Transformation of Azoxy Compounds to Azophenols

Reaction LXXIV. (b) Transformation of Azoxy Compounds to Azophenols. Azoxy compounds (see Reaction CLXX.) are converted by cone, sulphuric acid into p-hydroxyazo compounds (B., 13, 525). 

Most azoxy compounds under the influence of ultra-violet light are converted into o-hydroxyazo compounds. (J. C. S., 127, 2374.) 

The unsym. azoxy compound has been isolated by the action of light on ococ -azoxynaphthalene (J. C. S., 123, 2466). When the latter is heated with benzaldehyde the unsym. azoxy compound is also formed, whilst if a base such as quinoline is present, the further transformation to the o-hydroxyazo compound takes place. 

Reaction LXXV. Fusion of Aromatic Sulphonic Acids with Caustic Alkalis. (Z. Ch (1876), 3, 299 J. pr., [2], 17, 394 20, 300.)—This method is of technical importance as it is employed to prepare phenols and naphthols from the parent hydrocarbons. These phenols and naphthols are much used as intermediates in the dye industry. The method cannot easily be applied to determine structure, owing to rearrangement liable to occur at the elevated temperatures. Caustic potash is more convenient than soda, since it generally yields a more easily fusible mixture. 

For dealkylation of cresols to phenol under pressure, see E.P., 427145. Preparation 141.—j8-Naphthol (2-HydroxynapMhalene). 

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