DE2110343C3 - Process for the production of an indophenol - Google Patents

Description

The invention relates to a process for the preparation of an indophenol of the general formula

OH

40

where R ₁ , R ₂ , R ₃ , R _{4 are} branched or unbranched alkyl groups and substituted or unsubstituted aryl radicals from 4-nitroso-2,6-dialkyl- or -ditrylphenol.

It has been shown that indophenol for qualitative • nd quantitative determination of aliphatic and cycloaliphatic alcohols are suitable. It is true tin process for the production of indophenol • ben known structure. After this Process is made from 2,6-dialkyl- or -diarylphenol ■ nittcls in acidic solution, for example in hydrochloric acid dissolved sodium nitrite 4-nitroso-2,6-dialkyl- or -diarylphenol. Following this, the The aforesaid nitroso compound reduced with sodium dithionite to 4-amino-2,6-dialkyl- or -diarylphenol.

In a subsequent process step, a dimerizing process then takes place at the reflux temperature Condensation and oxidation to 2,2 ', 6,6'-tetra-alkyl- or -arylindophenol. The total yield of indophenol however, this method does not exceed 45%. Other than that, this procedure is proportionate laborious.

The object of the invention is to provide a process for the preparation of an indophenol of the above structure to create that is much easier and more economical to implement and in particular a much higher yield of idophenols

This object is achieved in the method of the type indicated above in that 4-nitroso-2,6-di- • ilkvl- or -diarylphenol is treated with zinc dust in an alcohol-water solution at the boiling point, then the resulting suspension boiled under reflux for a few hours, filtered hot and then the cooled Solution until it turns red with 5N sulfuric acid acidified and then mixed with a multiple volume of water and several times with Ether is extracted and the ether layer is dried and concentrated in a manner known per se. It was found that the overall yield was 50% higher than in the previously known process. Depending on the intended use case, this can be the case with the method according to Invention resulting indophenol are recrystallized from hexane or heptane.

Working examples

1. Manufacture

of 2,2 ', 6,6'-tetra-tert-butylindophenol

There were 24 parts by weight of <-nitroso-2,6-di-tertiary-butylphenol Suspended in 100 ml of water and dissolved with the addition of 200 parts by weight of ethanol brought. Then 50 parts by weight of zinc dust were introduced in portions at the boiling point. The resulting dirty white suspension was refluxed for 3 hours after the addition had ended, filtered hot and the cooled, now greenish solution until it turned red with sulfuric acid Acidified 1: 1, then mixed with three times the volume of water and several times with ether shaken out. After drying with magnesium sulfate and concentration, about 17 parts by weight of the 2,2 ', 6,6'-tetra-tertiary-butyl-indophenol resulted is recrystallized from hexane or heptane. F. 131 to 133 ° C.

2. Manufacturing

of 2,2 ', 6,6'-tetra- «- naphthyl-indophenol

There were 30 parts by weight of 4-nitroso-2,6-di - "- naphthylphenol in 100 ml of water with the addition of 200 parts by weight of alcohol at boiling point in solution brought. 80 parts by weight of zinc dust were then introduced into the boiling solution. The one with it The resulting suspension was refluxed for 4 hours and filtered off while hot. The cooled solution concentrated sulfuric acid was added until the red color of the indophenol appeared. the The solution was then diluted to three times its volume with water and extracted several times with ether. After drying and concentrating the ethereal solution, 22 parts by weight of the 2,2 ', 6,6'-tetra-a-naphthylindophenol were obtained obtained, which is recrystallized from hexane or heptane. The melting range of the obtained indophenol compound was 160 to 190 ° determined.

3. Manufacturing

of 2,2 ', 6,6'-tetra- (i-isooctyl-indophenol

30 parts by weight of 4-nitroso-2,6-di-isooctyl-phenol were dissolved in 100 ml of water with the addition of 200 parts by weight Alcohol in solution at boiling point

brought 80 parts by weight of zinc dust were then introduced into the boiling solution. The resulting suspension was refluxed for 4 hours and filtered off while hot. Concentrated sulfuric acid was added to the cooled solution until the red color of the indophenol appeared. The solution was then diluted to three times its volume with water and extracted several times with ether. After drying and concentrating the ethereal solution, 20.5 parts by weight of 2,2 ', o.o'-Tctra-isooctyl-indophenol were obtained, which is recrystallized from hexane or heptane. ^{140 to 170 °} C. was determined as the melting range of this indophenol compound.

Claims (1)

Claim: Process for the preparation of an indophenol of the general formula where R ₁ , R ₂ , R ₃ , R _{4 are} branched or unbranched alkyl groups and substituted or unsubstituted aryl radicals, from 4-nitroso-2,6-dialkyl- or diarylphenol, characterized in that 4-nitroso-2,6-dialkyl- or diarylphenol in alcoholic-aqueous solution is treated with zinc dust at the boiling point, then the resulting suspension is refluxed for a few hours, filtered hot and then the cooled solution is acidified with 5N sulfuric acid until it turns red and then with a multiple volume Water is added and the mixture is extracted several times with ether, and the ether layer is dried and concentrated in a manner known per se.