1.4- Naphthalenedisulfonic acid, 2-hydroxy

Another example of manufacture in this series is the sulfonation of an aminonaphthalenesulfonic acid, followed by selected desulfonation, to make 6-amino-l,3-naphthalenedisulfonic acid (21). Thus, 2-amino-l-naphthalenesulfonic acid made by amination of 2-hydroxy-1-naphthalenesulfonic acid is added to 20 wt % oleum at ca 35°C. At this temperature, 65 wt % oleum is added and the charge is stirred for 2 h, is then slowly heated to 100°C and is maintained for 12 h to produce 6-amino-l,3,5-naphthalenetrisulfonic acid. The mass is diluted with water and maintained for 3 h at 105°C to remove the sulfo group adjacent to the amino group. After cooling to ca 20°C and filtration, 6-amino-l,3-naphthalenedisulfonic acid is obtained in 80% yield (55). 

Direct Blue 218 had reported sales of 623 t valued at 4.4 million ia 1987. It is produced from Direct Blue 15 (76) by metallizing and elimination of methyl groups from the methoxide to form the copper complex. Direct Blue 15 (76) is prepared by coupling o-dianisidine [119-90-4] to two moles of H-acid (4-amiQO-5-hydroxy-2,7-naphthalenedisulfonic acid) under alkaline pH conditions. Other important direct blues iaclude Direct Blue 80 (74), (9-dianisidine coupled to two moles of R-acid (3-hydroxy-2,7-naphthalenedisulfonic acid [148-75-4]) followed by metallizing to form a bis copper complex, and Direct Blue 22 (77), an asymmetrical disazo dye, prepared by coupling o-dianisidine to Chicago acid [82-47-3] and 2-naphthol. Direct Blue 75 (78) is an example of a trisazo dye represented as metanilic acid — 1,6-Q.eve s acid — 1,6-Q.eve s acid — (alb) Ai-phenyl J-acid. 

Interesting regioselectivities have been known for more than 100 years for azo coupling reactions with aminonaphthol derivatives such as 6-amino-4-hydroxy-2-naphthalenesulfonic acid (12.136, y-acid), 7-amino-4-hydroxy-2-naphthalenesulf-onic acid (J-acid), and 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid (H-acid). They give two types of isomeric azo compounds depending on the pH-value of the... 

Richfield-Fratz et al. (206) determined aniline, benzidine, 4-aminophenyl, and 4-amino-azobenzene in sunset yellow. The determination involved chloroform extraction followed by diazotization and coupling with the disodium salt of 3-hydroxy-2,7-naphthalenedisulfonic acid and analysis by reverse-phase HPLC. Using a similar system, Peiperl et al. (207) determined benzidine in sunset yellow. Dithionite was used to reduce any combined benzidine present. 

NAPHTHALENEDISULFONIC ACID, 3-HYDROXY- )-((4-SULFO-1 -NAPHTHYL) AZO) -, TRISODIUM SALT... 

FD C Yellow No. 6 is principally the disodium salt of 6-hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfonic acid. The trisodium salt of 3-hydroxy-4-[(4-sulfophenyl)azo]-2,7-naphthalenedisulfonic acid may be added in small amounts. 

Sum of the Trisodium Salt of 3-Hydroxy-4-[(4-sulfophe-nyl)azo]-2,7-naphthalenedisulfonic Acid and Other Higher Sulfonated Subsidiaries Not more than 5%. 

DISULPHONIC ACID EDICOL PONCEAU RS FENAZO SCARLET 2R HEXACOL PONCEAU MX HIDACID SCARLET 2R 3-HYDROXY-4-(2,4-XYLYL-AZO)-3,7-NAPHTHALENEDISULFONIC ACID, DISODIUM SALT 3-HATIROXY-4-(2,4-XYLYLAZO)-3,7-NAPHTHALENEDISULPHONIC ACID, DISODIUM SALT... 

DIMETHYLPHENYL)AZO)-3-HYDROXY-2,7-NAPHTHALENEDISULFONIC ACID, DISODIUM SALT see FMU070... 

Synonyms Amaranth FD C No. 2 Whortleberry red 3-Hydroxy-4-[(4-sulfo-l-naphthalenyl) azo]-2,7-naphthalenedisulfonic acid trisodium salt Chemical/Pharmaceutical/Other Class Azo dye Chemical Formula 20-HnN2O10S3Na3... 

Ponceau 3R. (3-hydroxy-4-[2,4,5-(trimethyl-phenyl)azo]-2,7-naphthalenedisulfonic acid, disodium salt Cl 16155). 

It is interesting to note that l-amino-8-hydroxy-3,6-naphthalenedisulfonic acid also condenses with HCHO to form a cyclic tetramer, but only one of the o-positions of each of the naphthalene units is involved the other bridges are formed to the amino function at C-1 Poh, B-L. Chin, L. Y. Lee, C. W. Tetrahedron Lett. 1995,36, 3877. 

Trypan Blue. 3,3 /(3,3 -DimetliyI/T,i -Mpfte i-yl] 4,4 -diyl)bisDirect Blue 14 C.l. 23850 3,3 -[(3,3 -dimethyl-4,4 -bipheny]ene)bis(azo)]bis-(5-amino-4-hydroxy-2,7-naphthalenedisulfonic acid) tetra-sodium salt tetrasodium 3,3 -[(3,3 -dimethyI-4,4 -biphen-ylene)bis(azo)]bi s(5 -amino. 4-hydroxy-2,7 -naphthal enedi-sulfonate) sodium ditolyl -diazobis - 8-amino-1 -naphthol-... 

Amino-5-hydroxy-3,6-bis((4-((2-(sulfooxy)ethyi)-sulfon-yl)phenyl)azo)-2,7-naphthalenedisulfonic acid tetra-sodium salt. 4-Amino-5-hydroxy-3,6-bis((4-((2-(sulfooxy)ethyl)-sulfon-yl)phenyl)azo)- C.l. 20505 C.l. Reactive Black 5 Cav-alite Black B Celmazol Black B DIamira Black B Dri-marene Black R/K 3B EINECS 241-164-5 Intraoron Black VS-B Levafix Black E-B Primazin Black BN Reactive Black 5 Remazol Black B Remazol Black GF Sumifix Black B. 

Naphthalenedisulfonic acid, 4-amino-5-hydroxy-, monosodium salt. 

Amino-5-hydroxy-2,7-naphthalenedisulfonic acid, monosodium 8-Amino-1-naphthol-3,6-disulfonic acid monosodium salt Ash acid EINECS 226-736-4 H acid monosodium salt 2,7-Naphthalenedisulfonic acid, 4-amino-5-hydroxy-, monosodium salt NSC 8632 Sodium hydrogen 4-amino-5-hydroxynaphthalene-2,7-disulphon-ate. 

Primary aromatic amines can be converted into the corresponding hydroxy compounds in various ways. In some cases this can be done by use of dilute acid or alkali under specific conditions, but that method is used mainly in industry and is rarely suitable for laboratory practice. 4-Amino-2,7- and -2,6-naphthalenedisulfonic acid and 8-amino-1,6-naphthalenedisulfonic acid are converted quantitatively into the corresponding hydroxynaphthalenedisulfonic acids when their acid salts are heated in water at 180° 555 and 2-methoxy-4-nitroaniline affords 4-nitroguaiacol in 86% yield when boiled for 30 hours with aqueous sodium hydroxide.556... 

Occasionally, however, direct sulfonation is applied also to ot-naphthol for instance, 4-hydroxy-l,3-naphthalenedisulfonic acid is obtained as acid sodium salt in 95% yield by means of sulfuric acid at 50° for 2 hours148 or of sulfuric acid monohydrate at 20° for 36-48 hours and then at 40° for a day.149b... 

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