Pigments with known chemical structure

Flavanthrone Yellow, together with its chemical structure, is listed in the Colour Index under Constitution No. 70600. It was temporarily known as Pigment Yellow 112, but now it is exclusively referred to as Pigment Yellow 24. Since some time sales products of P.Y.24 are not listed anymore in the catalogues of the manufacturers, but the grades are still available on the market. 

The continually increasing importance of iron oxide pigments is based on their nontoxicity chemical stability wide variety of colors ranging from yellow, orange, red, brown, to black and low price. Natural and synthetic iron oxide pigments consist of well-defined compounds with known crystal structures [3.1] ... 

The coefficients of extinction in acetone for each pigment are calculated from those given in the bibliography for chlorophylls and pheophytins in ethyl ether [194] by using a pigment solution of known concentration. It is assumed that the coefficients of extinction of compounds with different chemical structure but identical electron absorption spectrum (e.g., chlorophyll/chlorophyllide) do not differ significantly [251]. Thus, the specific coefficient of extinction (e ) can be calculated from a known molar coefficient (st) of another compound (i) with an identical spectrum ... 

Pigments are classified by an internationally recognised convention, published in the International Colour Index by the Society of Dyers and Colourists in Bradford, in association with the American Association of Textile Chemists and Colorists. The Index issues a generic name to chemically identical products (e.g., titanium dioxide is classified as C.I. Pigment White 6). Where structures are known, pigments are also given a constitution number (e.g., titanium dioxide has the constitution number Cl 77891).This number is reserved for the essential colorant, other ingredients, such as the carriers used in a masterbatch, do not affect this classification. 

The new Colour Index volume Pigments and Solvent Dyes lists some 350 solvent dyes and gives their chemical structures, unlike earlier editions which named 800 dyes but included few structures. This fall in numbers is not because of any decreased use but rather the general contraction in numbers of all dyes used in the textile industry. Solvent dyes have been introduced not by attempts to synthesise new colorants but by selection and in some cases modification of known disperse dyes to meet the technical requirements. The majority of solvent dyes are azo compounds but among the blue dyes there are anthraquinones. The aqueous solubility of some of the parent sulphonated dyes has been reduced to acceptable levels by formation of their salts with heavy metals or long-chain alkylamines. 

Pigment Red 177 [4051-63-2] has the chemical structure of 4,4 -diaminol,l -dianthraquinonyl and is prepared by intermolecular copper-catalyzed debromination of l-amino-4-bromoanthraquinone-2-sulfonic acid followed by desulfonation. It is the only known pigment with unsubstituted amino groups which are involved in both intra- and intermolecular hydrogen bonding (19). The bluish red pigment is used in plastics, industrial and automotive paints, and specialized inks (see Dyes, ANTHRAQUINONE). 

Copper phthalocyanine (1) was developed in the 1930s and is the most commonly used blue organic pigment in the coatings, paint, and printing inks industry. Phthalocyanine forms complexes with numerous metals. Various complexes with 66 chemical elements are known. Phthalocyanines are structurally related to naturally occurring dyes such as hemoglobin and chlorophyll A. 

On the other hand, the almost colorless fluid secreted by Murex brandaris, a shellfish of the Mediterranean Sea region, becomes reddish purple on contact with air. The fluid was used by the Phoenicians as a dye from about 1500 BC, and the purple dye is known as Tyrian purple, ancient purple, or shellfish purple, etc. Friedlander, in 1915, isolated about 1.5 g of the pigment from 12,000 specimens of M. brandaris, and clarified its chemical structure as 6,6 -dibromoindigo [5]. Subsequently, the origin of this pigment was identified as sodium tyrindoxyl sulfate [6]. 

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