Organic methyl orange

The utility of acid-base titrimetry improved when NaOH was first introduced as a strong base titrant in 1846. In addition, progress in synthesizing organic dyes led to the development of many new indicators. Phenolphthalein was first synthesized by Bayer in 1871 and used as a visual indicator for acid-base titrations in 1877. Other indicators, such as methyl orange, soon followed. Despite the increasing availability of indicators, the absence of a theory of acid-base reactivity made selecting a proper indicator difficult. 

In moderately acidic solutions bromocriptine mesilate readily forms ion pairs with anionic dyes such as picric acid, bromothymol blue, methyl orange, which are extractable with an organic solvent. A procedure has been developed both for direct assay and for assay following chromatographic separation from the impurities. Therein bromocriptine mesilate is allowed to react with bromothymol blue at pH 2.5. The resulting ion pair is then extracted with benzene and its concentration determined at 410 nm (25). ... 

Crooks et al. reported the transfer of amine-functionalized poly(amidoamine) dendrimers into toluene containing dodecanoic acid [198], The method is based on the formation of ion pairs between the fatty acids and the terminal amine-groups. These dendrimer-fatty acid complexes resemble unimolecular inverted micelles and could be used as phase transfer vehicles for the transport of Methyl Orange, an anionic dye molecule, into an organic medium. 

Costantino et al. [75] have shown, however, that treatment with gaseous or aqueous HCl can lead to replacement of carbonate with chloride, which itself can be replaced by large organic anions such as methyl orange [79] or fluorescein [80]. It has recently been suggested that use of HCl/NaCl mixtures also leads to more effective displacement of carbonate by chloride [81]. 

Similar to micellar assemblies in water, reverse micelles have also been utilized to bring about nonspecific binding interactions in organic solvents. Akiyoshi et al. (2002) have synthesized an amphiphilic block copolymer containing PEO and an amylase chain as receptor for methyl orange (MO Chart 2.2). Amylases are insoluble and methoxy-PEO (MPEO) is soluble in chloroform. Hence, an MPEO-amylase block copolymer forms reverse micelles in chloroform. Akiyoshi et al. established the capability of the buried receptors to extract the complementary analyte by studying the ultraviolet visible (UV-vis) spectra. A solution of polymer was shaken... 

It is well known that the aqueous phase behavior of surfactants is influenced by, for example, the presence of short-chain alcohols [66,78]. These co-surfactants increase the effective value of the packing parameter [67,79] due to a decrease in the area per head group and therefore favor the formation of structures with a lower curvature. It was found that organic dyes such as thymol blue, dimidiiunbromide and methyl orange that are not soluble in pure supercritical CO2, could be conveniently solubihzed in AOT water-in-C02 reverse microemulsions with 2,2,3,3,4,4,5,5-octafluoro-l-pentanol as a co-surfactant [80]. In a recent report [81] the solubilization capacity of water in a Tx-lOO/cyclohexane/water system was foimd to be influenced by the compressed gases, which worked as a co-surfactant. 

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. 

The Sulphites.—Sulphurous acid gives rise to normal sulphites of the type M2S03 and acid salts of the type MHS03, where M represents a univalent metal atom. The normal salts are odourless and do not resemble the free acid or sulphur dioxide in their very harmful effect on living organisms. On the other hand, the acid sulphites readily yield sulphur dioxide they have an acid reaction towards phenolphthalein, but are neutral towards methyl orange. 

Effect of /3-cyclodc trin on cis trans isomerization of azobenzenes was studied by Sanchez and de Rossi [26], It was found that the cis-trans thermal isomerization of / -Mcthvl Red, o-Methyl Red and Methyl Orange is inhibited by fi-CD at constant pH. The isomerization rate decreases 4, 8, and 1.67 times, respectively, in a solution containing 0.01 M /J-CD. This effect was attributed to the formation of inclusion complexes hindering rotation of the -N=N- bond. Isomerization of Methyl Yellow and naphthalene-l-azo-[4 -(dimethylamino)benzene] requiring mixed organic-aqueous... 

The reduction of organic dye methyl orange (MO) over CdS colloids with the particles size d = 2R - 5 nm has appeared to be a convenient reaction for detail studying the kinetics of photocatalytic processes. This dye is readily reducible with no dimers formation. The MO adsorption spectrum in the pH range of 10-12, practically does not change. This allows simplifying the interpretation of the experiments on redox transformations of MO and considering the reaction of photostimulated reduction of MO as a model one. 

Similarly, one-electron reduction of organic dyes such as thiazine, oxazine, phenazine, squaraine, and methyl orange as well as viologen and fullerenes have also been carried out in various colloidal semiconductors [44]. The values of quantum yield of reduction vary from 0.01 to 1.0. The quantum yield of reduction is dependent on both the association constant and the energetics of the conduction... 

During the neutralisation with alkali a sharp end-point was obtained (to methyl orange) when one equivalent of alkali had been added, while phenolphthalein gradually changed between 1-5 and 2-0 equivalents, showing that the second dissociation constant is lower than that of the majority of organic acids (see also Electrical Conductivity, p. 151). 

Ethylenediamine, (I I,NCH,), is a strong organic base miscible with water and alcohol. It is a colourless and viscous liquid with a density of 0.898 and a melting point of 8 °C. The pH of a 25% aqueous solution is 11.5. Like triethanolamine, it is an aliphatic amine soluble in water and, therefore, can be determined by the acid-base titration with methyl orange as an indicator. 

Another group of methods is based on ionic associates formed by acid dyes e.g., eosine, Bengal Rose, Methyl Orange) with hydrophobic cationic complexes of some metals [e.., Fe(II), Ag(I), Zr, Cd] with 1,10-phenanthroline and other organic bases [10,62],... 

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