JPS6116379B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing benzoins. Benzoin is useful, for example, as a polymerization initiator in producing photosensitive resins and as a pharmaceutical intermediate, and is usually produced by a condensation reaction of benzaldehyde. This reaction usually uses a water-soluble cyanide compound such as alkali cyanide as a catalyst, so it is necessary to use water as a solvent. The drawback is that the contact surface between benzaldehyde and the water containing the catalyst is small and the reaction does not proceed well. Therefore, in order to increase the contact surface between water and benzaldehyde, a method of using a mixed solvent of water and a lower alcohol such as methanol or ethanol is conventionally known. However, when this mixed solvent is used, it is necessary to treat the cyanide compound in the solvent after benzoin is recovered after the reaction is completed to render it harmless, but there is a drawback that this treatment is difficult to carry out sufficiently. Therefore,
From the viewpoint of solvent treatment after the completion of the reaction, it is desirable to use a water-only solvent, but when a water-only solvent is used, the reaction rate is very slow and the yield of benzoin is low. In view of the above circumstances, the inventors of the present invention have conducted various studies on methods for producing benzoin in high yield by reacting benzaldehyde in an aqueous solvent. They discovered that benzoin could be obtained in high yield by this method, and completed the present invention. That is, the gist of the present invention is to prepare benzaldehydes in an aqueous solvent using an alkali cyanide as a catalyst,
A method for producing benzoins by condensation reaction at a temperature of 80 to 100°C, characterized in that a cationic surfactant is present in the reaction system in an amount of 0.01 to 10 mol% based on benzaldehyde. It depends on the manufacturing method. The present invention will be explained in detail below. The method for producing benzoins targeted by the present invention is as follows:
This is a method in which a condensation reaction of benzaldehydes is carried out in an aqueous solvent in the presence of an alkali cyanide catalyst.
As the raw material benzaldehyde, in addition to benzaldehyde, for example, benzaldehyde having a substituent inert to the reaction such as a lower alkyl group or a halogen atom can also be used. The amount of water solvent used is usually 1.5 to 20 times the weight of the benzaldehyde, and if the amount of solvent used is too small, the reaction will not proceed well.
If the amount is too large, the burden of processing the solvent after the reaction becomes large, which is disadvantageous. The alkali cyanide used as a catalyst is usually sodium cyanide or potassium cyanide, and the amount used is usually 1 to 150 mol%, preferably 5 to 150 mol%, based on the benzaldehyde.
It is 30 mol%. If the amount of catalyst used is too small, the reaction will not proceed well, and if it is too large, there will be no problem with the reaction, but the subsequent cyan treatment will become troublesome, which is not preferable. The present invention requires the presence of a cationic surfactant in the reaction system. Specific examples of cationic surfactants include:
Examples include tetraalkylammonium halides such as dodecyltrimethylammonium chloride, benzyltrimethylammonium chloride, and tetrabutylammonium chloride, and alkylpyridinium halides such as dodecylpyridinium chloride. The amount of this surfactant used is 0.01 to 0.01 to benzaldehyde.
The amount is 10 mol %, preferably 0.05 to 3 mol %, particularly preferably 0.1 to 2 mol %. If the amount used is too small, the reaction rate will be slow, and if it is too large, the reaction mixture will foam, which is not preferable. The reaction of the present invention is carried out at 80 to 100°C, preferably from 85°C to
It is carried out at a temperature of 95 °C. The reaction time varies depending on the amount of catalyst used, etc., but is usually about 0.5 to 5 hours. To carry out the method of the invention, for example, a predetermined amount of solvent is added to a reactor equipped with a temperature controller and a stirrer.
After preparing a catalyst and a cationic surfactant, and then mixing benzaldehydes therewith,
The reaction can be carried out under stirring. After the reaction, the mixture is usually cooled to 30° C. or lower, and then benzoin crystals are recovered by filtration according to a conventional method. Since the reaction rate is fast in the method of the present invention, highly pure benzoin crystals can be obtained in high yield. However, if you want to obtain even higher purity benzoin crystals, The crystals can be easily purified to a highly pure product by washing with an organic solvent. The organic solvents used in this case are usually aliphatic alcohols with 1 to 8 carbon atoms such as methanol, ethanol, propanol, isopropanol, butanol, and octanol, and aliphatic alcohols with 3 to 6 carbon atoms such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. Ketone, methyl acetate, ethyl acetate, butyl acetate, etc. with 2 to 8 carbon atoms
Fatty acid esters are preferred. Furthermore, polyhydric alcohols such as methyl cellosolve and ethylene glycol, acetonitrile, diethyl ether, tetrahydrofuran, dioxane, toluene, and chlorobenzene can also be used. These organic solvents usually have a concentration of 0.3 to 10
Used in a range of double weight. The purification treatment may be carried out by suspension washing or sprinkling washing, but it is usually sufficient to carry out sprinkling washing in a Nutstie-type filter. As described above, according to the present invention, the presence of a specific surfactant in the reaction system allows the reaction to proceed well even in an aqueous solvent, and impurities in the obtained crystals can be easily removed with an organic solvent. Since it is a component, it is also suitable for obtaining high purity products. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 Water was added to a reactor equipped with a temperature controller and a stirrer.
Prepare 500g of sodium cyanide, 18.4g of soda cyanide, and the surfactant shown in Table 1, and add benzaldehyde to this.
After 265 g was added dropwise and mixed over 5 minutes, the reaction was carried out for 1.5 hours with stirring at a temperature of 90 to 92°C. After the reaction was completed, the mixture was cooled to 10° C., and then the benzoin crystals were filtered through a Nutsche type filter, and the crystals were washed by sprinkling with 800 g of water. The yield and purity of the crystals thus obtained were measured and the results shown in Table 1 were obtained.

[Table] Example 2 The benzoin crystals obtained by the method of Example 1 were sprinkled and washed twice with the organic solvent shown in Table 2 in an amount of 0.8 wt times the amount of the crystals on a Nutstie type filter, and then the crystals were washed. When the purity was measured, the results shown in Table 2 were obtained.

【table】

Claims (1)

[Claims] 1. A method for producing benzoins by subjecting benzaldehydes to a condensation reaction in an aqueous solvent using an alkali cyanide as a catalyst at a temperature of 80 to 100°C,
0.01 to 10 for benzaldehyde in the reaction system
1. A method for producing benzoins, characterized by the presence of a cationic surfactant with a leaky content of %. 2. Crystals of benzoins obtained by condensation reaction of benzaldehydes are mixed with at least one type selected from aliphatic alcohols having 1 to 8 carbon atoms, aliphatic ketones having 3 to 6 carbon atoms, and fatty acid esters having 2 to 8 carbon atoms. 2. A method for producing benzoins according to claim 1, which comprises washing with a compound.