GB1587965A

GB1587965A - Manufacture of dichloronitroanilines

Info

Publication number: GB1587965A
Application number: GB4389377A
Authority: GB
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1976-10-23
Filing date: 1977-10-21
Publication date: 1981-04-15
Also published as: CH628019A5; IT1084544B; DE2648054A1; DE2648054C3; FR2368465A1; DE2648054B2

Abstract

2,6-Dichloro-4-nitroaniline and 2,4-dichloro-6-nitroaniline are prepared by reacting 2- or 4-nitroaniline with hypochlorites in the presence of a strong acid. An alkali metal hypochlorite or alkaline earth metal hypochlorite is used in an amount of from 1 to 1.2 equivalents per mole of nitroaniline. A temperature of above 25 DEG C is used. The concentration of the strong acid is from 5 to 400% by weight of anhydrous acid, based on the weight of added water. This process gives dichloronitroaniline on an industrial scale in good yield and purity.

Description

(54) MANUFACTURE OF DICHLORONITROANILINES (71) We, BASF AKTIENGESELLSCHAFT, a German Joint Stock Company of 6700 Ludwigshafen, Federal Republic of Germany, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a new process for the manufacture of 2,6-dichloro4-nitroaniline and 2,4-dichloro-6-nitroaniline by reacting 2- and 4-nitroaniline, respectively, with a chlorine compound.

Houben-Weyl, Methoden der Organischen Chemie, volume 5/3, pages 705-713, discloses that direct chlorination of aromatic amines which possess a free amino group gives the corresponding chloro-derivatives in poor yield only, since the free amino group reacts with chlorine to give chlorine-nitrogen compounds which, because of their instability, are decomposed during the chlorination, giving tarry products. J. Chem. Soc., 93 (1908), 1,773 discloses that the reaction of 4-nitroaniline with chlorine at low or elevated temperatures, in the presence of hydrochloric acid and in very dilute aqueous solution, e.g. with 0.8 per cent strength by weight aqueous acid always gives contaminated 2,6-dichloro-4-nitroaniline, and the latter can only be obtained in the pure form by recrystallizing the crude product. The reaction was carried out with only from 2 to 10 grams of starting material. If the conditions of this process are employed on an industrial scale, for example with not less than 500 kg of starting material per batch, substantial proportions of resinous, discolored residues and decomposition products are obtained even at low temperatures and to a far greater extent still at higher temperatures. Similar observations, even on a laboratory scale, can be deduced from the remark on page 1,773 (J. Chem. Soc., loc. cit.) that under all circumstances low temperatures should be used and the end product should be recrystallized.

Further, Houben-Weyl, loc. cit., page 706, discloses that the undesirable formation of chlorine-nitrogen compounds can be prevented if the free amino group of the aromatic amine which is to be chlorinated is protected by substitution, e.g. by acetylation, in a reaction step prior to the chlorination reaction; the acyl group must then be split off again in a third reaction step after the chlorination has been carried out. At times (page 170) it is more advantageous to convert these free aromatic amines, before chlorination, into the corresponding sulfonic acids by sulfonation; the sulfonic acids are then chlorinated at a low temperature, and finally the sulfonic acid group is split off again by raising the temperature. In this way, 2,6-dichloro-4-nitroaniline is obtained, via 4-nitroanilinesulfonic acid, in 87 per cent yield. Houben-Weyl expressly states that the reaction of 2-nitroaniline or 4-nitroaniline with sulfonic acid, sodium chloride and sodium hypochlorite solution at room temperature gives a good yield of the corresponding monochloronitroaniline which has the chlorine atom in the 4-position or 2-position relative to the amino group.

Direct chlorination of 4-nitroaniline with 47 per cent strength by weight hydrochloric acid and 30 per cent strength by weight H202 gives a 74 per cent yield of 2,6dichloro-4-nitroaniline (Houben-Weyl, loc. cit., page 710).

All these processes are unsatisfactory from the point of view of yield and purity of the end product, and simplicity and economy of operation, particularly on an industrial scale.

We have found that a dichloronitroaniline of the formula

where R' is chlorine, one of the two radicals R2 and R is chlorine and the other of the two radicals R2 and RX is nitro, can be obtained in an advantageous manner by reacting a nitroaniline with a chlorine compound, if a nitroaniline of the formula

where one of the two radicals Rf and R5 is nitro and the other is hydrogen, is reacted with an alkali metal hypochlorite or an alkaline earth metal hypochlorite, using from I to 1.2 equivalents of hypochlorite per mole of starting material II, at above 25"C, in the presence of added water and a strong acid used at a concentration of from 5 to 400 per cent by weight, based on the amount by weight of added water.

Where sodium hypochlorite, 4-nitroaniline and sulfuric acid are used, the reaction can be represented by the following equation:

Compared to the prior art, the process of the invention is able to give 2,6-dichloro4-nitroaniline and 2,4-dichloro-6-nitroaniline more simply and more economically and in better yield and higher purity, particularly on an industrial scale. Special purification operations, or conversion of the starting material to its acyl derivative or sulfonic acid derivative, are unnecessary. No significant formation of resinous or tarry by-products or decomposition products is observed. All these advantageous results are particularly surprising in view of the prior teaching that the reaction should be carried out in the cold. It was also unexpected, in view of the prior art, that under the conditions of the invention the dichloro compound would be obtained without significant formation of the monochloro compound and furthermore the end product would be obtained in better yield and higher purity.

Suitable starting materials II are 2-nitroaniline, 4-nitroaniline and mixtures of these. The other starting materials are hypochlorites, as a rule in the form of appropriate aqueous, alkaline solutions. From 1 to 1.2, preferably from 1.05 to 1.1, equivalents of hypochlorite are used in the reaction per mole of starting material II. The equivalent amount is taken to be that corresponding to the above equation; for example, 2 moles of sodium hypochlorite or 1 mole of calcium hypochlorite are equivalnet to 1 mole of nitroaniline. It is advantageous to use calcium hypochlorite, magnesium hypochlorite, barium hypochlorite, lithium hypochlorite or preferably potassium hypochlorite or especially sodium hypochlorite. The aqueous hypochlorite solution used, advantageously an alkali metal hypochlorite solution, in general contains from 5 to 15, preferably from 12 to 14, per cent by weight of hypochlorite and may additionally contain from 0.2 to 2.5 moles of alkali metal hydroxide per mole of hypochlorite.

Water is added to the starting mixture; this is referred to, in the present text, as added water. In addition, more water forms during the reaction. Advantageously, from 500 to 5,000, preferably from 1,000 to 4,000 per cent by weight of water, based on the amount by weight of starting material II, are added to the starting mixture; the water is added partially or, advantageously, entirely in the form of appropriate aqueous acid solutions and/or hypochlorite solutions.

The reaction is carried out at above 25"C, usually at from 27"C to 60"C, advantageously from 30"C to 55"C, more especially from 35 to 50 C, preferably from 40"C to 45 C, under atmospheric or superatmospheric pressure, continuously or batchwise.

Usually, the components of the starting mixture, e.g. water or acid or, in most cases, the entire starting mixture, serve as the solvent medium for the reaction.

For the purposes of the invention, strong acids are organic or inorganic acids which are inert under the reaction conditions and have an acid exponent (pKa) of from - 7 to +2.16; the definition of the acid exponent or pKa may be found in Ullmanns Encyklo pädie der technischer Chemie, volume 15, page 2. Examples of suitable acids are concentrated sulfuric acid, advantageously aqueous sulfuric acid of from 90 to 98 per cent strength by weight, phosphoric acid, advantageously aqueous phosphoric acid of from 85 to 90 per cent strength by weight, hydrochloric acid, advantageously aqueous hydrochloric acid of from 30 to 38 per cent strength by weight, nitric acid, advantageously aqueous nitric acid of from 60 to 65 per cent strength by weight, perchloric acid, advan tageously aqueous perchloric acid of from 65 to 70 per cent strength by weight, or formic acid, advantageously aqueous formic acid of from 85 to 99 per cent strength by weight.

Hydrogen chloride gas, boric acid, trichloroacetic acid, trifluoroacetic acid and acidic ion exchangers in the form of polyfluoroethylenesulfonic acids may also be used. Preferred acids are hydrochloric acid and sulfuric acid, especially of the above concentrations. The acid is advantageously used in amounts of from 1.0 to 20, preferably from 5 to 15, parts by weight of acid per part by weight of starting material II. Concentrations of from 5 to 400, preferably from 10 to 100, per cent by weight of acid, based on the amount by weight of added water, are suitable. In specifying these concentrations and amounts, the acid is taken to be 100 per cent anhydrous acid, regardless of its actual constitution or. of the amount of water mixed with the acid when the latter is added.

If excess alkali is added with the hypochlorite solution, which is frequently done in order to stabilize such solutions, the above advantageous amounts of acid are in general in creased by appropriate amounts equivalent to the excess alkali.

The reaction may be carried out as follows: a mixture of the starting material II, hypochlorite, acid and water is kept at the reaction temperature for from 0.5 to 15 hours. Advantageously, the hypochlorite, e.g. the aqueous sodium hypochlorite solution, is allowed to run into the mixture of the reactants, at any desired rate within a wide range. The end of the reaction in most cases coincides with the end of the addition of the hypochlorite. The end product is isolated from the reaction mixture in the con ventional manner, e.g. by filtration.

The compounds which may be manufactured by the process of the invention are valuable starting materials for the manufacture of drugs, dyes and pesticides. For ex ample, the manufacture of dyes which contain 2,6-dichloro-4-nitroaniline as the diazo component is described in German Patents 916 968, 888 290, 1 011 545, 894422 and 924 763 and in Swiss Patent 365,809. Alternatively, the end product I can be converted to 3,5-dichloronitrobenzene, for example in accordance with the method described in our copending British Patent Application No. 51644/76 (Serial No. 1 563 846) using an alcohols and a nitrosating agent at an elevated temperature not less than 35"C in the presence of acid and water. 3,5-dichloronitrobenzene is a valuable starting material for the manufacture of drugs, dyes and pesticides. With regard to uses, reference may be made to the above publication and to Ullmanns Encyklopädie der technischen Chemie, volume 12, pages 798-800.

In the Examples, parts are by weight.

EXAMPLE 1.

138 parts of 4-nitroaniline are introduced into 2,400 parts of 38 per cent strength by weight aqueous hydrochloric acid and the mixture is heated to 40"C. 1,250 parts of technical sodium hypochlorite solution (containing 162 parts of sodium hypochlorite and 87 parts of sodium hydroxide) are added in the course of one hour at 44"C. The mixture is cooled and filtered. 213 parts (97% of theory) of 2,6-dichloro-4-nitroaniline of melting point 180-1820C are obtained.

EXAMPLE 2.

If the reaction described in Example 1 is carried out with 800 parts of 80 per cent strength by weight aqueous sulfuric acid instead of hydrochloric acid, 195 parts (94 jO of theory) of 2,6-dichloro-4-nitroaniline of melting point 175--180"C are obtained.

EXAMPLE 3.

138 parts of 2-nitroaniline are introduced into 1,000 parts of 30 per cent strength by weight aqueous hydrochloric acid and the mixture is then heated at 35"C. 5,000 parts of technical sodium hypochlorite solution (containing 157 parts of sodium hypochlorite and 87 parts of sodium hydroxide) are added at 41"C. The mixture is cooled and the product is filtered off. 195 parts (94 ", of theory) of 2,4-dichloro-6-nitroaniline of melting point 93--95"C are obtained.

EXAMPLE 4.

138 parts of 4-nitroaniline are introduced into 500 parts of formic acid and the mixture is then heated to 40"C. 1,400 parts of technical sodium hypochlorite solution (containing 164 parts of sodium hypochlorite and 89 parts of sodium hydroxide) are added in the course of two hours at 40 C. The mixture is cooled and the product is filtered off. 187 parts (90% of theory) of 2,6-dichloro-4-nitroaniline of melting point 174--178"C are obtained.

EXAMPLE 5.

If the reaction described in Example 4 is carried out with 700 parts of 50 per cent strength by weight aqueous nitric acid, 186 parts (90% of theory) of 2,6-dichloro-4nitroaniline of melting point 177--179"C are obtained.

WHAT WE CLAIM IS:- 1. A process for the manufacture of a dichloronitroaniline of the formula

where R' is chlorine, one of the two radicals R2 and RJ is chlorine and the other of the two radicals R2 and R is nitro; which comprises reacting a nitroaniline of the formula

where one of the two radicals R and R" is nitro and the other is hydrogen, with an alkali metal hypochlorite or an alkaline earth metal hypochlorite, using from 1 to 1.2 equivalents of hypochlorite per mole of starting material II, at above 25 C, in the presence of added water and a strong acid used at a concentration of from 5 to 400 per cent by weight, based on the amount by weight of added water.

2. A process as claimed in claim 1, in which the reaction is carried out with from 1.05 to 1.1 equivalents of hypochlorite per mole of starting material II.

3. A process as claimed in claim 1 or 2, in which the reaction is carried out at from 27 to 60"C.

4. A process as claimed in claim 1 or 2, in which the reaction is carried out at from 30 to 55"C.

5. A process as claimed in claim 1 or 2, in which the reaction is carried out at from 35 to 50"C.

6. A process as claimed in any of claims 1 to 5, in which the reaction is carried out with an acid concentration of from 10 to 100 per cent by weight, based on the amount of water added.

7. A process as claimed in any of claims 1 to 6, in which the reaction is carried out with the addition of from 500 to 5,000 per cent by weight of water, based on the amount by weight of starting material II, to the starting mixture.

8. A process as claimed in any of claims 1 to 7, in which the reaction is carried out with aqueous sulfuric acid of from 90 to 98 per cent strength by weight, aqueous phosphoric acid of from 85 to 90 per cent strength by weight, aqueous hydrochloric acid of from 30 to 38 per cent strength by weight, aqueous nitric acid of from 60 to 65 per cent strength by weight, aqueous perchloric acid of from 65 to 70 per cent strength by weight and/or aqueous formic acid of from 85 to 99 per cent strength by weight.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

parts of technical sodium hypochlorite solution (containing 157 parts of sodium hypochlorite and 87 parts of sodium hydroxide) are added at 41"C. The mixture is cooled and the product is filtered off. 195 parts (94 ", of theory) of 2,4-dichloro-6-nitroaniline of melting point 93--95"C are obtained.

EXAMPLE 4.

138 parts of 4-nitroaniline are introduced into 500 parts of formic acid and the mixture is then heated to 40"C. 1,400 parts of technical sodium hypochlorite solution (containing 164 parts of sodium hypochlorite and 89 parts of sodium hydroxide) are added in the course of two hours at 40 C. The mixture is cooled and the product is filtered off. 187 parts (90% of theory) of 2,6-dichloro-4-nitroaniline of melting point 174--178"C are obtained.

EXAMPLE 5.

If the reaction described in Example 4 is carried out with 700 parts of 50 per cent strength by weight aqueous nitric acid, 186 parts (90% of theory) of 2,6-dichloro-4nitroaniline of melting point 177--179"C are obtained.

WHAT WE CLAIM IS:- 1. A process for the manufacture of a dichloronitroaniline of the formula

where R' is chlorine, one of the two radicals R2 and RJ is chlorine and the other of the two radicals R2 and R is nitro; which comprises reacting a nitroaniline of the formula

where one of the two radicals R and R" is nitro and the other is hydrogen, with an alkali metal hypochlorite or an alkaline earth metal hypochlorite, using from 1 to 1.2 equivalents of hypochlorite per mole of starting material II, at above 25 C, in the presence of added water and a strong acid used at a concentration of from 5 to 400 per cent by weight, based on the amount by weight of added water.
2. A process as claimed in claim 1, in which the reaction is carried out with from 1.05 to 1.1 equivalents of hypochlorite per mole of starting material II.
3. A process as claimed in claim 1 or 2, in which the reaction is carried out at from 27 to 60"C.
4. A process as claimed in claim 1 or 2, in which the reaction is carried out at from 30 to 55"C.
5. A process as claimed in claim 1 or 2, in which the reaction is carried out at from 35 to 50"C.
6. A process as claimed in any of claims 1 to 5, in which the reaction is carried out with an acid concentration of from 10 to 100 per cent by weight, based on the amount of water added.
7. A process as claimed in any of claims 1 to 6, in which the reaction is carried out with the addition of from 500 to 5,000 per cent by weight of water, based on the amount by weight of starting material II, to the starting mixture.
8. A process as claimed in any of claims 1 to 7, in which the reaction is carried out with aqueous sulfuric acid of from 90 to 98 per cent strength by weight, aqueous phosphoric acid of from 85 to 90 per cent strength by weight, aqueous hydrochloric acid of from 30 to 38 per cent strength by weight, aqueous nitric acid of from 60 to 65 per cent strength by weight, aqueous perchloric acid of from 65 to 70 per cent strength by weight and/or aqueous formic acid of from 85 to 99 per cent strength by weight.
9. A process for the manufacture of a dichloronitroaniline carried out substantially

as described in any of the foregoing Examples.
10. Dichloronitroanilines when manufactured by a process as claimed in any one of claims 1 to 9.
11. Drugs, dyes and pesticides when made from a dichloroaniline as claimed in claim 10.
12. 3,5-dichloronitrobenzene when obtained from a dichloroaniline as claimed in claim 10 by means of an alcohol and a nitros of not a tin agent at an elevated temperature less than 35 0C in the presence of an acid and water.