Phenyl-azo- P-naphthol

Dissolve 5-0 g. (4-9 ml.) of aniline in 16 ml. of concentrated hydrochloric acid and 16 ml. of water contained in a small beaker or conical flask. Diazotise by the addition of a solution of 4-0 g. of sodium nitrite 

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It is interesting to note that azo dyestuffs may be conveniently reduced either by a solution of stannous chloride in hydrochloric acid or by sodium hyposulphite. Thus phenyl-azo-p-naphthol 3delds both aniline and a-amino-p-naphthol (see formula above), and methyl orange gives p-aminodimethylaniline and sulphanilic acid ... 

Phenyl diazonium chloride is obtained first hy the diazotization of aniline with nitrous acid as explained earlier, which on coupling with (l-naphthol in the presence of NaOH solution yields the desired coupled product phenyl-azo-P-naphthol. A mole of HCl is eliminated which instantly reacts with NaOH from the medium to produce NaCl and H2O. Importantly, hoth diazotization and coupling reactions are required to he carried out between 0-5°C. 

A red colour develops and crystals of crude phenyl-azo-P-naphthol separate out. Allow the reaction mixture to stand for 30-40 minutes with stirring in between so as to complete the reaction. Filter the red product in a Buchner funnel using suction, and wash the same with ice-cold water. Drain the water by pressing with an inverted glass-stopper. 

Recrystallization. The crude product (9.5 g) may be recrystallized bum approximately 100-110 ml glacial acetic acid, and biter the deep red crystals with suction, wash with a little ethanol (or methylated spirit) to get rid of any residual glacial acetic acid. Finally dry the pure crystallized product upon biter paper. The 3rield of pure phenyl-azo-P-naphthol mp 130.5-13 rC is 9.1g. 

CAS 85-86-9 EINECS/ELINCS 201-638-4 Synonyms Benzeneazobenzeneazo-p-naphthol Cl 26100 Oil red Oil scarlet 1-[[4-(Phenylazo) phenyl] azo]-2-naphthalenol 1-((p-Phenylazo) phenyl) azo-2-naphthol ... 

Naphthol-3,6-disulfonic acid-8-azo-4 -[N-phenyl-1 -naphthylamine]-8 -sulfonic acid trisodium salt. See Acid blue 92 2-Naphthol ethyl ether P-Naphthol ethyl ether. See P-Naphthyl ethyl ether Naphthol green Naphthol green B. See Acid green 1... 

Phenylazo)-2-naphthalenamine. See 1-(Phenyl azo)-2-naphthylam i ne 1 -(Phenylazo)-2-naphthalenol 1-Phenylazo-2-naphthol 1-Phenylazo-p-naphthol. See Solvent yellow 14... 

The simplest azo-dye—devoid of technical importance, however— is forded from phenyl diazotate and phenol the diazo-group takes up the p-position—in the case of j8-naphthol the adjacent a- or o-position. 

Attempts to produce dyes other than azamethines and indoanilines as images have been reported. The compound (45) with a naphtholic coupler gives a blue azo dye (46) (57GEP963297, 57GEP1000689) and the magenta azine dye (48) is formed from the p-phenyl-enediamine (47) and phenol. The formation of this dye requires six equivalents of silver halide (53MI11400>. 

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