JP2003012573A - Method for producing 4,4'-dibromobiphenyl - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing 4,4'-dibromobiphenyl in high yield. SOLUTION: This method for producing 4,4'-dibromobiphenyl is characterized by reacting biphenyl with bromine in a reaction solvent, depositing the resultant crude 4,4'-dibromobiphenyl as a crude crystal in the reaction solvent, heating and cooling slurry containing the crude crystal and recrystallizing 4,4'- dibromobiphenyl to obtain a pure crystal. Since the separated liquid (mother liquor) after depositing the pure crystal does not require a well-known purification, etc., and the liquid can be reused as the solvent for reaction of biphenyl with bromine, the production method simplifies treating operation and is excellent in production efficiency.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing 4,4′-dibromobiphenyl, and more particularly, to reacting bromine with biphenyl in a reaction solvent to produce crude crystals of 4,4′-dibromobiphenyl. Then, the slurry containing the crude crystals is then recrystallized by heating and cooling the slurry without separating 4,4′-dibromobiphenyl from the slurry.
The present invention relates to a method for producing 4,4'-dibromobiphenyl having a simplified production procedure for obtaining pure crystals of 4'-dibromobiphenyl.

[0002]

2. Description of the Related Art 4,4'-Dibromobiphenyl can be hydrolyzed to 4,4'-dihydroxybiphenyl or further oxidized to 4,4'-dicarboxybiphenyl. The compound is useful as an oxidation stabilizer of a resin, a dye intermediate, and a raw material for producing a resin such as polyester, polyepoxide, polyurethane and polycarbonate, and is used for a copolymer such as organic silicon and an oxide film. In addition, N, N, N ′, N′-obtained by reacting 4,4′-dibromobiphenyl with a secondary amine
Tetraphenylbenzidine can be used as a starting compound for organic electroluminescence and the like. Furthermore, 4,
Insect growth regulator ethyl-4- (isopropylphenyl) benzoate can be produced from 4'-dibromobiphenyl, and 4,4'-dibromobiphenyl is a pesticide.
It is a highly useful compound related to polymers and dyes.

There are various methods for producing 4,4'-dibromobiphenyl. When biphenyl and bromine are used as raw materials, a method of brominating biphenyl with bromine using a catalyst in a solvent, and There is a method of reacting biphenyl with bromine in a solvent without using a catalyst.

For example, in US Pat. No. 3,518,316, 2.1 mol of bromine is reacted with 1 mol of biphenyl in the presence of sulfur dioxide in the range of -40 to -5.degree.
A method of making 4'-dibromobiphenyl is disclosed. In the examples, bromine was added to an anhydrous sulfur dioxide solvent containing biphenyl at a temperature of -6 ° C over 65 minutes.
Since the temperature is lowered by hydrobromic acid generated when the solvent is stirred, the reaction temperature is set to -22 ° C after the addition of bromine.
The temperature is maintained for 6 hours, then hydrogen bromide is removed, and when the temperature rises to −10 ° C., the solvent is filtered. In this example, this gives 4,4'-dibromobiphenyl in a yield of 92.2%.

Further, in JP-A-55-64532, a compound such as o-dichlorobenzene, nitrobenzene or a specific halogenated saturated aliphatic hydrocarbon having a dielectric constant of 6.5 or more is used as a solvent. Then, a method for producing 4,4′-dibromobiphenyl by reacting biphenyl and bromine in the reaction solvent is disclosed. The invention is a method for producing 4,4′-dibromobiphenyl at room temperature and atmospheric pressure without using a catalyst, and has a dielectric constant of 6.5.
The above solvents were used as the reaction solution because of its excellent yield. In Example 6 of the publication, dichlorobenzene was used as a solvent, a mixed solution of bromine and dichlorobenzene was added dropwise over 1 hour while maintaining the temperature at 30 to 35 ° C, and the temperature was raised to 50 ° C after the addition was completed. The same temperature is maintained and reaction is carried out for 5 hours. Next, 10% sodium hydroxide aqueous solution is added to the reaction system at 50 ° C. or lower to neutralize excess bromine and dissolved hydrogen bromide, the reaction product is cooled to 10 to 15 ° C., filtered, washed with water, and dried. To obtain 4,4′-dibromobiphenyl (primary crystal). Then, the solvent is distilled off from the filtrate and concentrated, and then cooled in the same manner, filtered, washed with water and dried to 4,4′-
A secondary crystal of dibromobiphenyl is obtained. The yield converted to charged biphenyl is 80.0%.

[0006] On the other hand, Japanese Patent Application Laid-Open No. 1-1479740 discloses a method of reacting biphenyl with bromine in a halogenated hydrocarbon solvent using a simple substance of antimony, titanium, tin or zinc or a compound thereof as a catalyst. Is disclosed. When a nitro compound is used as a solvent, a violent heat is generated when bromine is added to biphenyl, and it is difficult to control the reaction when it is carried out on a large scale. Therefore, a halogenated hydrocarbon is used as a solvent to prevent a violent heat generation. It is a thing. On the other hand, when halogenated hydrocarbons are used, many of them stop at monobromobiphenyl, so addition of a catalyst prevents isomer by-products.
In the examples of the publication, 1,2-dichloroethane, 1,
Using 1,1-trichloroethane, chloroform, chlorobenzene and the like, bromine was added dropwise to the solvent at a temperature of 30 to 35 ° C in the presence of a catalyst, and then the temperature was raised to a liquid temperature of 38 to 50 ° C for aging for 5 hours, then The reaction solution was cooled to 0 ° C., a bromine treating agent was added dropwise, and the crystals were filtered, washed with water, and vacuum dried to obtain 4,4′-dibromobiphenyl. In addition, 4,4'-dibromobiphenyl was also obtained from the organic phase separated from the filtrate.

[0007]

4,4'-Dibromobiphenyl is a compound widely used as described above, and when used as a raw material compound for pharmaceuticals and agricultural chemicals, the product purity is 99% by mass or more. Is required. However, in general, it is difficult to easily produce such a product having a product purity. For example, US Pat.
In the method of No. 18,316, in the reaction, bromine is changed to hydrogen bromide in the presence of water, and sulfur dioxide is changed to sulfuric acid to cause a decrease in yield, so that water should not be mixed. You need to be careful. Further, when the temperature is out of the above range when bromine is added to biphenyl, isomers are by-produced and the yield is lowered.

Further, in the methods described in JP-A-55-64532 and JP-A-1-1479740, separation of the reaction product from the reaction solution, washing with water, drying, and filtration of the target product from the reaction solution are carried out. It is necessary to wash with water for separation and dry, and the operation of isolating the desired product is extremely complicated. In addition, JP-A-1-
Since the catalyst is used in Japanese Patent No. 1479740, it is necessary to separate the catalyst from the desired product, 4,4′-dibromobiphenyl, which further increases the manufacturing process. 4,4 '
Since -dibromobiphenyl is a useful raw material, it is preferable that -dibromobiphenyl can be produced in a high yield, but the above method does not satisfy them.

[0009]

Means for Solving the Problems As a result of detailed study on the process for producing 4,4′-dibromobiphenyl by reacting biphenyl with bromine in a reaction solvent without using a catalyst, 4,4'-Dibromobiphenyl can be produced in a high yield while suppressing the by-product of the isomer, and the desired product can be recrystallized to obtain a pure crystal only by raising the temperature and cooling the solvent. It is possible to produce highly pure 4,4′-dibromobiphenyl very easily, and the solvent after separation of the target substance can be reused as a reaction solvent for biphenyl and bromine. Even when bromobiphenyl was by-produced, it was found that the yield can be further improved because it can be recovered as 4,4′-dibromobiphenyl in the next reaction system, and the present invention has been completed. That is, the present invention provides the following (1) to (5).

(1) Biphenyl and bromine are reacted in a reaction solvent to precipitate crude 4,4'-dibromobiphenyl in the reaction solvent as crude crystals, and then a slurry containing the crude crystals is heated and cooled. Recrystallization to obtain a pure crystal of 4,4′-dibromobiphenyl.
A method for producing 4,4′-dibromobiphenyl.

(2) Reaction of biphenyl with bromine in the reaction solvent and precipitation of crude crystals of crude 4,4'-dibromobiphenyl are carried out at a temperature of -5 to 50 ° C., and the slurry is precipitated after the precipitation of the crude crystals. The method for producing 4,4′-dibromobiphenyl according to the above (1), which comprises heating to a temperature of 80 to 130 ° C. and then cooling to obtain a pure crystal.

(3) The bromine remaining in the slurry is removed after the precipitation of the crude crystals, and then the slurry is heated and cooled, which is characterized in the above (1) or (2).
The method for producing 4,4′-dibromobiphenyl described.

(4) The reaction solvent after separating pure crystals from the slurry is reused as a reaction solvent for the reaction of biphenyl and bromine, the above (1) to (1)
The method for producing 4,4′-dibromobiphenyl according to any one of (3).

(5) The reaction solvent is benzene, monochlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, monobromobenzene,
4,4'- according to any one of (1) to (4) above, which is one or more of o-dibromobenzene, m-dibromobenzene, p-dibromobenzene and bromochlorobenzene. A method for producing dibromobiphenyl.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The first aspect of the present invention is to react crude biphenyl with bromine in a reaction solvent to precipitate crude 4,4'-dibromobiphenyl in the reaction solvent as crude crystals, and then to precipitate the crude crystals. The method for producing 4,4′-dibromobiphenyl is characterized in that pure slurry of 4,4′-dibromobiphenyl is obtained by heating and cooling a slurry containing

Recrystallization is a method for purifying the crude product obtained in crystalline form, and heating and cooling operations are generally performed in a solvent. Recrystallization is a method in which a target substance in a solvent is heated to form a saturated solution, which is then cooled to precipitate a solute again as a crystal due to the difference in solubility due to a temperature difference and then purified to leave a small amount of impurities in the solvent. Is. For this reason, it is usual to use a solvent different from the reaction solvent due to the difference in solubility between the raw material compound and the target compound in the specific solvent. Particularly, by reacting biphenyl with bromine, 4,4'-
When dibromobiphenyl is produced, the temperature of the solution rises due to the heat of reaction. For this reason, it is necessary to select an optimal reaction solvent in consideration of the solvent having a small heat generation amount, the raw material compound or the target compound, the reactivity with by-products, etc., and the types of reaction solvents that can be used conventionally are limited. It is a thing. Therefore, it has not been known at all to obtain a crystal of 4,4'-dibromobiphenyl having a higher purity by heating and cooling the reaction solvent in which 4,4'-dibromobiphenyl is deposited and recrystallizing it. However, in the present invention, by finding the reaction conditions and the optimum recrystallization conditions, recrystallization is performed using a reaction solvent containing crude crystals, and a highly pure 4,4′-dibromobiphenyl can be prepared very simply. be able to. Hereinafter, the present invention will be described in detail.

First, the reaction solvent that can be used in the present invention is one that dissolves biphenyl and is 4,4'-
Dibromobiphenyl was precipitated as crystals in the solvent,
In addition, it does not react with the raw material compound or the target substance and does not decompose even when the temperature is raised during recrystallization. Such reaction solvents include benzene, monochlorobenzene, o
-Dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, monobromobenzene, o-dibromobenzene, m-dibromobenzene, p-dibromobenzene,
Bromochlorobenzene and the like. In the present invention, these 1
A single species may be used alone, or two or more species may be used in combination. In the present invention, benzene, monochlorobenzene, o
-Dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, monobromobenzene, o-dibromobenzene, m-dibromobenzene, p-dibromobenzene,
Preference is given to using bromochlorobenzene alone. Of these, monochlorobenzene is particularly preferably used alone. It has excellent selectivity for 4,4'-dibromobiphenyl, and recrystallizes because it dissolves by-products such as 4-bromobiphenyl, 2,4'-dibromobiphenyl, and 3,4'-dibromobiphenyl during recrystallization. This is because the efficiency of is excellent.

Generally, a reactor equipped with a cooling device,
The reaction solvent, bromine and biphenyl are charged. The reaction raw material, biphenyl, has a concentration of 20 to 80 mass / in the reaction solvent.
It dissolves at a concentration of volume%, more preferably 30 to 70 mass / volume%, and particularly preferably 40 to 60 mass / volume%.
If it exceeds 80 mass / volume%, it may be difficult to control the temperature during the reaction with bromine, and the purity of the target product may decrease during recrystallization. On the other hand, if it is less than 20 mass / volume%, the yield may decrease.

The molar ratio (bromine / biphenyl) of bromine and biphenyl, which are reaction raw materials, is 2.0 to 3.
0, more preferably 2.4 to 2.8, and particularly preferably 2.5 to 2.6. When it is less than 2.0, not only the yield of the target product is lowered, but also the amount of monobromide is increased and the purity may be lowered. On the other hand, if it exceeds 3.0, by-products may increase and purification may be difficult. On this occasion,
The bromine and the reaction solvent used do not need to undergo a treatment such as dehydration. In the present invention, since the reaction is carried out in a hydrophobic reaction solvent such as benzene or monochlorobenzene, even if water is mixed, the reaction itself rapidly progresses in these reaction solvents, and bromine is decomposed by water. This is because there are few side effects. In this way, the pretreatment of the raw material used is eliminated, so that the target product can be efficiently produced.

When bromine and biphenyl are mixed, heat of reaction is generated. Since the 4,4'-dibromobiphenyl isomer is by-produced by the generated heat, it is preferable to maintain the reaction solution at a low temperature. When mixing bromine and diphenyl, the reaction solution should be at a temperature of -5 to 50 ° C, preferably Is -5 to 2
0 ° C, more preferably 0 to 15 ° C, particularly preferably 5 to
Limit to 10 ° C. For example, when monochlorobenzene is used as the reaction solvent, the solution temperature decreases due to the heat of dissolution when biphenyl is dissolved in the reaction solvent, and when bromine is added dropwise thereto, the solution temperature gradually rises due to the reaction heat. Therefore, the temperature is controlled in the reactor equipped with a cooling device. Conventionally, bromine is added dropwise to biphenyl in order to prevent sudden heat generation, but in the present invention, if the above temperature range can be maintained, biphenyl is added to a reaction solvent such as monochlorobenzene and then bromine is added to the stock solution. Biphenyl may be added as it is, or biphenyl may be added to the reaction solvent such as monochlorobenzene in which bromine is dissolved in advance, and there is no limitation on the mixing order. At this time, the reaction solvent can be used not only to dissolve biphenyl but also to dissolve bromine. Since hydrogen bromide is by-produced by mixing with the reaction solvent, bromine and biphenyl, it can be recovered by introducing it into the collection liquid from the upper part of the reactor.

The present invention does not require the addition of a catalyst.
This is because by reacting in a specific reaction solvent such as monochlorobenzene, 4,4′-dibromobiphenyl can be produced with high selectivity without adding a catalyst.

Next, a reaction solution prepared by mixing biphenyl and bromine in a reaction solvent such as monochlorobenzene is heated at a temperature of -5.
Aging is carried out in the range of -50 ° C, preferably 15-50 ° C, more preferably 15-40 ° C, especially 20-38 ° C. This is because the bromination of biphenyl proceeds and crude crystals of 4,4′-dibromobiphenyl are precipitated in the reaction solvent. At this time, there is no limitation on the aging time, and it is sufficient that the target crude crystals of 4,4′-dibromobiphenyl are sufficiently precipitated. Generally, it is 8 to 36 hours, more preferably 12 to 24 hours, especially 16 to 20 hours. The temperature at the time of aging may be the same as the temperature at the time of mixing the reaction solvent, bromine and biphenyl, but in order to promote the reaction, it is preferable to keep the temperature higher than this. Therefore, it is more preferable to maintain the temperature for adjusting the reaction solution, that is, the time for mixing with the reaction solvent, biphenyl, and bromine at a temperature of −5 to 20 ° C. and then at a temperature of 15 to 40 ° C. for aging.

By adjusting and aging the reaction solution as described above, crude crystals of 4,4'-dibromobiphenyl are precipitated in the reaction solvent. The purity of this crude crystal is 96 to 97% by mass, and the by-product is monobromobiphenyl of 3 to 4%.
%, And other isomers of 4,4′-dibromobiphenyl are 0.1 to 0.3% by mass.

Then, excess bromine contained in the reaction solvent is removed. As a method for removing such bromine, a conventionally known method can be adopted. For example, a slurry containing crude crystals (in the present specification, the reaction solvent after precipitation of 4,4′-dibromobiphenyl crystals is used as It may be referred to as “slurry” with or without) at 50 ° C. or lower by adding an alkaline substance such as sodium hydroxide to remove excess bromine and hydrogen bromide (JP-A-55-64532). The slurry containing the crude crystals may be cooled to 0 ° C., and a bromine treating agent (bromine removing agent) such as sodium hydroxide or sodium hydrogen sulfite may be added thereto to remove bromine present in the slurry. Alternatively, excessive bromine may be removed by adding sulfurous acid or sodium bisulfite (Japanese Patent Laid-Open No. 1-131035). In the present invention, as a method of such a bromine treatment, the slurry is cooled to a temperature of -5 to 20 ° C, and then sulfurous acid, an aqueous solution of sodium sulfite or the like is treated using a neutralized amount of bromine.

In the present invention, the temperature of the slurry after adding the bromine removing agent is 80 to 130 ° C., more preferably 90 to 12 ° C.
Heating to 0 ° C, especially 100-105 ° C, causes 4,4'-dibromobiphenyl to dissolve in the slurry. Then, when cooled, high-purity 4,4′-dibromobiphenyl is deposited. If the heating temperature is lower than 80 ° C., the purity of the target product may decrease, while if the temperature exceeds 130 ° C., further melting of the target product does not occur, which is wasteful. Incidentally, when an aqueous solution is used as the bromine treating agent, or when the bromine and the reaction solvent contain water, it may be difficult to heat the reaction solvent to the boiling point or higher due to an azeotropic phenomenon, If the temperature can be raised to the above range, there is no particular problem.

In the present invention, the slurry is cooled after the temperature is raised to the above temperature, but the cooling temperature, cooling rate, cooling time, etc. are not limited as long as the target substance is deposited. Generally, the slurry may be cooled to room temperature in 2-3 hours.

In the present invention, high-purity 4,4'-dibromobiphenyl is precipitated in the slurry by the above treatment and the by-product is dissolved in the slurry, whereby high-purity 4,4'-dibromobiphenyl is crystallized. Can be obtained in the form. The bromine removing agent added to remove bromine and the reaction compound with bromine are dissolved in the aqueous phase in the slurry, and the target 4,4′-dibromobiphenyl is precipitated in the solvent phase in the slurry. If the solvent phase is separated,
Crystals of 4'-dibromobiphenyl can be collected. The pure crystals of 4,4′-dibromobiphenyl can be separated from the slurry by any other conventionally known method. The purity of the pure crystal at this time is
99.5 to 99.8% by mass, the by-products are monobromobiphenyl 0.1 to 0.5% by mass, and other 4,4 '
-0.1 to 0.2 mass% of dibromobiphenyl isomer
Is.

The 4,4'-dibromobiphenyl obtained by recrystallization can be recrystallized again in another solvent or the same fresh reaction solvent in order to further purify it.

In the present invention, the solvent obtained by separating pure crystals is
It can be reused as a reaction solvent for the reaction of biphenyl with bromine. In the present invention, the specific reaction solvent is heated to the specific temperature to recrystallize the target product, and suppresses the production of by-products and the decomposition of the target product. It was found that the reaction solvent such as or monochlorobenzene can be stably used without being brominated and can be reused. The present invention is based on the extremely simple principle of utilizing the activity of bromine itself and brominating the 4th and 4'positions of biphenyl with bromine. Therefore, the reaction solution may be brominated. high. However, in the present invention, the reaction solvent used by the treatment under the above-mentioned specific conditions is decomposed without brominating by the raw material compound, or by the product or by-product, or the heat of reaction or heating of recrystallization. It is possible to re-use it very stably without using. This is the same even when a treating agent for removing bromine and hydrogen bromide is added prior to recrystallization. The present invention is
The above reaction solution is used as it is and recrystallized to obtain the desired product with higher purity.
-It contributes to the increase in the productivity of dibromobiphenyl.

Solvent after fractionation of pure crystals ("crystallization mother liquor")
Also called. ) Can be reused as a reaction solvent, an insufficient amount of the reaction solvent may be added to the crystallization mother liquor so that the above-mentioned molar ratio of diphenyl and bromine and the concentration of diphenyl in the solvent can be maintained. At this time, the crystallization mother liquor contained monobromobiphenyl, 2,4′-dibromobiphenyl,
3,4'-dibromobiphenyl and further 4,4'-dibromobiphenyl may be contained. Originally, the present invention has excellent selectivity for 4,4′-dibromobiphenyl,
The amount of by-products is extremely small, but monobromobiphenyl, for example, is the target compound in the next reaction system, 4,4 '.
This is because the target product 4,4′-dibromobiphenyl, which becomes −dibromobiphenyl and is dissolved in the crystallization mother liquor, can improve the yield by reuse. Moreover, the crystallization mother liquor is excellent in that it can be used as it is without being subjected to treatments such as distillation, decolorization, column treatment and dehydration.

The 4,4'-dibromobiphenyl obtained by the present invention has an extremely high purity, and a high-purity target product can be obtained by synthesizing other derivatives by a conventional method. For example, 4,4′-dihydroxybiphenyl is a compound useful as a resin production raw material for resin oxidation stabilizers, dye intermediates and polyesters, polyepoxides, polyurethanes, polycarbonates and the like. Various methods for synthesizing 4,4'-dihydroxybiphenyl are also known. Examples of such a method include the method described in JP-A-52-36057 and the method described in JP-A-55-17304. Specifically, as described in JP-A-55-17304, 4,4′-dibromobiphenyl is hydrolyzed in an alkaline aqueous solution in the presence of a copper compound catalyst to produce a by-product from an alkaline aqueous solution containing a reaction product. , An alcohol or a ketone that is sparingly soluble or insoluble in water, the aqueous alkali solution is neutralized with a mineral acid, the same reaction solvent as above is used for extraction, and then crystal precipitation is performed.
According to the present invention, 4,4′-dibromobiphenyl, which is a raw material of 4,4′-dihydroxybiphenyl, can be produced in high purity, and therefore, 4,4′-dihydroxybiphenyl can be produced in high yield using the compound. Biphenyl can be synthesized.

It should be noted that 4,4'-dihydroxybiphenyl produced by the present invention has the same meaning as 4,4'-dihydroxybiphenyl.
4-Bromo-4'-hydroxybiphenyl can also be produced by partially hydrolyzing 4'-dibromobiphenyl by a conventionally known method. 4,4'-dihydroxybiphenyl can be oxidized by a known method, It is also possible to produce 4'-dicarboxybiphenyl. All of these compounds are useful as intermediates for organic EL applications, pharmaceuticals, and agricultural chemical applications.

[0033]

EXAMPLES The present invention will be described in detail below with reference to examples. (Example 1) In a 500-liter GL reactor, 154 liters of monochlorobenzene and 77 kg of powdered biphenyl (5
(00 mol) was charged and stirred to dissolve. While maintaining the temperature of the solution at 0 to 12 ° C., 208 kg of bromine was added thereto.
(1300 mol) was added dropwise over 1 hour and 30 minutes. The generated hydrogen bromide was introduced from the upper part of the reactor into a receiver filled with water and collected. After the dropping, the temperature of the solution is gradually raised,
It was aged at 20 ° C. for 20 hours. Then, the liquid temperature was raised to 38 ° C. and the mixture was aged for 1 hour. Crude crystals of 4,4′-dibromobiphenyl were precipitated in the solution. 4,4'- of the crude crystals
The dibromobiphenyl content was 97.0 mass%.

Then, the slurry containing the crude crystals was cooled to 0 ° C., and a 23.2 mass% Na ₂ SO ₃ aqueous solution 162.8 k was obtained.
g was added to remove excess bromine. Then, the slurry was heated to 100 ° C. and immediately cooled. The precipitated crystals were separated by centrifugation and dried with a conical dryer. The crystals contained 99.8% by mass of 4,4′-dibromobiphenyl, and the yield based on biphenyl was 94.
%Met. The crystallization mother liquor after centrifugation was 160 kg.
And monobromobiphenyl is 2% by mass / volume, and other isomers of 4,4′-dibromobiphenyl are 0.5 to
1 mass / volume%, 4,4′-dibromobiphenyl was 4 mass / volume%.

The purity of 4,4'-dibromobiphenyl and the content of each component in the crystallization mother liquor were measured by gas chromatography.

(Example 2) The crystallization mother liquor 1 obtained in Example 1 was replaced with 154 liters of monochlorobenzene of Example 1.
Other than using 9.4 kg of monochlorobenzene newly added to 60 kg to make a total of 169.4 kg,
The same operation as in Example 1 gave 4,4'-dibromobiphenyl. The content of 4,4′-dibromobiphenyl in the crude crystals was 96.5% by mass. As for the purity of the crystal obtained by recrystallization, the crystal was 99.8% by mass of 4,4′-dibromobiphenyl, and the yield based on biphenyl was 96%. The crystallization mother liquor is 158 k
g, 2% by mass of monobromobiphenyl, and 0.5 of other 4,4′-dibromobiphenyl isomers.
~ 1 mass / volume%, 4,4'-dibromobiphenyl is 3
It was mass / volume%.

(Example 3) The crystallization mother liquor 1 obtained in Example 2 was used instead of 154 liters of monochlorobenzene in Example 1.
4,4'-Dibromobiphenyl was obtained in the same manner as in Example 1 except that 11.4 kg of monochlorobenzene was newly added to 58 kg to make a total of 169.4 kg. The content of 4,4'-dibromobiphenyl in the crude crystals was 96.8% by mass. Regarding the purity of the crystal obtained by recrystallization, the crystal was 99.8% by mass of 4,4′-dibromobiphenyl, and the yield based on biphenyl was 97%. The crystallization mother liquor was 15
8 kg, monobromobiphenyl is 2 mass / volume%, other isomers of 4,4′-dibromobiphenyl are 0.5 to 1 mass / volume%, and 4,4′-dibromobiphenyl is 2.5 mass / volume%. It was% by volume.

(Example 4) A 500-liter GL reactor was charged with 208 kg (1300 mol) of bromine, and
77 kg (500 mol) of powdered biphenyl was added to monochlorobenzene 154 while maintaining the temperature of the solution at 0 to 12 ° C.
Crude crystals of 4,4′-dibromobiphenyl were obtained in the same manner as in Example 1 except that the solution dissolved in liter was added dropwise over 1 hour and 30 minutes. The content of 4,4′-dibromobiphenyl in the crude crystals was 97.0% by mass.

A slurry containing the crude crystals was prepared in Example 1.
A pure crystal of 4,4′-dibromobiphenyl was obtained by the same treatment as described above. Its purity was 99.8% by mass, and the yield based on biphenyl was 94%. The crystallization mother liquor was 160 kg, and monobromobiphenyl was 2 mass /
%, Other isomers of 4,4′-dibromobiphenyl were 0.5 to 1% by mass / volume, and 4,4′-dibromobiphenyl was 4% by mass / volume%.

(Example 5) A 500-liter GL reactor was charged with 208 kg (1300 mol) of bromine dissolved in 54 liters of monochlorobenzene, while maintaining the temperature of the solution at 0 to 12 ° C. Crude crystals of 4,4′-dibromobiphenyl were obtained in the same manner as in Example 1 except that 77 kg (500 mol) of powdered biphenyl dissolved in 100 liters of monochlorobenzene was added dropwise over 1 hour and 30 minutes. It was The content of 4,4′-dibromobiphenyl in the crude crystals was 97.0% by mass.

A slurry containing the crude crystals was prepared in Example 1.
A pure crystal of 4,4′-dibromobiphenyl was obtained by the same treatment as described above. Its purity was 99.8% by mass, and the yield based on biphenyl was 94%. The crystallization mother liquor was 160 kg, and monobromobiphenyl was 2 mass /
%, Other isomers of 4,4′-dibromobiphenyl were 0.5 to 1% by mass / volume, and 4,4′-dibromobiphenyl was 4% by mass / volume%.

Example 6 A 500-liter GL reactor was charged with 77 kg (500 mol) of powdered biphenyl dissolved in 100 liters of monochlorobenzene, and the temperature of the solution was maintained at 0 to 12 ° C. While bromine 2
Crude crystals of 4,4′-dibromobiphenyl were obtained in the same manner as in Example 1 except that 08 kg (1300 mol) dissolved in 54 liters of monochlorobenzene was added dropwise over 1 hour and 30 minutes. The content of 4,4'-dibromobiphenyl in the crude crystals was 96.7% by mass.

A slurry containing the crude crystals was prepared in Example 1.
A pure crystal of 4,4′-dibromobiphenyl was obtained by the same treatment as described above. Its purity was 99.8% by mass, and the yield based on biphenyl was 94%. The crystallization mother liquor was 160 kg, and monobromobiphenyl was 2 mass /
%, Other isomers of 4,4′-dibromobiphenyl were 0.5 to 1% by mass / volume, and 4,4′-dibromobiphenyl was 4% by mass / volume%.

[0044]

INDUSTRIAL APPLICABILITY According to the present invention, by reacting a starting compound, biphenyl, and bromine in a reaction solvent of either benzene or a benzene derivative, by-products such as isomers can be suppressed while suppressing the by-production. '-Dibromobiphenyl can be synthesized, and by heating and cooling the reaction solvent,
4'-Dibromobiphenyl can be recrystallized and produced in high purity. For this reason, conventionally, it was general to recrystallize using a reaction solvent different from the reaction solution, but the recrystallization treatment was simply performed without separating the crude crystals, and 4,4'- Dibromobiphenyl can be produced. Moreover, under the reaction conditions, since the reaction solvent can be stably recovered without decomposition, the crystallization mother liquor after obtaining 4,4′-dibromobiphenyl by recrystallization,
It can be used again as a reaction solution of biphenyl and bromine. Therefore, for example, even if monobromobiphenyl is present, it can be converted to 4,4′-dibromobiphenyl which is the target product in the next step, so that the yield can be further improved.

Claims (5)

[Claims] 1. Crude 4,4′-dibromobiphenyl is precipitated as crude crystals in the reaction solvent by reacting biphenyl and bromine in a reaction solvent, and then a slurry containing the crude crystals is heated and cooled. Recrystallization to obtain pure 4,4'-dibromobiphenyl crystals, 4,4 '
-Method for producing dibromobiphenyl. 2. The reaction of biphenyl and bromine in the reaction solvent and the precipitation of crude crystals of crude 4,4′-dibromobiphenyl are performed at a temperature of −5 to 50 ° C., and the slurry is heated to a temperature after the precipitation of the crude crystals. 4. A pure crystal is obtained by heating to 80 to 130 [deg.] C. and then cooling to obtain a pure crystal.
Method for producing 4'-dibromobiphenyl. 3. The method according to claim 1 or 2, characterized in that, after the precipitation of the crude crystals, bromine remaining in the slurry is removed, and then the slurry is heated and cooled.
Method for producing 4'-dibromobiphenyl. 4. The reaction solvent after separating pure crystals from the slurry is reused as a reaction solvent for the reaction of biphenyl and bromine, according to any one of claims 1 to 3. A method for producing 4,4′-dibromobiphenyl. 5. The reaction solvent is benzene, monochlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, monobromobenzene, o-
5. The method for producing 4,4′-dibromobiphenyl according to any one of claims 1 to 4, which is one or more of dibromobenzene, m-dibromobenzene, p-dibromobenzene, and bromochlorobenzene. .