DE3117481A1 - Process for perbrominating phenol and diphenyl ether - Google Patents

Abstract

A process for perbrominating phenol and diphenyl ether by brominating the corresponding compound in bromine as the only reaction medium using metal and metal-containing catalysts at an elevated starting temperature of at least about 35 DEG C, preferably at least about 45 DEG C, increases the productivity of the reaction considerably without disadvantageously affecting the product yield or quality.

Description

description

The invention relates generally to a method of perbromination of phenol and diphenyl ether by brominating the appropriate compounds in a Temperature above 350C in bromine as the only reaction medium in the presence of selected ones Catalysts.

In the past, there have been numerous methods of replacing all nuclear hydrogen atoms in aromatic compounds such as diphenyl ether and the like. None this procedure has proven completely successful; all showed disadvantages.

Conventional perbromination processes generally used up to about 20% excess bromine in the presence of a wide variety of reaction media and Solvents such as dibromoethylene, carbon tetrachloride, chloroform, methylene bromide, Tetrachloroacetylene and the like. Depending on the particular to be brominated aromatic compound used. The perbromination of aromatic compounds also became more fuming in reaction media such as oleum, concentrated sulfuric acid Sulfuric acid, liquid sulfur dioxide and the like. Performed.

Each of these process solutions has serious disadvantages for the perbromination, especially for commercial Operation. The use of halogenated organic solvent has disadvantages, including low productivities, undesirable low reaction rates and the necessary: since the recovery of the Solvent for reuse. In some cases this technique leads to Introducing a small but substantial amount of chlorine into the final product, thereby creating the product quality is limited. It also experiences a number of non-condensed aromatic compounds under slightly halogenated organic solvents conditions to be used do not perform perbromination in a satisfactory manner.

Disadvantages of using oleum as a reaction medium include along with all of the usual problems associated with its large-scale handling the necessary use of large volumes, which reduces reactor productivity, there are difficulties in product isolation, in removing large volumes Sulfuric acid and finally products of poor quality due to the presence sulfur-containing impurities such as brominated benzenesulfonic acids. This latter The pollution problem also occurs when using liquid sulfur dioxide as a reaction medium.

The given difficulties with a perbromination in Large scale are linked by various exotic ones, for hexabromobenzene suggested synthesis solutions illustrated. For example, ie describes chemical Literature the pyrolysis of Octabromcyclohexeno en and the implementation of hexabromocyclopentadiene with tribromoacetaldehyde at superatmospheric pressure and greatly increased temperatures.

Another way of making hexabromobenzene and others Perbrominated aromatic compounds was the use of bromine / chlorine mixtures'als Brominating agents.

This method suffers from the serious drawback of introduction small but substantial amounts of chlorine in the end products, what ultimately theirs Final quality limited.

Yet another process that is used for aromatic polybromination Connections has been described requires the use of powerful mechanical Mixer for partially brominated, solid intermediates in a liquid or liquid to keep vaporous bromine in a sufficiently fine state of division, so as to try to achieve high degrees of bromination.

It has also been suggested that fully brominated derivatives be more aromatic Compounds with one or more phenyl groups by using bromine as Solvent (100% of the excess or more) and a bromine transfer catalyst at relatively low reaction temperatures of about 100 ° C. to room temperature (i.e., about 20-25 "C). A similar procedure was used to perform ring bromination aromatic compounds using a minimum excess of 20% bromine in the presence of halogenation catalysts at room temperature (20 to 250C). Although these processes perbrominated until they were terminated To obtain products in good yield could only have such results is achieved with the acceptance of economic losses. As a result, lower Reactor bromination temperatures occur. Inadequacies make the application such processes are even less desirable on a commercial scale.

The aim of the invention is therefore the production of pentabromophenol and decabromodiphenyl ether in high yield and purity after a relative simple implementation using excess bromine both as a reaction component as well as the sole reaction medium. Perbrominated compounds should also be used of the type described, essentially free of less brominated products will.

There should be at least a 75% excess of bromine over the stoichiometric Amount to be used for the perbromination. Finally, the perbromination should of the type described can be carried out at elevated temperatures in order to increase productivity of the system per volume unit and time unit to increase considerably without reducing the product yield and quality.

These and other objects, advantages and features of the invention can be made with practically perbrominated phenol and diphenyl ether by implementing Phenol or diphenyl ether in the case of increased Starting reaction temperature of about 35 to about 80 ° C. in the presence of at least one about 75% excess and no more than about 400% excess of the stoichiometric Amount of bromine and a small but catalytically effective amount of a catalyst from the group of iron, iron halides, iron compounds under the reaction conditions Form iron bromide, aluminum, aluminum halides and aluminum compounds that form aluminum bromide under the reaction conditions and continue the reaction at an elevated temperature of about 35 to about 80 ° C. after the addition of the reaction components has ended while maintaining the bromine excess for practically complete perbromination the aromatic compound.

Fig. 1 is a diagram that demonstrates how critical the minimum bromination temperature is of 35 "C in the case of perbromination of diphenyl ether; Fig. 2 is a diagram showing this demonstrates how critical the minimum bromination temperature of 350C in the case the perbromination of phenol.

According to the invention, practically perbrominated phenol and perbrominated phenol can be used Diphenyl ether by reacting such a compound in the presence of a significant Excess bromine both as a reaction component and as the only reaction medium can be obtained. Desirably the bromine is in an excess of at least 75% but not more than about 400 8, present.

The reaction takes place in the presence of a .leinen, but catalytically effective amount of a bromination catalyst containing iron and aluminum, their halides and vials, which under the reaction conditions are iron or aluminum bromide form, may include.

According to the invention it is particularly important that the conversion at increased Starting reaction temperature takes place. The bromine reaction medium should be on a Temperature of at least about 350C and preferably at least about 45 to about 800C before starting the addition of the phenol or the diphenyl ether will. The reaction medium is used throughout the addition of the aromatic compound held at such an elevated reaction temperature even after the addition of the Phenol or diphenyl ether, preferably at reflux, while maintaining of the bromine overc: husses.

The bromination of diphenyl ether and phenyl using Excess bromine as reaction medium proceeds much faster than the bromination using an excess of bromine at room temperature or lower temperatures, and yet product yield and quality remain compromised. The response time is even shorter compared to reactions between molar equivalents or even with the usual small excess of bromine of up to 20% and an ol ionic Brominating solvents.

Isolation and purification of the perbrominated, in the invention Products obtained from the bromine reaction medium can be done in a number of ways, and the steps required are much easier and simpler than for after products manufactured using conventional methods and also deliver higher yields of purer and more uniform products.

Through the use of bromine as a reaction medium and the application elevated reaction temperatures are essentially quantitative yields of the Perbrominated products with only very small amounts of less brominated materials obtain.

The perbromination carried out according to the method according to the invention in bromine, when either fresh material is used, the desired organic takes place Starting reaction component or mixtures of the lower brominated by-products, which may have been obtained in previous reactions as starting materials in essentially identical fashion with essentially the same results. So are e.g. when using either fresh diphenyl ether or partially brominated Diphenyl ethers as the starting reaction components give practically the same results achieved. In some cases, these by-products are preferably an Ar distillation or subjected to other cleaning prior to reuse.

Although the exact percentage of excess bromine compared to the required stoichiometric amount that is used as the reaction medium, Not critical, have bromine excesses of about 75% and up to and over 300 and up to 400% proved necessary. About 100 to 200% excess have become proved to be optimal and preferred for the perbromination of phenol and diphenyl ether.

The bromination in a large excess of bromine in the range of about 100 to 200% excess gives homoc: nere and more highly brominated reaction products, while with VE use lower bromine excesses (i.e. less than 75% oil soot) slower response rates, longer response times and lumpy and more or less impure reaction products, which are less brominated material contain (i.e. incomplete bromination) are the result.

Typical experiments that make use of the method according to the invention, can be made using both "dry" bromine (i.e. common bromine with up to about 15 ppm, water) and so-called "wet" bromine (i.e. bromine with more lls about 15 ppm water). The so-called dry bromine is used in preferably used for carrying out the bromination reactions (i.e. as a brominating agent and single reaction medium). With wet bromine, several disadvantages have been found Influences on the implementation shown.

rrie implementation is much slower when using wet bromine being, the degree of slowdown more or less directly related to the existing Related to the amount of water. Also, the reaction products are themselves after prolonged reaction time can be obtained, more or less underbrominated (i.e., not all available nuclear hydrogen atoms are replaced by bromine), whereby the The extent of the exchange depends more or less on the amount of water available.

The presence of water also increases the amount needed Bromination catalyst well beyond the normally optimal amounts.

As noted, is an essential parameter of the invention Process that the bromination reaction of phenol or diphenyl ether using excess bromine as the reaction medium at elevated temperatures, well above room temperature (i.e. 20 to 250C) temperatures are started; i.e., the implementation will at temperatures above about 350C up to about 800C, preferably at one Temperature started from about 45 up to about 600cm.

After the addition of the phenol or diphenyl ether is complete, the temperature can advantageously increased to reflux during later stages of bromination will. In the case of the perbromination of phenol, reflux temperatures are typical.

observed from 60 to 64 "C, while in the case of perbromination from Diphenyl ether reflux occurs at about 59-60C.

Considerable advantages accrue from the use of increased starting reaction temperatures, as high as practical within the specified range. The solubility of the Products and / or the partially brominated intermediate stages value through the work higher temperatures, which are significantly above room temperature, significantly increased. This solubility-increasing effect provides products with better analysis in any given response time, which leads to higher plant productivity. Around thus the completion of the perbromination reaction with the highest power level ensure it is desirable to use reaction mixture temperatures that as high as permissible by the composition of the reaction mixture, which are dependent on the boiling point of the bromine contained therein considerably depends on the mixture composition can exceed and in some cases even be 800C or above where above atmospheric Pressures are applied.

Working at temperatures in the upper part of this range achieved, including higher yields in connection with better analyzes of the desired products. Surprisingly, the implementation at elevated starting reaction temperatures can be carried out successfully without Adversely affect the desired goals of product quality.

In suitably designed production facilities that operate at temperatures operating above 35 "C, preferably at about 45 to 55" C, i ;; t the bromination cycle reduced, the product analysis better, the reactor productivity per unit of time considerably increased and a significant commercial advantage achieved. If desired, can Perbromination even at temperatures well above the boiling point of the mixture done by applying superatmospheric pressure.

E.ne reaction time of 1 to 100 h in total, mainly fromE: awesome of the organic reaction component, al .: has been found to be adequate for the full Implementation under the conditions according to the invention proved to be the starting materials q: to convert antitatively into perbrominated products in which practically all are replaceable Nuclear hydrogen atoms have been replaced by bromine, by using of bromine as the only reaction medium (perbromination). That length of time became complete has been used satisfactorily for both laboratory and larger scale approaches. In general, a total action time of up to 20 hours has proven to be sufficient for the product.sn high yields of high quality products in the experiments carried out shown. In some cases, the perbromination turns out to be in three hours or more less completed.

The duration of the addition of the aromatic compound is in no way critical. Desirably, the addition of the aromatic compound is sufficient low speed to minimize the loss of reaction components overhead to hold and the desired elevated reaction temperature below To be able to keep control and safe conditions.

The order in which the reaction components are added (i.e. the aromatic, the compound to be brominated and the bromine) can be varied somewhat as desired, and no method appears to be inappropriately critical. However, to get the full To achieve advantages of the invention for the preparation of the perbrominated compounds, should be the required excess bromine in the reactor during the latter stages the bromination may be present. For best results, the stoichiometric Excess of 75 to 400% bromine, preferably during the last half of the reaction time be present.

The more common and preferred mode of operation is slow addition of phenol or diphenyl ether to excess bromine, which is used as the reaction medium as well acts as a brominating agent, whereby the temperature to the desired value through Cooling or heating, as required, is regulated. However, it is desirable add the aromatic compound feed slowly enough to cause the Loss of bromine, volatile reaction products and lower brominated intermediates to be kept to a minimum overhead.

A modification of the above preferred embodiment of FIG Adding the aromatic compound to the whole Bromine loading can also be used advantageously to increase reactor productivity. The variation is to initially put some of the total bromine in the reactor to give and then to add the aromatic compound described above. With advancing Bromination decreases the volume of the reaction mass, and when this decrease occurs, the remainder of the total excess bromine is added.

The method according to the invention can also be carried out in such a way that the bromine is added to the phenol or diphenyl ether, preferably in liquid form will. An advantage of this addition method is that the bromine is in the reaction mixture is introduced when it reacts, which also reduced to a reaction mixture Volume and thus leads to increased productivity. A disadvantage of this way of working is that a relatively large amount of the reactant is bromine and the bromination reaction is much more difficult to control. In order to the possibility of overheating the reaction mixture is considerably greater compared to the other methods of contacting the reactants. This can, if not is controlled, to a loss of bromine, organic reaction component and run volatile, brominated products upside down. Another disadvantage is that that the reaction mixture can go through a solid or semi-solid state, causing difficulty in stirring.

As noted, the inventive method of bromination in Bromine is advantageously used as starting materials for phenol or diphenyl ether will.

A number of different forms of metal-containing catalysts are available been tested. The catalysts which have been found to be most effective are based either iron or aluminum as a metal component. Have proven to be useful e.g. metallic iron, iron bromide, iron chloride. metallic aluminum, aluminum chloride and aluminum brol.id.

Iron and iron compounds, which under dez reaction conditions iron bromide form, have become the catalysts of choice for the production of pentabromophenol by brominating phenol in a bromine reaction medium. bo provides iron powder as a catalyst, the highest yield of perbrominated product with the highest analytical values. The iron powder also remains active during the entire bromination period.

Iron bromide (iron (III) bromide) and iron chloride (iron (III) chloride) have also shown themselves to be quite satisfactory.

Iron (III) bromide appears to initiate bromination a little faster than To yield iron powder. However, it has the disadvantage of delivering products that do something show lower analytical values for the desired product. Ferric chloride as a catalyst was slightly less effective than iron powder and iron bromide and can Deliver perbiomized products that are slightly contaminated with chlorine. Aluminum chloride was somewhat less active than iron and produced products with somewhat lower analytical values. It also tends to be inactivated more quickly than iron in the course of bromination, what the introduction of additional parts of the catalyst during the conversion period (the Bromination) makes necessary. However, aluminum chloride has the advantage that it is colorless and therefore does not add color to the products. For perbrominated finished products, whose purity requirements are not exactly chemical purity allows their use the omission of a purification stage or at least one of aluminum chloride simplified cleaning.

Aluminum and aluminum compounds under the bromination reaction conditions Forming aluminum bromide have proven to be the catalysts of choice for the production of Decabromodiphenyl ether proved by bromination in a bromine reaction medium. Aluminum metal, e.g. in the form of foil or powder, which presumably under the reaction conditions is rapidly converted to aluminum bromide has been found to be an effective catalyst for proved the bromination process. Often, however, it has been found to be more convenient to use finished, anhydrous aluminum bromide or aluminum chloride as a catalyst. In some of these cases, aluminum bromide or aluminum chloride leads to something more rapid Brominations and / or more complete perbrominations when used as catalysts for the Bromination. Another benefit for aluminum, aluminum halides and aluminum compounds which under the bromination reaction conditions are aluminum bromide is that these types of catalysts are colorless and the end products are none Give color if they remain in it, so that in the end products for which the Purity requirements are not those of chemical purity that use omitting or simplifying the purification stage of aluminum compounds enables. Metallic iron, iron halides and compounds under reaction conditions Forming iron halides can also be used in the perbromination of diphenyl ether will.

The required amount of catalyst, i.e. iron, iron compound, Aluminum or aluminum compound, calculated as metal, has proven to be very small, but has been found to be catalytically effective for the perbromination and can be between about 0.1 and about 10 percent metal based on the weight of the organic substrate as a reaction component, fluctuate.

Amounts of catalyst up to 15% by weight or more, based on the metal, are considered satisfactory but economically impractical. It however, it has been shown that within the above limits, relatively large Amounts of metal catalyst required under certain specific conditions for example, when "wet" (i.e., hydrous) bromine is used. Large quantities Catalyst can used where aluminum and iron halides can be added as a catalytic material.

The from the inventive method using bromine as a perbromination reaction medium and using an elevated initial reaction temperature Originating reaction mixtures can be worked up by a number of work-up methods to isolate the perbrominated products. The crude reaction mixture that the brominated products, excess bromine reaction medium and excess Catalyst may, for example, either at atmospheric pressure or preferably stripped off under reduced pressure at about 80 ° C. to constant weight of the residue will.

The crude product so isolated can be further purified, e.g.

by digestion with methanol, dibromoethylene or dilute hydrochloric acid. This peel isolation is quick, easy, and provides reliable yield data and relatively pure product. It has the disadvantage that it contains metal-containing residual catalyst can leave behind in the product.

The perbromination product can also become excess due to displacement Bromine in the reaction mixture through water and then filtering the aqueous Reaction mixture are isolated. The crude product obtained can then by proportionately simple digestion processes as described above can be purified. This isolation can pose manufacturing and / or engineering problems on a large scale.

The excess bromine in the reaction mixture can also be replaced by dibromoethylene displaced and then filtered. The crude product can then be digested, can be further cleaned as described above.

In a preferred embodiment of the isolation step transferred the entire reaction mixture into hot, acidified water, whereby the Excess Brcn is volatilized and the aqueous mixture is filtered. Clean by digestion with suitable organic solvents, as above described. When performing this procedure, the excess evaporates Bromine almost immediately after contact with the hot water, which causes the solid, Perbrominated product particles disintegrate, which increases their effective contact surface, residual catalyst dissolves. When the bromine is completely removed, will the crude reaction product is isolated by filtration.

This method has numerous advantages. This includes removal the greater proportion of the residual catalyst and the easy removal of the excess Broms can be reused after drying.

The latter isolation level can also be modified, whereby Isolation and cleaning are essentially combined. The aqueous Product not filtered, but not directly with one with water Miscible organic solvents brought together. The product enriches itself in the organic phase, from which the aqueous phase is then removed, whereby the catalyst is separated from the product. The product can then be made from the organic Phase can be isolated and purified according to known measures.

In general, organic solvents are used to isolate, Digestion and / or purification can be used, for example the low molecular weight Alkanols such as methanol, methanol, the propanols and butanols, low molecular weight halogenated Compounds such as dibromoethylene, chlorobenzene, chloroform, acetylene tetrachloride and Carbon tetrachloride, as well as ketones such as acetone, and other suitable solvents.

Perbrominated products resulting from the application of this bromination in bromine are decabromodiphenyl ether and pentabromophenol.

It is generally possible to predict the products that will be used when of the perbromination process under optimal reaction conditions to any special starting material is created. The general rule is that every nucleus has a hydrogen atom is replaced by a bromine atom when the reaction is carried to completion, i.e., until the evolution of hydrogen bromide has ceased. This degree of bromination can by suitable adjustment of the reaction temperature and the catalyst concentration and the response time can be achieved. The perbromination process will be continued until until the sampling shows that the desired degree of bromination has been reached. or the bromination reaction can continue until the evolution of hydrogen bromide has practically stopped. The continuation of the bromination and the extension of the reaction time It serves no useful purpose beyond the point of bromination desired and in some cases can lead to decomposition of products, fragmentation of the organic materials and the formation of tarry or resinous by-products to lead.

Among the advantages of the bromination process according to the invention The achievement of practically quantitative yields is more crude at elevated temperature Perbrominated products of relatively high purity. The very small amounts of impurities that may be present are metal catalysts and catalytic Metal compounds and tiny amounts of lower brominated products of the organic Reaction component, if desired, as reaction components for further Perbromization can be traced back.

Surprisingly, the benefits of starting the reaction are at elevated temperatures, as disclosed here, quite specific for phenol and diphenyl ethers, and similar benefits are seen with other non-condensed aromatics such as toluene and xylenes, not observed.

The process shows high productivity (i.e. a large amount of product per unit used reactor volume).

It has also been shown that the process perbrominated the easy production Phenol and diphenyl ethers made possible, which were previously not commercially viable or only after more difficult unc / or more complicated synthesis methods and with special plants was possible. The reaction conditions used in practicing the invention are relatively mild and only require simple installation, which is essential which means economic and safety factors in system operation. Lie bromination reactions run much faster when bromine is the reaction medium compared to the Speed when other solvents are used, both organic oil also inorganic, such as fuming sulfuric acid.

As both the heat resistance and the color of the perbrominated Products are essential factors for flame retardants, the production provides these perbrominated derivatives in a relatively pure state have great advantages for their end use in flame retardants. The accessibility and purity of the Products is also suitable for their use as chemical intermediates for example important for the production of possible pesticides and pharmaceuticals.

Any partially brominated by-products that can be formed are light recoverable and become complete perbromination in the same Process and the same plant.

Processing, isolation and cleaning processes are manifold flexible. As described here, in combination with the disclosed increased rubs Starting from the reaction temperature, a number of process measures which can be varied can, when the reaction components are brought together, the bromine reaction medium and the catalysts, or when isolating the products and cleaning the products, suitable combinations lead to good results.

The following examples only illustrate that according to the invention Methods and in no way are it intended to limit the invention to the particulars described herein Restrict features.

Example 1 Decabromodiphenyl Ether A one liter, four neck, round bottom flask was made with a: mechanical stirrer, a double-walled reflux condenser, a sampling tube, Thermometer and a reagent addition tube. The flask was about a Water trap vented to collect hydrogen bromide as a by-product. 1164 grams of bromine (7.26 moles, 150% total excess) were added to the reaction flask brought, then 250 mg (0.0093 mol) aluminum of a particle size corresponding to a clear Screen mesh size of 0.84 mm (20 mesh). The mixture was stirred for 15 min the aluminum has been completely converted to aluminum bromide.

The container temperature was set to + 10C by a Therm-O-Watch temperature controller (Model L7 / 800 from Instruments for Research and Industry, Cheltenham, PA. 19012) controlled in connection with a Jack-O-Matic (model JOM-3).

The bromine / catalyst mixture in the container was heated to 350C, and it became with the addition of 49.5 g (0.29 mol) of diphenyl ether at constant rate started via an injection pump for about 51 minutes. The reaction temperature was held at 35 + 10C during the entire diphenyl ether addition.

When the addition of diphenyl ether was complete, heating was continued and the reaction temperature increased increased to about 590C within about 20 minutes. After about 120 minutes of heating after the Addition, 300 ml of water were added to the reaction slurry, the reflux condenser, the The sampling tube and reagent addition tube were removed.

A distillation head with a thermometer, a condenser and a receiver were attached to a flask joint, and excess bromine was distilled off, until a temperature of 1000C has been reached.

Decabromodiphenyl ether was filtered off from the aqueous slurry, with water washed and dried in a forced air oven at 1100C.

Vapor phase chromatographic analysis of the product obtained showed 94.7% in area for decabromodiphenyl ether, a total of 4.5 * for the nonabromodiphenyl ether isomers and a total of 0.5% for the octabromodiphenyl ether isomers.

Example 2 Decabromodiphenyl Ether The procedure of Example 1 was repeated except that the bromine / catalyst mixture was set to a temperature heated by 45 + 10C before the start of the diphenyl ether addition and this temperature was maintained during the addition.

Gas chromatographic analysis of the product obtained showed an area for decabromodiphenyl ether of 96.4%, for nonabromodiphenyl ether of 3.2% and for octabromodiphenyl ether of 0.4%.

Example 3 Decabromodiphenyl Ether The procedure of Example 1 was repeated except that the initial temperature of the bromine / catalyst mixture increased to 55 + 10C before the addition of the diphenyl ether and at this temperature was held until the addition of the diphenyl ether was completed. About 5 min after the application of heat after the addition, the reflux temperature of 590C was reached.

Gas chromatographic analysis of the product obtained showed 96.3 % Decabromodiphenyl ether, 3.3% nonabromodiphenyl ether and 0.3% octabromodiphenyl ether.

Example 4 Pentabromophenol The bromination of the phenol was carried out in a reaction vessel consisting of a reaction flask equipped with a Adding funnel, stirrer, thermometer and a water-cooled condenser that comes with a Waterfall was connected. In the reaction flask was 1198.7 g (7.5 mol, 150% strength Excess) bromine and 0.57 g iron powder brought. phenol (56.7 g, 0.6 mol) was added dropwise from the dropping funnel with stirring over 100 min. While during this time the reaction temperature was controlled to about 46-470C.

After the addition of phenol was complete, the reaction mixture was brought to reflux temperature (about 60-640C) and the reaction was allowed to continue until development heard from HBr.

The total reaction time was 3 hours.

The reaction mixture was cooled to about 50 "C and poured into 328 ml of aqueous Hydrobromic acid transferred. The excess bromine was under atmospheric pressure distilled out over about 2.5 h. The suspension was cooled to room temperature, filtered and the solid reaction product washed with water and dried. That The crude product was in the form of a cream-colored solid, m.p. 229.90C (Lit. 229.50C) obtained with a gas chromatographic analysis of 99.6%.

The yield of the crude product was practically quantitative.

Test evaluation To determine the influence of temperature the addition of diphenyl ether on the reaction productivity and the decabromodiphenyl ether yield and quality, an investigation was carried out. The test results were by recording the gas chromatographic area in% for brominated product as a function of the temperature of the diphenyl ether Addition and reflux time obtained after the addition.

In the preparations described in Examples 1 to 3 were Reaction mixture samples at the end of the diphenyl ether addition, after 15, 45, 75 and 120 min taken from the diphenyl ether addition.

The samples taken were analyzed by gas chromatography at least 1 g each in dibromomethane or dibromomethane in a ratio of 1 g sample dissolved in 40 ml solvent and an HP 5754 device with flame ionization detector and a glass column ID X 2 mm in diameter and 1.22 m (4 feet) long programmed with 3 8 Dexsil 300 on 100/120 mesh Supelcoport, at a temperature of 200-3400C at 100C / min.

For comparison purposes, similar runs were made at diphenyl ether addition temperatures from + 15 "C or -1 ° C and + 250C or -10C, taking samples in the same Were removed and analyzed at intervals after the addition.

Table I lists the decabromodiphenyl ether analyzes (gas chromatographic Area percent) as a function of the diphenyl ether addition temperature and the reflux time after adding on: Table I output temp. 150C 250C 35 "C 45'C 55" C the diphenyl ether addition time after diphenyl decabromodiphen.läther, ether addition (min) gas chromatographic analysis (area%) 0 31.9 35.5 83.4 86.9 87.2 15 73.0 75.5 92.8 95.2 95.1 45 90.5 92.2 93.8 95.6 95.7 75 92.8 93.2 94.1 95.4 96.2 120 94.1 94.6 94.7 96.4 96.3 The data in Table I show that at room temperatures of 15 and 25 "C of the diphenyl ether addition, an undesirably low rate of product formation what can be observed is what requires a full 2 hours of reflux after the addition to achieve the desired to obtain at least 94% decabromodiphenyl ether. In sharp contrast were for reactions performed at 45 and 550C; results essentially identical achieved, with the analysis content of 95% after only 15 min reflux (i.e. after 1/8 of the time).

At a temperature of 350C for the diphenyl ether addition (corresponding to the minimum addition temperature that can be used, taking advantage of the invention obtain we den) a slightly longer time is required (approx 75 min), over still significantly shorter than the 2 h in the case of room temperature approaches required are.

The data of Table I are plotted in FIG. 1 and show in FIG graphical form the rate of formation of the decab omdiphenylether as a function the diphenyl ether addition temperature and the reflux time after the addition. The curves fü; - 45 and 55 "C are identical and show the high speed of product formation, which occurs at such reaction temperatures. The curve for 350C describes a slightly slower reaction, which is nevertheless considerably faster than the unacceptable one low speeds, which result when the diphenyl ether is added under ambient conditions or below (i.e. at 15 and 250C).

By applying the increased starting reaction temperatures according to of the invention in the perbromination of diphenyl ether, heating after the Addition can be reduced by 75% or more without compromising product yield or quality adversely affecting the usability of the implementation and productivity can be increased significantly.

Another investigation shows that the advantages of the working method can be achieved very selectively at high temperature. At 25, 35, 45 and 550C respectively for phenol, toluene and Approaches carried out with p-xylene do not show only that it is highly desirable to use phenol at elevated starting temperatures to perbrominate, but also that it is undesirable to do so in the cases of toluene and do p-xylene.

The following general procedure was used for each approach: The substrate to be brominated (toluene, p-xylene and phenol) became an excess of bromine (300% compared to the amount theoretically required for ring perbromination) and iron catalyst (1% w / w based on substrate) at the respective temperature (25, 35, 45 and 55 "C) was added dropwise over 1 h. When the substrate addition was complete, the reaction mixture was stirred at the stated temperature for a further 2 hours.

Sampling from the reaction mixture for gas chromatographic Analysis took place immediately after the addition of substrate (0 min) and 15, 45, 75 and 120 min afterwards.

The results of these approaches are summarized as follows: Im In the case of pentabromophenol, the increased initial reaction temperature was found to be extremely beneficial.

The highest analysis value (99.4%) of the desired perbrominated product was obtained at the highest reaction temperature of 55 "C. At the highest temperature the reaction was also the fastest. The data observed with the phenol batches are listed in Table II, and this data is also plotted in Fig. 2, which shows the rate of formation for pentabromophenol.

Table II Phenol addition exit temperature 250C 350C 450C 550C Time after pentabromophenol, phenol addition gas chromatography (min) analysis (area%) 0 60.6 82.6 88.0 88.3 15 79.5 93.4 95.5 98.2 45 93.2 98.6 99.0 99.3 75 97.5 98.9 99.2 99.3 120 98.5 99.2 99.2 99.4 As these data show, at starting temperatures corresponding to the ambient temperature (250C) an undesirably slow formation rate observed for pentabromophenol. At this starting temperature a duration of Required 2 hours after the addition to achieve a product analysis of 98.5%.

A significantly shorter heating time after the addition (35-45 min) If the reaction is started at 35 and 450C, it is only necessary about 30 to 40 % of the time required at room temperature. At an initial temperature of 55 "C are only 15 min heating after addition, i.e. 1/8 of the corresponding time for room temperature, required to achieve a 98.2% product analysis.

These findings are graphically illustrated in Fig. 2, which shows that the approaches at elevated temperature (35, 45 and 550C) are significant as a group differ from the approach at room temperature (250C).

Tables III and IV contain the data for the runs with toluene and p-xylene. In each case they show that, unlike diphenyl ether and phenol, the highest analysis values are obtained at room temperature (i.e. 250C) and the increased Starting reaction temperatures actually have a detrimental effect on the implementation to have.

Table III Starting temperature for the addition of toluene: 25 OC 350C 45 "C 550C time after addition of toluene (min) pentabromotoluene, analysis by gas chromatography (Area%) 0 94.0 88.2 84.6 84.3 15 91.0 90.2 85.7 84.5 45 92.5 91.0 84.8 86.7 75 93.0 90.9 87.3 87.7 120 93.0 91.7 85.1 88.0 Table IV Starting temperature for p-xylene addition 250C 350C 450C 550C time after p-xylene-tetrabromo-p-xylene, addition (min) gas chromatographic analysis (area%) 0 91.1 93.0 91.5 90.1 15 94.8 92.9 91.1 90.9 45 95.6 93.3 91.9 91.1 75 95.4 93.6 93.0 92.0 120- 95.7 93.9 93.9 92.1 As the above data shows, it is unique to diphenyl ether and phenol among the evaluated non-condensed aromatic compounds with regard to the Product yield and plant productivity extremely beneficial, increased starting reaction temperatures apply (i.e. 35 "C or above), the room conditions (i.e. about 25" C or below) exceed significantly.

Claims (4)

Process for perbrominating phenol and diphenyl ether Claims Process for perbrominating an aromatic compound from the phenol group and diphenyl ether, characterized in that the aromatic compound at increased Starting temperature of about 35 to about 550C to a mixture of at least one 75% excess and no more than about 400% excess of the stoichiometric Amount of bromine and a small but catalytically effective amount of a catalyst from the group iron, iron halides, iron compounds, the iron bromides among Form reaction conditions, aluminum, aluminum halides and aluminum compounds, which form aluminum bromide under the reaction conditions, given and the implementation at an elevated temperature, at which point after the addition of the aromatic compound has ended Reflux can occur, is continued, the bromine excess to practically complete Perbromination of the aromatic compound is maintained. 2. The method according to claim 1, wherein the implementation initially at a Temperature of about 45 to about 550C is controlled. 3. The method according to claim 1, characterized in that it is at a Excess bromine from about 100 to about 200% of the stoichiometric amount for perbromination the aromatic compound is carried out. 4. The method according to any one of the preceding claims, characterized in that that it is in the presence of an amount of catalyst from about 0.1 to about 10% by weight on the metal equivalent weight, relative to the amount of aromatic compound, is carried out.