JPH0745436B2 - Method for producing 2- (4-hydroxyphenoxy) alkanoic acid ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides highly pure 2- (4 hydroxyphenoxy).
The present invention relates to a production method capable of obtaining an alkanoic acid ester in high yield.

[Prior Art] A 2- (4-hydroxyphenoxy) alkanoic acid ester is usually obtained by reacting hydroquinone with a 2-haloalkanoic acid ester under basic conditions. In this method, both of two hydroxyl groups of hydroquinone are obtained. Reacts with a 2-haloalkanoic acid ester, or is accompanied by a side reaction in which the ester bond is hydrolyzed, which is the desired product 2- (4-
The hydroxyphenoxy) alkanoic acid ester could only be obtained in low yields. JP-A-54-19925 discloses a method of reacting hydroquinone with chloroacetic acid ester in the presence of 2 mol of alkali metal alkoxide per mol of hydroquinone. However, in the case of this method, it is not an economical method because an alkali metal alkoxide, which is an expensive reagent, must be used in an amount of 2 mol per 1 mol of hydroquinone. Also unique to the West 3,
No. 150,233 discloses a method in which ethyl 2- (4-hydroxyphenoxy) propionate is obtained by reacting hydroquinone and ethyl 2-bromopropionate in the presence of calcium hydroxide. In the presence of calcium oxide, hydroquinone, for example 2-
When the reaction is performed with ethyl 2-chloropropionate, which is cheaper than ethyl bromopropionate, the reactivity is extremely low, and it is difficult to obtain ethyl 2- (4-hydroxyphenoxy) propionate in a high yield.

[Problems to be Solved by the Invention] The present invention solves the problems that the conventional method for producing a 2- (4-hydroxyphenoxy) alkanoic acid ester is inefficient and has a low yield. Another object of the present invention is to provide a method for producing a highly pure 2- (4-hydroxyphenoxy) alkanoic acid ester.

[Means for Solving the Problems] The present invention includes a dialkali metal salt of hydroquinone and the following formula (I); R ¹ CHXCOOR ² (I) (wherein, X represents a halogen atom; R ¹ represents a hydrogen atom or Represents a lower alkyl group; R ² represents a linear or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group or an aralkyl group) in a lower alcohol (hereinafter, referred to as "reaction" And a step of neutralizing the reaction solution by adding an acid (hereinafter, referred to as a "neutralization step"); a method for producing a 2- (4-hydroxyphenoxy) alkanoic acid ester comprising: ) A lower alcohol and an unreacted compound represented by formula (I) are separated and recovered from the neutralization reaction solution, and (B) a lower alcohol and an unreacted compound represented by formula (I) are separated and recovered. From residual liquid After transferring hydroquinone and an inorganic salt to an aqueous phase using a mixed solvent of water and an organic solvent, the aqueous phase is fractionated, and then the organic solvent is removed from the remaining organic solvent phase, (C) The low-boiling unnecessary substances and the high-boiling unnecessary substances are removed from the residual liquid from which the organic solvent has been removed, and 2- (4-hydroxyphenoxy) alkanoic acid ester is recovered as the balance. It relates to a method for producing a phenoxy) alkanoic acid ester.

As the dialkali metal salt of hydroquinone, which is a raw material for producing 2- (4-hydroxyphenoxy) alkanoic acid ester obtained by applying the production method of the present invention, use of dilithium salt, disodium salt, dipotassium salt or the like of hydroquinone The disodium salt is preferred because it is economical. The dialkali metal salt of hydroquinone can be obtained by reacting hydroquinone with a hydroxide of an alkali metal such as sodium hydroxide.

In the compound of formula (I) which is the other starting material, the meaning of each symbol in the formula is as described above,
The details are as follows.

Examples of the halogen atom for X include chlorine, bromine and iodine atoms, and among these, chlorine atom and bromine atom are particularly preferable.

Examples of the lower alkyl group of the group R ¹ include a methyl group, an ethyl group and a propyl group, and among these, a methyl group is preferable.

A linear or branched alkyl group having 1 to 10 carbon atoms of the group R ² ,
Among the cycloalkyl group and the aralkyl group, a linear or branched alkyl group having 1 to 4 carbon atoms is particularly preferable.

Examples of the compound represented by the formula (I) include methyl chloroacetate, methyl bromoacetate, ethyl chloroacetate, ethyl bromoacetate, methyl 2-chloropropionate, n-propyl 2-chloropropionate, and 2-chloropropione. T-Butyl acid, cyclohexyl 2-chloropropionate, benzyl 2-chloropropionate and 2-
Ethyl bromopropionate or the like can be used.

The above-mentioned reaction of the dialkali metal salt of hydroquinone with the compound represented by the formula (I) is carried out in a lower alcohol, for example, ethanol in an equivalent amount. Reaction temperature is 10
~ 70 ℃, preferably set to 20-40 ℃, the reaction time is 0.
It is 5 to 10 hours, preferably 4 to 7 hours.

Such a reaction is shown by the following reaction formula.

(In the reaction formula, M represents an alkali metal) That is, a monoanion of 2- (4-hydroxyphenoxy) alkanoic acid ester represented by the formula (II) is produced, and an inorganic salt represented by the formula; MX, for example, Alkali metal halides such as sodium chloride and potassium chloride are by-produced. Further, with respect to a part of the monoanion represented by the formula (II) generated in the reaction formula, the reaction represented by the following reaction formula proceeds further, and the dimer represented by the formula (III) and the formula; The inorganic salts shown are by-produced. Further, in order to suppress the amount of the dimer represented by the formula (III) produced in the reaction represented by this reaction formula as much as possible, in the above reaction formula, an equivalent amount or more of the formula (I) with respect to the dialkali metal salt of hydroquinone is used. It is preferable to react the compound represented by The excess amount of the dialkaline metal salt of hydroquinone can be separated and recovered and reused as a raw material for production.

After completion of the above reaction, 2- (4-hydroxy) is obtained by neutralizing the reaction solution by adding an organic acid such as acetic acid or propionic acid or an acid such as mineral acid such as sulfuric acid, hydrochloric acid or phosphoric acid to the reaction solution. This produces a phenoxy) alkanoic acid ester. In such a neutralization step, it is easy to remove the water mixed with the recovered lower alcohol and the unreacted compound represented by the formula (I) in the subsequent step by using the acid in the highest possible concentration. For example, when using sulfuric acid, it is preferably 95% or more. In addition, since inorganic salts such as sodium sulfate and sodium chloride are by-produced also in the neutralization step, they are removed in a subsequent step.

The desired 2- (4-
A neutralization reaction liquid containing a hydroxyphenoxy) alkanoic acid ester will be described below (A),
The processes of (B) and (C) are sequentially performed. By performing the treatment in each of these steps, the desired high purity 2-
(4-Hydroxyphenoxy) alkanoic acid ester can be obtained in high yield and separated in each step.
It is possible to reuse substances other than the collected target substance. Hereinafter, each step will be described.

In the step (A), the lower alcohol used in the reaction step and the unreacted compound represented by the formula (I) from the neutralization reaction solution obtained in the previous neutralization step (hereinafter, referred to as "lower alcohol, etc."")) Is separated and collected.

The method for separating and recovering the lower alcohol and the like in the step (A) is not particularly limited, and may be heated to a temperature above the boiling point for distillation or evaporation, but in order to efficiently recover the alcohol, the amount of 60 to 760 Torr It is preferable to distill under reduced pressure at 60 to 140 ° C. The lower alcohol and the like separated and recovered in this manner are returned to the reaction step for reuse.

In the step (B) provided after the step (A), the residual liquid obtained by separating and recovering the lower alcohol and the like from the neutralization reaction liquid (hereinafter, referred to as
This residual liquid is referred to as "main stream of reaction liquid"), unreacted hydroquinone using water and an organic solvent, an inorganic salt by-produced in the reaction step represented by the above reaction formula and the inorganic salt formed in the neutralization step ( Hereinafter, when the term “inorganic salt” is used, it means an inorganic salt produced as a by-product in both steps) is extracted and removed as an aqueous phase, and the organic solvent is removed from the remaining organic solvent phase to obtain a crude It is a step of obtaining a 2- (4-hydroxyphenoxy) alkanoic acid ester-containing liquid.

The treatment method in the step (B) is not particularly limited. For example, after adding water and an organic solvent to the main stream of the reaction solution, mixing them sufficiently, and allowing them to stand, to separate them into an aqueous phase and an organic solvent phase,
This is done by separating each phase. That is, by such a method, hydroquinone and an inorganic salt can be transferred to an aqueous phase, and 2- (4-hydroxyphenoxy) alkanoic acid ester can be transferred to an organic solvent phase. Examples of the organic solvent used here include benzene, toluene, xylene, dichloromethane and carbon tetrachloride, and among these, xylene is preferable.

The larger the amount of water used in the step (B) is, the higher the removal rate of hydroquinone and inorganic salts can be. However, on the other hand, the amount of 2- (4-hydroxyphenoxy) alkanoic acid ester transferred to the aqueous phase is large. It is not preferable because it increases. Therefore, the amount of water depends on the concentration of inorganic salts in the aqueous phase.
It is preferable to adjust it so as to be 15 to 20% by weight. Further, the larger the amount of the organic solvent is, the higher the recovery rate of 2- (4-hydroxyphenoxy) alkanoic acid ester can be. However, in view of economical efficiency, 2- (4-hydroxy) in the organic solvent phase is considered. It is preferable to adjust the phenoxy) alkanoic acid ester concentration to be 15 to 20% by weight. The extraction temperature is 50 to 60 to prevent the formation of a mixed phase of water and an organic solvent at the interface between the water phase and the organic solvent phase.
C. is preferred.

In this way, the desired product 2- (4-hydroxyphenoxy) alkanoic acid ester can be separated from hydroquinone and an inorganic salt, and then the organic solvent is removed from the separated organic solvent phase by distillation or evaporation. Thus, a crude 2- (4-hydroxyphenoxy) alkanoic acid ester-containing liquid can be obtained. In addition, from the hydroquinone and inorganic salt separated as the aqueous phase, only hydroquinone can be further separated and reused as a raw material for producing a 2- (4-hydroxyphenoxy) alkanoic acid ester. That is, first, only hydroquinone is extracted and separated from an aqueous phase containing hydroquinone using an organic solvent such as ethyl methyl ketone or methyl isobutyl ketone that is azeotropic with water. Then, water is added to the extracted and separated phase of the organic solvent, and the organic solvent is removed by performing azeotropic distillation. The distilled organic solvent can be reused as the above-mentioned extraction solvent. The hydroquinone aqueous solution which is the distillation residual liquid is reused after being concentrated or crystallized.

The step (C), which is provided subsequent to the step (B), removes unnecessary substances having a low boiling point and a high boiling point from the crude 2- (4-hydroxyphenoxy) alkanoic acid ester-containing liquid obtained in the step (B). 2- (4-hydroxyphenoxy) as the balance
This is a step of recovering the alkanoic acid ester.

The removal of such undesired substances can usually be carried out by distillation or evaporation, but by appropriately setting the temperature, low-boiling substances and high-boiling substances (mainly the dimer represented by the formula (III) in the above reaction formula) It is preferable to remove it separately. Further, the slightly mixed 2- (4-hydroxyphenoxy) alkanoic acid in the content liquid is increased by converting it to an alkali metal salt with an equivalent amount of an alkali metal hydrogen carbonate or an alkali metal carbonate. It can be removed as a boiling material. Examples of the alkali metal hydrogencarbonate used here include sodium hydrogencarbonate, potassium hydrogencarbonate and the like;
Examples of the alkali metal carbonate include sodium carbonate, potassium carbonate and the like; among these, sodium hydrogen carbonate is preferable. The conditions for removing the unnecessary substances in the step (C) are not particularly limited, but the temperature is
When the temperature exceeds 220 ° C, 2- (4-hydroxyphenoxy) alkanoic acid ester may decompose, so at a temperature lower than the above temperature, preferably 10 Torr or less,
More preferably, it is desirable to carry out under reduced pressure of 5 Torr or less in the shortest possible time.

EXAMPLES Example 1 Hydroquinone disodium salt (1.00 kg) under nitrogen atmosphere 6.
After being dissolved in 49 l of ethanol, 0.806 kg of ethyl 2-chloropropionate was added at the same time, and the mixture was reacted at 35 ° C. for 6 hours. Next, the reaction solution was neutralized with 98% by weight concentrated sulfuric acid to obtain 7.32 kg of a neutralization reaction solution having the following composition.
The process of each process of (A)-(C) was performed.

Content (wt%) Hydroquinone 2.3 Ethyl 2-chloropropionate 0.9 Ethyl 2- (4-hydroxyphenoxy) propionate
13.4 Inorganic salt (sodium chloride, sodium sulfate) Step 11.4 (A): Next, the obtained neutralization reaction solution was subjected to simple distillation at 70 ° C. for 4 hours to recover ethanol and ethyl 2-chloropropionate (neutralization reaction Recovery rate of ethyl 2-chloropropionate from the liquid is 90%).

Step (B): Next, water is added to the residual liquid after removing ethanol.
Add 3.67 kg and 4.32 kg of xylene and stir well at 50 ° C.
After mixing, let stand and separate into water phase and xylene phase,
After that, each phase was separated. The inorganic salt concentration in the separated aqueous phase and the ethyl 2- (4-hydroxyphenoxy) propionate concentration in the xylene phase were both 18% by weight.
Next, 5.29 kg of water was added to the separated xylene phase, and the remaining unreacted hydroquinone was extracted and separated as an aqueous solution. By this extraction operation, the inorganic salt still remaining with hydroquinone was also extracted. The separated hydroquinone was made into a disodium salt and then reused as a raw material for production. The recovery rate of ethyl 2- (4-hydroxyphenoxy) propionate from the neutralization reaction solution in the xylene phase thus treated was 96%. Inorganic salts were completely removed and 97% of unreacted hydroquinone was removed. Then, the crude 2- (4
A liquid containing -hydroxyphenoxy) ethyl propionate was obtained.

Step (C): Then, 1.01 kg of the obtained containing liquid is added to 190
Simple distillation was performed at 1 ° C for 1 hour to remove unnecessary substances having a low boiling point, and further simple distillation was performed at 230 ° C for 3 hours to remove unnecessary substances having a high boiling point. In this way, 0.95 kg of ethyl 2- (4-hydroxyphenoxy) propionate having a purity of 94% was obtained. The recovery rate from the neutralization reaction solution was 91%.

Example 2 1.21 kg of dipotassium hydroquinone salt and 2 as raw materials for production
-Using 0.89 kg of n-propyl chloropropionate,
Example 1 except that the treatment of step (B) was performed as follows:
In the same manner as above, 0.89 kg of n-propyl 2- (4-hydroxyphenoxy) propionate having a purity of 93% (recovery rate from the neutralization reaction solution: 91%) was obtained.

Step (B): In the step (A), 4.58 kg of water and 4.32 kg of xylene were added to the residual liquid from which ethanol had been added, and the mixture was thoroughly stirred at 50 ° C., mixed, and then allowed to stand, and the aqueous phase (first Water phase)
And xylene phase were separated, and then each phase was separated. Inorganic salt concentration in the separated aqueous phase and 2- (4-
The concentration of ethyl hydroxyphenoxy) propionate was 18% by weight in each case. Next, 4.3 kg of water was added to the separated xylene phase, and the remaining unreacted hydroquinone was extracted and separated as an aqueous solution. The separated aqueous phase was added and mixed with the separated aqueous phase.

The aqueous phase thus obtained, 10.0 kg, was then concentrated until the concentration of the inorganic salts contained therein was 20% by weight. Then, 2.26 kg of methyl isobutyl ketone was added, and the mixture was sufficiently stirred and mixed, and allowed to stand to separate into an aqueous phase and a methyl isobutyl ketone phase. By this operation, unreacted hydroquinone was transferred to the methyl isobutyl ketone phase.
Then, after the methyl isobutyl ketone phase was separated, 0.6 kg of water was added thereto, and azeotropic distillation was carried out at 140 ° C. for 4 hours to distill off the methyl isobutyl ketone. After that, the residual liquid was cooled to 20 ° C, and the hydroquinone crystal was
0.17 kg (purity 80%, recovery rate from the first aqueous phase 85%) was obtained.

The hydroquinone thus recovered was made into a dipotassium salt and then reused as a raw material for production.

[Effects of the Invention] As described above, according to the production method of the present invention, the lower alcohol used in the reaction and the unreacted production raw material can be efficiently recovered and reused, and the inorganic salt and the It is possible to efficiently separate and remove unnecessary substances having a low boiling point and a high boiling point. Therefore, not only high-purity 2- (4-hydroxyphenoxy) alkanoic acid ester can be obtained in a high yield, but also useful substances can be effectively recovered and reused, resulting in reduction of manufacturing cost. Is also possible.

Claims (3)

[Claims] 1. A dialkaline metal salt of hydroquinone and the following formula (I); R ¹ CHXCOOR ² (I) (wherein X represents a halogen atom; R ¹ represents a hydrogen atom or a lower alkyl group; R ² represents A compound represented by a linear or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group or an aralkyl group) in a lower alcohol; and a step of adding an acid to neutralize the reaction solution. In the method for producing a 2- (4-hydroxyphenoxy) alkanoic acid ester comprising: (A) a lower alcohol and an unreacted compound represented by the formula (I) are separated and recovered from the neutralization reaction solution; ) Then, from the residual liquid obtained by separating and recovering the lower alcohol and the unreacted compound represented by the formula (I), hydroquinone and the inorganic salt are transferred to the aqueous phase using a mixed solvent of water and an organic solvent. , The water The organic solvent is removed from the remaining organic solvent phase, and then (C) the low-boiling unnecessary substances and the high-boiling unnecessary substances are removed from the residual liquid from which the organic solvent has been removed. A method for producing a 2- (4-hydroxyphenoxy) alkanoic acid ester, comprising recovering 4-hydroxyphenoxy) alkanoic acid ester. 2. The production method according to claim 1, wherein the lower alcohol is ethanol. 3. The acidic unwanted substance is removed by adding an alkali metal hydrogen carbonate or an alkali metal carbonate to the residual liquid from which the organic solvent has been removed in the step (C). The manufacturing method described.