Nitro, acids naphthols

Solochrome black (eriochrome black T). This substance is sodium 1-(1-hydroxy-2-naphthylazo)-6-nitro-2-naphthol-4-sulphonate, and has the Colour Index reference C.I. 14645. In strongly acidic solutions the dye tends to polymerise to a red-brown product, and consequently the indicator is rarely applied in titrations of solutions more acidic than pH = 6.5. 

Nitro-1 -Naphthol (8-Nitro-l-oxy-naphthalene). (O2N)C10H6.OH,mw 189.18, N 7.41%, OB to C02 —173.38%, mp 212° (decompn). Prepn from 1-naphthy 1-m-nitrobenzene sulfonate by nitration with nitric acid in AcOH, then hydrolysis with piperidine... 

Nitro-3,4,6-Tribromo-2-Naphthol (1-Nitio-3,4,6-tribromo-2-oxy-naphthalene). 02N.CloH3Br3.OH, mw 425.87, N 3.29%, OB toC02 -71.38%, turns black at 135°, mp 136° (decompn). Prepn from l,3,4,6 tetrabromo-l-nitro-2-naphthol by reaction with nitric acid, then alkali Ref Beil 6,655... 

The hydroxy-nitro dye Naphthol Yellow S (6.233 Cl Acid Yellow 1) was discovered in 1879 by Caro and is still manufactured. It is produced by sulphonation of 1-naphthol to give l-naphthol-2,4,7-trisulphonic acid, followed by replacement of the 2- and 4-sulpho groups in nitric acid medium. Nucleophilic substitution of l-chloro-2,4-dinitrobenzene with 4-aminodiphenylamine-2-sulphonic acid gives Cl Acid Orange 3 (6.234). 

Nitration of arenes. Reaction of 1-naphthol with CAN in acetic acid results in 2,4- and 4,6-dinitro derivatives. The reaction with CAN absorbed on silica gel results in 2-nitro- and 4-nitro-l-naphthol in 42 and 38% yield, respectively. Polynuclear arenes are not oxidized to quinones by CAN supported on silica but are converted mainly into mononitro derivatives. Thus phenanthrene is converted into 2-nitrophenanthrene (45% yield) and 3-nitrophenanthrene (28% yield).1... 

Davis and his co-workers [127,128] found chlorobenzene also undergoes oxynitration by action of 65% nitric acid, with formation of trinitro-m-chlorophenol along with chlo-ronitrobenzenes, while naphthalene when nitrated with more dilute acid, for example, at a concentration of 65%, yielded 2,4-dinitro-a-naphthol besides 2-nitro-a-naphthol. 

Nitrophthalic acid has usually been prepared by nitration of phthalic add or phthalic anhydride, followed by separation from the accompanying 3-nitrophthalic acid. It has also been prepared from 6-nitro-2-naphthol-4-sidfonic acid (obtained from the technical diazo-anhydride of 6-nitro-i-amino-2-naphthol-4-sulfonic acid). The present procedure is more convenient than any of the earlier methods. 

This acid is obtained bj reducing the corresponding nitro-acid (p. 171) with ferrous chloride and alkali. It is instantly soluble in an excess of normal hydrochloric acid, and with sodium nitrite gives an orange-brown solution which couples with j8-naphthol. The monohydrochloride of the arsinic acid crystallises in clear prisms calcium, magnesium and barium salts may be obtained. The acetyl derivative separates in small prisms, sparingly soluble in boiling water, readily soluble in acids, sym.-Carbamide of 3-amino-4-piperidinophenylarsinic acid,... 

Naphthol Yellow S.—A sulphonic acid derivative of this, viz., 2-4-di-nitro i-naphthol 7-sulphonic acid in the form of the potassium salt is known as Naphthol Yellow S. 

Sodium i-nitro-2-naphtholate, 13, 78 Sodium perbenzoate, 13, 86 Sodium succinate, 12, 72 Sodium sulfide, 12, 68, 76 Stannous chloride, 13, 28 Strecker s synthesis, 11, 4 Styrene, 14, 89 Succinic acid, 12, 66 Succinic anhydride, 12, 66 13, 12 Sugar, 14, 62... 

Benzotropolones take part in electrophilic substitution reactions, for example halogenation [293,328,331] and coupling with aryldiazonium salts [332]. They may undergo rearrangement to benzenoid compounds in some instances, for example treatment of 3,4-benzotropolone with excess bromine gives 2,3-dibromonaphtho-quinone and with excess concentrated nitric acid leads to 2,4-di-nitro-l-naphthol [333]. Like other tropolones, 3,4-benzotropolone is photochemically converted into a bicycloheptadienone [334]... 

Naphthol AS dyestuffs were invented as early as 1912 by Adolph Winther, August Leopold Laska and Arthur Zitscher of Hoechst AS is the abbreviation of Amid einer Saure (amide of an acid). Naphthol AS dyestuff components are distinguished from the unsubstituted 2-naphthol derivatives by their increased affinity for the dyed substrate and by higher chemical stability in the atmosphere. Nitro-, chloro-, methyl- and methoxybenzene derivatives can serve as aromatic moieties of the amide group. The coupling reaction with the diazo salt takes place in the 1-position. Examples of early important naphthol AS dyestuffs are Gries-heim Red, discovered in 1912, and Indra Red. 

The Sn+ ion reduces the nitro group and the resulting product fluoresces strongly. The 6-nitro-2-naphthol-8-sulfonic acid seems to be the best of all reagents for tin ions. 

Procedure. One drop of the test solution is placed on a filter paper and sprayed with a 0.1 % solution of 6-nitro-2-naphthol-8-sulfonic acid followed, after 6 minutes, with cone, ammonia. Under u.v. light, an intense blue fluorescence indicates the presence of Sn i ions. 

Michler s ethyl ketone 959 l-Naphthylamine-8-sulfonic acid 368 l-Nitro-2-naphthol 8127... 

Aromatic nitro compounds have been used as qualitative and quantitative indices for metallic ions. It has been known that l-nitro-2-naphthol forms a stable complex with Co ions by the cooperative effect of nitro and hydroxyl groups. We have evaluated the interaction between EGT-N and transition metal ions at pH 10.5 where the nitric acid-treated Trp starts dissociating using the absorption intensity of die UV spectrum. There are no spectral changes when metallic ions are added to the uiurelated EGT. On the contrary, when the Co ions are added to EGT-N, die absorption intensity decreased and a green precipitate resulted. 

Naphthalenol also is used ia the preparation of azo, iadigoid, and nitro, eg, 2,4-dinitro-l-naphthol, dyes, and ia making dye iatermediates, eg, naphtholsulfonic acids, 4-chloro-1-naphthalenol, and l-hydroxy-2-naphthoic acid. 1-Naphthalenol is an antioxidant for gasoline, and some of its alkylated derivatives are stabilizers for plastics and mbber (68). 

Sodium Bisulfite. Sodium bisulfite [7631-90-5] NaHSO, is occasionally used to perform simultaneous reduction of a nitro group to an amine and the addition of a sulfonic acid group. For example, 4-amino-3-hydroxyl-l-naphthalenesulfonic acid [116-63-2] C qH NO S, is manufactured from 2-naphthol in a process which uses sodium bisulfite (59). The process involves nitrosation of 2-naphthol in aqueous medium, followed by addition of sodium bisulfite and acidification with sulfuric acid. 

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