The Chemistry of Dyestuff. Dyestuffs. XX. Acridine and Quinoline Dyestuffs.

A Manual for Students of Chemistry and Dyeing
M. Fort, M.Sc. (Leeds) Late Lecturer in Dyeing in the Bradford Technical College and L. L. Lloyd, Ph.D. (Bern) Lecturer in Organic and Technical Chemistry in the Bradford Technical College
Cambridge: at the University Press 1919
(First edition 1917, reprinted 1919)
Acridine Dyestuffs. - These are allied to diphenylnie thane and xanthene dyes tuffs. Dihydroacridine is obtained by heating o-diamido-diphenylmethane, ammonia being split off, giving [-] which on oxidation gives acridine which is represented by  [-].

Acridine is found in coal tar also; it is a yellow basic body, fluorescent in solution. Phenylacridine is thus a derivative of triphenylmethane. The introduction of auxochrome groups para to the methane carbon in acridine gives yellow and orange dyestuffs mostly showing a greenish fluorescence in solution. Those of commercial importance are all basic.

Phosphine or Leather Yellow is obtained as a by-product of the Magenta melt. The residues from this process are reduced, the triphenylmethane bodies from stable leuco compounds; the Phosphine may be then separated as the difficultly soluble nitrate. The chief colouring matter has been called Chrysaniline.

It is formed in Magenta manufacture by a partial ortho condensation instead of the main para condensation giving Rosanilines. On diazotisation and boiling with alcohol Chrysaniline gives phenylacridine. The dyestuff can be synthesised from o-nitro-benzaldehyde and two molecules of aniline by heating to get a triphenylmethane which is further reduced and oxidised.
The dye gives orange yellow solutions with green fluorescence and is used in cotton dyeing, printing, and in the dyeing of leather.

Acridine Orange R extra is obtained by condensation of benzaldehyde with m-amido-dimethylaniline in alcoholic hydrochloric acid solution. By heating the triphenylmethane derivative thus formed with hydrochloric acid under pressure, ammonia is split off and a nitrogen bridge formed also. The leuco compound is then oxidised to the dyestuff with ferric chloride.

A similar condensation of benzaldehyde with m-tolylene diamine gives Benzoflavin (G.E.).

The above are phenylacridines, the simpler acridines have been since obtained by the use of formaldehyde. Thus Acridine Yellow is obtained by condensing formaldehyde with m-tolylene diamine.

When m-amido-dimethylaniline is used as above an Acridine Orange NO (L.) is obtained.

It is put out as a double zinc salt, i.e. +ZnCl2

Rheonine (B.), a brownish yellow dye with green fluorescence, of good fastness when dyed, is obtained from tetra-methyl-diamido-benzophenone by heating with m-phenylene diamine hydrochloride and zinc chloride.

In this way m-amido-phenylauramine (I) is formed intermediately by splitting off of water, and on further heating to 200°C. gives a leuco compound oxidising to the dyestuff (II).

Various Patent Phosphines, etc. are obtained by alkylating acridine dyestuffs, whereby acridinium coinpounds are formed which are strongly basic dyes, e.g., with methyl chloride and diamidoacridine.

Quinoline Dyestuffs. - A small group of which Quinoline Yellow is by far the most important. It is obtained from quinaldine by heating with phthalic anhydride.

It should be noted that water is split off with the other oxygen of phthalic anhydride to that involved in xanthene syntheses. The dye thus obtained is insoluble in water but soluble in spirit.

Quinoline Yellow S (or water-soluble) is obtained by sulphonation of the above dye with fuming sulphuric acid. The resulting disulphonic acid, containing some mono-sulphonic acid, has these acid groups in the quinoliue residue. It is an acid dye giving the purest greenish yellow shades obtainable on textile fibres, possessing also good fastness to light. It is necessarily rather expensive.

Quinoline Red, obtained by action of benzotrichloride on raw quinoline (containing isoquinoline) along with zinc chloride, is used in colour photography, being sensitive to light, as is also Quinoline Blue or Cyanin, obtained by the action of caustic alkalis on the condensation product of amyliodide and a mixture of quinoline and lepidine (γ-methyl quinoline).

Pinacyanol (M.) and other Pina- dyes belong to this class.

(For the application of these dyes in photography see "Photography in Colour," by A. E. Woodhead, Journ. Soc. Dyers, p. 78, 1914.)

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