, electro-assisted and photocatalytic processes. 

Preparation of an Azo Dye Methyl Orange (Section 629). —Dissolve 10 grams of sulphanilic acid and 3 grams of anhydrous sodium carbonate in 150 cc. of water. To the solution first add 4 grams of sodium nitrite dissolved in 20 cc. of water, and then a mixture of 7 cc. of concentrated hydrochloric acid and 10 cc. of water. (Eq.) Dissolve 6 cc. of dimethylani-... 

Of the azo dyes, Methyl Orange has been successfully applied. 

In situ degradation of the azo dye methyl orange in aqueous solution was performed in the presence of various pure and Ag metal ion-doped titania thin films, prepared with and without surfactants. The main aim of the study was to analyze the effect of non ionic surfactant (Pluronic F-127), Ag metal ion doping and their combined effect on the photo-induced hydrophilicity and photocatalytic degradation of ambient air contaminants (gas-solid interface), methyl stearate (solid-solid interface) and azo dye methyl orange (liquid-solid interface). 

Three 3-CD polymers were prepared using different amounts of hexamethylene diisocyanate (HMDI) as a crosslinking agent and were applied as sorbents for the removal of azo dyes Methyl Orange (6), Orange II (7) and Direct Violet (8) from aqueous solutions [40]. 

The decolorization potential of immobilized P. chrysosporium MTCC 787 for azo dyes Acid Orange, Acid Red 114, triphenylmethane dye Methyl Violet, diazoic dye Congo Red, vat dye Vat Magenta, thiazine dye Methylene Blue, and anthraqui-none Acid Green was demonstrated by Radha et al. [53]. Decolorization experiments were carried out with immobilized calcium alginate (Ca-ALG) beads of different sizes (2-6 mm). 

These diazonium salts are good electrophiles for activated aromatic rings, such as amines and phenols, and this is how azo dyes are prepared. Diazotization of the salt of sulfanilic acid, which we have just made by sulfonation of aniline, gives an inner salt that combines with N,N-dimethylaniline to form the water-soluble dye, methyl orange. 

In general, the azo colors are useful for coloring polystyrene, phenoHcs, and rigid poly(vinyl chloride). Many are compatible with poly(methyl methacrylate), but in this case the weatherabiUty of the resin far exceeds the life of the dyes. Among the more widely used azo dyes (qv) are Solvent Yellows 14 and 72 Orange 7 and Reds 1, 24, and 26. 

Suitably substituted azo compounds constitute an important class of dyes—the azo dyes. Some derivatives such as /j-dimethylaminoazobenzene- p -sulfonic acid Na-salt (trivial name methyl orange) are used as pH-indicators. 

The portions of the methyl orange molecule set off by the dotted lines come from aromatic amines like aniline. Aniline is indeed the starting material from which methyl orange and related dyes ( azo dyes ) are made. 

Devi LG, Kumar SG, Reddy KM, Munikrishnappa C (2009) Photodegradation of methyl orange an azo dye by advanced Fenton process using zero valent metallic iron Influence of various reaction parameters and its degradation mechanism. J Hazard Mater 164 459 167... 

The azo-dye obtained is the indicator methyl orange which is much used in alkalimetry. The yellow dilute solution of helianthine is turned red by acids. 

Reaction of chlorosulfonic acid with mono- [141] or disazo dyes [142] yields sulfonyl chlorides, which can then be transformed into cationically substituted sulfonamides by reaction with dialkylaminoalkylamines. The coupling product of diazotized 2-anisidine with 2-hydroxynaphthoic acid arylide upon such treatment dyes paper red, and the azo dye from tetrazotized dianisidine and l-phenyl-3-methyl-5 -pyrazolone gives yellowish orange shades. 

Folkers and coworkers - found that when sufliciently pure concentrates of streptomycin were treated with methyl orange (the sodium salt of helianthine) a crystalline salt was formed with the sulfonic acid group of this dye. On recrystallization from aqueous methanol, pure streptomycin helianthate was obtained. The helianthate could be converted to streptomycin hydrochloride, sulfate or any other suitable salt for chemical or therapeutic purposes. All of these salts with the common inorganic acids are amorphous. They - also obtained a crystalline salt of streptomycin and p-(2-hydroxy-l-napthylazo)-benzenesulfonic acid from streptomycin hydrochloride and the azo dye Orange II. Streptomycin helianthate was converted directly into a crystalline streptomycin trihydrochloride-calcium chloride double salt. The chemistry of streptomycin was thus put on a crystalline basis. 

Methyl Orange.— Another important dye compound related to the above is the well-known methyl orange which, though not used as a dye, is very widely used as an indicator. It is the mono-sulphonate derivative of di-methyl amino azo benzene. The alkali salts are orange yellow in color while the free acid is red violet, and these are the colors obtained when the indicator is used in acidimetric titrations. 

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