JPS6332775B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing organic carboxylic acid chloride, and further relates to a method for producing an organic carboxylic acid chloride, and further relates to a method for producing an organic carboxylic acid chloride in a high yield and by reacting a carboxylic acid or anhydride thereof with phosgene in the presence of a lower aliphatic amide catalyst. The present invention relates to an improved method for producing the corresponding carboxylic acid chlorides of high quality.

In recent years, carboxylic acid chloride has been used in heat-resistant resins, pharmaceuticals,
It has become industrially important as a raw material for agricultural chemicals, etc.

A common method for producing this type of carboxylic acid chloride is to salt a carboxylic acid with thionyl chloride, phosphorus pentachloride, phosphoryl chloride, or the like. However, these chlorinating agents are expensive, treatment of by-products is a problem, and industrial-scale production is accompanied by various disadvantages and difficulties.

A method using phosgene has been known for some time, but it has lower reactivity than the above-mentioned chlorinating agents and requires the use of a catalyst. In recent years, as catalysts, dimethylformamide (Japanese Patent Publication No. 43-10613), quaternary ammonium salts and phosphonium salts (Japanese Patent Publication No. 44-27363), tetraalkylthiourea (Japanese Patent Publication No. 44-27362), imidazole (Japanese Patent Publication No. 47-13021), or Although compounds such as trimethylphosphine oxide (Japanese Unexamined Patent Publication No. 30821/1982) have been proposed, lower aliphatic amides such as dimethylformamide are generally used as catalysts that have high activity and are available at low cost.

These catalysts are used to react a number of carboxylic acids or carboxylic acid anhydrides with phosgene,
The corresponding carboxylic acid chlorides are usually obtained in high yields and of high quality.

However, even when certain carboxylic acids such as phthalic acid or phthalic anhydride are reacted with phosgene in the presence of the above-mentioned known lower aliphatic amide catalysts, the corresponding carboxylic acid chlorides are obtained in extremely low yields. Not too much. For example, according to the method described in U.S. Pat. No. 3,810,940, phthalic anhydride and phosgene are reacted in a monochlorobenzene solvent using dimethylformamide as a catalyst, thereby yielding phthalic acid chloride. It is obtained at 71.6%. Furthermore, it has been reported that when a similar method was carried out in a hexane solvent, the desired product could not be obtained (US Pat. No. 3,318,950 (specification)).

As a result of intensive investigation into the cause of the low yield in the method disclosed in the above US patent, the present inventors found that if the cause is a high phosgene supply rate, the catalyst becomes a tar-like product from the early stage of the reaction and loses its catalytic activity. I learned that this is because the reaction stops progressing. Therefore, this is an extremely easy method from an industrial standpoint, in which the phosgene is supplied at such a rate that virtually no unreacted phosgene is detected in the exhaust gas until near the end of the reaction by adjusting the phosgene supply rate. The present invention was completed by discovering that the corresponding carboxylic acid chloride can be obtained in high yield and high quality.

Any method may be used to detect unreacted phosgene in the exhaust gas, but it can be easily confirmed, for example, by directly measuring the exhaust gas with a gas chromatograph.

The carboxylic acid or its anhydride that can be used in the present invention may be any known carboxylic acid or its anhydride, but in order for the effects of the present invention to be manifested, up to now, even if they are phosgenated, they can only be obtained in low yields. Carboxylic acid, such as phthalic acid, tetrahydrophthalic acid, or their anhydrides, succinic acid, maleic acid, or their anhydrides, which have two carboxyl groups and are located in a position within the molecule that allows them to form an anhydride. This is the case when applied to acids or their anhydrides.

As a catalyst, a lower aliphatic amide such as dimethylformamide is used.

The amount of the catalyst is preferably 0.01 mol or more, particularly 0.05 to 0.1 mol, per 1 mol of carboxylic acid; even if more than this is used, the reaction rate will not increase so much and only a tar-like product will be produced and the effect will be weak.

The operating temperature range is 50° to 120°C, especially 70° to 90°C. Below this, the reaction rate becomes low, and above this, the rate of formation of tar-like substances increases dramatically.

The reaction can be carried out in the presence or absence of a solvent. Any known solvent can be used as such a solvent, but aliphatic hydrocarbons such as hexane and heptane take a long reaction time and are not practical. Examples include oxygen-containing compounds such as tetrahydrofuran, carboxylic acid chlorides, and the like.

Next, examples of the present invention will be described.

Example 1 In a 300 ml four-necked flask equipped with a stirrer, gas inlet tube, thermometer and Dimroth condenser, 2.6 g (0.035 mol) of dimethylformamide, 74.1 g (0.50 mol) of phthalic anhydride and 74.1 g of toluene were added as catalysts.
I prepared g. While stirring, phosgene was blown in at a rate of 7 g/hour, and the reaction was carried out at 70°C for 10 hours. During this period, unreacted phosgene began to be detected in the exhaust gas when the conversion rate was approximately 90%.

After the reaction was completed, the catalyst layer was separated into a lower layer, and toluene was distilled off from the reaction solution under reduced pressure.

Continue to distill until the boiling point is 151°~154°C/20mmHg
100.5 g of a fraction (crude yield 99.0%) was obtained. The obtained o-phthalic acid chloride had a gun density of 99.4% and contained 0.4% of unreacted phthalic anhydride.

Comparative Example 1 The reaction was carried out in the same manner as in Example 1, except that the phosgene feed rate was 11 g/hour. During that time, the conversion rate was approximately
Unreacted phosgene was detected in the exhaust gas from the 50% point, and the reaction stopped in 7 hours.

It was treated in the same manner as in Example 1 to obtain 99.8 g of a fraction containing o-phthalic acid chloride. This fraction is 85%
of o-phthalic acid chloride, and the rest was unreacted phthalic anhydride.

Comparative Example 2 Reaction temperature was 100℃, phosgene supply rate was 14g/
The reaction was carried out in the same manner as in Example 1, except for the time.
During this period, unreacted phosgene was detected in the exhaust gas from the beginning of the reaction, and the conversion rate was approximately 50% for 4 hours after the start of the reaction.
At this point, the reaction stopped progressing.

It was treated in the same manner as in Example 1 to obtain 100.0 g of a fraction. This fraction contained 52% o-phthalic acid chloride, the remainder being unreacted phthalic anhydride.

Example 2 The reaction was carried out in the same manner as in Example 1, except that o-dichlorobenzene was used instead of toluene. The reaction was completed in 11 hours.

After the reaction was completed, the catalyst layer separated into the upper layer was separated, and the reaction solution was treated in the same manner as in Example 1, and 100.2 g
(crude yield 98.7%) was obtained. The o-phthalic acid chloride obtained had a purity of 99.1% and contained 0.7% of unreacted phthalic anhydride.

Example 3 Into a 200 ml reactor equipped with the apparatus described in Example 1, 50.0 g (0.5 mol) of succinic anhydride and toluene were added.
50 g and 2.6 g (0.035 mol) of dimethylformamide were charged. While stirring, add 10g of phosgene/
The reaction was carried out at 70°C for 6 hours.
During this period, unreacted phosgene began to be detected in the exhaust gas when the conversion rate was approximately 90%.

After the reaction is completed, the catalyst layer is separated into the upper layer, and the reaction solution is distilled under reduced pressure to produce succinic acid chloride.
76.7g (crude yield 99.0%) was obtained. The purity of the obtained succinic acid chloride was 99.8%.

Comparative Example 3 The reaction was carried out in the same manner as in Example 3, except that the phosgene feed rate was 14 g/hour. During that time, the conversion rate was approximately
Unreacted phosgene was detected in the exhaust gas at 30%, and the reaction stopped progressing at about 50% conversion, 6 hours after the start of the reaction.

The distillate was treated in the same manner as in Example 3 to obtain 70.5 g of a fraction containing about 48% succinic chloride, with the remainder being unreacted succinic anhydride.

Claims (1)

[Claims] 1 A benzene-based carboxylic acid or its anhydride, which has two carboxyl groups and is present in a position where they can mutually form an anhydride within the molecule;
Alternatively, when producing a carboxylic acid chloride by reacting a lower aliphatic carboxylic acid or its anhydride with phosgene in the presence of a lower aliphatic amide catalyst, substantially no gas is present in the exhaust gas until near the end of the reaction. A method for producing a carboxylic acid chloride, comprising supplying phosgene at a rate at which unreacted phosgene is not detected.