DE2212848C3 - Process for the production of dinitrophenols by direct nitration - Google Patents

Description

OH

in which Ri is an alkyl radical with at least 2 carbon atoms or a cycloalkyl radical, an aralkyl radical or an optionally substituted aryl radical and R _{2 is} a hydrogen atom or an alkyl radical, a direct nitration with dilute nitric acid alone with a concentration below 70% by weight at a temperature between 10 ° C and the boiling point of the reaction medium, using an excess of nitric acid, so that the final content of residual acid is at least 4%. However, the dinitrated product thus obtained is not pure and a dinitrophenol is obtained, the content of which is in fact hardly more than 90%.

The aim of the invention is therefore a process for the preparation of 2,4-dinitrophenols with better Yield and preferably greater purity than any of the foregoing processes, wherein in particular, greater simplicity of implementation is also sought.

The invention relates to a method of manufacture

bo of dinitrophenols of the general formula:

Q ₂ N

OH

Y NO ₂

in which R is a hydrogen atom, a linear or branched alkyl radical having 1 to 8 carbon atoms or a cycloalkyl, phenyl or benzyl radical optionally substituted by an alkyl radical having 1 to 4 carbon atoms or a halogen atom,
by direct nitration of the corresponding phenols at temperatures above 30 ° C in an aqueous medium, which is characterized in that an aqueous solution of an alkali metal phenolate of the general formula:

OM

IO

15th

in which R has the meaning given and M is an alkali metal atom,

and aqueous 50 to 70% nitric acid gradually and introducing simultaneously at temperatures between 40 and 8O ⁰ C with stirring in initially introduced aqueous solution of nitric acid, so that a reaction mixture is formed with a nitric acid content of 10 to 50 wt ° / o.

It has been found that the nitration of phenol with nitric acid alone by the conversion of the Phenol in alkali phenolate, especially sodium phenolate, is facilitated, and that you get a better one Yield and nitrated derivatives of greater purity are obtained than by the methods previously used.

According to the invention, therefore, particularly satisfactory results are obtained by one through Relatively little concentrated nitric acid predetermines the "sediment" formed and precedes it a temperature within the above range gradually heated sediment and at the same time a relatively concentrated aqueous nitric acid solution and a concentrated solution of Introduces alkali phenolate.

According to a preferred embodiment, the temperature of the reaction mixture is kept precisely between 50 and 70 ^° C. during the entire duration of the reaction.

According to a preferred embodiment, a concentrated alkali phenolate solution and an aqueous 50 to 70% nitric acid are gradually introduced into a sediment formed by approximately 30% nitric acid and heated to a temperature within the specified range, and the temperature is then maintained completion of the reaction, at least one hour between about 40 to 8O ⁰ C, subsequently cooled and filtered from the precipitate formed and washed with water until the pH of the washing water 4-5 lying and sucking then off and dried.

According to a preferred embodiment, a concentrated aqueous alkali metal phenolate solution is first prepared, for example, by adding an equimolar amount of phenol to sodium hydroxide solution with 15 to 40% NaOH and then gradually leaving this solution with stirring and at the same time with an appropriate volume of 50 to 70% iger aqueous nitric acid solution flow into the sediment previously heated to a temperature between 40 and 70 ⁰ C ₁ , which is formed by an aqueous nitric acid solution of lower concentration in the region of 30%. Then keeping the Reaklionsmischung during the total duration of the reaction in the aforementioned temperature range (40 to 70 ⁰ C), cooled and filtered to separate the crystals so dinitrophenol which is washed with water and then filtered off with suction or centrifuged and dried.

In the following, the preparation of some dinitrophenols according to the invention is illustrated in examples Procedure described.

example 1
Dinitrophenol

A sodium phenolate solution is made by adding 94 g (1 mol) phenol to 133 g 30% sodium hydroxide solution (corresponding to 40 g or 1 mol sodium hydroxide) manufactured.

250 g of 30% strength aqueous nitric acid solution are placed in a 2.5 liter round-bottomed flask equipped with a stirrer and thermometer, which is heated to 40 ° C. and then gradually mixed with the sodium phenolate solution prepared as described above within one hour and with stirring 600 g of 63% strength aqueous nitric acid are added. After completion of the addition of the reagents, the reaction mixture is heated 30 minutes 50 ⁰ C and for 30 minutes at 6O ⁰ C.

It is then cooled to 20 ° C., filtered and the dinitrophenol formed is washed on the filter with water until the pH of the wash or waste water is between 4 and 5. The dinitrophenol is filtered off with suction or centrifuged and then dried at 50 ° C. to constant weight. 135 g of yellow-beige dinitrophenol are thus obtained with a yield of 73.5% (based on the phenol used). The melting point of this product is 104 ^° C. A potentiometric determination of the content shows a content of 99% dinitrophenol.

According to the titanium chloride method by Knecht and Hubert (described by S. Siggia in »Quantitative Organic Analysis via Functional Group, "3rd Edition, John Wiley & Sons, N.Y., page 526) The nitrogen content of the product is 15.0% (calculated: 15.2%).

The dinitrophenol thus obtained is a mixture of the 2,4- and 2,6-isomers.

Example 2
4,6-dinitro-2-tert-butylphenol

First, an aqueous phenolate solution is prepared by adding 133 g of sodium hydroxide solution with 30% NaOH (1 Mol) gradually in 150 g (1 mol) of o-tert-butylphenol are given.

In addition, in a 2.5 1 round bottom flask with Stirrer and thermometer as a sediment 250 g of 30% aqueous nitric acid solution heated to 70.degree. Under Maintaining this temperature and stirring are then gradually and simultaneously within the sodium o-tert-butylphenolate solution for 1 hour and 600 g of an aqueous solution containing 63% by weight of nitric acid was introduced. After introducing the reagents stirring is continued, the temperature being kept at 70.degree. It is then cooled to ambient temperature off, filtered and washed the product obtained on the filter with water until the pH of the Wash water is between 4 and 5. It is then filtered off with suction and dried at 50.degree. 205 g are obtained in this way

Dinitro compound with a yield of 85% (based on the tert-butylphenol used).

The melting point of the product is 124 ° C (Literature value: 127 ° C). The content of dinitro-tertiary phenol determined by chromatography is 5 95%. The nitrogen content determined by Knecht and Hubert's titanium chloride method is 11.2% (theoretical: 11.66%).

10

Example 3
4,6-dinitro-2-sec-butylphenol

The procedure is the same as in Example 2, but using an aqueous solution of sodium 0-sec.butylphenolat instead of the aqueous Sodium o-tert-butylphenolate solution. After nitriding and cooling, a red oil separates, which is washed by stirring or shaking with water until the pH of the wash water is between 4 and 5. After drying, 210 g are obtained Product with a yield of 87.5% (based on the o-sec-butylphenol used).

The nitrogen content determined by Knecht and Hubert using the Titanchiorid method is 10.9% (calculated: 11.66%).

The content determined by potentiometric determination is 97%.

With this working method, the actual consumption of concentrated nitric acid is (calculated than 100% nitric acid) only 378 g per mole of o-sec-butylphenol. If, on the other hand, you have that in the FR-PS 12 94 254 uses the method described, the necessary amount of nitric acid per mole Phenol 450 g. The method according to the invention therefore allows a substantial saving in nitric acid

Eg game 4

4,6-dinitro-2-methylphenol

It is first an aqueous sodium o-cresolate solution prepared by adding 135 g of 30% strength sodium hydroxide solution (1 mol) to 108 g (1 mol) of o-cresol.

250 g of 10% strength nitric acid are then placed in a 1.5 liter round bottom flask equipped with a stirrer and thermometer Bred sediment and heated to 50 ° C. While maintaining this temperature and stirring then over the course of 1 hour the above sodium o-cresolate solution and at the same time 525 g 50% nitric acid added. Then 15 Stirring is continued for minutes at 50 ° C., and 250 g of 63% strength nitric acid are then added over the course of 30 minutes added. When this addition is complete, the mixture is stirred for a further 1.5 hours at 50.degree. C., then cooled and the precipitate obtained is filtered off and washed with water until the pH of the washing water is between 4 and 5. After filtering off with suction and drying at 50 ° C., 145 g of dinitro compound are obtained with a yield of 73% (based on the o-cresol used). The melting point of this product is 84 ° C, that of the chemically pure product at 85 ° C. The potentiometric determination of the content gives a Content of 97% 4,6-dinitro-2-methylphenol. The nitrogen content determined using the titanium chloride method is 13.90% (calculated: 14.14%).

Example 5
4,6-dinitro-2-cyclohexylphenol

First, an aqueous phenolate solution is made by adding 176 g (1 mol) of o-cyclohexylphenol to 135 g 30% sodium hydroxide solution (1 mol) produced, a thick slurry being obtained.

In addition, in a 2.51 round bottom flask with Stirrer and thermometer placed 250 g of 30% strength aqueous nitric acid solution as a sediment.

The contents of the flask are heated to 70 ° C and then are stirred and maintained the temperature simultaneously for 1 hour 600 g of 63% nitric acid and that prepared above Cyclohexylphenolate slurry introduced. After the addition is complete, the temperature becomes an additional hour kept at 70 ° C, then cooled and filtered to separate the precipitate obtained, the is washed with water until the pH of the wash water is between 4 and 5. spun off and dries at 50 ° C and thus receives 230 g of product with a yield of 86% (based on the o-Cyclohexylphenol used). The melting point is 90 ° C (with the chemically pure product included 108 ° C). The potentiometric determination of the content shows a 93% purity.

Example 6
4,6-dinitro-2-phenylphenol

The procedure is analogous to the preceding examples, 170 g (1 mol) of o-phenylphenol in 270 g (1 mol) of 15% sodium hydroxide solution are added.

400 g of aqueous 50% strength nitric acid solution are placed in a 2.5 l round bottom flask equipped with a stirrer and thermometer given as sediment.

After the contents of the flask have been heated to 50 ° C., 750 g of 63% strength nitric acid and the phenolate solution prepared as above are added simultaneously over 1 hour, with stirring. After completion of the addition, the reaction mixture is kept 30 minutes at 60 ° C and then 30 minutes at 7O ⁰ C. It is then cooled and filtered to separate the precipitate obtained in this way, which is washed with water until the pH of the wash water is between 4 and 5. It is then filtered off with suction and dried at 50 ° C. to constant weight. This gives 240 g of crude product with a yield of 92% (based on the o-phenylphenol used) which melts at 198.degree. The potentiometric determination of the content shows that this crude product contains 98% 4,6-dinitro-2-phenylphenol. The nitrogen content determined by determination with titanium chloride is 10.3% (calculated: 10.7%).

Example 7
4,6-dinitro-2- (4'-chlorobenzyl) phenol

To prepare the phenolate, 270 g of 15% strength sodium hydroxide solution (1 mol) are added to 218.5 g (1 mol) of o- (p-chlorobenzyl) phenol poured.

In addition, 250 g of 40% strength nitric acid are placed in a 2.5 liter round bottom flask with a stirrer as the sediment Given thermometer.

After heating the flask to 60 ° C and turning on the stirrer, gradually over 1 Hour and at the same time 800 g of 63% strength nitric acid and that prepared as described above

Sodium phenolate solution added. When the addition is complete, 30 minutes at 60 ° C. and then 30 minutes Stirred at 70 ° C. for a further minutes. It is then allowed to cool to room temperature. It separates itself from it yellow product, which is filtered off and washed with water until the pH of the washing water is between 4 and 5. The product is suctioned or spun off and dried at 50 ° C up to Weight constancy. In this way, 280 g of product are obtained with a yield of 91% (based on the phenol used). The potentiometric determination of the content gives a 96% content of 4,6-dinitro-2- (4'-chlorobenzyl) phenol. The determination of the nitrogen content by the titanium chloride method gives a value of 8.90% (calculated: 9.08%).

The synthesis of intermediates, Pesticides, selective herbicides, etc.

Claims (1)

Claim: Process for the preparation of dinitrophenols of the general formula: OH OtN NO ₂ in which R is a hydrogen atom, a linear or branched alkyl radical having 1 to 8 carbon atoms or a cycloalkyl, phenyl or benzyl radical optionally substituted by an alkyl radical having 1 to 4 carbon atoms or a halogen atom, by direct nitration of the corresponding phenols at temperatures above 30 ⁰ C in an aqueous medium, characterized in that an aqueous solution of an alkali metal phenolate of the general formula: OM in which R has the meaning given and M is an alkali metal atom, and introducing aqueous 50 to 70% strength nitric acid gradually and simultaneously at temperatures between 40 and 80 ^° C. with stirring into the aqueous nitric acid solution so that a reaction mixture with a nitric acid content of 10 to 50% by weight is formed. The invention relates to a process for the preparation of dinitrophenols of the general formula: OH O ₂ N- NO ₂ in which R is a hydrogen atom, a straight or branched alkyl radical having 1 to 8 carbon atoms or a cycloalkyl, phenyl or benzyl radical optionally substituted by an alkyl radical having 1 to 4 carbon atoms or a halogen atom, by direct nitration of the corresponding phenols at temperatures above 30 ⁰ C in an aqueous medium. There are already various processes for the preparation of 2,4-dinitrophenols from the corresponding Phenols known through direct nitration with dilute nitric acid alone. With this direct nitration no organic solvents are used and no previous sulfonation (as in the US-PS 20 48 168 and 22 56 195) or nitrosation of the phenols used as starting material. For example, the direct nitration of o-cresol with relatively highly concentrated nitric acid is known (between 60 and 99% by weight). However, it must work in a tubular reactor of special design be to avoid oxidation phenomena, taking into account the relative instability and susceptibility to oxidation of the o-cresol could occur, as far as possible to avoid. If on the other hand nitric acid with at a concentration below 60% by weight is used, the yield is poor and is also observed incomplete nitration, which may be accompanied by more or less strong oxidation. Chemical Abstracts 60, 1964, 2840 fg, describes a process for the production of dinitro-o-cresol by nitrating o-cresol with HNO3 (a concentration of 44 to 47%) at 20 to 30 ° C. After a reaction time of 30 to 35 minutes, the reaction mixture is left to stand at 60 to 70 ° C. for 3 hours. However, nothing can be inferred from this description with regard to the yield and the purity of the product. From FR-PS 12 94 254 a process for the production of 4,6-dinitro-2-sec-butylphenol is also known, however, in which an unfavorably large amount of concentrated nitric acid is consumed. In FR-PS 14 52 911 of August 6, 1965 (= DE-OS 15 43 548) a method for the production of substituted dinitrophenols, according to which a substituted phenol of the general formula: