JPH07242596A - Production of alpha-hydroxyisolactic acid esters - Google Patents

Abstract

PURPOSE:To obtain the subject compounds in high yield while suppressing by-products by separately mixing acetonecyanhydrin and water with sulfuric acid and subjecting the mixture to hydration reaction, adding an alcohol thereto and subjecting the reactional product to esterification reaction. CONSTITUTION:Acetonecyanhydrin and water are fractionated without previously mixing and these substances are each mixed with sulfuric acid and then, hydration reaction is carried out at 30-100 deg.C for 0.5-8hr. Specifically, e.g. acetonecyanhydrin and water are simultaneously and separately added to sulfuric acid or acetone cyanhydrin is previously mixed with sulfuric acid and water is added to the mixture or the acetonecyanhydrin and water are divided and the divided substances are successively added to sulfuric acid. Then, an alcohol (e.g. methanol) in an amount of 1-10 times by mol based on 1mol of acetonecyanhydrin is added to the reactional product and esterification reaction of the reactional product with the alcohol is carried out at 50-180 deg.C for 1-12hr. alphaHydroxyisolactic acid esters in the resultant reaction mixture are distilled while continuously feeding the alcohol to the reaction mixture to provide the objective alpha-hydroxyisolactic acid esters.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing .alpha.-hydroxyisobutyric acid esters from acetone cyanohydrin, more specifically, acetone cyanohydrin is reacted with water and sulfuric acid, and the reaction product is reacted with alcohol. The present invention relates to an improvement in the method for producing α-hydroxyisobutyric acid esters by adding an ester to the esterification reaction.

[0002] α-Hydroxyisobutyric acid esters are used as low toxicity solvents for paints, photoresists, printing inks, etc., and are also widely used as raw materials for monomers, raw materials for medicines and agricultural chemicals.

[0003]

2. Description of the Related Art Various methods for producing α-hydroxyisobutyric acid esters from acetone cyanohydrin have been known. For example, a method in which alcohol and concentrated sulfuric acid are added to acetone cyanohydrin to perform hydrolysis and esterification all at once (US Patent Specification No. 2041820).
), A method of reacting hydrochloric acid in place of concentrated sulfuric acid (US Pat. No. 2,245,483), reacting acetone cyanohydrin and alcohol in the presence of hydrogen chloride in a substantially anhydrous state to form an imidate, Next, there is a method of adding water and alcohol to the reaction product and reacting by heating (European Patent Publication No. 436676).

However, acetone cyanohydrin,
The method of reacting sulfuric acid and alcohol all at once has a drawback that methyl methacrylate (MMA) is a large byproduct, and the method of using hydrochloric acid or hydrogen chloride is an industrial manufacturing method such as requiring special equipment materials for corrosion. Is hard to adopt. In addition, acetone cyanohydrin has the following formula [1]
Since there is a dissociation equilibrium as shown in, in the conventional method, it is also considered that the dissociation of acetone cyanohydrin is occurring, the yield of the target α-hydroxyisobutyric acid ester decreases, There is also the problem of producing hydrogen cyanide, which is a toxic substance.

[0005]

[Chemical 1]

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems in the conventional method, and its object is to provide a method for producing α-hydroxyisobutyric acid esters which can be industrially advantageously carried out. Specifically, it is to provide safety in the reaction by suppressing side reactions such as dissociation of acetone cyanohydrin as a raw material, and to obtain α-hydroxyisobutyric acid esters in high yield. It is to provide a manufacturing method capable of

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, the dissociation of acetone cyanohydrin was promoted in the presence of water. When carrying out the sum reaction, if acetone cyanohydrin is separated from water and added to sulfuric acid to carry out the reaction, as shown in the examples below, the amount of by-product of acetone is small and the dissociation of acetone cyanohydrin is suppressed. It was found that the desired product, α-hydroxyisobutyric acid ester, can be obtained at a high yield. The present invention has been achieved based on such knowledge.

The present invention produces α-hydroxyisobutyric acid esters by reacting acetone cyanohydrin with water and sulfuric acid to carry out a hydration reaction, and adding alcohol to the reaction product to carry out an esterification reaction. In the above method, the hydration reaction is carried out by separating acetone cyanohydrin and water and mixing them with sulfuric acid to carry out the reaction.
The present invention relates to a method for producing hydroxyisobutyric acid esters.

The present invention will be described in detail below. The method of the present invention comprises the steps of separating acetone cyanohydrin and water, mixing them with sulfuric acid to cause a reaction to carry out a hydration reaction, and adding alcohol to the reaction solution to carry out an esterification reaction.

In carrying out the hydration reaction in the present invention, it is important to separate the raw materials acetone cyanohydrin and water without mixing them beforehand and to mix them with sulfuric acid before carrying out the reaction. Specifically, a method in which acetone cyanohydrin and water are separately added to sulfuric acid at the same time, a method in which water is added to a mixture of acetone cyanohydrin and sulfuric acid in advance, or acetone cyanohydrin and water are added respectively. A method of dividing and sequentially adding them to sulfuric acid is used. Further, when the raw materials are mixed, it is preferable that the temperature of the liquid does not suddenly rise to a high temperature. It is preferable to mix while maintaining a constant temperature within the range of room temperature to about 70 ° C.

The sulfuric acid used in the hydration reaction is selected from industrially available ones having a purity of about 90 to 98%, and the amount used is 0.5 to 1 mol of acetone cyanohydrin.
It is appropriately selected in the range of 1.5 times mol, preferably 0.8 to 1.2 times mol.

The amount of water used is 0.6 to 2 times mol, preferably 0.7 mol, relative to 1 mol of acetone cyanohydrin.
It is appropriately selected in the range of up to 1.5 times mol. The required water amount includes the water content in sulfuric acid. The amount of water used is
If the amount is less than 0.6 times by mole, the hydration reaction may be insufficient, or the operability may be deteriorated due to solidification in the system. If the amount is more than 2 times by mole, the reaction may proceed to hydrolysis. I may end up doing it.

The temperature of the hydration reaction is 30 to 100 ° C., preferably 40 to 70 ° C., and the reaction time is 0.5 to 8 hours, preferably 1 to 5 hours.

Examples of the alcohol used in the esterification reaction in the present invention include methanol, ethanol, propanol, isopropanol, butanol and the like.
The amount of alcohol used is appropriately selected in an equimolar amount or more, preferably in a range of 1 to 10 times by mol, relative to 1 mol of acetone cyanohydrin.

The temperature of the esterification reaction is 50 to 180.
C., preferably 60 to 160.degree. C., and the esterification reaction time is 1 to 12 hours, preferably 1 to 8 hours.

After the esterification reaction, the α-hydroxyisobutyric acid esters can be obtained from the reaction solution by neutralizing the esterification reaction mixture with a base such as ammonia or sodium hydroxide and then distilling it, or by esterification reaction mixture. Can be carried out by a method such as distilling the product while continuously supplying alcohol to the product, and then distilling it. However, from the viewpoint of both purification yield and operability, the product is continuously supplied while supplying alcohol. The method of distilling is preferable. At this time, the alcohol used for distilling is 2 to 20 times mol, preferably 3 to 1 mol, relative to 1 mol of acetone cyanohydrin.
It is appropriately selected within a range of 2 times the mole. Alcohol is water 3
A water-containing product of 0% by weight or less may be used. The distillation time is optional, but is usually 1 to 10 hours, preferably 2 to 7 hours.
It's time.

[0017]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 50.6 g (0.5 mol) of 97% sulfuric acid was charged into a reactor equipped with a stirrer, a thermometer, a dropping funnel, and a distillation apparatus, and 7.5 g (0.42) of water was stirred at room temperature. Mol) and 42.6 g (0.5 mol) of acetone cyanohydrin were gradually added simultaneously from separate dropping funnels. After dripping, 2 at 60 ℃
The reaction continued for an hour. Next, methanol 32.
After adding 0 g (1.0 mol) and reacting at 65 ° C. for 1 hour, 150 g (4.7 mol) of methanol was continuously fed while simultaneously distilling the product through a distillation apparatus. The reaction temperature at this time is from 65 ° C. to 13
The temperature was continuously raised to 0 ° C. Then, the distillate was purified by distillation to obtain 58.2 g of methyl α-hydroxyisobutyrate. As a result of gas chromatographic analysis, the purity is 99.9%.
And the yield of methyl α-hydroxyisobutyrate is 98.
It was 5%.

Example 2 In a reactor similar to that of Example 1, 50.6 g of 97% sulfuric acid (0.
(5 mol) was charged, and 21.3 g (0.25 mol) of acetone cyanohydrin was gradually added dropwise from the dropping funnel at room temperature with stirring, and subsequently 3.8 g (0.21 mol) of water was added from another dropping funnel. It was dripped slowly. The same dropping operation was repeated once again. After the completion of dropping, the reaction and distillation purification were performed in the same manner as in Example 1. As a result, the amount of methyl α-hydroxyisobutyrate obtained was 57.6 g, and the yield was 9
It was 7.5%.

Example 3 In a reactor similar to that of Example 1, 50.6 g of 97% sulfuric acid (0.
(5 mol) was charged, and 42.6 g (0.5 mol) of acetone cyanohydrin was gradually added dropwise from the dropping funnel at room temperature with stirring, and then 7.5 g (0.42 mol) of water was gradually added from the dropping funnel. Dropped. After the completion of dropping, the reaction and distillation purification were performed in the same manner as in Example 1. As a result, the amount of methyl α-hydroxyisobutyrate obtained was 54.3 g, and the yield was 91.9%. In addition, in the above-mentioned Examples 1 to 3,
In each case, the by-product of acetone was 0.5% or less.

Comparative Example 1 50.6 g of 97% sulfuric acid (0.
5 mol) and 7.5 g (0.42 mol) of water were charged,
42.6 g of acetone cyanohydrin (0.
5 mol) was gradually added dropwise from the dropping funnel. After the dropping is completed,
Reaction and distillation purification were carried out in the same manner as in Example 1. As a result, the obtained methyl α-hydroxyisobutyrate was 4
The amount was 7.2 g, and the yield was 79.9%. Also, 5% of acetone was by-produced.

Comparative Example 2 In a reactor similar to that of Example 1, 50.6 g of 97% sulfuric acid (0.
5 mol), and 42.6 g (0.5 mol) of acetone cyanohydrin and 7.5 g (0.4 mol) of water at room temperature with stirring.
A mixed solution of 2 mol) was gradually added dropwise from the dropping funnel. After the completion of dropping, the reaction and distillation purification were performed in the same manner as in Example 1. As a result, the amount of methyl α-hydroxyisobutyrate obtained was 42.5 g, and the yield was 72.0%. In addition, 6.1% of acetone was by-produced.

Comparative Example 3 50.6 g of 97% sulfuric acid (0.
5 mol), 7.5 g (0.42 mol) of water and 32.0 g (2 mol) of methanol were charged, and 42.6 g (0.5 mol) of acetone cyanohydrin was gradually added dropwise from the dropping funnel at room temperature with stirring. did. After the dropping was completed, stirring was continued at 60 ° C. for 2 hours. Then, distillation purification was performed in the same manner as in Example 1 except that the esterification step was omitted. as a result,
The amount of methyl α-hydroxyisobutyrate obtained was 26.8 g, and the yield was 45.4%. In addition, 9.4% of acetone was by-produced.

Examples 4 to 6 The reaction and distillation purification were carried out in the same manner as in Example 1 except that ethanol, propanol or butanol was used instead of methanol. The results are shown below. Also,
In each case, the by-product of acetone was 0.5% or less.

Example 4 Example 5 Example 6 Alcohol Ethanol Propanol Butanol Alcohol usage amount (esterification reaction) 46 g 60 g 74 g (distillation of reaction mixture) 150 g 200 g 250 g Final heating temperature at the time of distillation 145 ° C. 160 ° C. 180 ° C. Yield of α-hydroxyisobutyric acid ester 96.9% 95.3% 93.2%

[0026]

According to the method of the present invention, it is possible to suppress the production of hydrogen cyanide which is a toxic substance during the reaction and to obtain the α-hydroxyisobutyric acid ester in a high yield. The present invention also has the following advantages. (1) Safety is improved because hydrogen cyanide and its derivatives (formic acid, formic acid ester, etc.), which are toxic substances, are not generated during the reaction. (2) Since dissociation of acetone cyanohydrin is suppressed, the basic units of acetone cyanohydrin and alcohol are improved. (3) There are few by-products, and purification can be easily performed.

Claims (5)

[Claims] 1. A method for producing α-hydroxyisobutyric acid esters by reacting acetone cyanohydrin with water and sulfuric acid to carry out a hydration reaction, and adding alcohol to the reaction product to carry out an esterification reaction. In the method for producing α-hydroxyisobutyric acid ester, the hydration reaction is carried out by separating acetone cyanohydrin and water and mixing with sulfuric acid. 2. The method for producing α-hydroxyisobutyric acid esters according to claim 1, wherein the hydration reaction is a method in which acetone cyanohydrin and water are separately added to sulfuric acid at the same time. 3. The method for producing α-hydroxyisobutyric acid esters according to claim 1, wherein the hydration reaction is a method in which water is added to a mixture of acetone cyanohydrin and sulfuric acid previously mixed. 4. The method for producing α-hydroxyisobutyric acid esters according to claim 1, wherein the hydration reaction is a method in which each of acetone cyanohydrin and water is divided and these are sequentially added to sulfuric acid. . 5. The method according to claim 1, wherein after the esterification reaction, α-hydroxyisobutyric acid esters are distilled off while continuously supplying alcohol to the reaction mixture.
3. The method for producing an α-hydroxyisobutyric acid ester according to 3 or 4.