DE1112990B - Process for the preparation of diphenylamines - Google Patents

Description

GERMAN

PATENT OFFICE

F29417IVb / 12q

NOTICE DAY: SEPTEMBER 18, 1959

NOTICE THE REGISTRATION AND ISSUE OF EDITORIAL: AUG U S T 24, 1961

It is known that diphenylamines are mediated by decarboxylation of diphenylamine-2-carboxylic acids dry heating. This process as well as the fusing of the alkali salts of the However, carboxylic acids with excess alkali often lead to unsatisfactory yields and impure End products.

It has now been found that diphenylamines in a technically simple manner by heating the solutions or melts of diphenylamine-2-carboxylic acids in aniline or aniline derivatives, or mixtures of various aniline derivatives to temperatures of about 150 to 25O ⁰ C, in particular 180 to 210 ⁰ C, can produce. According to this procedure, the decarboxylation takes place at a lower temperature than in the previously known processes; the diphenylamine bases are obtained in particularly pure form with generally excellent yields.

The ratio of the diphenylamine carboxylic acids to be decarboxylated to the solvent or flux should be held in such a way that the reaction solution or Melt remains stirrable. This condition is generally met with a ratio of 0.8 to 10: 1.

A particular embodiment of the method according to the invention is that as Solvent or flux that diphenylamine derivative used, which in the decarboxylation the carboxylic acid in question is formed. This embodiment is particularly advantageous because it as Reaction product provides the melt of a uniform compound, so that the removal of the solvent not applicable.

Suitable solvents or fluxes are, for example, aniline, 2-, 3- and 4-toluidine, 2-, 3- and 4-aminoethylbenzene, 2,6-diisopropylaniline, 2-, 3- and 4-chloroaniline, 2-, 3- and 4-amino-methoxybenzene, 2-, 3- and 4-aminoethoxybenzene, N-monomethylaniline, N-monoethylaniline, Diphenylamine, 4-ethoxydiphenylamine, N-dimethylanilm, N-diethylaniline, N-methyldiphenylamine, N-ethyl-diphenylamine and mixtures thereof.

The parts mentioned in the following examples are parts by weight.

example 1

100 parts of 4'-ethoxy-diphenylamine-2-carboxylic acid are heated at 120 to 300 parts of N-dimethylaniline over 15 up to 30 "minutes at 150 to 16O ⁰ C. At about 150 ⁰ C, the CO ₂ elimination begins Man. raises the temperature initially within 1 to 2 hours at about 180 ⁰ C and more within 2 to 3 hours at about 200 ° C. the reaction procedures for the preparation of
of diphenylamines

Applicant:

Paint factories Bayer Aktiengesellschaft,
Leverkusen-Bayerwerk

Dr. Werner Müller, Cologne,

and Dr. Alfred Brack, Leverkusen,

have been named as inventors

The process can be traced from the CO ₂ development.

After about 15 hours, no more CO _{2 can} generally be detected. The dimethylaniline is then distilled off under reduced pressure and almost completely recovered. The leftover

4-Ethoxydiphenylamine crystallizes on cooling and

. is already sufficiently pure for most purposes.

By vacuum distillation (bp. _{0, 2} = 140 ° C) it is purely with excellent yield with a melting point of 75 ° to 76 ° C (uncorrected).

Instead of dimethylaniline, the others indicated above can be used in the same way Use solvents or flux in this example.

Using the solvents and temperature conditions given in the table overleaf the following carboxylic acids were decarboxylated using the procedure of this example.

Example 2

100 parts of 4'-ethoxy-diphenylamine-2-carboxylic acid are introduced into 150 to 300 parts of molten 4-ethoxydiphenylamine. One heated in the course of 2 to 3 hours at 190 to 200 ° C and lasts for 15 hours at this temperature. Crystallizes on cooling

the melt to uniform 4-ethoxydiphenylamine. The reaction product can easily be obtained completely pure by vacuum distillation.

109 679/217

R ' R " solvent Time temperature Kp. Of decarb- Γ Q R. (Hours) CQ oxylated product 142 to 145 3-ethoxy H N-dimethylaniline 20th 200 (mm) 118 to 120 H 2-ethoxy H N-dimethylaniline 15th 200 0.3 112 to 113 H 2-methoxy H N-diethylaniline 15th 200 to 210 0.3 150 H 4-chlorine H o-toluidine 24 210 0.2 190 to 195 H 4-phenyl H N-MonomethylaniKn - 20th 190 0.2 150 H 4-methoxy 2-methoxy aniline 12th 180 to 190 0.3 200 to 205 H 3-ethoxy 6-ethoxy aniline 15th 180 to 190 0.3 180 H 2-methoxy 4-chlorine N-dimethylaniline 24 200 2.0 180 H 3-methoxy 4-methoxy aniline 24 180 to 190 0.5 150 H 2-chlorine 4-chlorine N-dimethylaniline 24 200 0.5 185 to 190 H 4-chlorine H N-dimethylaniline 24 200 0.4 185 to 188 3-ethoxy 4-chlorine H N-dimethylaniline 24 200 0.5 3-methoxy 0.5

Claims (2)

PATENT CLAIMS: 1. A process for the preparation of diphenylamines by decarboxylating diphenylamine-2-carboxylic acids, characterized in that diphenylamine-2-carboxylic acids with aniline, aniline derivatives or mixtures thereof as a solvent or flux to temperatures of about 150 to 25O ⁰ C, in particular 180 to 210 ⁰ C, heated. 2. The method according to claim 1, characterized in that the solvent or flux the amine used that is used in the decarboxylation of the diphenylamine carboxylic acid in question arises. © 109 679/217 8.61