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[2] [3] Most azo dyes contain only one azo group but there are some that contain two or three azo groups, called "diazo dyes" and "triazo dyes" respectively. Azo dyes comprise 60–70% of all dyes used in food and textile industries. [3] Azo dyes are widely used to treat textiles, leather articles, and some foods. Chemically related derivatives ...
In the modern synthesis, zinc is the reductant in the presence of a base. [10] Industrial electrosynthesis using nitrobenzene is also employed. [11] trans-Azobenzene isomer is planar with an N-N distance of 1.189 Å. [12] cis-Azobenzene is nonplanar with a C-N=N-C dihedral angle of 173.5° and an N-N distance of 1.251 Å. [13]
The point of the ether bond is controlled by selectively protecting alcohol groups on the sugar, or by choosing an azo dye with a different alcohol group position. An unprotected alcohol group of either the sugar or the dye is reacted with an n-carbon, terminal dibromoalkane in a solution of potassium hydroxide and 18-crown-6 ether, using non ...
Many other azo dyes have been prepared by similarly. Several procedures have been described in detail. [5] [6] [7] Naphthols are popular coupling agents. One example is the synthesis of the dye "organol brown" from aniline and 1-naphthol: Synthesis of organol brown from aniline and 1-naphthol
Azo compounds are organic compounds bearing the functional group diazenyl (R−N=N−R′, in which R and R′ can be either aryl or alkyl groups).. IUPAC defines azo compounds as: "Derivatives of diazene (diimide), HN=NH, wherein both hydrogens are substituted by hydrocarbyl groups, e.g. PhN=NPh azobenzene or diphenyldiazene.", where Ph stands for phenyl group. [1]
The dye is simple to prepare because the diamine serves both as a source of the diazonium cation and as the coupling partner in the azo coupling reaction. The synthesis is thought to start with double diazotization of 1,3-phenylenediamine: (H 2 N) 2 C 6 H 4 + 2 H + + 2 HNO 2 → [C 6 H 4 (N 2) 2] 2+ + 2 H 2 O
In 1858 Peter Griess passed ‘nitrous fumes’ (N 2 O 3) into a solution of picramic acid (2-amino-4,6-dinitrophenol) and isolated a product belonging to a new class of compounds: azo dyes. Later, a new class of azo dyes that were based on "coupling" reactions entered the market. The new azo dyes were easy to make and assumed a vast variety of ...
Alizarine Yellow R is a yellow colored azo dye made by the diazo coupling reaction. It is usually commercially available as a sodium salt. In its pure form, it is a rust-colored solid. [2] It is mainly used as a pH indicator.