1,2-Naphthoquinone salts

Dissolve 100 mg l,2-naphthoquinone-4-sulfonic acid sodium salt in 40 ml ethanol and add 20 ml perchloric acid (70%), 18 ml water and 2 ml formaldehyde solution in that order. 

The reaction mechanism has not been elucidated. It is possible that formaldehyde reacts by oxidation as in the Marquis reaction (see formaldehyde — sulfuric acid reagent), whereby colored salts are formed with naphthoquinone sulfonic acid. 

Dipping solution For aromatic amines Dissolve O.S g l,2-naphthoquinone-4-sulfonic add sodium salt in 30 ml water and add 65 ml ethanol and S ml acetic add [5]. 

Spray solution For amino acids Dissolve 0.2-0.3 g l -naphthoquinone-4< sulfonic acid sodium salt in 100 ml aqueous sodium carbonate solution (5-10%) [1]. 

For aromatic amines Dissolve 0.5 g 1 -naphthoquinone-4 sulfonic acid sodium salt in 95 ml water and treat with 5 ml glacial acetic acid [1,6] if necessary, filter off the insoluble part [1],... 

For aliphatic amines Dissolve 0.6 g l,2-naphthoquinone-4-sulfonic acid sodium salt in 12 ml water, make up to 200 ml with ethanol (90%) and add 10 ml pyridine [8]. 

In the case of diuretics the chromatogram is Erst sprayed with sodium hydroxide solution (c = 1 mol/L) and then with a saturated solution of l,2-naphthoquinone-4-sulfonic acid sodium salt in ethanol — water (50-1-50) [11]. Stable orange-colored chromatogram zones appear over a period of ca. 15 min, their intensity increases on storage in the dark (1-2 days) [11]. 

Substances l,2-Naphthoquinone-4-sulfonic acid sodium salt... 

Reagent 3 Spray solution 3 A saturated solution of 1,2-naphthoquinone-sulfonic acid sodium salt in ethanol — water (1+1). 

Salama and Omar have described a rapid, specific, and convenient colorimetric method for the determination of procaine hydrochloride in pharmaceutical preparations [40]. The method is based on an intensity measurement of the orange-red color developed when the drug is allowed to react with l,2-naphthoquinone-4-sulfonic acid (sodium salt) in an aqueous solution. The method is suited for routine analysis of official preparations of procaine. 

Dihydro-3,4-dioxo-l-naphthlene sulphonic acid sodium salt (l,2-naphthoquinone-4-sulphonic acid sodium salt) [521-24-4] M 260.2. Yellow crystals from aqueous EtOH and dry at 80° in vacuo. Solubility in H2O is 5% Synth Coll Vol III 633 1955 Danielson JBC 101 507 1933 UV Rosenblatt et al. AC 27 1290 7955]. 

Naphthoquinone-4-sulphonic acid sodium salt see 3,4-dihydro-3,4-dioxo-l-naphthlene sulphonic acid sodium salt. 

Stabilization of a radical anion of humic acid may be caused by an adsorption effect. Bijl (3) observed that solid barium hydroxide octahydrate turned blue when placed in a solution of quinhydrone the blue solid was highly paramagnetic. Under the conditions we used for preparing these salts, insoluble sodium humate (with a large surface area) could have stabilized the anion radical by adsorption from the basic solution. Weiss and McNeil (18) observed a similar phenomenon with base soluble xanthenes, and proposed that biradicals may be formed in such a system. His compounds, however, do not appear to have the structural requirements to satisfy such a stabilized system. The recent report by Weber (29) on the spin content increase associated with the basification of a naphthoquinone-naphthohydroquinone system seems to parallel our observations quite closely. 

After the mixture has been cooled to o°, the ammonium i,2-naphthoquinone-4-sulfonate is collected on a 20-cm. Buchner funnel and as much of the mother liquor is removed as possible by pressing the cake with a porcelain spatula or glass stopper. The product is washed with three equal portions of a cold mixture of 150 cc. of saturated ammonium chloride solution and 100 cc. of water. The wash solution is removed as completely as possible and the product washed twice with 50-cc. portions of alcohol, followed by 300 cc. of ether in small portions (Note 5). The ammonium i,2-naphthoquinone-4-sulfonate is spread out in a thin layer and dried to constant weight at 35-40°. An orange, microcrystalline product of bright appearance is thus obtained. The yield is 350-365 g. (94-98 per cent of the theoretical amount). The ammonium salt is of good quality and is sufficiently pure for many purposes. No satisfactory method has been devised for its further purification, but it can be converted into a pure potassium salt as follows. 

Salts of 1,2-naphthoquinone-4-sulfonate have been prepared by the oxidation of 2-amino-i-naphthol-4-sulfonic acid with nitric acid,2 or by the oxidation of the more readily available i-amino-2-naphthol-4-sulfonic acid with the same reagent.3,4 5... 

With 1,4-naphthoquinones, the corresponding naphth-[2,l-d]-l,3-oxathiol-2-ones 207 are formed 362 whereas, with tetra-substituted thioureas and 1,4-benzoquinone, the benz[d]oxathiolium salts 208 are produced.363,364... 

The potassium salt of pcrfluoro-1-naphthol is oxidized similarly but to a mixture of quinoidal structures which are difficult to separate.170 In contrast, quinone structures are obtained in preparative yields by the oxidation of perfluoro-2-naphthol with concentrated nitric acid. The isolable l-nitronaphthalen-2(l //)-one 10 is easily transformed to 1,2-naphthoquinone 11 in high yield.120... 

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