Method of obtaining pentafluorophenol

FIELD: chemistry.

SUBSTANCE: method of obtaining pentafluorophenol can be used for obtaining medications, fluoridated monomers and reagents for peptide synthesis by reaction of hexafluorobenzol with water solutions of alkali and earth alkali metal hydroxides. Process is carried out in presence of catalyst of interphase transfer at temperature 100-140°C. As a rule, as catalysts of interphase transfer, chlorides or bromides of tetrakis(dialkylamido)phosphonium, or N,N',N" - hexa-alkyl-substituted guanidinium, or their mixtures are used, and catalyst of interphase transfer is used in concentration from 0.5 to 1 wt % of initial hexafluorobenzol amount. Usually 2.05-2.35 equivalent of alkali reagent with respect to hexafluorobenzol is used in form of 20-30% water solution.

EFFECT: obtaining pentafluorophenol with high purity degree and simplification of its synthesis technology.

4 cl, 5 ex

 

The invention relates to the field of chemical technology of obtaining derivatives of fluoroaromatic compounds, namely pentafluorophenol6F5OH. The specified connection is used to get drugs, fluorinated monomers and reagents for peptide synthesis. One of the basic conditions of practical application of pentafluorophenol is getting this connection a high degree of purity.

The level of technology

A known method of producing pentafluorophenol decomposition pentacarbonyliron esters; the latter is obtained by reaction of the corresponding alcoholate with geksaftorbenzola (output for pentaverate 72%). The decomposition is carried out by acid or aluminium chloride, the output of pentafluorophenol 20-58% (E.Forbes, R. Richardson, M. Stasey, J.Tatlow, J.Chem. Soc., June, p.2019-2021, 1959).

The characteristics which are common to the known and the inventive method are used as initial compounds available in industrial quantities of hexaferrite.

The reason getting in the known method the required technical result is used to obtain pentafluorophenol from hexaferrite two-stage scheme. Another reason is the low overall yield of the target product. In addition, the thus obtained pentafluorophenol requires additional is Noah purification from impurities due to incomplete conversion, decomposition pentacarbonyliron esters and formation of any side products.

A known method of producing pentafluorophenol directly from hexaferrite and potassium hydroxide in the medium of organic solvent. In tert-butanol output pentafluorophenol reaches 71% (J.M.Birchall, R.N.Haszeldine, J. Chem. Soc., Jan., p.13-17, 1959). In the medium of anhydrous pyridine output pentafluorophenol is 52% (W.Pummer, L.Wall, Science, 127, R, 1958).

Signs that are common to known and inventive method, are used as starting compounds of potassium hydroxide and available in industrial quantities of hexaferrite.

The reason getting in the known method the required technical result is the need to use organic solvents and their subsequent regeneration, which significantly limits the industrial implementation of these methods. Another significant limitation of these methods is the low yield and poor quality of the target product. So, pentafluorophenol obtained in the environment of tert-butanol has a melting point of only 25-30°instead 34-36°and requires additional cleaning of traces of solvents and by-products.

The closest analogue (prototype) is a method of obtaining pentafluorophenol reaction hexaferrite with a concentrated aqueous solution of potassium hydroxide in an autoclave at paramesh is the training and a temperature of 175° With access to 83.5% (L.Wall, W.Pummer, J.Fearn, J.Antonucci, J.Rcs. NBS, 67A, p.481-497, 1963).

Signs that are common to known and inventive method, are used as starting compounds of potassium hydroxide and available in industrial quantities of hexaferrite.

The reason getting in the known method the required technical result is the necessity of carrying out reactions at high pressure (above 15 ATM.), that significantly limits the industrial implementation of this method. In addition, the process at high temperature leads to the formation of undesirable by-products further substitution of fluorine atoms in the aromatic ring tetrafluorobenzene and tetrafluorohydroquinone.

The invention

The problem to which the invention is directed, is to improve the technology of producing pentafluorophenol high purity by overcoming the disadvantages of the known methods.

The technical result causing the problem lies in the fact that the synthesis of pentafluorophenol occurs under mild conditions, allowing the use of standard equipment and does not lead to the formation of by-products.

The technical result is achieved by the reaction of hexaferrite with aqueous solutions of hydroxides school is full-time or alkaline-earth metals in the presence of a phase transfer catalyst at a temperature of 100-140° C.

The phase transfer catalysts in the reaction of hexaferrite with alkali, preferably taken in quantities from 0.5 to 10 weight percent relative to the amount of the original hexaferrite, better than 2-5%.

In the present method as phase transfer catalysts preferably used chlorides and bromides tetrakis(dialkylamino)of phosphonium, or N,N',N"-hexadecylamine guanidine, or a mixture thereof.

For the implementation of the reaction it is preferable to use aqueous solutions of hydroxides of alkali metals, taken in a small surplus against stoichiometry, most commonly used is 2.05-2.35 equivalent of an alkaline reagent in relation to hexaferrite. Most use 20-30% water solutions.

New (relatively prototype) characteristics of the claimed method consists in carrying out the reaction hexaferrite with hydroxides of alkali metals in the presence of phase transfer catalysts at elevated temperature.

Industrial applicability

Synthesis of pentafluorophenol in the presence of phase transfer catalysts can significantly reduce the temperature of the process and, accordingly, to reduce the excess pressure in the reactor to the working pressures of the industry standard devices. In addition, the use of phase transfer catalysts, persistent the ri temperatures of 100-140° With, you can reduce the quantity of generated by-products and increase the yield of the target product.

The most commonly used chlorides and bromides tetrakis(dialkylamide)of phosphonium and N,N',N"-hexadecylamine guanidine, which are quite affordable and have a high resistance in concentrated aqueous solutions of alkalis at elevated temperatures and high efficiency in the nucleophilic substitution of fluorine atom in the aromatic ring. The use of iodides is possible, but inefficient due to their high cost.

The reaction hexaferrite with hydroxides of alkaline or alkaline-earth metals in the presence of phase transfer catalysts carried out with stirring and heating in a typical reactor to work under pressure.

The amount of catalyst in the reaction is from 0.5 to 10% weight percent relative to hexaferrite, better than 2-5%. The use of low concentrations of catalyst leads to a slow reaction and the yield of target products, and increase the amount over 10% is not economically feasible.

As the alkaline agent used hydroxides of sodium and potassium, as alkaline-earth - hydroxide of calcium. The hydroxides of lithium, rubidium, cesium and strontium expensive for widespread use.

The amount of hydroxide is determined stehe the scopy of the reaction and is usually taken with an excess of not more than 35% of stoichiometric.

Temperature of the reaction is selected on the basis of the hardware design. The use of high temperatures above 140°With, will lead to the formation of high pressure and temperatures below 100°With greatly slow down the reaction and will not give a complete conversion of the reactants. The optimum can be considered interval 100-140°preferably 120-130°C, the pressure in the reactor is less than 5 atmospheres.

Embodiments of the inventions

The following examples show the ability of the method of obtaining pentafluorophenol according to the invention, but do not exhaust it.

Example No. 1 (comparing with the prototype without the use of a catalyst).

In a steel reactor with a volume of 2.5 l to work under pressure, equipped with a stirrer, placed 930 g (5.0 mol) of hexaferrite and a solution of 440 g (11.0 mol) of NaOH in 1000 ml of water. The reaction mass is heated with stirring to 125°C for 48 hours, the pressure reaches 4.5 ATM. Then unreacted phenyl distilled from the reactor. Selected 874 g of unreacted hexaferrite, the conversion of the source reagent is 6%.

Example No. 2.

In a steel reactor with a volume of 2.5 l to work under pressure, equipped with a stirrer, placed 930 g (5.0 mol) of hexaferrite (basic substance content of 99.7%), a solution of 440 g (11.0 mol) of NaOH in 1000 ml of water and 30 g (7.5 mmol) of br is foreign tetrakis(diethylamino)phosphonium. The reaction mass is heated with stirring to 125°within 12 hours, the pressure drop of 4.5 ATM. to 2.2 ATM., and conversion hexaferrite reaches 100%. Then the reaction mass is then cooled, filtered from sodium fluoride, the filtrate is acidified with sulfuric acid. The organic layer containing pentafluorophenol and up to 20% water, rectificatum. Received 846 g pentafluorophenol BP. 142-143°, TPL 35-36°and a basic substance content of 99.4% (water content of 0.4%). Yield 92%.

Example No. 3.

In a steel reactor with a volume of 2.5 l to work under pressure, equipped with a stirrer, placed 930 g (5.0 mol) of hexaferrite (basic substance content of 99.7%), a solution of 220 g (5.5 mol) of NaOH in 1000 ml of H2O add 203,5 (2,75 mol) of CA(Oh)2and 30 g (7.5 mmol) of bromide tetrakis(diethylamino)phosphonium. The reaction mass is heated with stirring to 125°within 12 hours, the pressure drop of 4.5 ATM. to 2.2 ATM., and conversion hexaferrite reaches 100%. Then the reaction mass is then cooled, filtered from the calcium fluoride, the filtrate is acidified with sulfuric acid. The organic layer containing pentafluorophenol and 20% water, rectificatum. Received 853 g pentafluorophenol BP. 142-143°, TPL 35-36°and a basic substance content of 99.3% (water content of 0.4%). The yield of 92.7%.

Example 4

In a steel reactor with a volume of 2.5 l to work under pressure to the eat, equipped with a mixer, placed 930 g (5.0 mol) of hexaferrite (basic substance content of 99.7%), 1540 g of 40% aqueous solution of potassium hydroxide (11.0 mol) and 25 g (8.1 mmol) of bromide N,N',N"-hexamethyleneimino guanidine. The reaction mass is heated with stirring to 130°C for 16 hours, the pressure drop from 4.9 ATM. to 2.2 ATM., and conversion hexaferrite reaches 100%. Then the reaction mass is then cooled, filtered fallen pentafluorophenol potassium, to which is added 2 liters of 40% sulfuric acid. The organic layer is separated and dried by azeotropic distillation of water, the obtained pentafluorophenol rectificatum. Allocate 819 g pentafluorophenol BP. 142-143°, TPL 35-36°and a basic substance content of 99.4% (water content of 0.4%). Yield 89%.

Example No. 5 (scaling).

In a steel reactor with a volume of 63 l to work under pressure, equipped with a stirrer, placed 25 kg (RUR 134.4 mol) hexaferrite (basic substance content of 99.7%), a solution of 12.5 kg (312,5 mol) of NaOH in 35 l of water and 0.75 kg of 1.85 mol) of bromide tetrakis(diethylamino)phosphonium. The reaction mass is heated with stirring to 120°within 24 hours, the pressure drop from 4.8 ATM. to 2.1 ATM., and conversion hexaferrite reaches 100%. Then the reaction mass is then cooled, filtered, the filtrate is acidified with sulfuric acid. The organic layer containing pentafluorophenol and 20% water, separate and rectificatum. Get 22,75 kg pentafluorophenol BP. 142-143°, TPL 35-36°and a basic substance content of 99.4% (water content of 0.4%). Yield 92%.

1. The method of producing pentafluorophenol reaction hexaferrite with aqueous solutions of hydroxides of alkali and alkaline earth metals, wherein the process is carried out in the presence of a phase transfer catalyst at a temperature of 100-140°C.

2. The method of producing pentafluorophenol according to claim 1, characterized in that the phase transfer catalyst is used in concentrations from 0.5 to 10 wt.% the number of the original hexaferrite, better than 2-5%.

3. The method of producing pentafluorophenol according to any one of claims 1, 2, characterized in that the phase transfer catalysts used chlorides or bromides tetrakis(dialkylamide)of phosphonium, or N,N',N"-hexadecylamine guanidine, or a mixture thereof.

4. The method of producing pentafluorophenol according to any one of claims 1 to 3, characterized in that use is 2.05-2.35 equivalent of an alkaline reagent in relation to hexaferrite in 20-30%aqueous solution.



 

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