CS210178B1 - Method of preparation of the p-chlorbenzoylchloride - Google Patents

Description

The invention relates to a process for the preparation of p-chlorobenzoyl chloride. p-Chlorobenzoyl chloride is a dyeing semi-finished product which, among other applications, can also be a starting material in the preparation of p-chlorobenzoic acid.

Its preparation is little described. Known prior processes (Beilstein: Organische Chemie, 2nd Edition, Vol. 9, 227 (1949)) use the chlorination of benzoyl chloride to the nucleus under the catalysis of ferric ions, or start from toluenesulfochloride.

Cs. No. 206,485 claims a process for its preparation by partial hydrolysis of p-chlorobenzotrichloride. It has now been found that, similarly to the process for the preparation of benzoyl chloride by condensation of benzotrichloride with benzoic acid, published by Shearon, Hall and Stevens (Ind. Eng. Chem. 41, 1812 (1949)) and introduced in the domestic production, chlorobenzoyl chloride by condensation of p-chlorobenzotrichloride with p-chlorobenzoic acid.

In the preparation of benzoyl chloride by this process, the molten benzoic acid is fed at a temperature of 122 to 126 ° C in the presence of ferric chloride as the benzotrichloride catalyst. Both components react under these conditions to form benzoyl chloride and hydrochloric acid. However, it has been found that in the case of the preparation of p-chlorobenzoyl chloride from p-chlorobenzoic acid and p-chlorobenzotrichloride by the same procedure, the reaction must be carried out at a temperature above 240 ° C, which entails operational difficulties.

It has now been found that a better way to carry out the reaction is to introduce p-chlorobenzotrichloride into the non-molten p-chlorberiaic acid.

The process for the preparation of p-chlorobenzoyl chloride by condensation of p-chlorobenzotrichloride with 210178 p-chlorobenzoic acid under the catalytic action of anhydrous aluminum chloride or gelatinous chloride according to the present invention consists in introducing into the pre-p-cis-orbenzoic acid successive p-chlorobenzotrichloride 20 to. 50 ° C, the mixture is reacted and liquefied at 50 to 100 ° C, then the remainder of p-chlorobenzotrichloride is added and the process is repeated, or the total amount of p-chlorobenzotrichloride is added simultaneously at 20 to 50 ° C in the reaction space. p-chlorobenzoic acid and the mixture is gradually heated with stirring while the progress of the reaction is controlled by the evolution of hydrochloric acid and controlled by maintaining the reaction temperature at 50 to 150 ° C. For complete reaction, this is increased to 200-240 ° C.

The examples below illustrate an embodiment of the process of the invention.

Examples

He did

In a 700 ml reaction flask equipped with a stirrer, thermometer, reflux condenser, p-chlorobenzotrichloride feed meter and nitrogen inlet, placed in a heating bath, 136 g (0.87 mol) of p-chlorobenzotrichloride and nitrogen inlet were placed. 136 g (0.87 mol) of p-chlorobenzoic acid and 0.2 g of ferric chloride powder were introduced in the bath. The contents flask was heated to 240 ° C and then p-chlorobenzotrichloride was continuously metered at a rate of 200 g (0.87 mol) over 80 to 90 minutes.

The reaction mixture was then further stirred at that temperature, reacting, becoming liquid and darkening. The total reaction time was 5 to 6 hours. The reaction mixture was then transferred to a distillation cell and fractionally distilled under reduced pressure (3.5-4 kPa). The conversion was 96%, dest. the remainder 4.0 to 4.5%. The course of the reaction was monitored according to the development of HC1 after its absorption in water by conductometry.

This process is hampered by the fact that at a high temperature above 240 ° C, which is necessary to melt the p-chlorobenzoic acid and to achieve good mixability, the p-chlorobenzoic acid also sublimates and settles on the cooler walls of the device, worsens the course of the reaction. As the amount of p-chlorobenzoyl chloride formed increases, the settled acid is washed off and reacted gradually during the distillation in the apparatus, but the reaction time is prolonged and the p-chlorobenzoic acid is generally released completely from the condenser by warming it.

Example 2

136 g (0.87 mole) of p-chlorobenzoic acid and 0.2 g of ferric chloride at 50-60 ° C were charged several times with 50 g of p-chlorobenzotrichloride. The temperature was further increased gently with stirring. The reaction mixture reacted slightly and liquefied within 30 to 40 minutes. Thereafter, a continuous dosing of the remaining amount (150 g) of p-chlorobenzotrichloride was started and the temperature was gradually raised to 220-230 ° C with stirring. The course of the reaction was followed by conductometry as in Example 1. The distillation of the p-chlorobenzoyl chloride formed was also carried out in the same manner.

Example 3

200 g (0.87 mol) of p-chlorobenzotrichloride, 0.1 g of ferric chloride and 136 g (0.87 mol) of p-chlorobenzoic acid were charged simultaneously to the reaction flask as in Example 1. The mixture was continuously heated slowly with stirring, and the reaction was checked according to the development of hydrochloric acid, monitored as in Example 1 by conductometry. The flask was heated to 200-220 ° C in 200-240 minutes. During this time, the mixture reacts. It was then stirred at boiling point of p-chlorobenzoyl chloride (222 ° C) for an additional 30-60 minutes. It was then cooled and transferred to a distillation flask for fractional distillation under reduced pressure. Up to 99% conversion was achieved. The distillation residue was 1.37% by weight to distil the reaction mixture.

Example

In a reaction flask as in Example 1, 200 g (0.87 mol) of p-chlorobenzotrichloride and 136 g (0.87 mol) of p-chlorobenzoic acid were reacted with catalytic treatment with 0.1 g of chloride as described in Examples 1 to 3. aluminum. The further procedure was the same as in Examples 1-3.

Claims (1)

Process for the preparation of p-chlorobenzoyl chloride by condensation of p-chlorobenzotrichloride with p-chlorobenzoic acid under the catalytic action of anhydrous aluminum chloride or iron (III) chloride, characterized in that p-chlorobenzotrichloride is introduced successively into the pre-p-chlorobenzoic acid at 20 to 50 ° C. the mixture is allowed to react and liquefy at a temperature of 50 to 100 ° C, then the remainder of p-chlorobenzotrichloride is added and the process is repeated, or the total amount of p-chlorobenzotrichloride and p- chlorobenzoic acid, and the mixture is gradually heated with stirring while the progress of the reaction is controlled by the evolution of hydrochloric acid and controlled by maintaining the reaction temperature at 50-150 ° C and increasing the temperature to 200-240 ° C to fully react the components.