JPS6116252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing 4,4'-dibromobiphenyl. The 4,4′-dibromobiphenyl according to the present invention is
It is extremely useful as a stabilizer for poly(oxyalkylene) polyols, sulfonated aliphatic alcohols, dye intermediates, and intermediate raw materials for producing heat-resistant resins. Conventionally, the following methods are known for producing 4,4'-dibromobiphenyl by reacting biphenyl and bromine in the presence or absence of a solvent. (1) Pure biphenyl was dissolved in carbon disulfide, bromine was added, and the mixture was heated under reflux for 2 days.Additionally, some bromine was added and heat treated at 90°C for 2 hours in a sealed tube.
Method for obtaining the desired 4,4'-dibromobiphenyl [Journal of the Chemical Society (JCS.) 47 , 586 (1885)]. (2) A method for obtaining 4,4'-dibromobiphenyl by adding bromine to a glacial acetic acid solution in which biphenyl is dissolved, heating under reflux for 3 hours, cooling and filtering to obtain 4,4'-dibromobiphenyl [Chem. ) 44 , 1087 (1911)]. (3) Method of reacting biphenyl with bromine in sulfuric acid [Journal.
JACS. 43 , 3061 (1921)]. (4) Reacting biphenyl and bromine in sulfur dioxide at -40 to -5°C4,
Method for obtaining 4'-dibromobiphenyl [German Open Gazette, No. 1930594 (1970)]. (5) A method to obtain 4,4'-dibromobiphenyl by contacting fine biphenyl powder with bromine vapor at room temperature and recrystallizing the crude reaction product with benzene [Organic Synthesis Collective Volume ( Org.Syn.
Coll. Vol.) 4 , 256] etc. However, all of these methods have the following drawbacks and cannot be adopted as industrial production methods. That is, in method (1), the reaction time is extremely long, 2 days, and is not practical. Method (2) has a low yield of 71%, and furthermore, a portion of the reaction between the solvent acetic acid and bromine occurs, resulting in a large loss of bromine. In method (3), the yield of the target product is extremely low at 13%. Method (4) is preferable in terms of reaction time and target product selectivity, but requires a large investment in equipment and safety measures because the reaction is carried out in a large amount of liquefied toxic gas at extremely low temperatures. It is difficult to industrialize it unless it is produced on a large scale. Since method (5) involves the reaction of fine biphenyl powder with bromine vapor, it involves mechanical difficulties in handling the powder, making it difficult to react uniformly to the inside of the powder. Dibrome compounds other than the target compound are produced as by-products, the reaction composition is slightly sticky, and recrystallization is required to obtain the product, making this method unsuitable for industrial production. For the above reasons, the present inventors have developed a new and improved industrial production method that eliminates the drawbacks of these conventional methods, that is, a method that allows easy bromination at room temperature to slightly heated temperature and normal pressure without using a catalyst. With the aim of providing a method in which 4,4'-dibromobiphenyl, the target product, can be obtained in good yield, the present invention, in which the reaction is carried out in a specific solvent, was developed as a result of detailed studies. completed. That is, the present invention provides o-dichlorobenzene,
Nitrobenzene and the general formula R・Cl _o (in the formula R
represents a saturated aliphatic hydrocarbon residue having 2 to 5 carbon atoms, and n represents 1 to 5. ) and the general formula R′・NO ₂
(In the formula, R' represents a saturated aliphatic hydrocarbon residue having 1 to 3 carbon atoms.) 1 selected from the group of compounds having a dielectric constant of 6.5 or more at room temperature.
This is a method for producing 4,4'-dibromobiphenyl by reacting biphenyl with bromine in one or more solvents. The bromination reaction can be carried out by adding bromine to a mixed system of biphenyl and a solvent while stirring, or by completely dissolving the biphenyl and adding bromine diluted with a similar solvent to the solvent system. However, the latter is more preferred. During the reaction, hydrogen bromide gas is generated, which is introduced into water or an alkaline aqueous solution and absorbed. Most of the 4,4'-dibromobiphenyl produced is precipitated as crystals, but by-products are dissolved in the solvent layer. Next, in order to remove excess bromine and dissolved hydrogen bromide remaining in the reaction system, the reaction system is neutralized by adding an aqueous solution of an alkaline substance such as sodium hydroxide, filtered, washed with water, and dried. 4,4'-dibromobiphenyl can be obtained. Further, by concentrating and cooling the solvent layer of the liquid, a small amount of dissolved 4,4'-dibromobiphenyl can be recovered as crystals. The concentration ratio at this time is preferably about 90%. The solvent used in the present invention is a solvent for biphenyl, which is a raw material, and can be characterized by o-dichlorobenzene, nitrobenzene, or the general formula and dielectric constant ε, as described above. This is because when looking at the correlation between many solvents and yield, when ε is approximately 6.5 or less, the smaller ε becomes, the more rapidly the yield decreases.
At 6.5 or higher, the yield is maintained at 80% or more and almost 90%. The above-defined solvent is not only excellent as a solvent, but also stable against bromine and by-product hydrogen bromide. Examples of solvents belonging to the general formula R.Cl _o include 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,
These include 1,2,2-tetrachloroethane and 1,2-dichloropropane, and examples of solvents belonging to the general formula R'.NO ₂ include nitroethane and nitropropane. Nitrobenzene and 1,2-dichloroethane among the above are preferred solvents because they are industrially stably available. Carbon tetrachloride, chloroform, 1,1,1,2-
Tetrachloroethane, pentachloroethane, n-
When using a solvent with a small dielectric constant such as hexane or m-dichlorobenzene, the bromination reaction is slow and the selectivity of the target product is also poor. The amount of solvent used varies depending on the solubility of biphenyl, but is generally based on the weight of biphenyl.
1.5 to 3.5 times is preferable. In carrying out the present invention, the amount of bromine used is 2.0 to 2.4 times the mole of biphenyl, but preferably
It is 2.1 to 2.2 times the mole. The reaction temperature is 10 to 60°C, preferably 30°C.
~50℃. That is, add bromine at about 30℃,
After the addition is completed, it is preferable to raise the temperature to 45 to 50°C to complete the reaction. The reaction is usually complete within several hours. In the solvent of the present invention, the bromination reaction proceeds with a good conversion rate and also has a good selectivity of the target product.
In addition, as mentioned above, this solvent has poor solubility for the target product, 4,4'-dibromobiphenyl, and the solubility of by-products is high, so the filtered crystals and the crystals obtained by concentrating the liquid are combined. A highly pure target product can be obtained in good yield. Also, 4- in the by-product
Bromobiphenyl can be recovered from the concentrate and recycled for the next reaction. According to the method of the present invention, since the solvent has high chemical stability, there is little loss when the solvent is distilled and recycled, and the target 4,4'-dibromobiphenyl can be produced in a significantly higher yield than the conventional method. Since it can be obtained in high yield, its economic effect is significant. The present invention will be further explained below with reference to Examples. Example 1 23.1 g of biphenyl and 40 g of 1,2-dichloroethane are placed in a 300 ml four-necked flask equipped with a stirrer and completely dissolved. Keeping the temperature at 30~35℃, 52.7g of bromine and 6g of
A mixed solution with 1,2-dichloroethane was dropped over about 1 hour, and after the dropping was completed, the temperature was raised to 50°C, and the same temperature was maintained for 5 hours of reaction. At this time, a portion is sampled and analyzed by gas chromatography (hereinafter referred to as GC).
The results are shown in Table 1. Hydrogen bromide generated during the reaction was introduced into a gas absorption bottle containing water and absorbed. Next, add 10% to this reaction system at below 50°C.
% aqueous sodium hydroxide solution to neutralize excess bromine and dissolved hydrogen bromide, the reaction mixture was cooled to 10-15°C, filtered, washed with water, and dried to produce 4,4'-dibromobiphenyl. The primary crystal of was obtained. In addition, 90% of the solvent is distilled off and concentrated from the liquid, cooled, filtered,
After washing with water and drying, secondary crystals of 4,4'-dibromobiphenyl were obtained. A total of 42.8 g was obtained by combining this with the primary crystal. The yield was 90% (based on biphenyl charged). Crystal purity by GC analysis is 98.6%, melting point is
The temperature was 165.5-167℃. Examples 2, 3, 4, 5, 6, 7 Table 1 shows the results of the same treatment as in Example 1, except that only the reaction solvent was changed. Comparative Example 1 23.1 g of finely ground biphenyl and 58.5 g of bromine were placed in separate evaporation dishes, both were placed in a dessicator with a diameter of 35 cm and a gas vent equipped with a ceramic shelf, and the biphenyl was placed on the top of the shelf. , bromine was placed at the bottom, and powdered biphenyl and bromine vapor were allowed to contact react at room temperature for 12 hours. Collect a sample of a portion of the crude reaction product,
The results of GC analysis are shown in Table 1. This crude reaction product was recrystallized with 113 ml of benzene to obtain 35.6 g of white crystals. The yield of 4,4'-dibromobiphenyl was 75% (based on the charged biphenyl). G.C.
The purity of the crystal by analysis is 98.5%, the melting point is 165.5~
It was 167℃. Comparative Example 2 Table 1 shows the results of the same treatment as in Example 1, except that the reaction solvent, the reaction temperature after dropping bromine, and the time were changed. Comparative Examples 3, 4, 5, 6 Table 1 shows the results of the same treatment as in Example 1 except that the reaction solvent was changed. 【table】

Claims (1)

[Claims] 1 By reacting biphenyl with bromine, 4,4'-
When producing dibromobiphenyl, o-dichlorobenzene, nitrobenzene, and the general formula R・Cl _o (wherein R represents a saturated aliphatic hydrocarbon residue having 2 to 5 carbon atoms, and n represents 1 to 5) ) and the general formula R′・NO ₂ (in the formula, R′ is a carbon atom number of 1 to 3
represents a saturated aliphatic hydrocarbon residue. ), and the reaction is carried out in one or more solvents selected from the group of compounds having a dielectric constant of 6.5 or more at room temperature.