Bayer Aktiengesellschaft

Guido Skipka

Friedrich Durholz

Heinz U Blank

Rudolf Sundermann

Axel Vogel

Walter Bohm

Hans-Ulrich Alles

Manfred Niese

Gert Randau

4,4-40 -Dinitrostilbene-2,2'-disulphonic acid salts are prepared by the oxidation of 4-nitrotoluene-2-sulphonic acid or salts thereof in an aqueous alkaline medium, by adding potassium, calcium and/or magnesium ions during the reaction at the rate of which 4,4'-dinitrostilbene-2,2'-disulphonic acid is formed, the amount of added potassium, calcium and/or magnesium ions at any point during the reaction being 10 to 150 mol %, relative to the amount of 4,4'-dinitrostilbene-2,2'-disulphonic acid present in the reaction mixture at that particular time, and by removing the precipitated salt of 4,4'-dinitrostilbene-2,2'-disulphonic acid.

Process for the preparation of 4,4'-dinitrostilbene-2,2'-disulphonic

A process for the preparation of 4-amino-3-methyl-phenol from 4-nitroso-3-methyl-phenol, which comprises contacting said 4-nitroso-3-methyl-phenol with iron in an acid aqueous medium at a temperature of 20.degree. to 100.degree. C. said medium having pH in the range from 2 to 6.5.

Process for the preparation of 4-amino-3-methyl-phenol

1,5- AND 1,8-DINITRONAPHTHALENES ARE ISOLATED FROM MIXTURES OF ISOMETRIC DINITRONAPHTHALENES AT LEAST CONTAINING THE SAME. The mixture of isomers is treated successively with a more polar solvent and a less polar aromatic solvent for dinitronaphthalenes thereby dissolving the mixture of isomers except for 1,5-dinitronaphthalenes which remains largely undissolved in the more polar solvent. The residual mixture of isomers is subsequently treated, after removal of the more polar solvent, with a less polar aromatic solvent at elevated temperatures in which 1,8-dinitronaphthalenes remains as a largely insoluble residue.

Process for isolating dinitronaphthalenes

Nitroderivates of aromatic compounds which are difficult to nitrate, can readily be obtained by nitration providing that the aromatic compound is treated with nitric acid or another nitrating agent in the presence of aliphatic or cycloaliphatic hydrocarbons monosubstituted or polysubstituted by halogen, the nitro group or an alkyl sulphonyl group, and the nitro derivative formed subsequently isolated.

Process for the production of nitro derivatives of aromatic compounds

Diamino naphthalene having the formula ##STR1## wherein R.sup.1 is hydrogen or amino is prepared by treating dinitro naphthalene having the formula ##STR2## wherein R.sup.2 is hydrogen or nitro WITH HYDROGEN IN THE PRESENCE OF HYDROGENATION CATALYSTS AND ORGANIC SOLVENTS HAVING THE FORMULA ##STR3## wherein R.sup.3 is hydrogen, halogen or alkyl;

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Leverkusen, Germany

Guido Skipka