Hydroxynaphthalenes

The reversibility of the Bucherer reaction is utilised in the preparation of 2-p-tolylamino-5-hydroxynaphthalene-T-3ulphonic acid (II) from 2-amino-... 

Naphthalenol. 1-Naphthol, a-naphthol, or l-hydroxynaphthalene/P(9-/j5 -iJ forms colorless needles, mp 96°C, bp 288°C, which tend to become colored on exposure to air or light. It is almost insoluble in water, but readily soluble in alcohol, ether, and benzene. 1-Naphthol and 2-naphthol are found in coal tar (56). 

Naphthalenol. 2-Naphthol or p-naphthol or 2-hydroxynaphthalene/7i3 -/5 -i7 melts at 122°C and boils at 295°C, and forms colorless crystals of characteristic, phenoHc odor which darken on exposure to air or light. 2-Naphthol [135-19-3] is manufactured by fusion of sodium 2-naphthalenesulfonate with sodium hydroxide at ca 325°C, acidification of the drowned fusion mass which is quenched ia water, isolation and water-washing of the 2-naphthalenol, and vacuum distillation and flaking of the product. A continuous process of this type has been patented (69). The high sulfate content ia the primary effluent from 2-naphthol production is greatiy reduced ia modem production plants by the recovery of sodium sulfate. 

Naphthalenediol. This diol is prepared by the alkah fusion of 2-hydroxynaphthalene-6-sulfonic acid (Schaffer acid) at 290—295°C. Schaffer acid is usually produced by sulfonation of 2-naphthol with the addition of sodium sulfate at 85—105°C. This acid is also used as a coupling component in the production of a2o dyes such as Acid Black 26. 2,6-Naphthalenediol is used as a component in the manufacture of aromatic polyesters which, as is also tme of the corresponding amides, display Hquid crystal characteristics (52). 

Milling Red SWB l-[4-[4-[4-toluenesulfonyloxy]phenylazo](3,3 dimethyl-l,l -biphenyl)-4 -azo]-2-hydroxynaphthalene-6,8-disulfonic acid di-Na salt, Acid Red 114 [6459-94-5] M 830.8, m dec >250", Cl 23635, X,max 514nm. Salted out three times with sodium acetate, then repeatedly extracted with EtOH. [McGrew and Schneider J Am Chem Soc 72 2547 1950.] See Solochrome Violet R on p. 352 in Chapter 4. 

Calcichrome. This indicator, cyclotris-7-( l-azo-8-hydroxynaphthalene-3,6-disulphonic acid), is very selective for calcium. It is in fact not very suitable as an indicator for EDTA titrations because the colour change is not particularly sharp, but if EDTA is replaced by CDTA (see Section 2.26), then the indicator gives good results for calcium in the presence of large amounts of barium and small amounts of strontium.13... 

Discussion. An excellent method for the colorimetric determination of minute amounts of cobalt is based upon the soluble red complex salt formed when cobalt ions react with an aqueous solution of nitroso-R-salt (sodium 1-nitroso-2-hydroxynaphthalene-3,6-disulphonate). Three moles of the reagent combine with 1 mole of cobalt. 

Benzoxepins require drastic conditions for the thermal rearrangement to naphthols. When 3-benzoxepin-2,4-dicarboxylic acid is heated to 300 C, a decarboxylation reaction takes place and 3-hydroxynaphthalene-2-carboxylic acid (10) is formed in 44% yield.91... 

Modified PAN fibres containing aldehyde groups can be used to obtain chemically stained fibres. The chemical addition of dyes can be conducted following two schemes A) The fibres of the above composition are treated with aromatic amines, e.g., l-amino-8-hydroxynaphthalene-3,6-disulfonic acid ( H-acid ), and then azocoupling is carried out with a diazonium salt ... 

Trimethyl-5-quinoxalinamine (152) gave 5-(2-hydroxynaphthalen-l-ylazo)-2,3,6-trimethylquinoxaline (153) substrate, 50% H3PO4 NaN02/ H20, 3°C, 1 h then p-naphthaol/2.5M NaOH dropwise, 3°C 94%). ... 

This comprises a heterogeneons gronp of enzymes that is used for the degradation of snbstrates including gentisate, salicylate, and l-hydroxynaphthalene-2-carboxylate by pathways that do not involve catechols ... 

Under certain conditions, dry mixtures of lead chromate pigments with the azo-dyes l-(2. 4 -dimtrobenzcncazo)-2-hydroxynaphthalene (dinitroaniline orange) or l-(4 -chloro-2 -nitrobenzcncazo)-2-hydroxynaphthalene (chlorinated para-red) may lead to violent explosions dining mixing/blending operations. 

Complete degradation after 2-(6-Hydroxynaphthalen-2-yl) [12] 6 h and 5 h, propanoic acid ... 

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