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Publication numberUS3232959 A
Publication typeGrant
Publication dateFeb 1, 1966
Filing dateDec 26, 1961
Priority dateDec 5, 1961
Publication numberUS 3232959 A, US 3232959A, US-A-3232959, US3232959 A, US3232959A
InventorsHahn Heinrich
Original AssigneeKalk Chemische Fabrik Gmbh
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process for the production of bromine derivatives of aromatic compounds devoid of condensed benzene nuclet containing over 3 bromine atoms per molecule
US 3232959 A
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Description  (OCR text may contain errors)

United States Patent PROCESS FOR. PRODUCTION OF BRQMINE DERIVATIVES OF AROMATIC. COMPOUNDS DE- VOID OF CONDENSED BENZENE N .UCLEICON- TAINENG' OVER 3 BROMINE ATOMS PER MOLECULE Heinrich Hahn, Cologne-Deutz, Germany, assignor to Chemisohe Fabrik Kalk G.m.hrH., Col'oge-Kalk, Germany N0 Drawing. FiledDec. 26,.196 1,.S'er.. No. 161,270 4 Claims. ((-31. 260-389).

The present invention. relates to an improved process for the. production of aromatic bromine compounds containing more. than 3 bromine atoms per molecule from aromatic compounds which do not contain condensed benzene nuclei. The starting aromatic compounds can contain one or more uncondensed benzene nuclei, such as in way when 3 to 4 times the quantity of'bromine was used as was necessary for the production of the desiredbromine derivative. During the bromination a quantity of bromine is converted to HBr which is equivalent to that actually used in bIOIHlIIalZiOH. The portion of bromine. thus bound as HBr can be recovered and again made use ful for the bromination by oxidation in a separate ap paratus to set free the bromine which then could be recycled to the bromination.

A. number of other procedures have been developed and reported for the production of bromine derivatives of aromatic hydrocarbons containing less than 4 bromine atoms per molecule, As these bromine. derivatives in general are more easily formed than the more highly brominated derivatives of the same aromatic hydrocarbons, they;

can be produced with the aid of only a small bromine excess. Thus it has been proposed to produce the monobromo derivatives of aromatic hydrocarbons by reacting the aromatic hydrocarbons with aqueous hydrobromous acid containing a. quantity of bromine dissolved therein about 2.5 times that required for formation of the desired bromine derivative.

It also is known that brominated aromatic hydrocarbons containing up to 4 bromine atoms per molecule can be produced by treatment of aqueous suspensions of monosulfonic acid derivatives of such aromatic hydrocarbons with an excess quantity of bromine. These bromine derivatives can also be produced by the action of hydrochloric acid and a mixture of bromideand bromate on the monosulfonic acid derivatives of aromatic hydrocarbons. According to the latter process the aromatic brominated derivatives which can contain up to 4 bromine atoms are either produced directly or they are obtained by hydrolytic cleavage of the sul-fo group from the brominated sulfonic acids produced.

These processes, however, have the disadvantage that the monosulfonic acid derivatives of the aromatic compounds used therein must be prepared in a separate process step and isolated.

According to another process for the preparation of monoor dibromo derivatives of aromatic compounds, the bromine is introduced directly into the aromatic hydrocarhon in the presence of concentrated or fuming nitric acid ice alone or in combination with concentrated or fuming sulfuric acid; As in all previously described processes, only up to about 40% of the brominesupplied is actually utilized in the formation of themonoor dibromo derivatives, evenwhen the reaction mixture is heated. According to another known process, the bromination ofar-omatic hydrocarbons to form the mono-or-dibromoderivatives thereof .is carried out with bromine in the presence of sulfuric acid containing up to 10% of sulfur'trioxide. Inthis case-also nobetter-utilization of thebromine supplied can be achieved. Furthermore, in both last mentionedprocesses only; about 50%- of the-arom atic hydrocarbon used as the star-ting material is converted to the dcsiredbromihated product, the remainder being decomposed or converted to other products by the oxidizing action of acid used as the reaction medium or the gases contained therein.

The introduction of the fourth and every further bromine atom into the molecule of an aromatic hydrocarbon is normally only achieved under considerably harsher reaction conditions than required for the introduction of the first 3 bromine atoms. Asa consequence, it was to be expected that such harsh conditions wouldbe required for the introduction of 4 or more bromine atoms in one.

process stepin the presence of sulfiur trioxide that more than 50% ofthe; aromatic hydrocarbon to 'be brominated would not be available for production of. the desired bromine derivative because of oxidation. and other side reactions.

In order toprovide a process for the production ofaromatic compounds containing more than 3 bromine atoms in satisfactory yields when carried out on a large commercial scale, it was necessary to find reaction conditions which hinder the previously mentioned side reactions and provide for better utilization of the bromine supplied or respectively reduce the requirements for bromine.

According to theinvention- .aprocess was found for the production of bromine derivatives of aromatic hydrocarbons devoidofcondensed benzene nuclei containingmore than 3 bromine atoms per molecule from the corresponding aromatic hydrocarbons; and bromine in the presence of concentrated sulfuric acid containing free sulfur trioxide. According to the invention the aromatic compound to be bromina-ted and- 1.0 to 1.5g.-atoms (gramatoms) of bromine per g.-atom of hydrogen to be substituted are introduced into concentrated sulfuric acid containing go to 65% by weight offree sulfur trioxide, the quantity of sulfur tri'oxide being sufficient to bind the water produced in the reaction mixture and alsoto reoxidize the HBr produced during the reaction to bromine, and reacted with intensive. mixing at 20 to 150 C.

It is essential for the process according to the invention that the sulfur trioxid'e content of the reaction mixture is at least sufficient to bind the water formed as well as to reoxidize the HBr formed to. bromine. It is only under these special conditions that it is possible to introduce more than 3 bromine atoms in one process step into aromatic com-pounds devoid of condensed benzene nucleiat temperatures between 20' and 150 C. with supply of only 1.0-4.5 g.-atoms of bromine per atom of hydrogen to be substituted.

According to an especially advantageous embodiment of the process according to the invention, the aromatic compound to be brominated is first introduced slowly at temperatures between 20 and C. into a sufficient quantity of concentrated sulfuric acid containing 20 to 65% by weight of sulfur trioxide dissolved therein for the monosulfonation of such aromatic compound. If the aromatic compound to be brominated' does not contain substituents as, for instance, is the ease in benzene, its admixture with the sulfuric acid is preferably effected at a temperature between 60 and 90 C. On the other hand, if the aromatic compound introduced into the sulfuric acid contains substituents which facilitate their sulfonation, as in phenol or toluene, the sulfonation mixture is preferably maintained at a temperature between 20 and 50 C. In the selection of the most favorable temperatures within the ranges given it should be borne in mind that the easier the aromatic compound to be brominated can be converted to its sulfonic acid the lower should be the temperature.

. Evidently the aromatic compound introduced into the concentrated sulfuric acid is first converted into the corresponding monosulfonic acid with liberation of Water. This monosulfonic acid then reacts with the bromine introduced into the reaction mixture to produce the desired bromine derivative and a quantity of HBr equivalent to the substituted hydrogen. The HBr thus produced is reoxidized by a portion of the sulfur trioxide present in the reaction mixture to produce free bromine which again reacts with the aromatic compound.

. The water produced in the monosulfonation of the aromatic compound introduced into the sulfuric acid as well as that produced by the oxidation of the HBr and also the simultaneous reduction of the sulfuric acid concentration by consumption in the monosulfonation normally cause rapid dilution of the sulfuric acid employed as the reaction medium. When concentrated sulfuric acid is employed which does not contain sulfur trioxide, such dilution can be so great that the sulfonation reaction stops by itself as the sulfonation of aromatic compounds can only be effected by sulfuric acid whose concentration is above the specific minimum for the specific aromatic compound concerned. The minimum con centration required for the sulfonation of unsubstituted aromatic compounds is very high but it can be considerably lower for substituted aromatic compounds, depending upon the type of substituent concerned.

a In the sulfonation of aromatic compounds which already contain substituents, the reaction temperature employed may also influence the location of the introduction of the sulfo group. In such instances, it is advantageous for the process according to the invention to employ reaction temperatures for the production of the sulfonation mixtures employed for the bromination which strongly repress or completely hinder the production of m-sulfonic acids.

Small quantities of halogenation catalysts, such as,

for example, iodine, iron, aluminum and the like, which expedite the bromination are added to the sulfonated reaction mixtures thus prepared. However, not more than 5 g. and preferably 0.1 to 5 g. of such catalytically active elements should be added per mol of aromatic compound present in the reaction mixture. Thereafter, the quantity of bromine required and, if desired, a to 50% excess, for the production of the desired bromine derivative containing more than 3 bromine atoms per molecule is slowly dropped into the reaction mixture. The quantity of bromine required is l g.-atom of bromine per 1 g.-atom of hydrogen to be substituted.

. The temperature of the reaction mixture is preferably maintained within the same temperature range as employed in the preparation of the sulfonation mixtures from the concentrated sulfuric acid and the aromatic compound to be brominated until about to 30% of the total amount of bromine to be added has been supplied. During the addition of the remainder of the bromine the temperature of the reaction mixture is raised to 50150 C.

The desired bromine derivative upon bromination of the aromatic compound according to this embodiment of the process according to the invention is obtained in the reaction mixture as an easily filtered solid and is filtered off from the reaction mixture and washed free of sulfate after completion of the reaction. The product thus obtained is very pure and only requires recrystallizati n from appropriate solvents if extremely high purity re quirements must be met.

According to another very advantageous embodiment of the process according to the invention the bromine and the aromatic compound to be brominated can be added sequentially in the order indicated or simultaneously at spaced locations to the free sulfur trioxide containing sulfuric acid, the addition being slow and care being taken that an excess of at least 0.2 g.-atom of bromine per mol of aromatic compound to be brominated already present is maintained and that a temperature of 4570 C. is maintained during the entire reaction.

The quantity of sulfuric acid employed for this em bodiment of the invention should be sufficiently large that the bromine derivative produced remains well sus pended therein. In addition, the quantity of sulfuric acid employed depends upon the quantity of sulfur trioxide required for carrying out the desired bromination dissolved therein as well as its concentration in the sulfuric acid, as there is a certain concentration range of sulfur trioxide in the sulfuric acid for each bromine derivative to be produced from any aromatic compound which causes formation of the desired bromine derivative in an especially short time. This concentration range, as indicated, is specific for each bromine derivative but is easily ascertained by simple preliminary tests. For example, in the production of hexabromobenzene it is advantageous to employ a concentrated sulfuric acid containing 20 to 27% of sulfur trioxide. While the desired bromine derivative would also be obtained with sulfur trioxide concentrations above or below the favorable range indicated the yield would be decreased or the reaction period required increased considerably.

The quantity of sulfur trioxide employed in this embodiment of the process according to the invention should be so selected that the reaction mixture contains about 1 mol of sulfur trioxide and a slight excess for every .g.-atom of hydrogen to be substituted in the aromatic compound employed as the starting material. The sulfur trioxide containing concentrated sulfuric acid required according to the invention can advantageously be prepared by admixing concentrated sulfuric acid and high: percentage oleum as such admixture can be carried out so as to provide a temperature between 45 and C. in the resulting mixture which is especially adapted for the following bromination. It is, of course, also possible to provide the desired solution of sulfur trioxide in con.- centrated sulfuric acid by other means.

Advantageously up to about 5 g. of a halogenation catalyst, such as indicated above, per mol of aromatic compound to be brominated are added to the solution of sulfur trioxide in concentrated sulfuric acid to accelerrate the bromination of the aromatic compound under the conditions employed according to the invention. The entire quantity of bromine to be employed for the production of the desired bromine derivative can then be added to the reaction mixture simultaneously with the aromatic quantity of bromine employed should be 1.0 to 1.5 g.-atom per g.-atom of hydrogen which is to be substituted. Thereafter the aromatic compound to be brominated is added to such mixture maintained at 45 to C. while stirring intensively, the rate of addition being selected that such temperature range can be maintained during the entire reaction with efiicient cooling.

It is also possible at first only to mix a smaller quantity of bromine than that indicated above to the sulfur trioxide and halogenation catalyst containing sulfuric acid reaction mixture and then suplying the remainder required to the reaction mixture simultaneously with the aromatic compound to be brominated but spatially separated therefrom with intensive mixing of the reaction mixture. Also in this case it is advantageous that the temperature of the reaction medium before addition of the aromatic compound to be brominated is adjusted to 45 to 7 and maintained at this temperature during the bromination.

In order that the bromination of an aromatic compound be successfully carried out according to this variation of the process according to the invention a quantity of bromine must be maintained in the reaction mixture which is in excess of that required for the formation of the desired bromine derivative from the aromatic compound already present. This bromine excess should be at least 0.2 g.-atom per mol of aromatic compound supplied during the entire reaction period. Preferably, the starting mixture of sulfur trioxide, catalyst and sulfuric acid is saturated with bromine before introduction of the aromatic compound and such saturation is maintained during the entire reaction period.

The hydrogen bromide produced during the brominationof aromatic compounds according to the invention is practically completely reoxidized to bromine by the sulfur trioxide and sulfuric acid contained in the reaction medium so that it can reenter the bromination reaction. Because of this oxidation reaction which runs simultaneously with the bromination, it is possible to introduce more than 3 bromine atoms into an aromatic compound molecule with the aid of only 1.0 to 1.5 g.-atom of bromine per g.-atom of hydrogen which is to be substituted and the bromine supplied is utilized largely for the formation of the desired bromine derivative. In addition sulfur oxide is formed in such oxidation reaction which substantially accelerates the bromination of the aromatic compound in conjunction with the other catalysts present.

The procedure of introducting the aromatic compound to be brominated into a mixture of sulfuric acid, sulfur trioxide and a halogenation catalyst which already contains bromine leads to immediate initiation of the bromination without first having the sulfonic acid formed. This renders it possible to produce bromine derivatives of aromatic compounds containing more than 3 bromine atoms as substitutents with high yields in the presence of sulfur trioxide containing sulfuric acid already at temperatures of 45-70 (3., whereas the substitution of sul- -fonic acid groups primarily introduced into the aromatic compounds to be brominated, as is known, can only be effected at substantially higher temperatures. This modification of the process according to the invention renders it possible to produce bromine derivatives of aromatic compounds containing more than 3 bromine atoms in short reaction periods and with considerably higher yields than has previously been possible with all other known processes. The bromine derivatives produced are also easily recovered from the reaction mixture and are so pure after thorough washing and drying that they can be used directly for technical purposes.

The following examples will serve to illustrate several embodiments of the invention.

Example 1 had been added and during the addition of the remainder of the bromine it was slowly raised to 150 C. The hexabromobenzene formed was filtered off the reaction mixture and washed with water until sulfate free and dried. The yield of dried product which had a melting point of 315 C. was 200 g. which is 72.5% of the theoretical based on bromine or benzene.

Example 2 A benzene and catalyst containing sulfonation mixture was prepared as in Example 1 at 70 C. Thereafter 312 g. of bromine were slowly dropped in over 6 a period of 16 hours with intensive stirring. The temperature of the reaction mixture was maintained at 70 C. until about g. of the bromine had been added and then slowing raised to C. during the addition of the remainder of the bromine. The hexabromobenzene produced after separation, washing and drying had a melting point of 315 C. The yield was 252 g. which is 91.5% of the theoretical based on benzene and 70.5% based on bromine.

Example 3 A benzene and catalyst containing sulfonation mixture was prepared as inExarnple 1 at 80 C. Thereafter, 312 g. of bromine were slowly dropped in over a period of 11 hours with intensive stirring. The temperature of the reaction mixture was maintained at 80 C. until about 80 g. of bromine had been added and then slowly raised to C. during the addition of the remainder of the bromine. The hexabromobenzene produced after separation, washing and drying had a melting point of 316 C. The yield was 255 g. which is 92.5% of the theoretical based on benzene and 71.2% based on bromine.

Example 4 5 g. of iodine were added to 920 g. of concentrated sulfuric acid and then 93 g. of freshly distilled aniline were stirred into the mixture over a period of 30 minutes. Thereafter, 480 g. .of bromine were dropped into the resulting mixture while stirring intensively over a period of 8 hours. The reaction mixture was maintained at room temperature until 130-432 g. of bromine had been added. During the addition of the remaining bromine 492 g. of oleum containing 65% of sulfur trioxide were simultaneously slowly stirred in and the temperature gradually raised to 50 C.

After completion of the bromination the tetrabromoaniline produced was separated from the reaction mixture and washed with cold water until sulfate free and dried. The yield of dried product which had a melting point of120 C. was 368 g. which is 89% of the them retical based on aniline and 60% based on bromine.

Example 5 5 g. of iodine were added to 920 g. of concentrated sulfuric acid and then 94 g. of phenol were stirred into the mixture over a period of 30 minutes. Thereafter 600 g. of bromine were dropped into the resulting mixture while stirring intensive over a period of 10 hours. The reaction mixture was maintained at room temperature until 110 g. of bromine had been added. During the addition of the remaining bromine 615 g. of oleum containing 65% of sulfur trioxide were simultaneously slowly stirred in and the temperature gradually raised to 110 C.

After completion of the bromination the pentabromophenol produced was separated from the reaction mixture and washed with cold water until sulfate free and dried. The yield of dried product which had a melting point of 312-315 C. was 396 g. which is 81% of the theoretical based on phenol and 53.5% based on bromine.

Example 6 41.5 g. of melted diphenyl were stirred into 389 g. of sulfuric acid containing 48.2% of $0 at a temperature of 70-80" C. over a period of 15 minutes. 1 g. of each of ironand iodine were added to such mixture and then 240 g. of bromine dropped slowly into such mixture over a period of 8 hours while stirring intensively. The temperature of the reaction mixture was'maintained at 80 C. until 48-50 g. of the bromine had been added. During the addition of the remainder of the bromine 142 g. of oleum containing 65% of S0 were added simultaneously and the temperature of the reaction mixture gradually raised to 150 C.

The octabromodiphenyl which was produced after a total reaction period of 9 hours was filtered off from the 7 reaction mixture and washed sulfate free with cold water and dried. The yield of dried product which had a melting point of 365-367 C. was 212 g. which is 100% of the theoretical based on diphenyl and 72% based on bromine.

Example 7 41.5 g. of melted diphenyl were stirred into 389 g. of sulfuric acid containing 48.2% of S at a temperature of 7080 C. over a period of 15 minutes. 1 g. of each of iron and iodine were added to such mixture and then 298 g. of bromine dropped slowly into such mixture over a period of 8 hours while stirring intensively. The temperature of the reaction mixture was maintained at 80 C. until 85 g. of the bromine had been added. During the addition of the remainder of the bromine 214 g. of :oleum containing 65% of S0 were added simultaneously and the temperature of the reaction mixture gradually raised to 150 C.

The decabromodiphenyl which was produced after a total reaction period of 9 hours was filtered off from the reaction mixture and washed sulfate free with cold water and dried. The yield of dried product which had a melting point of 378-379 C. was 212 g. which is 92.5% of the theoretical based on diphenyl and 67% based on bromine.

Example 8 2.5 g of iodine, 2.5 g. of iron and 578 g. of bromine were introduced into 2,200 g. of concentrated sulfuric acid containing 19.4% of S0 dissolved therein. Subsequently 78 g. of benzene were dropped into the mixture over a period of 4060 minutes at a temperature of 60 C. while stirring intensively. Thorough cooling of the reaction mixture was required to maintain the 60 C. temperature. The solid hexabromobenzene produced was filtered off from the reaction mixture, washed with water and dried. The yield of dried hexabromobenzene which had a melting point of 315316 C. was 532 g. which is 96.5% of the theoretical based on benzene and 80.5 based on bromine.

Example 9 2.5 g. of iodine, 2.5 g. of iron and 150 g. of bromine were added to 1,650 g. of concentrated sulfuric acid containing 25.6% of dissolved S0 Subsequently, 422 g. of bromine and 78 g. of benzene were simultaneously dropped int-o such mixture at spaced locations over a period of 80 minutes at 60 C. while stirring intensively. Thorough cooling of the reaction mixture was required to maintain the reaction temperature of 60 C.

The solid hexabromobenzene produced was filtered off from the reaction mixture, washed with water and dried. The yield of dried hexabrornobenzene which had a melting point of 315 C. was 525 g. which is 95% of the theoretical based on benzene and 80% based on bromine.

Example 10 2.5 g. of aluminum chloride, 2.5 g. of iodine and 384 g. of bromine were introduced into 1,219 g. of concentrated sulfuric acid containing of dissolved S0 Subsequently, 78 g. of benzene were dropped into the mixture over a period of 90 minutes at a temperature of 70 C. while stirring intensively. Thorough cooling of the reaction mixture was required to maintain the 70 C. temperature.

The solid tetrabromobenzene produced was filtered off from the reaction mixture, washed with water and dried. The yield of dried tetrabromobenzene which had a melting point 05174" C. was 382 g. which is 97% of the theoretical based on benzene and 79.5% based on bromine.

I claim:

1. A process for the introduction of more than 3 bromine atoms into an aromatic compound having at least 4 replaceable hydrogen atoms and being devoid of condensed benzene nuclei selected from the group consisting of benzene, toluene, phenol, aniline, diphenyl, diphenyl ether, diphenyl methane, triphenyl methane, tetraphenyl methane and their homologues which comprises supplying the aromatic compound to be brominated, a bromination catalyst selected from the group consisting of iodine, iron and aluminum and 1 to 1.5 g.-atoms of bromine for every g.-atom of hydrogen to be substituted in the aromatic compound to a reaction medium of concentrated sulfuric acid containing 20 to 65 by weight of free S0 dissolved therein, the quantity of S0 being sutficient to reoxidize the HBr produced during the bromination to bromine and also sufiicient to bind the water formed in the bromination mixture and reacting the aromatic compound with the bromine in such medium at 20 to 150 C. while mixing intensively.

2. The process of claim 1 in which the aromatic compound to be brominated is first slowly supplied at a temperature between 20 to C. to a quantity of concentrated sulfuric acid containing 20 to 65 by weight of S0 dissolved therein sufficient to effect monosulfonation of such aromatic compound, then introducing 20 to 30% of the bromine required for the bromination into the resulting solution at the same temperature and subsequently introducing the remaining portion of the bromine required while gradually raising the reaction temperature to 50 to C., the bromination catalyst being supplied to the reaction medium prior to the introduction of bromine.

3. The process of claim 1 in which at least a portion of the bromine required for the bromination is first introduced into the concentrated sulfuric acid containing the free S0 and also containing the bromination catalyst and the aromatic compound to be brominated and any remaining portion of the bromine required is then slowly supplied thereto at spaced locations while maintaining at least a 0.2 g.-atom excess of bromine per mol of aromatic compound already present in the reaction mixture until the end of the bromination reaction and maintaining a temperature between 45 and 70 C. during the entire reaction.

4. The process of claim 1 in which the bromine and the aromatic compound to be brominated are introduced simultaneously but at spaced locations into the concentrate containing the free S0 and also containing the bromination catalyst while stirring intensively and maintaining at least a 0.02 g.-atom excess of bromine per mol of aromatic compound already present in the reaction mixture until the end of the bromination reaction and maintaining a temperature between 45 and 70 C.

References Cited by the Examiner UNITED STATES PATENTS 2,452,154 10/1948 Ross 260-650 FOREIGN PATENTS 641,102 4/ 1927 France.

OTHER REFERENCES Datta et al., J.A.C.S. 43, pp. 303-313 (1921).

Eckert et al., Monatshefte fur Chemie, Bd. 36, s. 279 (1915 Huston et al., J.A.C.S. 55, pp. 3880 (1933).

LEON ZITVER, Primary Examiner.

I. W. WILLIAMS, K. H. JOHNSON, K. V. ROCKEY,

Assistant Examiners.

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US7378449Oct 23, 2006May 27, 2008Albemarle CorporationPoly(bromoaryl)alkane additives and methods for their preparation and use
US7776289Aug 17, 2010Chemtura CorporationMethod and apparatus for producing decabromodiphenyl alkanes
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Classifications
U.S. Classification552/101, 568/776, 570/206, 568/639, 564/412
International ClassificationC07C37/62, C07B39/00, C07C17/12
Cooperative ClassificationC07C17/12, C07B39/00, C07C37/62, C07C209/74
European ClassificationC07C17/12, C07C37/62, C07B39/00