Indigo from naphthalene

Starting in the 1980s, scientists in Amgen Inc. discovered that a genetically modified strain of bacteria can produce indigo from naphthalene. [28] Recombinant Escherichia coli are able to produce indigo from glucose. [17,29]... 

As an oxidant, mercury may be used in the presence of sulphuric acid. One of the most important examples of this is the oxidation of naphthalene to phthalic acid, nsed on the large scale in the first stage of the process for preparing indigo from tin hydrocarbon. 

The broad substrate activity of naphthalene dioxygenase was used to produce indigo from indole by monooxygenation followed by chemical dimerization (Ensley et al. 1983). 

Bieberich scarlet, one of the naphthol azo dyes, a very important group, is, like indigo, prepared from, naphthalene as starting material. 

Phthalic Acid, C6H4(COOH)2(l, 2), is formed when benzene derivatives which contain two side-chains in the ortho position, are oxidized by dilute nitric acid or potassium permanganate. Chromic acid can not be used, as it oxidizes ortho compounds completely to carbon dioxide and water. The acid is prepared on the large scale from naphthalene, and is used in the preparation of artificial indigo. The hydrocarbon is oxidized by heating it with concentrated sulphuric acid in the presence of mercuric sulphate, which serves as a catalytic agent. The acid can be prepared by the action of water in phthalic anhydride, which is now manufactured from naphthalene by oxidation with the air (558). 

Among later syntheses of indigo was that from phenylglycine carboxylic acid by Heumann. This was first made from aniline, but its preparation from naphthalene made the process technically workable. The research was carried out for the Badische Co. by their chemist E. Sapper (1891-7) and depended on the oxidation of naphthalene to phthalic acid by heating with concentrated sulphuric acid in presence of mercury as a catalyst (said to have been discovered accidentally by the breaking of a thermometer bulb). Phthalic acid was converted into phthalic anhydride, phthalimide, and anthranilic acid, and phenylglycine carboxylic acid by condensation of this with chloracetic acid. On fusion with caustic potash, or better sodamide, this formed indoxylic acid, and indoxyl, which was easily oxidised to indigo. 

Creosote oil is of value as a source of naphthalene, and for preserving wood from the action of. the weather and destructive insects. Naphthalene, once a waste product, is now used largely in the manufacture of dyes, being the parent substance of artificial indigo, as an insecticide, and in other minor rdlea. Anthracene oil is the source of anthracene, a condensed hydrocarbon of the benzene sories, from which the alizarin dyes are made. 

Indigo is manufactured in large quantities by a synthesis which involves the use of naphthalene and acetic acid. From the former anthranilic acid (605) is prepared and from the latter chloroacetic acid. These compounds react to form phenyl-glycocoll-o-carboxylic acid —... 

There are over 8000 chemicals that exhibit commercially significant optical properties. Some of these are natural products such as indigo, chlorophyll, and cochineal, but the majority are synthesized in a series of steps involving dye intermediates (any of the 3000 or more organic and inorganic chemicals used as raw material precursors to manufactured dyes, the most important of which are benzene and naphthalene). Coal tar dyes refers to the dyestuffs originating from the complex mix of hydrocarbons (benzene, toluene, xylene, pyrene, naphthalene, anthracene, etc.) present in coal tar (8007-45-2). Petroleum has succeeded coal as the dominant source of dye intermediates. Dyes, pigments, and dye intermediates include... 

The so-called second Hemnann indigo synthesis started from anthranilic acid rather than aniline, and gave substantially better yields. Anthranilic acid was accessible by oxidation of naphthalene to phthalic anhydride, after Hoogewerf and van Dorp had shown that Hofmann degradation of the halfamide of phthalic acid leads to the desired product. 

Since Baeyer s work was more directed to the elucidation of the structure of indigo, the synthesis he had discovered could not be applied economically on a large scale. Karl Heumann, at the Federal Polytechnic in Zurich, discovered a method of synthesis which was based on phenylglycine, which can be produced from aniline and chloroacetic acid. The yield from this process, however, was still unsatisfactory. Heumann s second proposal used phenylglycine-o-carboxylic add, obtained by first oxidizing naphthalene to phthalic anhydride. 

The development of synthetic dyestuffs provided further impetus for advances in naphthalene chemistry. Towards the end of the last century, its oxidation into phthalic anhydride (PA) attained particular importance as a step in a successful route for the economical synthesis of indigo. In the 20 th century, the classic uses of naphthalene have been extended into new areas, for example, the development of the naphthol AS dyes from the parent naphthols, and the production of PA-based plasticizers and pesticides. The most recent developments in the field of industrial naphthalene chemistry concern the production of alkylnaphthalene-derivatives as solvents for use in carbonless copy papers, as well as the manufacture of naphthoquinone for the synthesis of anthraquinone. 

The transfer between B. circulans and S, kanamyceticus is not yet possible, but the technique has been used to transfer the enzyme naphthalene dioxygenase from Pseudomonas putida to Escherichia colL In . coli this dioxygenase will catalyse the oxidation of indole, which is a product of the breakdown of tryptophan. The E coli cells then excrete indoxyl which is further oxidized by air to the purple dye, indigo (Figure 6.20). This is a novel secondary metabolite for E. coli to produce, and while its utility is questionable, the effect of transferring the dioxygenase into E, coli was predicted. 

Figure 6.20 The synthesis of indigo by genetically-engineered strains of E. coli. E. coli. which naturally contains tryptophanase, oxidizes tryptophan to indole, pyruvate and ammonia. When the cells are genetically engineered so that they also contain the naphthalene dioxygenase derived from Pseudomonas putida, the indole is further oxidized to indigo.

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