6.6- Dibromoindigo purple

Indigoid dyes represent one of the oldest known classes of dyes. For example, 6,6 -dibromoindigo [19201 -53-7] (44) is Tyrian Purple, the dye made famous by the Romans. Tyrian Purple was so expensive that only the very wealthy were able to afford garments dyed with it. Indeed, the phrase "bom to the purple" is still used today to denote wealth. 

AD Strabo described dyeworks for obtaining tyrian purple (dibromoindigo) in his Geographica 100 Use of salt to purify noble metals... 

P. Friedlander showed that Tyrian Purple from Murex brandaris was 6,6 -dibromoindigo (previously... 

The magnificent purple pigment referred to in the Bible and known to the Romans as Tyrian purple after the Phoenician port of Tyre (Lebanon), was shown by P. Friedlander in 1909 to be 6,6 -dibromoindigo. This precious dye was extracted in the early days from the small purple snail Murex brandaris, as many as 12000 snails being required to prepare 1.5 g of dye. The element itself was isolated by A.-J. Balard in 1826 from the mother liquors remaining after the crystallization of sodium chloride and sulfate from the waters of the Montpellier salt marshes ... 

The Chemistry of Indigo Dyeing.—On account of its insolubility the dye itself cannot be applied directly to the fibre. Yet an indirect process of great antiquity is available, for Tyrian purple has been identified as 6 6 -dibromoindigo 1 by Friedlander. The indigo is made soluble... 

Cooksey, C. J. (2001), Tyrian Purple 6,6 -Dibromoindigo and related compounds, a review. Molecules 6, 736-739. 

Important indole derivatives (see Scheme 2) include (i) indigo, a vat dye known and widely used since antiquity, and originally obtained from indican, a (3-glucoside of indoxyl which occurs in some plants. Indigo is now prepared synthetically. Tyrian purple, a natural dye used since classical times, is 6,6 -dibromoindigo (ii) the numerous indole alkaloids, with complex derivatives such as yohimbine and strychnine (iii) tryptophan, an essential amino acid found in most proteins. Its metabolites include skatole and tryptamine and (iv) 3-indoleacetic acid, which is important as a plant growth hormone. 

Clark RJH, Cooksey CJ (1999) Monobromoindigos A New General Synthesis, the Characterization of All Four Isomers and an Investigation into the Purple Colour of 6,6 -Dibromoindigo. New J Chem 323... 

Solution spectrophotometry in the visible and ultraviolet can he used to determine the nature of dyes used to color textiles of archaeological or historical importance. The curves obtained are compared with those from solutions of known materials. The method requires dyeings made with known natural dyes from the region of interest. Collections of such materials have been obtained from Peru, The principle red dyes of Peru can be identified by means of a single solution curve. Blue, from indigo, can easily be distinguished from the purple dibromoindigo obtained from marine molluscs. Yellow dyes are more difficult to identify and require, in most cases, curves in more than one solvent. 

Chlorine was the first halogen to be isolated and sodium chloride, common salt, has been known from early times as being essential to the human diet as such it has been mentioned in the Bible. Aqua regia, a mixture of hydrochloric and nitric acids, has been known since the thirteenth century as a liquid for dissolving the very inert metal, gold. The ancient color mentioned in the Bible as purple has been identified as a brominated organic compound, namely 6,6-dibromoindigo, which used to be extracted from a small snail. 

Among indole compounds occurring in sea organisms, tyrindolsulfate 52 must be mentioned [55]. It occurs in molluscs of the type murex, purpura and dicathais, which are mainly found in the Mediterranean. The tyrian purple of antiquity (6,6 -dibromoindigo 53) was extracted from these animals ... 

Other dyes based on the indigo motif are known, many with different hues. Tyrian Purple, 6,6 -dibromoindigo, is a natural product isolated from cmshed sea shells that was quite valuable in ancient times but is not sold commercially today. However, the (5,7,5, 7 )-tetrabromo derivative (blue, Vat Blue 4B ) and the (5,5 )-bis-sulfonic acid analog (blue-green, Blue Saxon ) both are used as dyes in the... 

Dibromoindigo principal constituent of a dye known as Tyrian purple and prized by ancient cultures, isolated from a species of Mediterranean sea snail... 

In hindsight, this is remarkable in several respects. For one, purple stands out as one of the first known examples of natural brominated organic compounds. For another, the substitution pattern is unusual bromination of indigo in nitrobenzene gives 5,5 -, not 6,6 -dibromoindigo. 

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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