Hoechst Aktiengesellschaft

Kurt C Habig

Klaus Warning

Konrad Baessler

Klaus Hunger

Heinrich Frolich

Lothar Schulz

Heinz Schutte

Process for the continuous preparation of 3,3'-dichloro-benzidine

Process for the preparation of 4-chloro-2,5-dimethoxyaniline by catalytic reduction of 4-chloro-2,5-dimethoxynitrobenzene with hydrogen in the liquid phase at an elevated temperature and elevated pressure, which comprises carrying out the reduction at temperatures from about 80.degree. to about 110.degree. C. and under a pressure of about 5 to 50 atmospheres gauge in an aromatic solvent in the presence of a modified platinum-on-carbon catalyst in the presence of about 0.01 to about 0.2 mole of a compound which gives a pH of 8 to 10 in aqueous solution, and in the presence of about 0.1 to about 1.0% by weight of an aliphatic, open-chain, primary, secondary or tertiary amine or a cyclic amine, in each case relative to the amount in moles and weight, respectively, of 4-chloro-2,5-dimethoxynitrobenzene employed.

Process for the preparation 4-chloro-2,5-dimethoxy-aniline

The invention relates to 4,4'-diaminodiphenyl compounds of the formula I ##STR1## in which X denotes the n-propyl, isopropyl, n-butyl, isobutyl, 1-methylpropyl, n-propoxy, isopropoxy, isobutoxy, 1-methylpropoxy or 2-methoxyethoxy radical and A is 0 or the equivalent of an inorganic acid. The preparation is effected by reducing ortho-X-substituted nitrobenzene and benzidine rearrangement of the resulting hydrazobenzene derivative. The compounds of the formula (I) are suitable for use as components in the preparation of dyes and pigments.

4,4'-diaminodiphenyl compounds, process for their preparation and their

Nitrosation agent(s), contained as by-products in nitrated aromatic compounds after nitration with nitric acid or nitration acid, are removed by a water treatment, wherein the water is distilled off at least partially in vapor form, advantageously under reduced pressure. In the further reaction of the nitrocompounds treated in this manner undesired nitrosamines are practically not formed. The process is especially suitable for the manufacture of 4-di-n-propylamino-3,5-dinitrobenzotrifluoride (Trifluralin), a valuable herbicide, substantially free from nitrosamine(s).

Method for removing nitrosation agent(s) from a nitrated aromatic

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Morfelden-Walldorf, Germany

Kurt C Habig