Preparation method of propanil

Abstract

The invention belongs to the field of organic synthesis, and discloses a preparation method of propanil, the propanil has a structure shown in a formula (1), the method comprises the following steps: under the catalysis of titanate, directly carrying out condensation reaction on 3, 4-dichloroaniline and propionic acid as raw materials to obtain propanil (3, 4-dichlorophenyl propionamide), and carrying out condensation reaction on the propanil (3, 4-dichlorophenyl propionamide) to obtain the propanil (3, 4-dichlorophenyl propionamide). In the reaction process, water generated by the reaction is removed in an azeotropic manner. The catalyst used in the method is low in price and is commonly used in industrial production; as the catalyst is added, the reaction time is obviously shortened, and the production efficiency is improved; according to the method, redundant propionic acid cannot be generated; the synthesized propanil is high in purity and good in yield, and the yield and the product quality can reach 99% or above. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing propanil. Background Art

[0002] Propanil, chemical name: 3,4-dichlorophenylpropionamide, common name in English: propanil. Developed by Rohm & Haas Co. in 1961, it is an amide contact herbicide with excellent control effect on barnyard grass, gentian, crabgrass, duckweed, fescue, water celery, etc. in rice fields. As the only C2 group (HRAC) amide paddy field herbicide, propanil belongs to the PSII photosynthetic inhibitor, which blocks photosynthesis by destroying the membrane system, causing weeds to dry up and die. Propanil has no cross-resistance with other agents and is particularly selective. It can be quickly decomposed into non-toxic substances by amide hydrolases in rice, but barnyard grass and others lack this detoxification function. Due to its unique mechanism of action, propanil has become an irreplaceable rice field herbicide.

[0003] Unfortunately, the biological activity of propanil is low, the dosage per unit area is large, and the use cost is high, so reducing the production cost of propanil is a problem that needs to be solved. The typical preparation methods of propanil reported in the prior art generally have the disadvantages of high cost, large amount of three wastes, and low production efficiency.

[0004] CN115181033 discloses a catalytic synthesis method of propanil, which uses phosphorus trichloride as an acylating agent and pyridine as a catalyst to synthesize propanil by reacting 3,4-dichloroaniline and propionic acid. Phosphorous acid and hydrochloric acid are produced in the reaction. The yield is 92-95% and the product purity is about 96%.

[0005] CN114230478 discloses a catalytic synthesis method of propanil, using a molecular sieve and a mixture of phosphine / nitrogen compounds as catalysts, and synthesizing propanil by reacting 3,4-dichloroaniline with propionyl chloride or propionic anhydride, and the reaction is accompanied by the generation of propionic acid or hydrochloric acid. CN113402410 reports a similar synthesis method, using 3,4-dichloroaniline and propionic acid and propionic anhydride as raw materials to synthesize propanil under the action of a catalyst. The catalyst is a quaternary ammonium salt phase transfer catalyst and polyethylene glycol.

[0006] The above invention technology has the following obvious disadvantages: first, expensive acylating agents such as propionic anhydride and propionyl chloride are used to participate in the reaction; second, propionic acid, hydrochloric acid or phosphorous acid is produced during the reaction; third, the catalyst is removed or recovered. These disadvantages lead to high production costs of propanil, large amounts of three wastes, and low production efficiency.

[0007] As we all know, titanate catalyst is a highly efficient multifunctional catalyst and an indispensable catalyst for the production of ester chemical products. It can significantly improve the reaction rate and selectivity of esterification reaction. In addition, it is also used to synthesize organic compounds such as ethers and polyurethanes. Commonly used titanates include isopropyl titanate, n-butyl titanate, and tert-butyl titanate.

[0008] In order to develop a clean, efficient and low-cost method for producing propanil, we surprisingly found that catalytic titanate can also efficiently catalyze the reaction of 3,4-dichloroaniline and propionic acid to synthesize high-content propanil with high selectivity, high conversion rate and high yield. Since the amount of catalyst used is very small and the price is low, there is no need to recover the catalyst, the post-treatment is simple, the production process is clean, and the production cost is significantly reduced. Summary of the invention

[0009] Based on the above technical background, the main purpose of the present invention is to provide a method for preparing propanil to overcome the shortcomings of the prior art.

[0010] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0011] The invention provides a method for preparing propanil, which comprises the following steps: 1) using titanate as a catalyst and taking 3,4-dichloroaniline and propionic acid as raw materials to synthesize propanil; 2) under the catalysis of titanate, 3,4-dichloroaniline and propionic acid react and dehydrate to generate propanil, and water generated during the reaction is removed by azeotropic removal.

[0012] Preferably, the catalyst is selected from at least one of isopropyl titanate, n-butyl titanate or tert-butyl titanate or a mixture of several thereof.

[0013] Preferably, the molar ratio of the catalyst, 3,4-dichloroaniline and propionic acid is (0.005-0.1):1:(1-5).

[0014] Preferably, the solvent is selected from aromatic hydrocarbons, alkanes, halogenated hydrocarbons or other single solvents or mixed solvents that form an azeotrope with water.

[0015] Preferably, the reaction temperature of the condensation reaction is 80-170° C., and the reaction time is 2-15 hours.

[0016] More preferably, the aromatic hydrocarbon is selected from one or a mixed solvent of benzene, toluene and xylene;

[0017] The alkane is selected from one or a mixed solvent of n-hexane, n-heptane, cyclohexane and petroleum ether;

[0018] The halogenated hydrocarbon is selected from one or a mixed solvent of chlorobenzene and fluorobenzene.

[0019] The beneficial effects of the present invention are:

[0020] (1) The preparation method of propanil of the present invention overcomes the problems existing in the existing propanil synthesis process, such as the production of excess propionic acid, large amount of three wastes, slow reaction, high cost, etc. The preparation method uses 3,4-dichloroaniline and propionic acid as raw materials and is prepared under the action of a catalyst. The catalyst used is low in price. By adding the catalyst, the reaction time can be shortened and the production efficiency can be effectively improved. At the same time, the preparation method does not use propionic anhydride, so that the preparation cost is significantly reduced.

[0021] (2) The preparation method removes the water generated by the reaction simultaneously by azeotropic means during the reaction, and does not add other water absorbents, so no excess propionic acid is generated. At the same time, dehydration accelerates the reaction, which can further improve the preparation efficiency. The removal of the solvent does not affect the next use. In addition, the preparation method does not require water washing, does not generate wastewater, has simple post-treatment, is easy to carry out continuous industrial production, and is a synthetic method that meets the requirements of green modern industrial production.

[0022] (3) The propanil obtained by the preparation method has high purity and good yield, and the yield and product purity can both reach more than 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The NMR spectrum of propanil prepared in Example 1 is shown. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below, and the characteristics and advantages of the present invention will become clearer and more distinct with the description.

[0025] The present invention provides a method for preparing propanil, which comprises:

[0026] (1) adding 3,4-dichloroaniline and propionic acid in the presence of a catalyst and a solvent, heating the mixture to carry out a condensation reaction, and removing water generated by the reaction by azeotropic removal during the reaction;

[0027] (2) After the reaction is completed, the solvent is removed under reduced pressure and the temperature is lowered to obtain the product propanil.

[0028] The above steps are described in detail below.

[0029] In (1), the catalyst is selected from one or more of titanates, preferably one or more of isopropyl titanate, n-butyl titanate, and tert-butyl titanate, more preferably isopropyl titanate or n-butyl titanate.

[0030] The test found that titanate can efficiently catalyze the reaction of 3,4-dichloroaniline and propionic acid, and can obtain high-content propanil with high selectivity, high conversion rate and high yield. Since the amount of catalyst used is very small and the price is low, there is no need to recover the catalyst, the post-processing is simple, the production process is clean, and the production cost is significantly reduced.

[0031] The solvent is selected from aromatic hydrocarbons, alkanes, halogenated hydrocarbons or other single solvents or mixed solvents thereof that form an azeotrope with water.

[0032] Preferably, the aromatic hydrocarbon is selected from one or a mixed solvent of benzene, toluene and xylene.

[0033] The alkane is selected from one or a mixed solvent of n-hexane, n-heptane, cyclohexane and petroleum ether.

[0034] The halogenated hydrocarbon is selected from one or a mixed solvent of chlorobenzene and fluorobenzene.

[0035] The other solvents that form an azeotrope with water are selected from one or more mixed solvents of ethanol, isopropanol, n-propanol, n-butanol, and tert-butanol.

[0036] More preferably, the solvent is chlorobenzene.

[0037] The preparation method generates an azeotropic dehydration reaction after heating, and after the reaction is completed, the product propanil is obtained after desolventizing and concentrating. The present invention utilizes the characteristic of forming an azeotropic mixture with water to bring out or remove water from the reaction process, thereby improving the reaction efficiency.

[0038] The molar ratio of the catalyst, 3,4-dichloroaniline and propionic acid is (0.005-0.1):1:(1-5).

[0039] Preferably, the molar ratio of the catalyst, 3,4-dichloroaniline and propionic acid is (0.01-0.02):1:1.5.

[0040] The temperature is raised to 80-170° C. for condensation reaction for 2-15 hours, preferably, the temperature is raised to 128-130° C. for condensation reaction for 3-10 hours. The reaction time is related to the amount of catalyst used and the reaction temperature. The greater the amount of catalyst used and the higher the reaction temperature, the shorter the reaction time; on the contrary, the longer the reaction time.

[0041] The present invention directly prepares propanil by using 3,4-dichloroaniline and propionic acid as raw materials to carry out condensation reaction under the action of a catalyst. The catalyst used is commonly used in industrial production and is low in price. Since the water generated by the reaction is removed synchronously during the reaction, no other water absorbent is added, no excessive propionic acid is generated, and dehydration accelerates the reaction without affecting the application of the solvent.

[0042] (2), after the reaction is completed, the solvent is removed under reduced pressure at -0.09 to -0.1, and the temperature is lowered to room temperature to obtain propanil.

[0043] After the solvent is removed under reduced pressure and then cooled, the product is directly obtained, and the obtained propanil has high purity. No water washing is required in the post-treatment process, and no waste water is generated. Since the solvent has been dehydrated, it can be directly applied to the next preparation process. In comparison, the reaction process and post-treatment process of the present invention are simple and very suitable for industrial production.

[0044] The structural formula of the propanil prepared by the preparation method of propanil is shown in formula (1):

[0045]

[0046] The preparation process of the preparation method of the present invention is shown in formula (2):

[0047]

[0048] Example

[0049] The present invention is further described below by specific examples, which are limited to illustrating the present invention but not to limiting the scope of the present invention. The raw materials used in the examples of the present invention were all purchased.

[0050] Example 1

[0051] 328g of chlorobenzene was added to a 1L reactor, and 3,4-dichloroaniline (163.7g, 1.0mol), propionic acid (112.3g, 1.5mol) and isopropyl titanate (5.70g, 0.02mol) were added in sequence under stirring, and the temperature was raised to 130°C for reflux. During the reaction, the water generated by the reaction was removed by azeotropic means, and the reflux dehydration was timed for 3 hours. After the reaction was completed, the solvent was removed under reduced pressure at -0.095MPa, and then the temperature was lowered to obtain a propanil solid, which was crushed and dried to obtain 217.9g of propanil product. The yield was 99.2% and the content was 99.3%.

[0052] Take an appropriate amount of propanil 1 H NMR analysis, the NMR spectrum of propanil is as follows Figure 1 As shown, the results are as follows:

[0053] 1 H NMR (CDCl3, 400MHz): δ10.1(s,1H),8.0(d,1H),7.51(q,1H),7.47(d,1H),2.33(q,2H),1.07(t,3H).

[0054] Example 2

[0055] 328g of chlorobenzene was added to a 1L reactor, and 3,4-dichloroaniline (163.7g, 1.0mol), propionic acid (112.3g, 1.5mol) and isopropyl titanate (2.85g, 0.01mol) were added in sequence under stirring, and the temperature was raised to 130°C for reflux. During the reaction, the water generated by the reaction was removed by azeotropic means, and the reflux dehydration was timed for 10 hours. After the reaction was completed, the solvent was removed under reduced pressure at -0.095MPa, and then the temperature was lowered to obtain a propanil solid, which was crushed and dried to obtain 218.1g of propanil product. The yield was 99.3% and the content was 99.5%.

[0056] Example 3

[0057] 328g of chlorobenzene was added to a 1L reactor, and 3,4-dichloroaniline (163.7g, 1.0mol), propionic acid (112.3g, 1.5mol) and n-butyl titanate (6.9g, 0.02mol) were added in sequence under stirring, and the temperature was raised to 130°C for reflux. During the reaction, the water generated by the reaction was removed by azeotropic means, and the reflux dehydration was timed for 3 hours. After the reaction was completed, the solvent was removed under reduced pressure at -0.095MPa, and then the temperature was lowered to obtain a propanil solid, which was crushed and dried to obtain 217.8g of propanil product. The yield was 99.0% and the content was 99.1%.

[0058] Example 4

[0059] 328g of xylene was added to a 1L reactor, and 3,4-dichloroaniline (163.7g, 1.0mol), propionic acid (112.3g, 1.5mol) and isopropyl titanate (5.7g, 0.02mol) were added in sequence under stirring, and the temperature was raised to 128°C for reflux. During the reaction, the water generated by the reaction was removed by azeotropic means, and the reflux dehydration was timed for 3 hours. After the reaction was completed, the solvent was removed under reduced pressure at -0.095MPa, and then the temperature was lowered to obtain a propanil solid, which was crushed and dried to obtain 218.1g of propanil product. The yield was 99.0% and the content was 99.0%.

[0060] Example 5

[0061] 328g of toluene was added to a 1L reactor, and 3,4-dichloroaniline (163.7g, 1.0mol), propionic acid (112.3g, 1.5mol) and isopropyl titanate (5.7g, 0.02mol) were added in sequence under stirring, and the temperature was raised to 118°C for reflux. During the reaction, the water generated by the reaction was removed by azeotropic means, and the reflux dehydration was timed for 4 hours. After the reaction was completed, the solvent was removed under reduced pressure at -0.095MPa, and then the temperature was lowered to obtain a propanil solid, which was crushed and dried to obtain 217.9g of propanil product. The yield was 99.1% and the content was 99.2%.

[0062] Comparative Example

[0063] Comparative Example 1

[0064] 328g of chlorobenzene was added to a 1L reactor, and 3,4-dichloroaniline (163.7g, 1.0mol) and propionic acid (112.3g, 1.5mol) were added in sequence under stirring, and the temperature was raised to 130°C for reflux, and the reflux dehydration was timed for 15 hours. After GC detection showed that the remaining 3,4-dichloroaniline did not change, the solution was desolventized at -0.095MPa, and then the temperature was lowered to obtain a waxy substance, which was crushed and dried to obtain 221.1g of the product. The yield of propanil was 81.2%, and the content was 80.1%.

[0065] Compared with Example 1, in Comparative Example 1, no catalyst was added during the reaction. After the reaction time was extended, the product yield and product purity were significantly reduced.

[0066] Comparative Example 2

[0067] 328g of chlorobenzene was added to a 1L reactor, and 3,4-dichloroaniline (163.7g, 1.0mol), propionic acid (112.3g, 1.5mol) and isopropyl titanate (5.7g, 0.02mol) were added in sequence under stirring, and the temperature was raised to 130°C for reflux, and the reaction was timed for 20 hours. After GC detection showed that the remaining 3,4-dichloroaniline did not change, the solution was desolventized at -0.095MPa, and then the temperature was lowered to obtain a waxy substance, which was crushed and dried to obtain 213.0g of the product. The yield of propanil was 88.2% and the content was 90.3%.

[0068] Compared with Example 1, in Comparative Example 2, no dehydration was performed during the reaction. After the reaction time was extended, the yield and product purity were significantly reduced.

[0069] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing propanil, characterized in that: 1) Titanate is used as a catalyst, and 3,4-dichloroaniline and propionic acid are used as raw materials to synthesize propanil; 2) Under the catalysis of titanate, 3,4-dichloroaniline and propionic acid react and dehydrate to generate propanil, and the water generated during the reaction is removed by azeotropic removal.

2. The preparation method according to claim 1, characterized in that: The catalyst is selected from at least one of isopropyl titanate, n-butyl titanate or tert-butyl titanate or a mixture of several thereof.

3. The preparation method according to claim 1, characterized in that: The molar ratio of the catalyst, 3,4-dichloroaniline and propionic acid is (0.005-0.1):1:(1-5).

4. The preparation method according to claim 1, characterized in that: The solvent is selected from aromatic hydrocarbons, alkanes, halogenated hydrocarbons or other single solvents or mixed solvents that form an azeotrope with water.

5. The preparation method according to claim 1, characterized in that: The reaction temperature of the condensation reaction is 80-170° C., and the reaction time is 2-15 hours.

6. The preparation method according to claim 4, characterized in that: The aromatic hydrocarbon is selected from one or a mixed solvent of benzene, toluene and xylene; The alkane is selected from one or a mixed solvent of n-hexane, n-heptane, cyclohexane and petroleum ether; The halogenated hydrocarbon is selected from chlorobenzene, fluorobenzene or a mixed solvent of the two.

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