DE2408529C2 - Process for the preparation of o-benzyltoluenes - Google Patents

Description

R ¹

IO

in which the individual radicals R ¹ and R ^{2 are} identical or different and represent hydrogen atoms or chlorine atoms, the radicals R ² also represent alkyl radicals having 1 to 6 carbon atoms, by reaction of o-xylyl chlorides of the formula

R ^!

R ¹

CH ₂ Cl

CHj

Π.

20th

25th

R ¹

wherein R ^{1 has} the aforementioned meaning with benzenes of the formula

35

m.

40

wherein R ^{1 has} the aforementioned meaning, in the presence of sulfuric acid, characterized in that the molar ratio of starting material III to starting material II is less than 7: 1, and the reaction is carried out in the presence of 3 to 15 moles of sulfuric acid, based on 1 mole Starting material II, carried out with a volume ratio / on 0.5 to 2 volumes of organic phase per part by volume of aqueous phase in the reaction mixture and with thorough mixing.

2. The method according to claim I, characterized in that the reaction is carried out in a finely dispersed mixture of the organic phase in the aqueous phase with a droplet size dev organic phase of at most 1000 nanometers.

60

The invention relates to a method of manufacture of o-benzyl toluenes by reacting o-xylyl chlorides with benzenes in the presence of sulfuric acid.

o-Benzyltoluene is formed, along with other products, from Heating of toluene with Benzylchlorld in the presence of Zinc dust [chemical reports, volume 6, rare 906 ff. (1873)) or from beryllium chloride [chemical reports, Volume 72. Page 1414 ff. (1939) 1. Even when treating a mixture of o-xylyl chloride and benzene with zinc dust is formed in poor yield o-benzyltoluene [Chemical Reports, Volume 7, page 1544 ff. (1874)]. None of these processes are suitable for industrial use, since either poor yields are achieved or mixtures that are difficult to separate result. The hydrogenation of ethyl o-benzoylbenzoate in the presence of copper chromite at 250 ^° C. likewise gives o-benzyltoluene [Journal of the American Chemical Society, Volume 55 (1933), Rare 1669 ff.]. The preparation of the catalyst and, in particular, the multistage preparation of the starting material are cumbersome and uneconomical, so that even this process is unsatisfactory on an industrial scale with regard to simple, economical and trouble-free operation.

In Alkyllerungen with alkyl chlorides sulfuric found so far no industrial use, A is not expected with a uniform reaction. It had to be expected that alkyl chlorides would be saponified to alcohols and, at least to a certain extent, converted to sulfuric acid esters. Sulphonation on the benzene nucleus was also to be feared. In order to obtain uniform alkylation products, olefins were first produced from chlorinated paraffins by dehydrohalogenation in industrial processes, which then clearly react with benzene [Erdöl und Kohlen, Volume 20, Rare 786 to 787 (1967)].

In the case of the reaction of o-Xylylchlorld with benzene and its derivatives are aggravated by the fact that o-Xylylchlorld can be sulfonated very easily and thus low yields are to be expected. In addition, it had to be assumed that xylyl halides preferentially with themselves and only to a minor extent react with benzenes. An Arbelt In Compt. Rend., Volume 250, Selten 1659 to 1661 (1960) in the reaction of Benzylchlorld with Benzol in the presence of metal halides ^ such as SbCh, TlCU and BlCIi In aqueous solution already at 50 ° C a yield of over 20% of polybenzylbenzenes and only from 0 to 47% Dlphenylmelhan. The specific action of the catalyst as a crucial factor that was not predicted is highlighted.

Japanese Offenlegungsschrift 40 754/1973 describes that o-xylyl halide can also be condensed with aromatic compounds in the presence of sulfuric acid, provided that more than seven times the molar amount of aromatic compounds is used per mole of the halide. According to the description, it was to be assumed that dl «. Condensation of the halide with itself and sulfonation is suppressed to a substantial degree by the high dilution of the starting mixture, the aromatic compound acting as a diluent. It is described that the 2-phase reaction mixture is constantly present in 2 separate layers during the reaction. The sulfuric acid is always used in 0.5 to 2 times the molar amount, based on the o-xylyl chloride. The reaction temperature is 45 to 78 "C. As can be seen from the description and in particular the example, the volume ratio of organic layer to aqueous layer of the 2-phase reaction mixture is very high and well over 10 to 1. S The description mentions the use of Stirring ';'; devices, but does not provide any details about * suitable apparatus and conditions. \,

It has now been found that o-benzyltoluenes of Fe formula

in which the individual radicals R 'and R ^{2 are} identical or different and represent hydrogen atoms or chlorine atoms, the radicals R ² also represent alkyl radicals having 1 to 6 carbon atoms if o-xylyl chlorides of the formula

Π.

wherein R ^{1 has} the aforementioned meaning with benzenes of the formula

30th

ΠΙ.

35

wherein R ^{2 has} the aforementioned meaning, reacts in the presence of sulfuric acid, advantageously obtained, the molar ratio of starting material III to starting material II being less than 7: 1 and the reaction in the presence of 3 to 15 moles of sulfuric acid, based on 1 mole of starting material II, carried out with a volume ratio of 0.5 to 2 parts by volume of organic phase per part by volume of aqueous phase in the reaction mixture and with thorough mixing.

It has also been found that the method can be carried out advantageously in the aforementioned manner if the Implementation In a finely dispersed mixture of the organic phase in the aqueous phase with a droplet size the organic phase is carried out at a maximum of 1000 nanometers.

The reaction can be carried out by the following formulas in the case of using o-xyiylchlorld and benzene be reproduced:

55

CH ₃ Cl

CH,

+ HCI.

Compared to the known methods, the method according to the invention provides a simpler and more economical one Routes o-BenzyltoluoIe In good yield and purity. With regard to the former processes using aralkyl chlorides. Is the yield and The purity of the end product is better and the isolation of the end product from the reaction mixture is much easier and more reliable. With regard to the state of the art, aas method according to the invention is simpler,

ίο more interference-free and therefore especially suitable on an industrial scale. The starting materials are easily accessible and do not require laborious, multi-stage syntheses for their preparation.
In comparison to the process described in the Japanese publication, smaller amounts of starting material III are used, and the process is thus simpler and more economical. Since the starting materials IH are for the most part flammable solvents or toxic or easily evaporating substances that pollute the breathing air, the method according to the invention increases operational reliability, improves and simplifies, especially on an industrial scale. The standard is the control and regulation of the implementation as well as the health protection of the operating staff, reduces the problems of exhaust gas decontamination, wastewater treatment and air pollution and is therefore more environmentally friendly and more progressive from an ecological point of view.

With reference to the prior art, all of these beneficial results are surprising as one could have With regard to Friedel-Crafts syntheses and teaching the Japanese patent should expect that alkylated aromatics much more easily than z. B. benzene aralkylated and thus o-xylyl halides are preferred with himself and only to a subordinate extent with Benzene react. Since yes against this teaching with significantly lower amounts of starting material III and preferred In a much lower volume ratio of organic layer to aqueous layer of the reaction mixture, with higher amounts of sulfuric acid on starting material II, and is reacted at a higher temperature, it was to be feared that considerable Amounts of dibenzyl compounds and sulfonated end products and by-products would form. In contrast In addition to the known processes, the process according to the invention prefers particularly intensive mixing of the reaction mixture. In addition to the quantitative ratio of the starting materials are therefore with regard to the prior art precisely also the preferred features of the volume ratio of the phases, the Amount of sulfuric acid and the stirring speed surprising.

The starting material III is reacted with starting material II in a stoichlometric amount or in an excess of less than 7 moles of starting material III, preferably in a ratio of 2 to 6 moles. In particular, 4 to 6 moles of starting material III per mole of starting material H are reacted. Preferred starting materials II and IH and accordingly preferred end products I are, in their Formein the individual radicals Ri and R such ₂ may be identical or different and each represents a hydrogen atom or a chlorine atom, R ₁ moreover also in each case an alkyl radical having 1 to Represent 6 carbon atoms.

Examples of suitable starting materials II are: o-Xylylchlorld, S-chloro ^ -chloromethyl-toluene, 4-chloro-2-chloromethyl-toluene, 5-chloro-2-chloromethyl-toluene or 6-chloro-2-chloromethyl-toluene.

The starting materials III are ζ. B. Consider: Benzene, Toluene, o-xylene, m-xylene, p-xyloI, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, 1,2,3,4-tetramethylbenzene, 1,2,3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, pentamethylbenzene, chlorobenzene, 1,4-dichlorobenzene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene or tert-butylbenzene.

The reaction is generally carried out at one temperature from 40 to 160 ° C, preferably from 60 to 130 ° C, in particular from 75 to 90 ° C, without pressure or below Pressure, carried out batchwise or continuously. It is expedient to use solvents which are inert under the reaction conditions, such as water or aromatic solvents Hydrocarbons such as nitrobenzene, trichlorobenzene; Chlorinated hydrocarbons such as methylene chloride, ethylene chloride, Carbon tetrachloride, chloroform; Carbon disulfide; aliphatic hydrocarbons like ligroln, Petroleum ether, or equivalent mixtures. There are amounts of 10 to 100 wt .-% solvent, based on starting material II, to be considered. The starting material IH itself can also be used as a solution medium will.

As a rule, a concentrated sulfuric acid is used from 70 to 90%, especially from 78 to 82% by weight and in an amount of at least 3 moles, preferably 3 to 15 mol, in particular 3 to 6 mol sulfuric acid (calculated 100%), based on 1 mol starting material H. The starting materials II and III, optionally the solvent, and the sulfuric acid are in their Total volume preferably chosen so that in the 2-phase starting or reaction mixture during the overall implementation a volume ratio of 0.5 to 2, in particular 0.9 to 1.1 volume units of organic Phase per part by volume of aqueous phase is complied with.

The reaction can be carried out as follows: A mixture of starting materials II and III, the acid and if appropriate, solvent is kept at the reaction temperature for 2 to 15 hours with thorough mixing. Then the mixture is cooled and the fuel in usual catfish, e.g. B. by separation the organic phase and distillation, isolated.

In a preferred embodiment of the process, the reaction mixture is thoroughly mixed during the entire reaction, preferably at a stirring speed of at least 700, in particular from 850 to 2000 revolutions per minute. In the case of mixing devices with oil-ne agitators, preference is given to those that bring in shear energy corresponding to the aforementioned agitation speed. In this way, a finely divided mixture, preferably an emulsion, is achieved. If necessary, emulsifiers can also be added to form emulsions. Finely disperse mixtures of the organic phase in the aqueous phase, preferably emulsions, with a droplet size of at most 1000, advantageously from 1 to 600, preferably from 5 to 400, in particular from 5 to 300 nanometers, are expedient. Using the above-mentioned mixing conditions, widely known stirring devices can be used; Injectors, ball nozzles, DraüdQsen, turquoise stirrers, mixing nozzles, Lechler-Mlschdüse, blade stirrers, anchor stirrers, bar stirrers, propeller stirrers, Cramer stirrers, Vlbromlscher, constant stirrers, cross-beam stirrers, rotary stirrers, jet stirrers, flat blade stirrers, centrifugal stirrers, spiral stirrers, planetary stirrers , Rotary-edge stirrers, hollow stirrers, tubular stirrers, impeller stirrers, impeller stirrers and pulverizers are preferred. Apparatus and systems that allow intensive mixing are also available, such as stirred tanks, stirred tank cascades, flow tubes, mammoth agitators, homogenizing machines, centrifugal mixers, turbo mixers, emulsifier centrifuges, ultrasonic liquid pipes, continuous mixers, rotary drums, chamber reactors, circulatory reactors, loop reactors, jet reactors, jet reactors , Liquid ring pump, jet nozzle tubular reactors, thin-film reactors, in question; stirred tank cascades, loop reactors and jet nozzle reactors are preferred.

In the rare chain halogenation of chloroxylenes to the starting materials II, z. B. in the rare chain chlorination of 3-chloro-o-xylene or 4-chloro-o-xylene, two isomers of chloro-o-xylylchloride are formed, in the example 3-chloro-2-chloromethyl-toluene and ö-chloro ^ - chloromethyl-toluene or 4 and S-chloro ^ -chloromethyl-toluene, which on reaction with HI benzenes two corresponding isomeric provide oluole Benzyl-chlo ^r?. Oxidation of the mixtures with the corresponding o-benzoylbenzoic acids and subsequent ring closure leads to uniformly substituted anthraquinones. In the example case to 1-chloro-anthrachlion or 2-chloro-anthrachlnone. The end products I can indeed be obtained from the mixtures mentioned by suitable operations, e.g. B. fractional distillation or fractional crystallization, are separated. In general, however, such starting materials II will be reacted in a mixture and the resulting mixture of end materials I will be processed further directly. For the same reason, mixtures of 3-chloro-o-xylene and 4-chloro-o-xylene, such as those obtained, for example, in the chlorination of o-xylene, will usually also be chlorinated in the rare chain, the resulting mixture of 4 isomers Implement starting materials II by the process according to the invention and separate the resulting mixture of the 4 end products I only after cyclization to give the chloranthracers. The process according to the invention therefore plays a role not only for the production of individual end products, but also for the production of these mixtures, which are important as starting materials for dye synthesis, especially on an industrial scale.

The o-benzyltoluenes I produced by the process of the invention are valuable starting materials for production of anthracene and anthrachlnone and their derivatives. So deliver o-Benzyltoluenes when passing over the Vapors over lead oxide anthracender levates. Oxidation with nitric acid leads to o-benzoylbenzoic acid and Your derivatives. Pezüglllch the use is on the aforementioned publications and Ulimann's Encyclopedia of Industrial Chemistry, Volume 3, Rare 660 ff., v-T'vlesen.

Particularly preferred end products I are, for. B. 2-Benzyltoluene, 2 benzyl-3-chlorotoluene, 2-jenzyl-6-chlorotoluene, 2-benzyl-4-chlorotoluene, 2-benzyl-5-chlorotoluene, and 2,2'-dimethyl -5-chloro-phenylmethane.

The ones in the. The parts mentioned in the examples are parts by weight. ", ...
example 1

75% by weight of sulfuric acid is added in 350 parts 80 ° C with stirring at a speed of rotation of 900 U / mln In a stirred vessel with impeller stirrer a solution of 70 parts o-Xylylchlorld In 230 Share benzene. After a further 5 hours at 80 ° C. with thorough mixing of the mixture, the Organic phase from and isolated by distillation 73

IO

Parts (= 81.1% of theory) of o-BenzyltGldol, bp _02: 97 to 100 'C (NFT: 1.5749).

Example 2

The procedure is as in Example 1. Instead of the 75% by weight sulfuric acid, the same amount of 80% by weight sulfuric acid is used. Dent removal: 80.2 parts (= 89% of theory) o-benzyltoluene with a boiling point of ₀₂ : 97 to 100 ° C.

Example 3

The procedure is as in Example 1. Instead of 75% by weight sulfuric acid, 85% strength by weight sulfuric acid is used. The reaction temperature is 68 to 70 ° C. Yield: 78 parts (= 86.6% of theory) of o-benzyltoluene with a boiling point of ₀₂ : 97 to 100 ° C. ii

Example 4

In a loop reactor, 3660 parts of 80% by weight sulfuric acid are circulated using a centrifugal pump. At 75 to 77 ° C., a solution of 1120 parts of o-xylylchlorld and 3120 parts of benzene is added over the course of 3% hours, an emulsion being formed. At an overflow, part of the emulsion is allowed to run off continuously into a calming vessel. The organic phase is separated off and distilled, the inorganic phase is fed back into the circulation system. After distillation, 1334 parts (91.9% of theory) of o-benzyltoluene with a boiling point of ₀₃ : 100 to 104 ° C. are isolated from the organic phase.

Example p

850 parts of 80% by weight sulfuric acid are placed in a stirred vessel with an impeller stirrer. A solution of 70 parts of o-xylyl chloride and 156 parts of benzene in 200 parts of oil is allowed to run in at 75 to 80 ° C. with vigorous stirring. After a further 5 hours at 80 ° C the organic phase (83% of theory) of o-benzyltoluene is separated and isolated by distillation, 75 parts of boiling _02: 97 to 100 C. ^A

Example 6

A solution of 95 parts of 2-chloromethyl-6-chlorotoluene and 80 parts of 2-chloromethyl-3-chlorotoluene in 470 parts of benzene are added to 300 parts of 80% by weight sulfuric acid with vigorous stirring at 75 to 80 ° C. After a further 5 hours at 8O ⁰ C, the organic phase is separated and isolated by fractional distillation 170.9 parts (79% of theory) of a mixture in which the starting materials corresponding GcwiciuSverhSunlä from 2-benzyl-6-chlorotoluene and 2-benzyl 3-chlorotoluene (bp ₁₇ : 175 to 177 ° C).

Example 7

The procedure is as in Example 2. 250 parts of toluene are used instead of benzene. Yield: 82 parts (83.7% of theory) 2- (methylbenzyl) toluene with a boiling point of ₀ : 98 to 101 ° C.

Claims (1)

Patent claims: 1. Process for the preparation of o-benzyltoluene the formula R ¹ CH, CH ₃ R ²