JPH09255617A - Production of alkylbenzoyl chloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an alkylbenzoyl chloride useful as a raw material, etc., for agrochemicals in high yield by suppressing side reactions. SOLUTION: An alkylbenzaldehyde, e.g. p-ethylbenzaldehye is reacted with chlorine in the coexistence of tertiary amines, e.g. triethylamine at -10 to +80 deg.C temperature to provide an alkylbenzoyl chloride, e.g. p-ethylbenzoyl chloride. The selectivity for the p-ethylbenzoyl chloride according to this method is 86% and the acid chloride is obtained at a higher selectivity than 48% which is obtained when setting the reactional temperature at 150 deg.C.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an alkylbenzoyl chloride by chlorinating an alkylbenzaldehyde. Alkylbenzoyl chloride is widely used as a raw material and an intermediate for agricultural chemicals, chemical products and the like.

[0002]

2. Description of the Related Art Conventionally, as a method for producing benzoyl chlorides, a method obtained by hydrolysis of corresponding benzotrichloride has been considered economical. In addition, a method of obtaining a corresponding acid chloride by chlorinating an alkylbenzenecarboxylic acid as a raw material with a chlorinating agent such as thionyl chloride or phosphorus pentachloride, or to react benzaldehyde having no alkyl side chain with chlorine A method for obtaining acid chloride (US Pat. No. 3,894,923) and the like are known.

[0003]

Among these, when the corresponding alkylbenzoyl chloride is produced by the method by hydrolysis of benzotrichlorides, the alkylbenzotrichloride must be used as a raw material. In order to obtain alkylbenzotrichloride, only one methyl group on the alkylbenzene having at least two alkyl substituents must be selectively chlorinated, and it is extremely difficult to selectively carry out such a reaction. Is. Although the method of chlorinating alkylbenzene carboxylic acid with thionyl chloride has a high yield of acid chloride, the use of these chlorinating agents is more expensive than the case of using chlorine as a raw material, and the point of purification and post-treatment is required. There are many problems.

On the other hand, benzaldehyde reacts with chlorine to obtain benzoyl chloride in a high yield, and is therefore an excellent method for producing benzoyl chloride having no alkyl substituent. However, when an alkylbenzaldehyde having an alkyl side chain as a raw material is reacted with chlorine, it is difficult to obtain a corresponding alkylbenzoyl chloride in a high yield, and an industrial production method of such an alkylbenzoyl chloride has never been known so far. Not not.
This is because the side chain alkyl group of the alkylbenzaldehyde easily reacts with chlorine. For example, when the side chain alkyl group of the raw material alkylbenzaldehyde is reacted with chlorine by the method described in the above-mentioned US Pat. No. 3,894,923. In addition, a large amount of a side chain chlorinated product of the desired product, alkylbenzoyl chloride, is produced as a by-product, and the yield of the desired product, alkylbenzoyl chloride, is significantly impaired. Further, since the boiling points of these by-products and the target substance are close to each other, separation by distillation is difficult, which causes a problem of purification. In view of these facts, an object of the present invention is to provide a method for producing an alkylbenzoyl chloride from an alkylbenzaldehyde and chlorine at a high yield and at a low cost.

[0005]

Means for Solving the Problems As a result of intensive studies on the method for producing an alkylbenzoyl chloride from an alkylbenzaldehyde and chlorine, the present inventors have found that by allowing amines to coexist in the reaction system, The inventors have found that side reactions such as side-chain chlorinated compounds are significantly suppressed, and that the desired acid chloride can be obtained in an extremely high yield, and have reached the present invention. That is, in the present invention, alkylbenzaldehyde and chlorine are mixed in the presence of amines in the range of -10 to 80
A method for producing an alkylbenzoyl chloride, which comprises reacting at a temperature of ° C.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The alkylbenzaldehyde used in the present invention is represented by the following chemical formula.

Embedded image In the above formula, R is an alkyl group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group and an isobutyl group, and m and n are integers of 1 to 5 representing the number of substituents. m + n ≦ 6. Specific examples of the alkylbenzaldehyde are o-, m-, p-tolualdehyde, ethylbenzaldehyde, isopropylbenzaldehyde, isobutylbenzaldehyde, 2,4-dimethylbenzaldehyde, 2,
6-Dimethylbenzaldehyde, 2,4,5-trimethylbenzaldehyde and the like can be mentioned to obtain the corresponding alkylbenzoyl chloride.

The chlorine used in the present invention is not particularly limited as long as it is industrially available, but it is preferably dried. Chlorine is usually reacted by bubbling in a reaction solution, but the supply amount and supply rate are not particularly limited. The reaction pressure is 5 kg / cm ² or less, and the reaction is usually performed at normal pressure.

In the present invention, the coexistence of amines in the reaction system is very effective in increasing the yield of the desired alkylbenzoyl chloride. It is preferable to use tertiary amines as the coexisting amines,
More effective. Specific examples of the tertiary amines include saturated aliphatic amines such as triethylamine, triethylamine hydrochloride and tri-n-butylamine and salts thereof, substituted saturated aliphatic amines such as triethanolamine and tri-n-propanolamine, Aromatic amines such as pyridine, α-, β-, γ-picoline and the like can be mentioned. The amount of amines used is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 1 part by weight, based on 1 part by weight of the starting material alkylbenzaldehyde. If the amount used exceeds this range, it will not affect the reaction results, but excessive use is not economical. On the other hand, if the amount is less than this range, byproducts such as nuclear chlorinated compounds and side-chain chlorinated compounds as well as high-boiling products are generated, and the yield of the desired acid chloride is reduced, which is not preferable.

In carrying out the present invention, a solvent is not always required if the starting material alkylbenzaldehyde is a liquid under the reaction conditions. However, the use of a solvent is effective in suppressing side reactions such as side chain chlorination and increasing the yield of the intended alkylbenzoyl chloride. For this reason, a solvent inert to chlorination is used, and examples thereof include o-dichlorobenzene, chlorobenzene, carbon tetrachloride and benzonitrile. A small amount of the solvent is effective, and is preferably 0.5 to 100 parts by weight, more preferably 1.0 to 50 parts by weight, relative to 1 part by weight of the starting material alkylbenzaldehyde. If the amount used exceeds this range, it does not affect the reaction results, but it is uneconomical because the amount of solvent circulation increases. By using such a solvent, the production of byproducts such as chlorinated compounds and side-chain chlorinated compounds and high boiling point products is reduced, and the yield of the desired alkylbenzoyl chloride is improved.

The reaction of the present invention is usually carried out under exposure.
The light source is not particularly limited, but industrially, a mercury lamp, a tungsten lamp, or the like is installed as a light source in the reactor to obtain high reaction activity and selectivity for acid chloride. Further, the use of a radical generator such as benzoyl peroxide or 2,2-azobis (isobutyronitrile) instead of exposing it is also effective to enhance the activity of the reaction. In this case, the amount of radical generator used may be small,
The amount is about 0.001 to 0.01 parts by weight per 1 part by weight of the alkyl benzaldehyde as a raw material. Even if the amount of radical generator used exceeds this range, the yield does not change, and the use of a large amount is economically undesirable.

Control of the reaction temperature is extremely important in carrying out the present invention. The reaction temperature is in the range of -10 to 80 ° C, preferably 0 to 50 ° C. When carried out at a temperature higher than this range, side reactions such as chlorination of alkyl side chains and nuclear chlorination, and formation of high-boiling components due to polymerization of raw materials and products are likely to occur, resulting in a marked yield of the target product. descend. Further, when the reaction is carried out at a temperature lower than this range, not only the activity of the reaction is lowered, but also the raw materials and products may be below the freezing point.

[0012]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 500 m equipped with a gas blowing pipe, a reflux condenser and a stirrer
In a 1-flask, 70 g of p-ethylbenzaldehyde, 20 g of triethylamine, and 210 g of o-dichlorobenzene.
g was charged, and the temperature in the system was adjusted to 10 ° C. while introducing nitrogen gas from the gas blowing tube. After bubbling nitrogen gas for 1 hour, the reaction was started by stopping the supply of nitrogen and starting the irradiation of light with a mercury lamp simultaneously with the supply of chlorine. While maintaining the reaction temperature at 5 ° C., 38 g of chlorine was supplied over 1 hour to carry out the reaction. When the reaction product solution was analyzed by gas chromatography, the reaction results were 92% for p-ethylbenzaldehyde and 86% for p-ethylbenzoyl chloride.

Example 2 The reaction was carried out in the same manner as in Example 1 except that a 200 ml flask was used and o-dichlorobenzene was not used. As a result, the reaction rate of p-ethylbenzaldehyde was 90.
%, P-ethylbenzoyl chloride selectivity of 80% was obtained.

Example 3 Instead of triethylamine, triethylamine hydrochloride 1
The reaction was carried out in the same manner as in Example 1 except that 0 g was used. As a result, the reaction rate of p-ethylbenzaldehyde was 94%, and the selectivity of p-ethylbenzoyl chloride was 80%.
A reaction result of% was obtained.

Example 4 A reaction was carried out in the same manner as in Example 1 except that p-tolualdehyde was used instead of p-ethylbenzaldehyde and 42 g of chlorine was supplied. As a result, the reaction rate of p-tolualdehyde is 92% and the selectivity of p-toluoyl chloride is 85%.
The reaction result was obtained.

Comparative Example 1 The reaction was carried out in the same manner as in Example 1 except that triethylamine was not used. As a result, the reaction rate of p-ethylbenzaldehyde was 90% and the selectivity of p-ethylbenzoyl chloride was 75%.

Comparative Example 2 The reaction was carried out in the same manner as in Example 1 except that the reaction temperature was 150 ° C. As a result, a reaction rate of p-ethylbenzaldehyde of 97% and a selectivity of p-ethylbenzoyl chloride of 48% were obtained.

[0019]

As is apparent from the above examples, in the method for producing an alkylbenzoyl chloride from an alkylbenzaldehyde and chlorine according to the present invention, the presence of amines in the reaction system causes the formation of a nuclear chlorinated compound or a side chain. Side reactions such as chlorinated compounds are significantly suppressed, and the desired acid chloride can be obtained in an extremely high yield. The method of the present invention is advantageous in terms of equipment since the reaction for treating a chlorinated product is carried out at a low temperature, and is an industrially excellent method. Therefore, the industrial significance of the present invention is great.

Claims (2)

[Claims] 1. A process for producing an alkylbenzoyl chloride, which comprises reacting an alkylbenzaldehyde with chlorine in the presence of amines at a temperature of -10 to 80 ° C. 2. The method for producing an alkylbenzoyl chloride according to claim 1, wherein the coexisting amines are tertiary amines.