Dynamit Nobel Aktiengesellschaft

Dynamit Noble Aktiengesellschaft

Hans-Joachim Herrmann

Klaus-Dieter Steffen

Gunther Meyer

In a process for the hydrogenation of nitrobenzene with hydrogen to hydrazobenzene at temperatures ranging from 40.degree. to 110.degree. C. in the presence of a precious metal catalyst, an aqueous alkaline solution and an organic solvent, the reaction mixture being maintained in turbulent motion, the improvement wherein said nitrobenzene is o-, m- or p-chloronitrobenzene, the reaction is carried out in an organic solvent in which the dichlorohydrazobenzene being formed is readily soluble when warm and difficultly soluble when cold, and that the precious metal catalyst is used in such amount that the weight ratio of chloronitrobenzene used to precious metal catalyst is in the range 1:0.00005-less than 0.0002.

Process for preparation of hydrazobenzenes by catalytic hydrogenation of

An aromatic polyazomethine of the structural formula ##STR1## wherein R represents hydrogen, halogen, alkyl or alkoxy,

Polymeric azomethines

An aromatic bisazomethine prepared from the disubstituted benzidines and aromatic aldehydes, characterized by the general formula ##STR1## wherein each R=COOCH.sub.3, COOC.sub.2 H.sub.5, COOH, CH.sub.2 Cl, CHCl.sub.2, CH.sub.2 Br, CCl.sub.3, Cl or Br and

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Troisdorf, Germany

Hans-Joachim Herrmann