DE2550261A1 - Benzonitrile prepn. from benzotrichlorides - reacted with ammonia which is always in excess - Google Patents

Abstract

Prepn. of benzonitriles of formula (I) (where R1 is H, CN, halogen or an opt. substd. alkyl, aryl or alkoxy gp., R2 is H or halogen and R3 is H or -NO2) comprises reacting corresp. benzotrichlorides, having formula (II), with NH3, at 150-250 degrees C, in the presence of metal salts. Mol. ratio (II) : NH3 is 1 : >=4 (1:4.1 to 1:5). NH3 is present in excess at every moment of reaction, opt. in a solvent and/or diluent. (I) are intermediates for dyes, medicinal cpds. and plant protective agents. (I) are obtd. in high yields, e.g. 96.5%, with complete avoidance of trimerisation. In an example, 4-chloro-benzonitrile was prepd. from 100 g 4-chloro-benzotrichloride reacted with 16.4 g NH3 in the presence of 0.1 g FeCl3, at 200 degrees C.

Description

Benzonitriles

The present invention relates to a method for producing Benzonitriles from benzotrichlorides.

It is known that benzonitrile can be obtained by reacting benzotrichlorides can produce with ammonium chloride at elevated temperatures (J. Amer. Chem. Soc. 52, 2951 (1930)). The addition of catalytic amounts of metal salts during manufacture of benzonitriles from benzotrichlorides with ammonium halogenides at temperatures between about 150 and 2500C is known from DOS 1668 068. Of particular disadvantage however, are the low yields with which by the process of DOS 1,668,068 the benzonitriles can be produced.

There has been a process for the preparation of benzonitriles of the formula where R1 is hydrogen, cyano, halogen or an optionally substituted alkyl or alkoxy radical, R2 is hydrogen or halogen and R3 is hydrogen or nitro, by reaction of benzotrichlorides of the formula wherein R1, R2 and R3 have the meaning given above, found at temperatures between about 150 and 2500C in the presence of metal salts, in which the reaction of the benzotrichlorides with ammonia in a molar ratio of 1 to at least 4, the ammonia at any point in time of the reaction in Excess is present, optionally in a diluent, is carried out.

The process according to the invention can be illustrated using the example of the reaction of p-methylbenzotrichloride with ammonia: CC13 CN ammonia CH3 CH3 Halogens (R¹ and R²) can be fluorine, chlorine, bromine and iodine, preferably fluorine, chlorine and bromine.

An optionally substituted alkyl radical (R1) can be a straight-chain one or branched hydrocarbon radical with up to 6, preferably with up to 4 carbon atoms be. For example, the following radicals may be mentioned: methyl, ethyl, propyl, isopropyl, Butyl, isobutyl, pentyl, isopentyl, hexyl and isohexyl.

An optionally substituted aryl radical (R1) can be a carbocyclic, aromatic radical with 6 to 12 carbon atoms, preferably the phenyl radical.

An optionally substituted alkoxy radical (R1) can be a straight-chain one or branched aliphatic hydrocarbon radical with up to 6, preferably with contain up to 4, carbon atoms. Examples are the following alkoxy groups named: methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, pentoxy, isopentoxy, Hexoxy and isohexoxy.

Preferred compounds of the formula II are benzotrichlorides of the formula where R is hydrogen, cyano, chlorine, bromine or a R5 C1 to C4 alkyl radical, is hydrogen, chlorine or bromine and R6 is hydrogen or nitro.

It is also possible that the benzonitriles by one or two Trifluoromethyl groups are substituted.

Substituents of the radical R1 can be, for example: the halogens such as fluorine, chlorine, bromine and iodine, the nitro group, the C1 to C6 alkyl group such as methyl, Ethyl, propyl, iso-propyl, butyl, iso-butyl, pentyl, iso-pentyl, hexyl and iso-hexyl, and the C1 to C6 alkoxy group such as methoxy, ethoxy, propoxy, iso-propoxy, butoxy, iso-butoxy, pentoxy, iso-pentoxy, hexoxy and iso-hexoxy.

The preparation of the benzotrichlorides according to formula II is known per se, Ullmann, Enzyklopadie der Technischen Chemie, Volume 9, 4th edition, pp. 525 to 537). The following benzotrichlorides may be mentioned as examples: benzotrichloride, o-chlorobenzotrichloride, m-chloro-benzotrichloride, p-chloro-benzotrichloride, 2,4-dichloro-benzotrichloride, 3,4-dichloro-benzotrichloride, 2, 5-dichloro-benzotrichloride, 2-chloro-5-nitro-benzotrichloride, m-nitro-benzotrichloride, p-nitro-benzotrichloride, 2,4-dichloro-5-nitro-benzotrichloride.

Ammonia can be used in the process according to the invention in gaseous form or in Solution, preferably used in gaseous form.

It is also possible to use compounds instead of ammonia, which split off ammonia under the reaction conditions.

Examples are ammonium carbonate and urea.

For the process according to the invention, it is essential that ammonia is present in excess at any point in time during the reaction. Generally will the benzotrichloride and the ammonia are reacted in a molar ratio of 1 to at least 4.

The addition of larger amounts of ammonia is of no importance for that method according to the invention. However, it is useful to use the benzotrichloride and the To implement ammonia in a molar ratio of 1 to 4.1 to 5.

Compounds that may be mentioned as metal salts are the halogen complex compounds can form. For example, the salts of inorganic acids come with the elements Iron, aluminum, zinc and copper can be considered. Preferred are the halides of Iron, aluminum and zinc, particularly preferably iron (III) chloride, aluminum chloride and zinc chloride, called.

The metal salt is generally preferred in amounts of from 0.01 to 5% 0.1 to 2%, based on the benzotrichloride used.

The process according to the invention can optionally be carried out in a solution and / or diluents are carried out. As a solvent and / or diluent For example, solvents and / or diluents come under consideration under the Reaction conditions are inert. Examples are diphenyl ether and diphenyl called.

However, it can also be used advantageously as a solvent or diluent an excess of the benzonitrile formed in the reaction and / or as Use benzotrichloride as the starting material.

The process according to the invention can be discontinuous and continuous be performed.

According to the method of the invention, for example, the following benzonitriles known per se are produced: benzonitrile, o-chloro-benzonitrile, m-chloro-benzonitrile, p-chloro-benzonitrile, 2,4-dichloro-benzonitrile, 3,4-dichloro-benzonitrile, 2,5-dichloro-benzonitrile, 2-chloro-5-nitrobenzonitrile, m-nitro-benzonitrile, p-nitrobenzonitrile, 3,5-dichlorobenzonitrile, 2,4-dichloro-5-nitro-benzotrichloride.

In general, the process according to the invention can be carried out as follows are: In the reaction vessel, the respective benzotrichloride and metal salt, optionally in a solvent and / or diluent, and then ammonia initiated.

The process according to the invention can generally be carried out at one reaction temperature from about 150 to 250 ° C, preferably from about 170 to 220 ° C.

The process according to the invention can generally be carried out under normal pressure be performed. However, it can be advantageous, for example to complete the text the reaction or in the case of low-boiling starting or end products to achieve a sufficiently high reaction temperature, the reaction under an increased ammonia pressure perform. One then works, for example, under an ammonia pressure of 1 up to 100 bar, preferably from 1 to 10 bar.

After the reaction has ended, that which has arisen during the reaction can be used Ammonium chloride in a manner known per se, for example by suction or centrifugation, separated and then the remaining reaction mixture are fractionally distilled.

By adding bases, e.g. sodium hydroxide solution, to the separated ammonium chloride ammonia can be released, which is then used again in a further reaction can be.

According to DOS 1 668 068, the majority of the benzonitriles can only can be produced with low yields, since some of the benzonitriles are produced by trimerization get lost. For example, p-chloro-benzonitrile with a yield of get only 25%.

In contrast, the benzonitriles can by the process according to the invention in high yields and with practically complete avoidance of trimerization getting produced.

From an energetic point of view, the method according to the invention has the advantage that the heat of reaction of the reaction compared to that known from DOS 1,668,068 The process is better used because the heat of neutralization is generated at the beginning Hydrogen chloride with ammonia is released at the time of the reaction at which a high temperature for the inventive reaction of benzotrichloride with ammonia necessary is.

The benzonitriles produced by the process according to the invention are intermediates for dyes DOS 23 64 475, medicament DAS 1 280 878, US 3,133,081) and plant protection agents DOS 1,009,497.

Example 1 100 g of 4-chloro-benzotrichloride are in the presence of 0.1 g of iron (III) chloride heated to 2000C with stirring and at this temperature reacted by introducing ammonia. After about 2 hours you will get 16.4g Ammonia has been introduced.

The benzonitrile and 4-chloro-benzotrichloride are then separated with toluene and water from the ammonium chloride formed and the organic phase is distilled. at Bp28 1280C, 32.3 g of 4-chloro-benzonitrile are obtained (this corresponds to a yield of 96.5% based on converted 4-chloro-benzotrichloride).

Examples 2 to 6 Examples 2 to 6 are in the following table compiled. The benzonitriles are similar to those described in Example 1 Working method established. There are per 100 g of the benzotrichloride used 0.1 g of iron (III) chloride used as a catalyst.

Table 1 Nitriles from substituted benzotrichlorides and ammonia Example subst. Benzo- test-% nitrile- No. trichloride bediny, inefficiencies in conversion yield. % Cp Cl 2 g - CCl3 1 hour 2000 36.5 98.5 1100 / 15 mm 3 CCl3 1 hour 1800 33.2 99 1910 4 Cl <CCl3 2 hours 190 40.0 98.8 130 ° / Cl up to 2200 12 mm 5 Cl0CC13 3.5 hours 200 36.6 97.5 1300 / 5 up to 2200 16 mm Cl 6 Cl0CCl3 3.5 hours 2000 67.0 99 11g ' in 200 parts. 16 2-chloro-benzo- nitrile Example 7 50 g of o-chloro-benzotrichloride, 13 g of urea and 0.1 g of iron (III) chloride are stirred under reflux at 240 ° C. for 3.25 hours.

After the evolution of hydrogen chloride has ceased, it is distilled Reaction mixture. The distillate passing over at Kp22 120 to 1300C is 89.9 % from o-chloro-benzonitrile and 10.1% from o-chloro-benzotrichloride.

Claims (4)

Claims: 1) Process for the preparation of benzonitriles of the formula where R1 is hydrogen, cyano, halogen or an optionally substituted alkyl, aryl or alkoxy radical, R2 is hydrogen or halogen and R3 is hydrogen or nitro, by reaction of benzotrichlorides of the formula wherein R¹, R² and R³ have the abovementioned meaning at temperatures between 150 and 250 ° C in the presence of metal salts, characterized in that the reaction of the benzotrichlorides with ammonia in a molar ratio of 1 to at least 4, the ammonia at any point in time Reaction is present in excess, if appropriate in a solvent and / or diluent, is carried out. 2) Method according to claim 1, characterized in that the Implementation of the benzotrichloride with ammonia in a molar ratio of 1 to 4.1 to 5. 3) Method according to claims 1 and 2, characterized in that that the solvent and / or diluent that is formed in the reaction Benzonitrile is used. 4) Method according to claims 1 and 2, characterized in that that the benzotrichloride which is reacted is used as the solvent and / or diluent begins.