The Chemistry of Dyestuff. Intermediate Compounds. VIII. Quinones.

A Manual for Students of Chemistry and Dyeing
By
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)Quinones are substances obtained from aromatic hydrocarbons by the replacement of two atoms of hydrogen by two atoms of oxygen. The simplest member is quinone or more correctly para-benzoquinone which is obtained by the oxidation of many benzene derivatives. Quinone is easily reduced to hydroquinone and hydroquinone is readily oxidised to quinone; quinone on treatment with phosphorus pentachloride gives hexachlorobenzene. From these simple reactions Graebe assigned to it a peroxide formula [-] this being later replaced by the quinonoid formula [-] since quinone gives a monoxime and this in turn a dioxime [-]

The monoxime is identical with para-nitrosophenol which according to Sluiter exists as nitrosophenol [-] in the free state, whilst the salts are derived from the quinone-oxime.

Benzoquinones exist in two forms, the ortho and the para, the ortho again existing in two modifications, [-] a red coloured substance and [-] a colourless body. By rapid oxidation of catechol in an inert solvent with silver oxide the colourless compound is obtained, but if the reaction takes place slowly the more stable bright red compound is formed. Small amounts of the colourless body are produced when the red body is recrystallised. The ortho-quinones condense fairly readily with ortho-diamines to form azines. Diphenazine being obtained thus [-] from ortho-benzoquinone and ortho-phenylene diamine. Quinone derivatives are often formed as intermediate compounds during the preparation of dyestuffs. Thus the condensation of para-chlorophenol with a paraphenylene diamine or a para-amidophenol by means of oxidising agents gives ortho-quinone derivatives, e.g., [-]

Para-benzoquinone [-] is obtained by oxidation of aniline with chromic acid. It is also obtained by the further oxidation of aniline black by means of chromic acid, many other azine dyestuffs also giving para-quinones on oxidation.

Para-benzoquinone forms yellow prisms, sublimes readily in gold-coloured needles, and possesses a peculiar penetrating odour. Quinone is fairly active and reacts with many compounds containing the amido group, e.g., ortho-mtranilme, anthranilic acid, diamido-diphenylmethane, etc.

Tetrachloro-para-benzoquinone or Chloranil [-] is produced by the action of potassium chlorate and hydrochloric acid on aniline; or from pentachlorophenol by means of oxidising agents, the pentachlorophenol being obtained by the action of hydrochloric acid and a chlorate on phenol; by the action of chlorate and hydrochloric acid on para-phenylene diamine.

Chloranil readily sublimes and melts in a sealed tube at 290°C. It is used in melt processes as an oxidising agent to convert leucobases into dyestuffs.

Naphthoquinones. There are six possible naphthoquinones of which three are known and derivatives of a fourth are also known. They are coloured bodies and generally give coloured derivatives, a small number of these being commercial dyestuffs.

1.2-Naphthoquinone or β-naphthoquinone is often, obtained when azo dyestuffs are reduced and the separated bodies are subsequently oxidised. It may be obtained by oxidising a dilute solution of 2-amido-α-naphthol in 5 per cent, sulphuric acid with a cold solution of potassium bichromate.

It crystallises in red needles and decomposes with blackening at 115° to 120°C. It is odourless and nonvolatile in steam. Dilute caustic alkalis dissolve it, giving a yellow solution, which rapidly darkens on exposure to air.

When heated with acetic anhydride and sulphuric acid or zinc chloride, it gives a triacetate of 1.2.4trihydroxy-naphthalene. And when heated with sulphuric acid at 120° to 150°C., it is converted into naphthoquinone black or Naphthazarine.

1.4-Naphthoquinone or α-naphthoquinone [-] (M.P. 125°C.) may be obtained by the oxidation of naphthalene in acetic acid solution by chromic acid. It is also obtained by oxidation of simple α-or 1.4-disubstituted naphthalenes with chromic acid mixture.

It crystallises in yellow needles, sublimes below 100°C., has an odour similar to para-benzoquinone. is volatile in steam, and dissolves in most organic solvents. In caustic soda solution it absorbs oxygen from the air forming 2-oxy-α-naphthoquinone.

2.6-Naphthoquinone is obtained from the corresponding dioxy-compound by oxidation in boiling benzene solution with lead peroxide, it forms reddish yellow needles, is odourless, non-volatile, and is an oxidising agent similar to para-benzoquinone.

Naphthoquinone oximes may be obtained from the corresponding quinones by action of hydroxylamme, or by the action of nitrous acid upon naphthols or upon some of the oxynaphthoic acids. They are identical with the corresponding nitroso naphthols.

α-naphthoquinone oxime or 4-nitroso-α-naphthol is not a dye, it does not form lakes. If an oxy group is introduced in the ortho-position to the oxime or keto group a dye is produced which will form lakes with coloured mordants. E.g. 2-oxy-α-naphthoquinone oxime are dyes.

2-Nitroso-α-naphthol or 1-nitroso-β-naphthol [-] are dyes Gambine R and V (H) forming lakes, due, according to Tschugaeff and Werner, to the oxygen of the carbonyl group having a residual valency (shown by dotted line) which forms a lake with a basic mordant [-]

Acenaphthenequinone [-] This body although termed a qiiinone is not strictly a quinone, the two carbonyl groups being situated in a 5-membered ring.

Chromic acid oxidises acenaphthene [-] to acenaphthenequinone, the yield, however, is by no means good. It is prepared by adding 4 molecular proportions of amyl nitrite to a boiling solution of one molecular proportion of acenaphthene in alcohol, whilst a stream of hydrochloric acid gas is passed in. Two isomers are produced, one insoluble in sodium carbonate solution, which decomposes at 207°C., when rapidly crystallised from acetic acid. If the boiling with acetic acid is continued some time, the oxime (M.P. 230°C.) may be precipitated by addition of water. This oxime is dissolved in seven times its weight of 75 per cent, sulphuric acid and heated for one hour at 100°C.

Acenaphthenequinone condenses readily with substances containing an active methylene group. Vat dyestuffs may be produced in this way, e.g., Ciba Scarlet G.

[The student seeking more detailed information on these bodies should consult the section on "Quinones" in Thorpe's Dictionary of Applied Chemistry.

Anthraquinone [-] (M.P. 277°C., B.P. 380°C.) is prepared from crude or purified anthracene, in a finely divided condition (which is obtained by rapidly quenching the distillate when anthracene is distilled in superheated steam), by boiling in a leaden-lined vat with sulphuric acid and sodium bichromate. The crude anthraqiiinone is filtered off, dried, dissolved in cold concentrated sulphuric acid, boiled with water, the precipitated anthraqiiinone filtered, boiled with soda solution, again filtered, washed and dried. The impurities are sulphonated and removed as salts. Another method is to mix the anthracene with copper oxide and heat at 250° to 300°C., air containing some nitrogen oxides is passed through the material, anthraquinone being produced. The electrolytic oxidation of anthracene, in an anode bath, with chromic acid solution as electrolyte, is practically of great importance; the crude anthraquinone being then purified as above; or the impurities are removed by solution in liquid sulphm dioxide, etc.

Anthraquinone is sparingly soluble in most organic solvents, it sublimes to form lemon yellow needles; it dissolves, without action, in sulphuric acid (98 per cent.) at 100°C. When strongly heated with sulphuric acid it is converted into monoand di-sulphonic acids.

1.2 -Anthraquinone [-] and 1.4-anthraquinone [-] have been obtained from β-anthrol [-] and α-anthrol [-] respectively.

Anthraquinone-α-sulphonic acid [-] During the sulphonation of anthraquinone the action of catalytic agents plays an important part, different catalytic agents controlling the position in which the sulphonic acid group enters. The catalytic agents generally used are boric and arsenic acids, and mercury salts.
The α-sulphonic acid is prepared by heating 100 parts of anthraquinone, 110 parts of sulphuric acid (30 per cent. SO₃ ), and 0,5 part of mercury to 130°C.

The free acid is readily soluble in water or alcohol; the calcium salt is more soluble in cold than in hot water and is crystallised from the hot solution.

Anthraquinone-β-sulphonic acid [-]
One part of anthraquinone is mixed with one to one and a quarter parts of sulphuric acid (50 per cent. SO₃ ) and heated to 170°C., for about ten hours, the mixture being well stirred during the operation.

The product is diluted with water and filtered from the unchanged anthraquinone, sodium carbonate is next added, which causes the sparingly soluble sodium salt of the β-acid to separate out, leaving the easily soluble sodium salt of the disulphonic acid in solution.

By recrystallisation of the mono-sodium sulphonate from water the so-called "silver salt" for alizarin manufacture is obtained.

Anthraquinone-disulphonic acids. By the further sulphonation of the α-acid in the presence of mercury the 1.5-anthraquinone disulphonic acid mixed with the 1.7 and the 1.8-acids are obtained. These acids are separated by the crystallisation of the calcium salts, the 1.8 is the least soluble, followed by the 1.5, whilst the 1.7 is easily soluble. The α-β-disulphonic acids of anthraquinone are also obtainable by sulphonation in two stages, ordinary and catalytic.

Phenanthraquinone [-] is obtained from the portion of coal tar boiling at 320° to 340°C., which is easily soluble in light petroleum or in 90 per cent, alcohol. The crude hydrocarbon, after removal of bases and acids, is oxidised with sulphuric acid and sodium bichromate solution; a vigorous reaction sets in, when this has subsided, the reaction mixture is heated to boiling for some time. The quinone is then precipitated with water, washed, filtered, dried, mixed with concentrated sulphuric acid and allowed to stand for one day. The phenanthraquinone, which is insoluble, is filtered off, washed with dilute alkali, and then extracted with warm strong sodium bisulphite solution in which the pheiianthraquinone dissolves, and it is then precipitated from the filtered solution by sulphuric acid and bichromate.

Phenanthraquinone is a typical ortho-quinone, it gives the characteristic reactions of ortho-diketones: it condenses with ortho-diamines to give azines; it reacts with hot caustic alkali to give an oxy-acid, which on oxidation gives a ketone
[-]

Phenanthrene resembles naphthalene more than anthracene; it may be nitrated similarly to naphthalene whereas anthracene is oxidised to anthraquinone.

Nitro-phenanthraquinones may be obtained from nitro-phenanthrenes or by nitration of phenanthraquinone.