The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918
Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.
Nitrococcussic acid was obtained by W. de la Rue from carminic acid by the prolonged action of boiling nitric acid. It was subsequently studied by v. Kostanecki and Niementowski (Ber., 18, 250), and was found to be identical with the trinitrocresotinic acid, of the following constitution: [KUVA PUUTTUU]
When carminic acid dissolved in 50 per cent, acetic acid is treated with an excess of bromine, and the solution digested at the boiling heat, two substances, known as α- and β-bromcarmines, are produced (Will and Leymann, Ber., 18, 3180).
α-Bromcarmine, C10H4Br4O3, the more sparingly soluble substance, crystallises in colourless needles, and melts at 247-248°, with decomposition. When oxidised with potassium permanganate in alkaline solution, it gives dibrommethylhydroxyaldehydrobenzoic acid and dibrommethylhydroxyphthalic anhydride.
On treatment with hot caustic soda solution, a-bromcarmine yields, in addition to a purple-red colouring matter, dibrommethylhydroxyphthalic acid, and bromoform (Miller and Rohde). As a result of this reaction, these authors assigned to α-bromcarmine the constitution of a methylhydroxytetrabromdiketohydrindene for Zincke (Ber., 20, 3227; 21, 2388) had previously shown that dibromdiketohydrindene itself under similar treatment yields both phthalic acid and bromoform.
β-Bromcarmine, C11H5Br3O4, is obtained as a yellow amorphous powder, easily soluble in alcohol (Will and Leymann), and is best purified by means of its potassium salt. Crystallised from acetone, it separates in orange needles, melting at 232° (Will and Leymann) or 288° (Miller and Rohde). By the action of bromine in the presence of 50 per cent, acetic acid solution, it is converted into abromcarmine. As a result of their investigation, Miller and Rohde ascribed to β-bromcarrnine the constitution of a methyldihydroxytribrom-a-naphthaquinone, possessing one of the following formulæ: [KUVA PUUTTUU]
This suggestion was supported by the fact that bromoxynaphthaquinone, on treatment with bromine and caustic soda solution, is converted into dibromdiketohydrindene (Zincke, loc, cit.)
Additional support for this view was obtained by a study of the behaviour of β-bromcarmine with zinc-dust in alcoholic solution. Thus the acetyl compound of the reduction product, melting-point 206°, gave, on analysis, numbers agreeing with those of the acetyl derivative of a methyldibromdihydroxynaphthahydroquinone, possessing the following formula: [KUVA PUUTTUU]
From a consideration of the points above enumerated, Miller and Rohde considered that the constitution of carminic acid could be represented by one or other of the following expressions: [KUVA PUUTTUU]
As, however, such formulæ require C = 64.7 per cent., H = 3.92 per cent., figures which are much higher than those given by the analysis of carminic acid itself, these authors suggested the addition of two molecules of water of hydration, as shown below: [KUVA PUUTTUU]
A substance of this constitution would require C = 55 per cent., and H = 5 per cent.
Somewhat later, Liebermann and Voswinkel (Ber., 30, 688) studied the oxidation of carminic acid with alkaline potassium permanganate at the ordinary temperature, and in this way succeeded in producing two important acids.
Cochenillic acid, C10H8O7, crystallises in colourless needles, which melt at 224-225° with evolution of CO2. It is tribasic, and at 260° is converted into hydroxymethylphthalic anhydride. When heated with water in a sealed tube at 210° it yields symmetrical cresotinic acid and in the same manner at a lower temperature, 170°, gives α-coccinic acid or m-hydroxyuvitic acid. The constitution of cochenillic acid is therefore as follows: [KUVA PUUTTUU]
α-Coccinic acid, C9H8O5, the second product of the oxidation, which, as already indicated, can also be prepared from cochenillic acid, proved to be identical with the hydroxyuvitinic acid of Oppenheim and Pfaff (Ber., 7, 929). It consists of colourless needles, melting-point 239°.
Liebermann (ibid., 30, 1731), whilst agreeing with the diketohydrindene constitution which had been assigned to a-bromcarmine by Miller and Rohde, considered that β-bromcarmine was an indone rather than a naphthoquinone derivative, and could be better represented as follows: [KUVA PUUTTUU]
It was probable, indeed, that carminic acid itself was a hydrindene or bishydrindene derivative, and the following constitutions were at the time suggested for it: [KUVA PUUTTUU]
In a subsequent paper, however, Liebermann and Voswinkel (Ber., 37, 3344) consider that carminic acid is possibly a tetrahydrate of α-dimethyldihydroxynaphthacenequinonedicarboxylic acid and it was observed that the dimethyltetrahydroxynaphthacenequinone prepared by these authors not only possessed weak tinctorial property of a cochineal-like character, but in several respects closely resembled carminic acid itself.
Rohde and Dorfmuller (Ber., 1910, 33, 1363) further examined β-bromo-carmine, and obtained results which support the naphthoquinone constitution assigned to it by Miller and Rohde (loc. cit.), but disprove Liebermann's contention that it is a derivative of indone. By reduction with zinc-dust and acetic acid and subsequent acetylation, β-bromo-carmine gives the compound C17H14O8Br2 colourless needles, melting-point 208°C.
Simultaneous hydrolysis and oxidation converts this into the substance [KUVA PUUTTUU] orange prisms, melting-point 258°C.; and it thus appears that by the latter treatment an hydroxyl has entered the quinone nucleus. The diacetyl derivative melts at 233°C. When distilled with zinc-dust, this product, and also β-bromo-carmine itself, give naphthalene.
A valuable contribution to the subject was made by Dimroth (Ber., 1909, 42, 1611), who studied the oxidation of carminic acid with potassium permanganate at 0° in presence of sulphuric acid. The solution thus obtained gave nothing to ether, but on heating for three-quarters of an hour at 90°, it evolved carbon dioxide, and ether then extracted carminazarin.
Carminazarin crystallises from water in garnet-red needles, decomposing at 240-250°. It possesses the constitution, and is very similar to isonaphthazarin.
Its alkaline solution when treated with a stream of oxygen, is quickly decolorised with formation of 5:6-dicarboxy-4-hydroxy-o-tolylglyoxylic acid.
A further point of resemblance of carminazarine to isonaphthazarine is shown by its behaviour with nitric acid in glacial acetic acid, for whereas the latter gives tetraketotetrahydronapthalene, the former yields the analogous Carminazarinquinone crystallising in colourless prisms and which, when heated with water or acetic acid, passes back to carminazarin.
The intermediate product formed by the oxidation of carminic acid with permanganate at 0° insoluble in ether, and which, on heating, is transformed into carminazarin, is termed by Dimroth carminoquinone. The constitutions assigned to this substance and tentatively to carminic acid are given below: [KUVA PUUTTUU]
Carminic acid was, therefore, not a symmetrical compound, and the nature of the group C10H15O7 was not then determined. At the time, Dimroth considered that the coccinin (see above) of Hlasiwetz and Grabowski, and which is prepared by fusing carminic acid with potassium hydrate, had probably the constitution of a tetrahydroxymethylnaphthalene.
Later, Dimroth (Annalen, 1913, 399, 1) re-examined this product in detail, preparing it by fusing carminic acid with caustic potash at 170-200°C. To it he gave the formula C17H14O6, and described the pale yellow crystalline tetra-acetyl derivative, C17H10O6(CH3CO)4, melting-point 242-244°C.
When coccinin was oxidised by means of air, or oxygen, in alkaline solution (6 per cent. NaOH), the colour changes above described occurred, and when the pure violet colour had been obtained, acidification with hydrochloric acid yielded a substance coccinone, C17H12O7, which forms dark brown glistening crystals and decomposes at 250°C.; it yields a tri-acetyl derivative,
C17H9O7(CH3CO)3,
orange-red crystals, melting-point 210°C., and also ferms three different barium salts (one of which has a composition analogous to the sodium hydrogen salt of 2:6-dihydroxy-8-methyl-a-naphthoquinone-3:5-dicarboxylic acid). Coccinone is reconverted into coccinin by reduction with zinc-dust and ammonia; on the other hand, alkaline oxidation by means of hydrogen peroxide below 20°C. gives rise to two products, cochenillic acid, and an unexamined acid.
Dimroth now formed the opinion that coccinin and coccinone are derivatives of anthranol and anthraquinone respectively, and the position of one of the hydroxy, methyl, and carboxyl groups in coccinone is made clear by the production from it of cochenillic acid. To coccinone Dimroth ascribes the structure [EI KUVAA] and to coccinin either the structure [EI KUVAA].
When heated with water at 200° or dilute sulphuric acid at 170°C. coccinone loses carbon dioxide, yielding decarboxy-coccinone, to which the structure [EI KUVAA] is given; it forms red-brown crystals, and dissolves in alkalis to form purple-red solutions, and in concentrated sulphuric acid with a blue colour which becomes violet on addition of boric acid.
Not only coccinin, but carminic acid itself, has been further examined by Dimroth (loc. cit.), and as a result he considers that this substance is also a derivative of anthraquinone. He has oxidised carminic acid by means of hydrogen peroxide in aqueous caustic soda, using cobalt sulphate as catalyst, and in this way obtained in the first instance carminoquinone, but the reaction proceeded further with the formation, after acidification with 80 per cent, acetic acid, of a yellow crystalline compound, C26H13O16Na3, 5H2O, which, when triturated at 0°C. with dilute hydrochloric acid, yielded 2:6-dihydroxy-8-methyl-a-naphthoquinone-3:5-dicarboxylic acid: pale yellow, hygroscopic crystals - trisodium salt, C13H5O8Na3,4H2O, orange needles.
The orientation of this acid has been established by Dimroth by comparison of its colour reactions with those of 2:6-dihydroxy-α-naphthoquinone, synthetically prepared by Dimroth and Kerkovius, as also by its conversion into carminazarin by treatment with acid permanganate. Moreover, the structure previously assigned by Dimroth to carminazarin, viz. 2:3:6-trihydroxy-8-methyl-α-naphthoquinone-5-carboxylic acid, has been supported by conversion of carminazarin-quinone the oxidation product of carminazarin into a diphenazin, C24H14O3N4, by treatment with an alcoholic solution of ο-phenylene-diamine. The product crystallises in yellow needles, and yields an acetyl derivative, C26H16O4N4.
When 2:6-dihydroxy-8-methyl-α-naphthoquinone-3:5-dicarboxylic acid the oxidation product of carminic acid referred to above is warmed with water, carbon-dioxide is eliminated with the production of 2:6-dihydroxy-8-methyl-α-naphthoquinone-5-carboxylic acid: brown-yellow needles, potassium salt, C12H7O6K, lemon-yellow crystals; dipotassium derivative, C12H6O6K2, orange-red crystals.
This compound when brominated in glacial acetic acid at 40° yields a monobrom derivative, yellow needles, melting-point 240-244°, which on treatment with hydrobromic acid yields α-bromo-carmin, whilst with bromine in cold methyl alcohol, the product is β-bromocarmin (Will and Leymann), which proves that this body has the structure [KUVA PUUTTUU] assigned to it by Miller and Rohde.
Beyond the above-mentioned decomposition products of carminic acid, Dimroth has obtained a 5 per cent, yield of hydrocarbons of the anthracene series by distillation with zinc-dust in an atmosphere of hydrogen. After oxidation of the mixture of hydrocarbons he isolated anthraquinone, and possibly α-methyl-anthraquinone.
By treatment of carminic acid with boiling dilute sulphuric acid, Dimroth has also obtained a 10 per cent, yield of trihydroxy-methylanthraquinone carboxylic acid (C16H10O7), needles, melting-point above 300°, and this acid when heated with water at 230-240°, passes into trihydroxy-methyl-anthraquinone by loss of carbon dioxide.
Dimroth considered the possibility that the anthraquinone nucleus is produced during the reactions described above, but concluded that this is not the case, and that it is present as such both in carminic acid and coccinin. Dimroth formulates carminic acid thus [KUVA PUUTTUU]
On the other hand, C. and H. Liebermann (Ber., 1914, 47, 1213) bring forward arguments, chiefly the smallness of the yield of anthraquinone or anthracene derivatives obtained by Dimroth, in favour of the view that the anthracene nucleus is formed during the degradation reactions.
These authors have also re-examined the "ruficoccin" of Liebermann and van Dorp (see above), and conclude that it consists of a mixture of trihydroxy-methyl-anthraquinone carboxylic acid, and trihydroxy-methyl-anthraquinone, which is confirmation of the work of Dimroth, Incidentally they described carminic anhydride, C22H20O12, prepared by heating carminic acid with thionyl chloride vivid red powder, resembling carminic acid, though less soluble. It is reconverted into the latter by the action of aqueous alkalis.
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