CS201375B1 - Process for preparing n-chlormethylphthalimide - Google Patents

Description

The present invention relates to a process for the preparation of N-chloromethylphthalimide from hydroxymethylphthalimide and hydrogen chloride.

The preparation of N-chloromethylphthalimide by reacting hydrochloric acid in the form of concentrated hydrochloric acid to N-hydroxymethylphthalimide is known (Ber. 41, 242 (1908)). A similar process for the preparation of N-chloromethylphthalimide is based on the reaction of phthalimide with formaldehyde and hydrogen chloride also in the presence of concentrated hydrochloric acid (Hung. Teljes 6430 (C.A. vol. 80, 37097 q.)). The disadvantage of these processes, due to the fact that both the starting material and the reaction product is a slurry of hydrochloric acid crystals with difficult to control reaction progress and deteriorated mixing conditions, eliminates processes which use an inert organic solvent to isolate the resulting N-chloromethylphthalimide. No. 120,423, U.S. Pat. No. 4,013,685 or English Pat. No. 1,487,038).

Apart from the necessity of using hydrochloric acid, the volumes of which are not small, so that besides a considerable amount of undesirable polluting and polluting waste and a particularly low utilization of the apparatus, another disadvantage is the need to use crystalline N-hydroxymethylphthalimide as one of the starting components. The production of N-hydroxymethylphthalimide requires a number of accompanying technological operations, such as cooling, crystallization, centrifugation, drying as well as the actual preparatory handling and transport to the reaction equipment.

The aforementioned drawbacks are substantially eliminated by the process for the preparation of N-chloromethylphthalimide from N-hydroxymethylphthalimide and hydrogen chloride in the presence of an inert organic solvent according to the invention, characterized in that N-hydroxymethylphthalimide is in the form of an aqueous solution of the reaction mixture at 50-100 ° C; containing, for 1 mole of N-hydroxymethylphthalimide, 0 to 0.5 mole of formaldehyde and 2 to 25 mole of water are added to the aromatic organic inert solvent and the hydrogen chloride is replaced with chlorine by chlorine to N-chloromethylphthalimide.

In the process according to the invention, the isolation of N-hydroxymethylphthalimide associated with a number of the above-mentioned unit technological operations is eliminated. The hot aqueous solution of the reaction mixture of N-hydroxymethylphthalimide is desirably discharged into an inert organic solvent under conditions such that a good miscible suspension of N-hydroxymethylphthalimide crystals in the chosen solvent is formed. This is achieved by selecting a suitable stirrer and its speed as well as the temperature of the selected solvent.

Of the conventional organic inert solvents, especially benzene, toluene, xylene, chlorobenzene, alkylnaphthalenes, various hydrocarbon fractions, mixtures thereof and the like are suitable. The subsequent reaction with hydrogen chloride gas can be carried out over a wide temperature range - from the lahoratic temperature to the azeotrope temperature of the selected solvent with water. Optimally, however, the temperature range is between 50 and 70 ° C. At higher temperatures, some other side reactions take place which contaminate the N-chloromethylphthalimide formed and reduce yields, whereas lower temperatures would require cooling due to the exothermic reaction, which would be disadvantageous.

From the solution of N-chloromethylphthalimide obtained in the solvent, the desired N-chloromethylphthalimide in solid form can be obtained by distilling off the solvent. In most cases, it is more preferably used in the form of a solution directly to the next stages of preparation. It is particularly preferred for the manufacture of an insecticidal composition based on phosmet (O, O-dimethyl-S-phthalimidomethyldithio phosphate).

The following examples illustrate but do not limit the preparation of the N-chloromethylphthalimide of the invention.

Example 1

A mixture of 29.4 g of 98% phthalimide and 7.2 g of phonaldehyde in the form of 36 g of a 20% aqueous solution was heated under reflux for half an hour at a reflux temperature of 97-100 ° C. The resulting clear solution was poured in a thin stream into 160 g of well stirred toluene at this temperature, which was placed in a 500 ml three-necked flask equipped with a thermometer, a reflux condenser, a stirrer and an inlet tube for hydrogen chloride gas reaching under the stirrer. The flask was fitted with a stopcock at the bottom. Hydrogen chloride gas was introduced through the gas inlet tube while maintaining the temperature of the contents of the flask at 55-60 ° C. After chlorination, which took about 2.5 hours, two clear liquid layers were formed, the bottom of which weighed 41.7 g. The toluene solution of N-chloromethylphthalimide was washed while warm at 55-60 ° C with 40 ml of a 5% aqueous NaHCO ₃ solution, evaporated to dryness in a vacuum rotary evaporator, and the product was allowed to dry to constant weight. There were obtained 37.4 g of N-chloromethylphthalimide, mp 128-132 ° C, with a cleavable chlorine content of 16.48%, by weight, which represents an 88.8% yield calculated on the starting phthalimide.

Example 2

A mixture of 29.4 g of 98% phthalimide and 7.2 g of formaldehyde in the form of 20 g of a 36% aqueous solution was refluxed at 97-100 ° C for 1 hour. The resulting clear solution was poured in a thin stream into 160 g of well-mixed xylene, which was placed in the reaction flask as in the example.

1. Unchanged as in Example 1, 36.8 g of dry chloromethylphthalimide, m.p. t. 128 DEG-133 DEG C. with a cleavable chlorine content of 17.5%, which represents a 92.8% yield of theory.

Example 3

A mixture of 73.6 g of 99% phthalimide and 50.1 g of a 35.9% aqueous formaldehyde solution was heated to reflux at 97-100 ° C for half an hour with stirring. The resulting clear aqueous solution of N-hydroxymethylphthalimidium was then charged with 400 g of toluene, bringing the temperature of the flask to about 60 ° C. The reaction flask was provided with an inlet tube extending to the bottom and hydrogen chloride gas was introduced while maintaining the temperature of the contents of the flask at 55-60 ° C. The further procedure was identical to that described in Example 1. 92.1 g of N-chloromethylphthalimide were obtained with a cleavable chlorine content of 16.73% by weight. which represents 92.33% purity and yield

87.8% of theory, calculated on the starting phthalimide.

Claims (2)

2 of the stirrer and its rotational speed, as well as the temperature of the selected solvent. Among the common organic inert solvents are, in particular, benzene, toluene, xylene, chlorobenzene, alkylnaphthalenes, hydrocarbon fractions, and the like. The subsequent reaction with chlorine gas can take place over a wide range of temperatures - from the lahoratine temperature to the temperature of the azeotrope of the solvent selected by water. However, optimally the temperature range is 50 to 70 ° C. At higher temperatures, some other side reactions, which contaminate the resulting N-chloromethylphthalide and reduce yields, take place while lower temperatures required cooling for the exothermic course of the reaction, which would be disadvantageous. From the resulting N-chloromethylphthalimide solution in the solvent, the desired N-chloromethylphthalimide can be obtained by distilling off the solvent. In most cases, it is preferable to use it in the form of a solution directly to other stages of preparation. It is particularly advantageous to use it for the preparation of an insecticidal composition based on phosmet (0,0-dimethyl-S-phthalimido-methyldithiophosphate). The following examples illustrate, but do not limit, the preparation of N-chloromethylphthalimide according to the invention. EXAMPLE 1 A mixture of 29.4 g of 98% phthalimide and 7.2 g of formaldehyde in the form of 36 g of a 20% aqueous solution was heated under reflux for 97 minutes at reflux temperature of 97-100 ° C. The resulting solution was poured at this temperature with a thin stream of up to 160 g of good stirred toluene, which was placed in a 500 ml thrombone flask equipped with a thermometer, a low-temperature chiller, a stirrer, and a feed tube gaseous with hydrogen chloride reaching under the stirrer. The flask was fitted with a coarse layer to drain the layers at the bottom. Hydrogen chloride gas was introduced through the gas line and the flask temperature was maintained at 55-60 ° C. After chlorination, which lasted about 2.5 hours, a double layer of liquid formed, of which the bottom weight of 41.7 g was separated. The toluene solution of N-chloromethylphthalimide was washed with 40 ml of 5% aqueous NaHCO3 solution while hot at 55-60 [deg.] C., evaporated to dryness on a vacuum rotary evaporator, and the product was allowed to dry to constant weight. 37.4 g of N-chloromethylphthalimide (m.p. 128-132 ° C) with a chlorine-cleavable content of 16.48% by weight were obtained, representing a 88.8% yield of the starting phthalimide. Example 2 A mixture of 29.4 g of 98% phthalimide and 7.2 g of formaldehyde in the form of 20 g of a 36% aqueous solution under reflux was heated at 97-100 ° C for 1 hour. The resulting clear solution was poured into a thin stream of up to 160 g of good mixed xylene, which was placed in the reaction flask as in the example. 1. Unchanged as in Example 1, 36.8 g of dry chloromethylphthalimide (m.p. 128-133 ° C) was obtained with a cleavable chlorine content of 17.5%, representing a yield of 92.8%. Example 3 A mixture of 73.6 g of 99% phthalimide and 50.1 g of a 35.9% aqueous formaldehyde solution was heated under reflux for half an hour to a reflux temperature of 97 to 100 ° C under reflux. Thereafter, a clear aqueous solution of N-hydroxymethylphthalimide was added. g of toluene, whereby the temperature of the contents of the flask was adjusted to about 60 ° C. The reaction flask was fitted with a feed tube extending to the bottom and hydrogen chloride gas was introduced, maintaining the flask at 55-60 ° C. The next procedure was as described in Example 1. 92.1 g of N-chloromethylphthalimide with a chlorine-cleavable content of 16.73% was obtained, a weight of 92.33% purity and a yield of 87.8%. theory, based on the initial fta-limide. OBJECT OF THE INVENTION A method for producing N-chloromethylphthalimide from N-hydroxymethylphthalimide and hydrogen chloride in the presence of an inert organic solvent, characterized in that N-hydroxymethylphthalimide in the form of an aqueous solution is a reaction mixture at 50-100 ° C containing 0 to 0.5 moles per 1 mol of N-hydroxymethylphthalimide the formaldehyde and 2 to 25 moles of water are fed with a trihydric inert solvent with gaseous hydrogen chloride to replace the hydroxy group with chlorine to form N-chloromethyl-phthalimide.