Hydroxynaphthalenecarboxylic acids

Hamai S. and Sakurai H., Capilary electrophoretic separation of positional isomers of hydroxynaphthalenecarboxylic acids through the formation of inclusion complexes with P-cyclodextrin, Anal. Chim. Acta, 402, 53, 1999. 

On the other hand, since the angular derivative 19, whose constitution is characterized by two quasi-isolated hydroxynaphthalenecarboxylic acid subunits and whose structural analogy to a pair of scissors is removed for the most part, also yields an inclusion compound with dimethylformamide with strict stoichiometry of 1 237), and only and exclusively this one (Table 3), it is obvious that the free salicylic acid unit might be the decisive factor for the preferred binding of dimethylformamide of this class of compounds. 

From a practical point of view, the deviation from main-chain continuity is the most interesting one. Especially the concept of the so-called parallel offset of the main chain is favorized. It is realized in a commercial product made from 4-hydroxybenzoic acid and 2,6-hydroxynaphthalenecarboxylic acid. The incorporation of small amounts of 2,6-hydroxynaphthalenecarboxylic acid causes a discontinuity in the main chain but only in form of a parallel offset of some chain segments. Thus, the ability to form liquid crystalline states is largely maintained as well as the anisotropic properties of the molten and solid polyester. Instead, the melting point is significantly reduced, as desired. 

Some properties of selected hydroxynaphthalenecarboxylic acids are presented in Table 9. These acids are used in the manufacture of dyes (most importantly, naphthol AS dye stuffs), color film, and polyester. 

All phenolic acids and hydroxynaphthalenecarboxylic acids identified were found as OCD3-derivatives. The mass spectra showed the complete... 

The reduction by Na(Hg) of several o-hydroxynaphthalenecarboxylic acids in slightly acid solution containing boric acid has been investigated. 1-Hydroxynaphthalene-2-carboxylic acid [109] is, like salicyclic acid, reduced to the aldehyde (62% yield), isolated as the Schiff base, whereas 2-hydroxynaphthalene-3-carboxylic acid [110] under similar conditions yields mainly 2-hydroxy-1,2,3,4-tetrahydronaphtha-lene-3-carboxylic acid (75-80%) and 5% of the aldehyde. When hydrochloric acid rather than CO2 was used to neutralize the base formed during the reduction, the 2-oxo-l,2,3,4-tetrahydronaphthalene-3-carboxylic acid [111] was isolated (60%). On heating, the compound, a y6-keto acid, decarboxylated. 

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