Aminonaphthol Hydrochloride

In a 6-1. wide-mouth bottle, fitted with a mechanical stirrer and a separatory funnel, are placed 200 g. of a-naphthol melting at 910 or higher (Note 1) and 910 cc. of 10 per cent sodium hydroxide solution. The mixture is stirred for ten minutes, at the end of which time it has become a homogeneous solution. 

While the naphthol is dissolving, a solution of benzenedi-azonium chloride is prepared. In a 3-I. wide-mouth bottle are placed 128 g. of aniline and 1.5 kg. of cracked ice, and on to this mixture while it is stirred (by hand) is poured 410 cc. of concentrated hydrochloric acid (32 per cent sp. gr. 1.16). Some crystals of aniline hydrochloride separate at this point. A solution of 100 g. of sodium nitrite in 200 cc. of water is now run in slowly from a 500-cc. separatory funnel. The tip of the stem of the separatory funnel should dip well below the surface of the liquid. The mixture is stirred (by hand if desired) and a drop is tested from time to time with starch iodide paper. This is 

To the alkaline solution of a-naphthol is now added 1 kg. of cracked ice, the stirrer is started and the diazonium solution run in through a separatory funnel, the stem of which dips below the surface of the solution. The stirring must be uniform and efficient during the addition (Note 3). The addition of the diazonium solution should take ten minutes. Ice is added if necessary to keep the solution below io°. The mixture is stirred for half an hour after the addition of the diazonium solution. and then allowed to stand for three hours at 7-100 (Note 4), and finally filtered on a Buchner funnel, washed with a liter of water and sucked as dry as possible. 

To the deep-red solution is added 550 g. of sodium hydrosulfite (of at least 80 per cent purity) the mixture is stirred for five minutes and then for five 30-second periods during half an hour (Note 5). The solution slowly loses its red color (a thin layer of aniline collects on the surface), and the temperature rises from 25° to 50°. At the end of half an hour the solution should no longer be red it is then rapidly cooled to 20° in a freezing bath and by the addition of about 500 g. of ice. 

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Aminoacetic Acid, 4, 31 -Aminobenzoic acid, 7, 59 -Aminobenzophenone, 7, 26 -Aminocaproic Acid, 4, 3 1, 4-Aminonaphthol Hydrochloride,... 

EtjN (1.1 mmol) and an eqnivalent amonnt of aromatic aldehyde (freshly distilled if hqnid) were added to solution of the appropriate aminonaphthol hydrochloride (1 mmol) in absolute MeOH (20 mL). The mixture was left to stand at ambient temperature for 2 days. Oily erode products were purified by colunm chromatography. The physical data for some of the compounds, 3, are listed Table 39.1. 

The claret-colored solution (5200-5800 cc.) is filtered through a fluted filter paper in a 15-cm. funnel into 1200 cc. of concentrated hydrochloric acid in an 8-1. bottle. The aminonaphthol hydrochloride starts to precipitate immediately. The mixture is allowed to stand for at least two hours with occasional agitation to insure complete precipitation. The hydrochloride is collected on a 15-cm. Buchner funnel and washed successively with three small portions of 20 per cent hydrochloric acid and three 50-cc. portions of ether (Note 4). It is then dried in the air in thin layers on filter paper (Note 5). The yield is 180-200 g. of anhydrous material (Note 6) (66-74 per cent of the theoretical amount based on 200 g. of /S-naphthol). The hydrochloride is unstable in solution it decomposes rapidly, but this decomposition can be largely prevented by the addition of... 

The aminonaphthol hydrochloride (Org. Syn. 3, 7) need not be dried before using the directions as here written correspond to the average yield from 200 g. of alpha-naphthol. The free base is unstable in solution, being easily oxidized by the air the presence of bisulfite decreases this tendency. 

The oxidation is carried out in warm solution to prevent the separation of the aminonaphthol hydrochloride on cooling. However, if the temperature is too high (above 85°) a black product is obtained. 

Wash the crystalline aminonaphthol hydrochloride into a beaker, stir, add more water, and warm to about 35°C until the salt is dissolved. Filter the solution quickly by suction from a trace of residue and stir in the iron(III) chloride solution. 1,2-Naphthoquinone separates at once as a voluminous precipitate and is collected on a suction filter and washed thoroughly to remove all traces of acid. The yield from pure, salt-free Orange II is usually about 75%. 

Oxidation. The reagent oxidizes 1,2-aminonaphthol hydrochloride (1) in aqueous solution at 25-35° to directly pure 1,2-napthoquinone (2). When 10 g. of this yellow-... 

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