Azo-components

The most widely reported developments have been in category 4, ie, 4,4 -dinitro-2,2 -stilbenedisulfonic acid (1) condensations with amino-containing azo components, some of which ate copper complexes, to give dyes having excellent properties on leather (19—31) (Table 2). 

Dyestuffs. The use of thiophene-based dyestuffs has been largely the result of the access of 2-amino-3-substituted thiophenes via new cycHzation chemistry techniques (61). Intermediates of type (8) are available from development of this work. Such intermediates act as the azo-component and, when coupled with pyrazolones, aminopyrazoles, phenols, 2,6-dihydropyridines, etc, have produced numerous monoazo disperse dyes. These dyes impart yeUow—green, red—green, or violet—green colorations to synthetic fibers, with exceUent fastness to light as weU as to wet- and dry-heat treatments (62-64). 

In the presence of aprotonic organic solvents, both aromatic and aliphatic amines interact with 4-nitrophenyldiazonium in the same way. The first stage yields fast in corresponding triazenes. At the second stage, irrespective of initial amine nature, triazenes interact with an excess of diazo reagent and fonu l,3-bis(4-nitrophenyl)-triazene. Triazenes of aliphatic amines transform fast as well. In case of aromatic amines, the second stage yield depends on the inductive constants of substituents in an azo component. 

The method has also preparative significance since, ultimately, it is a way of introducing an amino-group. Compare the preparation of aminonaphthols from dyes of which the azo-components are a- or j8-naphthol. 

When one azo component is used, the colour is termed a mono-azo colour. 

When two azo components are used, e.g., with benzidine, dis-azo-colours are formed, e.g.,... 

From the data in Table 3.9 it can be seen that all three copolymers contain a slightly higher concentration of the azo component than that of the monomer mixtures. The molar masses of the products are essentially unaffected by the presence of the azo monomers and were identical with that of a polystyrene produced under identical conditions. That the azo monomers did not undergo thermolysis under these conditions is confirmed by the independence of the molar mass from the conversion since thermolysis would lead to an increase in the molar mass at higher conversion. 

Additionally, it is usually desirable to achieve UG as close to 100% as possible. This is, however, relatively easy to accomplish simply by increasing the azo content in the backbone. The degree of grafting it is dependent on the ratio of the concentrations of the backbone and the monomer to be grafted and is also influenced by the concentration of the azo component in the backbone polymer, the difference in the... 

In addition to the thermal initiation, the use of peroxides or azo components is a common and well established method to start the chain reaction. Peroxides increase the rate of the polymerization process and improve the grafting efficiency in the case of IPS. More recently, multifunctional peroxides have also been used in order to obtain products with special molecular weight distributions. 

In addition to molecularly distributed compounds, the material can also be encapsulated as aggregate, crystal, etc., as is the case for the encapsulation of pigments and, for thermally labile azo-components, photoinitiators, and highly fluorescent quantum dots in polymeric nanoparticles by using the miniemulsion process. 

The labile azo-component can also be part of the polymer and embedded in the shell. Here, polyurethane nanocapsules consisting of an aque-... 

Volz M, Walther P, Ziener U, et al. (2007) Nano-explosions of nanoparticles for sudden release of substances by embedded azo-components as obtained via the miniemulsion process. Macromol Mater Eng 292 1237-1244... 

Cellulose, PVA, and their derivatives can be used as polymers which have hydroxy groups on the surface. As azo component the commercially available 4,4 -azobis-4-cyanovaloyl chloride (AIVC) was employed. Whether or not the azo group is really introduced into the polymer can be verified, for instance, by further reaction with a spin-labeled compound like 2,2,6,6-tetramethyl-4-aminopiperidine-l-oxyl (TMPO). This reaction proceeds as follows ... 

It is used as a first component in the preparation of azo-dyes, amlnoazo-dyes See azo-dyes, o-aminobenzoic acid See anthranilic acid. 

Prepared by reduction of 4-nitrophenol or 4-nitrosophenoi. Can be diazotized and used as a first component in azo-dyes. Chief outlet is for sulphur dyes in which it is fused with sodium polysulphides. L/sed as a photographic developer. 

It is an important dyestuffs intermediate. It condenses with chloroethanoic acid to give phenylglycine-o-carboxylic acid for the synthesis of indigo. It can be diazotized and used as a first component in azo-dyes it condenses also with chloroanthraquinones to give intermediates for anthraquinone dyes. 

Usually prepared from the corresponding sulphonic acids by alkali fusion, methylation of phenol or from the aminotoluene by treatment with nitrous acid followed by boiling. Both o- and p-cresol are used as end components in azo dyes. 

The most important reaction of the diazonium salts is the condensation with phenols or aromatic amines to form the intensely coloured azo compounds. The phenol or amine is called the secondary component, and the process of coupling with a diazonium salt is the basis of manufacture of all the azo dyestuffs. The entering azo group goes into the p-position of the benzene ring if this is free, otherwise it takes up the o-position, e.g. diazotized aniline coupled with phenol gives benzeneazophenol. When only half a molecular proportion of nitrous acid is used in the diazotization of an aromatic amine a diazo-amino compound is formed. 

It was used as an end component in a few azo-dyes, but this use has been discontinued because of its carcinogenic character. 

Basic, forms a stable water-soluble dihydrochloride. Diazotization gives brown azodyes (Bismarck brown) owing to the coupling of the partially diazotized base with the excess of diamine. Is also used as an end component of many azo-dyes, readily coupling with one or two molecules of diazo compound. 

It is prepared by heating aniline sulphate for 8 hours at l C. It readily diazotizes and is used as first component in a large variety of azo dyes. 

The mixture of xylidines has been used as a first component of azo-dyes. The chief constituent of the mixture is m-xylidine (4-amino-1,3-xylene). It can be separated by crystallization from glacial ethanoic acid. It is also used for the preparation of azo-dyes. 

When the parent molecules connected by the azo group are different, azo is placed between the complete names of the parent molecules, substituted or unsubstituted. Locants are placed between the affix azo and the names of the molecules to which each refers. Preference is given to the more complex parent molecule for citation as the first component, e.g., 2-aminonaphthalene-l-azo-(4 -chloro-2 -methy Ibenzene). 

In an alternative method, the senior component is regarded as substituted by RN=N—, this group R being named as a radical. Thus 2-(7-phenylazo-2-naphthylazo)anthracene is the name by this alternative method for the compound named anthracene-2-azo-2 -naphthalene-7 -azobenzene. 

The principal uses for 2-naphthalenol are in the dyes and pigments industries, eg, as a coupling component for azo dyes, and to make important intermediates, such as 3-hydroxy-2-naphthalenecarboxyhc acid (BON) (28) and its anilide (naphthol AS), 2-naphtholsulfonic acids, aminonaphtholsulfonic acids, and l-nitroso-2-naphthol/77/-5 /-5(/ (29). 

Many of the pigments carry a nitro group ia the diazonium component, usually ia the ortho position (R = NO2). Among the acetoacetaryUde components the o-methoxy derivative (R2 = OCH, R3 = H) is one of the most important ia the production of azo pigments. The colors of these pigments range from red to green-shade yellows. Commercially important products ate shown ia Table 3. 

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