DE1668455B - Process for the production of mono- (chloromethyl) -benzenes or pory- (chloromethyl) -benzenes - Google Patents

Description

about 80% of that present as the starting compound Methylbenzene amounts to, and thus this compound has been converted into compounds that are a Have chlorine atom per methyl group. This conversion is conveniently carried out by means of more conventional means Working methods of gas-liquid chromatography measured.

The inventive method is carried out in a suitable reaction vessel which is equipped with a Cooling device such. B. a reflux condenser, mechanical stirrer, chlorine inlet tube and temperature control It can be a conventional reaction vessel for continuously carried out and large-scale production approaches are used. Appropriately meets provision is made for the recycling of only partially chlorinated by-products.

The products according to the invention can be separated according to conventional procedures, e.g. B. by means of distillation with removal of the solvent or by selective crystallization. The preferred procedure for separating Λ, α'-chloroxylenes consists in first distilling off the solvent, unreacted xylenes and monochlorinated xylenes and recovering them. The distillation can then be continued to recover the desired α, α'-dichloroxylenes by means of vacuum distillation, or the same can optionally be obtained by crystallization from an aliphatic hydrocarbon which is introduced as a solvent into the distillation vessel after the monochlorinated xylenes, solvents and unreacted Products have been removed.

The chlorinated xylenes according to the invention find numerous and different applications such . B. as chemical intermediates for the production of diamines, Dinitrilen.Glykolen and many other organic compounds, which in turn are useful as solvents, insecticides and polymer intermediates.

The invention is illustrated by the following examples:

example 1

45

13.6 grams of p-xylene and 100 ml of benzene are added to a 250 ml, 4-necked flask equipped with a mechanical stirrer, immersible UV light source, chlorine inlet tube, condenser and temperature controller. The mixture is brought to a temperature of 6O ⁰ C is turned on, the UV light, and allowing the chlorine at a rate of 1.74 moles of chlorine per mole of xylene to flow therethrough per hour. 1 ml samples are taken at intervals of 5 minutes and analyzed by means of gas chromatography. After 15 minutes 56.8 ° / ₀ of xylene are converted to obtain a yield of 1.3% α, α-Dichlorp-xylene, 6.2% α, α'-Dichlorp-xylene and 49.3% a -Chlor-p-xylene. The yield of α, α'-dichloro-p-xylene is thus 10.9%, based on the total amount of chlorinated methylbenzenes in the reaction product. The selectivity (percentage ratio was 82.5%.

Example 2
(Comparison)

The procedure of Example 1 is repeated, using an equal amount of moles of carbon tetrachloride takes the place of the benzene of Example 1, the following results being obtained.

After a reaction time of 15 minutes, 49.0% of xylene has been converted to yield a 1.8% α, α-dichloro-p-xylene, 5.5% α, α'-dichloro-p-xylene and 41.7% -chloro-p-xylene. This represents a 10% reduction in the yield of α, α'-dichloro-p-xylene according to Example 1. The yield of α, α'-dichloro-p-xylene is thus 11.3%, based on the Total amount of chlorinated methylbenzenes in the reaction product. The selectivity was 75%.

Examples 3 to 8

The procedure according to Examples 1 and 2 is repeated under identical conditions, other solvents are used. The results obtained in this way are summarized in the table:

example solvent % Around-
Change
to p-xylene <χ, λ '/ <χ, οι-
ratio 3 no 23.2
51.9 3.46
3.33 4th Tetrachlor
carbon 32.7
68.9 3.10
3.32 5 benzene 19.5
57.1 8.50
4.70 6th o-dichloro
benzene 30.3
75.9 9.83
6.23 7th p-dichloro
benzene 49.7
80.1 6.92
5.04 8th Benzene-10 moles
percent
Acetonitrile 33.5
67.9 11.04
5.94

As can be seen from the table above, there are two experiments for each of the solvents been carried out, with the reactions in each case to the specified percentage conversions p-xylene were performed. These different percentage conversions are the corresponding ones Ratios of a, a '/ <Xi «, and these experiments came to carry out the best ratios for the different percentage conversions ascertain. As demonstrated by the combination of benzene and acetonitrile as a solvent, the best selectivities for α, α'-dichloro-p-xylene result when the percentage conversion is kept relatively low.

Like the comparison of working on the one hand with carbon tetrachloride with working according to the invention on the other hand, shows a substantial improvement in the selectivity of the desired product α, α'-dichloro-p-xylene.

Claims (4)

where xylenes are particularly preferred as starting materials 1. Process for the 'production of mono-monochlorobenzene and o-dichlorobenzenes preferred. (Chloromethyl> benzenes or poly (chloromethyl) - 5 A mixture of 5 to is particularly useful benzenes from methylbenzenes, thereby about 30 and preferably 8 to about 20 mol percent indicates that one methylbenzenes, acetonitrile in benzene. The latter preferred which have 1 to 4 methyl groups per molecule, proves to be a solvent in its property with elemental chlorine in the presence of benzene, unexpectedly, acetonitrile as such does not exist Mono-, di- or trichlorobenzene as a solvent io an appropriate solvent for the and in the presence of free radical forming moderate processes Catalysts or corresponding irradiation It should be about 0.5 to about 100 and preferably at 0 to 200 ⁰ C converts. 1 to about 20, and most preferably 2 to about 2. The method according to claim 1, characterized in that 10 moles of the solvent per mole of the starting point is that 0.5 to about 100 moles of solution x ₅ compound applied methylbenzene are present,
average per mole of the methylbenzene used as the starting material. can be high enough to get the mixture out 3. Further development of the process according to methylbenzenes and solvents in the liquid ZuAnspruch 1 or 2, characterized in that to withstand, and be sufficiently low to be a mixture of 95 to ao significant evaporation of the UmseUungbteiliielniicr 70 mol percent benzene and 5 to as a solvent To prevent 30 mole percent under the reaction conditions. Acetonitrile used as a solvent. Temperatures from 0 to 200 ⁰ C, preferably from 15 to 150 ⁰ C and particularly preferably from 60 to about 100 ⁰ C are to be provided, with temperatures within As half of these ranges are chosen so that either solidification or excessive evaporation of the reactants is prevented.
The pressure is not particularly critical. In general A number of attempts have already been made to believe that the reaction should be carried out at about 0.8 to about various mono- and poly- (chlorine- 30 2 atmospheres pressure), since the methyl) -benzenes (benzenes that contain one or more Pressure generally only leads to containing the reac-monochloromethyl groups) without keeping equation participants in the liquid state,
early production of the less expedient mono-die by means of the method according to the invention and poly (dichloromethyl) benzenes (benzenes; the di- aimed products can be used as mono- (chlorochloromethyl) groups included). For example, 35 methyl) benzenes or poly (chloromethyl) benzenes are described z. U.S. Patent 2,446,430. The inappropriate products that are on Process for introducing a chlorine atom in the process of the present invention behind each Methyl group of xylene without formation of can be stopped as α, Λ-chlorinated Designate dichloromethylbenzene by chlorinating the xylene products, it being understood that in carbon tetrachloride as a solvent. Attempts to 40 this term refers to all methylbenzenes that these results of U.S. Patent 2,446,430 have two chlorine atoms on any of the present reproduce, and have one roughly on the same methyl groups. Harvey's level publication, The Applying of Various, Freer Education S mi th, S tacey and Tatlo w in J. Appl. Chem., Catalysts leading to radicals is required, Vol. 4, p. 319 (June 1954), have been found not to be 45 to increase the reaction rate, z. B. proved successful. Furthermore show theoretical actinic light such. B. Ultraviolet, Sunlight, Studies by Beltrame et al., J. Physical fluorescent tube light, organic peroxides and Hy-Chem., Vol. 70, p. 1150 (No. 4, 1966) and Tetrahedron droperoxide, e.g. B. those found in Industrial and Letters, Vol. 44, p. 3909 (1965) that the highest possible Engineering Chemistry, Vol. 58, pp. 25-32 (March Selectivity is about 75% of the targeted bis 50 1966) and the corresponding literature references of these (Chloromethyl) benzene amounts to, if you are given tetrachloro publication, further nitriles, uses carbon as a solvent. such as B. azodiisobutyronitrile or azo-bis - (<x, y-di- The process according to the invention for the preparation of methylvaleronitrile and other compounds of mono- (chloromethyl) benzenes or poly (chlorine- which is known to promote the reactions proceeding via free radicals methyl) benzenes from methylbenzenes is now
characterized in that one methylbenzenes, the 1 to It is preferred that the chlorine through relatively slowly Have 4 methyl groups per molecule, to introduce an inlet pipe with mechanical stirring of the tarem chlorine in the presence of benzene, mono-, di- reaction mixture. The Fließgeschwin- or trichlorobenzene as a solvent and in the opposite speeds of the chlorine amount to about 0.1 to 10, waiting of free radical forming catalysts and 60, more preferably about 1 to about 5 and insbeentsprechender irradiation at 0 to 200 ⁰ C. implements. particularly preferably to approximately 2 moles of chlorine per The solvent selected according to the invention hour. This amount should be possible per mole of that in the reactor es, a secVtivity of up to 85% of the methylbenzenes present in the ion mixture was added desired products. Will continue to be. according to the invention, the inexpedient, in essence 65 The addition of chlorine to the reaction mixture chlorinated by-products avoided. generally continues until the conversion occurs Preferred starting materials for the invention to about 20 to about 100, more preferably to 30 Corresponding processes are the di- and trimethylbenzenes, up to about 90 and particularly preferably up to 50