CS201536B2 - Process for preparing n-chlormethylphthalimide - Google Patents

Description

The present invention relates to a process for the preparation of N-chloromethylphthalide, which is the basic starting material in the preparation of [N- (mercaptomethyl) phthalimide] -S- (Ο, Ο-dimethylphosphorodithioate), also commonly referred to as esphosphorothiate.

[N- (mercaptomethyl) phthalimide] -S- (O, O-dimethylphosphorodithionate) is produced discontinuously by reacting N-chloromethylphthalimide (hereinafter abbreviated as CMP) with sodium O, O-dimethyldithlophosphate, hereinafter also referred to as dithioic acid salt, according to of this reaction scheme 1:

with

« ₊ Na3P (0CH)

CMP salt of methylphthalimide dithioacid (hereinafter abbreviated as HMP) with hydrochloric acid according to the following reaction scheme 2:

'(X

II o

NCH 2 FOCH 4 + NtCl (2) O-esterphosphorodithioate

M-chlormethylchlorid required in the above reaction 1 formed by the reaction of N-hydroxy201536. {Aq) ->'s HMP, ^{Ti <}

O

II -> Γϊ ^X NCH, Ct + HgO

II

O

CMP

Reactions 1 and 2 are carried out in a continuous manner.

The preparation of N-chloromethylphthalimide by treatment of hydroxymethylphthalimide with hydrogen chloride in the form of concentrated hydrochloric acid is known [S. Gabriel: Ber. 41, 242 (1908)]. Its advantage in comparison with the preparation using phosphorus oxychloride is its speed, unpretentiousness and simplicity. A disadvantage of the embodiment is that the reaction is carried out in a suspension of hydroxymethylphthalimide in hydrochloric acid, and as a reaction product again a suspension of chloromethylphthalimide in hydrochloric acid is formed. Since both components are insoluble under the reaction conditions, it is difficult to control the course of the reaction and, optionally, the unreacted starting hydroxymethylphthalimide and possibly the products of other side reactions which contaminate the end product having a lower melting point are present in the chloromethylphthalimide being prepared. a higher melting range or a lower chlorine content, which is undesirable for further processing of the product.

According to Czechoslovak Patent No. 120,423 to S. Truchlik and J. Macko, it is preferred that the reaction be carried out in the presence of an organic solvent which is immiscible with hydrochloric acid, since the hydroxymethylphthalimide starting material is insoluble in such solvent, unlike the chloromethylphthalimide formed. dissolves well in it. Of the organic solvents, for example, benzene, toluene, xylene, alkylnaphthalenes, various hydrocarbon fractions and mixtures thereof, and the like can be used. Preferably, a solvent is selected which, in the case of further processing, can be used directly as the reaction medium.

In the preparation of N-chloromethylphthalimide, using a solvent as described in Czechoslovak Patent No. 120,423, a solution of the desired product of high purity is obtained, with accompanying impurities as by-products of side reactions or remaining starting hydroxymethylphalimide in the event of incomplete reaction. separated from the desired product. The reaction may be carried out by mixing the necessary amounts of hydrochloric acid, hydroxymethylamide and solvent, and vortexing the suspension vigorously at a moderately elevated temperature, which usually does not exceed 50 ° C, until the mixture has reacted. Two layers are formed - hydrochloric acid and a true solution of chloromethylphthalimide in the solvent used. Smaller amounts of hydrochloric acid and unchanged amounts of the other components may also be used, the necessary hydrogen chloride being introduced in gaseous form into the reaction medium. In both cases, according to Czechoslovak Patent No. 120,423, a product of good purity is obtained in a yield of about 90% of theory.

Up to now, N-hydroxymethylphthalimide has been used as a wet mass in the production of chloromethylphthalimide. The moisture of this mass results in a decrease in the strength of aqueous hydrochloric acid, resulting in incomplete chlorination of the starting material with all the resulting consequences, particularly with regard to the possibility of utilizing the production equipment, the difficulty of separating the end product and the overall production cost.

It is an object of the present invention to overcome the disadvantages of the prior art processes.

A further improvement of the prior art is represented by the method of the invention, the details of which are set forth in the description which follows.

The present invention provides a process for the preparation of N-chloromethylphthalimide, characterized in that N-hydroxymethylphthalimide is also mixed with an organic solvent in an amount of 0.38 to 0.67 m ^{3 of} solvent per kg mol of N-hydroxymethylphthalimide and an aqueous solution of 35 to 40% by weight. . hydrochloric acid, in an amount of 0,21 to 0,42 m ^{3 of} aqueous hydrochloric acid solution per kgmol of N-hydroxymethylphalimide,

(b) reacting the prepared mixture at 65 ° C under a positive pressure of 0 to 343.5 kPa while thoroughly contacting the reaction mixture with anhydrous hydrogen chloride at a rate of 15 to 36 kg of hydrogen chloride per hour per kgmol of N-hydroxymethylphthalimide used to form the mixture of step ), maintaining an aqueous hydrochloric acid concentration of 35 to 40 percent by weight, based on N-chloromethylphthalimide, in a mixture of water and an organic solvent, thereby separating the organic phases containing the N-chloromethylphthalimide dissolved therein from a mixture of water and an organic solvent;

d) recovering N-chloromethylphthalimide from the organic phase.

According to the invention, the wet N-hydroxymethylphthalimide is mixed with an aqueous hydrochloric acid solution. Anhydrous hydrogen chloride was bubbled through the reaction mixture. The reaction proceeds in the presence of an organic solvent such as benzene in an amount sufficient to dissolve the produced N-chloromethylphthalimide in the reactor. The organic phase containing N-chloromethylphthalimide is then separated from the aqueous phase.

For carrying out the process according to the invention, the following technological procedure is recommended:

1. Fill the reactor with a wet cake of N-hydroxymethylphthalimide;

2. Add 35% aqueous hydrochloric acid in an amount of about 0,42 m ³ / kgmol of N-hydroxymethylphalimide;

3. Add benzene in an amount of about 1.08 m ³ / kgmol of N-hydroxymethylphthalimide;

4. Anhydrous hydrogen chloride is bubbled through the reaction mixture at a rate of about 15-25 kg per hour per kgmol of N-hydroxymethylphthalimide dosed in Step 1. The hydrogen chloride gas is maintained at 45 ° C using cold water. The reaction is controlled by the strength of the acid that increases when the reaction is complete when N-hydroxymethylphthalimide no longer consumes hydrogen chloride,

5. Aqueous hydrochloric acid phases are removed after completion of the reaction.

6. isolate the product being manufactured. This manufacturing operation is omitted when N-chloromethylphthalimide is further used in the preparation of [N- (mercaptomethyl) phthalimide] -S- (O, O-dimethylphosphorodithioate), in which case it is pumped as a benzene solution into a second reactor for further processing.

It has been found that the following two advantages are achieved with the method of the invention:

1. the reactor's production capacity will increase without changing its volume;

2. the cost of removing the solvent and its loss per unit weight of product produced is reduced.

The advantage of the above-mentioned advantage (1j is that the total batch size can be increased by 60 to 100% over the prior art process. This advantage is particularly suitable for new production plants since they can be used to achieve the production capacity of a smaller reaction vessel than previously. way.

According to advantage (2), the amount of solvent per unit weight of the product as well as the cost of removing it in the purification of the product can be reduced by about 70% over the prior art. Both advantages (1) and (2) are achieved without incurring costs in terms of yield and purity of the product.

In the process according to the invention, N-hydroxymethylphthalimide is reacted with aqueous hydrochloric acid to form N-chloromethylphthalimide. The reaction is carried out in the presence of an organic solvent in an amount of 0.38 to 0.67 m ^{3 of} solvent per kgmol of N-hydroxymethylphthalimide at a temperature of 45 to 75 ° C and an overpressure of P to 343.5 kPa under intimate contact with anhydrous hydrogen chloride. Anhydrous hydrogen chloride is bubbled through the mixture at a rate of 15 to 65 kg of hydrogen chloride per hour per kgmol of N-hydroxymethylphthalimide until the reaction is complete, manifested by an increase in pressure in the reaction vessel.

The pressure selected from the above pressure range varies with the progress of the reaction and is dependent upon the degree of completion of the reaction. Since anhydrous hydrogen chloride is bubbled through the reaction mixture to maintain a hydrogen chloride concentration in the aqueous phase of 35-40% by weight, the reaction is preferably carried out in a closed vessel until the reaction is near completion, when hydrogen chloride vapors and both N-chloromethylphthalimide and reaction concentrations begin to accumulate. speed decreases. As a result of the higher reaction temperature of the process of the invention, when the temperature is elevated relative to the normal process, there is an increase in pressure that accompanies the vapor accumulation of hydrogen chloride before the reaction is completed, which is faster and more pronounced than the previous process. The reaction is stopped by this pressure increase and it is no longer necessary to control the acid strength when the reaction is complete. When the pressure rises, the anhydrous hydrogen supply is stopped. An overpressure of up to 343.5 kPa may be used, but it is preferred that the hydrogen chloride supply is interrupted when the pressure reaches about 137.4 kPa or less.

A further improvement of the process according to the invention is that the rate of addition of anhydrous hydrogen chloride increases to about 15 to 65 kg of hydrogen chloride per hour per kgmol of N-hydroxymethylphthalimide initially metered, or preferably about 45 to 65 kg of hydrogen chloride per hour per kgmol of N-hydroxymethylphthalimide. The heating of the solution caused by the dissolution of hydrogen chloride in the reaction mixture is used to heat the reactor contents to the desired reaction temperature. The additional heat may be supplied by sensitive heating to optionally increase the rate of temperature rise in the reactor, but such additional heating is not normally necessary. Once the desired temperature has been reached, the temperature can be maintained by the action of cold water.

Organic solvents useful in the present invention generally include benzene, toluene, 1,2-dichloroethane and similar non-polar solvents.

These improvements cause a significant increase in the production of N-chloromethylphthalimide over the prior art.

The following example serves to illustrate the process of the invention in more detail, but does not limit the invention in any way. Since the advantages of the process according to the invention are particularly pronounced in the further processing of N-chloromethylphthalimide up to [N- (mercaptomethylphthalimide) -S- (O, O-dimethylphosphorus o201536 dithioate), the example does not merely mention the actual production of N-chloromethylphthalimide from N hydroxymethylphthalimide as well as further processing of the compound produced by the process of the invention.

Example

This example compares the usefulness of the prior art process with that of the process of the invention on a conventional apparatus. The vessel corresponding to the first reactor, which has a volume of 7.53 m ³ , is charged with the amount of material shown in Table I, both in the prior art process and in the process of the invention. The conditions under which both procedures are carried out are shown in Table II.

Table I

First reactor charge

the current method the method of the invention 35% aqueous hydrochloric acid, cm ³ 1.89 X IO ³ 1,89X106 N-hydroxymethylphthalimide, kgmol 4.76 7.48 benzene added before chlorination, cm ³ δ, ΙΙΧΙΟ ⁶ 3,88Χΐ0θ benzene added after removal of the aqueous acid 0 1.93X10 ⁶ hydrochloric acid, cm ³ total benzene, cm ³ 5,11X106 5,81X106 Reaction conditions in the first reactor Table II the current method the method of the invention reactor volume, cm ³ 7.57 x 10 ⁶ 7.57 x 10 ⁶ temperature, ° C 45 65 reaction time, h 3.5 1.5 rate of anhydrous addition hydrogen chloride, kg / h 104 to 136 435 first and second reactors total cycle time, h 8.0 7.5

In the example of the prior art, the total volume of the first reactor is utilized. In the example of the process according to the invention, 57% of N-hydroxymethylphthalimide is fed to the first reactor more than in the prior art process. Despite the large amount of N-hydroxymethylphthalimide in the process according to the invention, the first amount of benzene to be chlorinated is smaller and the first reactor operates only at 87% by volume.

In the example of the invention, a further charge of benzene is added to the first reactor after removal of the aqueous hydrochloric acid solution, the total amount of benzene used being greater than in the prior art process. However, the higher total amount is only 0.78 m ³ / kgmol of N-hydroxymethylphthalimide compared to 1.07 m ³ / kgmol of N-hydroxymethylphthalimide in the example illustrating the prior art. Therefore, the cost of separating the unit of product weight in the purification section that follows the second reactor is about 72% of the cost required in the prior art process.

As shown in Table II, the reaction time of the process of the invention is considerably shorter than that of the prior art process. However, most of the time advantage is lost over the total cycle time due to the increase in time required to process larger amounts of N-hydroxymethylphthalimide and N-chloromethylphthalimide per batch in the process of the invention. Thus, the total dosing time is approximately the same in both methods.

The actual production is followed by phase separation in the second reactor. It is carried out in both the present and the present invention, and the organic phase containing the product is first washed with 10% sodium hydroxide solution and then with water. The solvent contained in the organic phase is then removed from the product. The yield of the product is in each case approximately 73% and the purity of the produced ester phosphorodithioate is about 95% in both processes. This similarity in both yield and purity occurs despite the use of a higher temperature where higher amounts of by-products would normally be expected.

Claims (5)

SUBJECT What is claimed is: 1. A process for the preparation of N-chloromethylphthalimide which comprises: a) mixing N-hydroxymethylphthalimide with an organic solvent in an amount of 0.38 to 0.67 m ^{3 of} solvent per kgmol of N-hydroxymethylphthalimide, and 35 to 40 wt. aqueous hydrochloric acid solution, in an amount of 0.21 to 0.42 m ^{3 of} aqueous hydrochloric acid solution per kgmol of N-hydroxymethylphthalimide, bj the prepared mixture is reacted at 65 ° C under an overpressure of 0 to 343.5 kPa with thorough contact of the reaction mixture with anhydrous hydrogen chloride, in an amount of 15 to 65 kg of hydrogen chloride per hour per kgmol of N-hydroxymethylphthalimide used to form the mixture in step a), while maintaining an aqueous hydrochloric acid concentration of 35 to 40 why. by weight, based on N-chloromethylphthalimide, in a mixture of water and an organic solvent, i.e. separating the organic phases containing the N-chloromethylphthalimide dissolved therein from a mixture of water and an organic solvent, and d) recovering N-chloromethylphthalimide from the organic phase. OF THE INVENTION 2. The process according to claim 1, wherein in step a) from 0.42 to 0.58 m ^{&lt; 3 &gt; of} organic solvent is used per kgmol of N-hydroxymethylphthalimide. 3. A process according to claim 1, wherein the reaction in step b) is carried out at a pressure of 0 to 137.4 kPa. 4. The process of claim 1 wherein the reaction mixture in step bj is thoroughly contacted with anhydrous hydrogen chloride at a rate of 45 to 65 kg hydrogen chloride per hour per kg mol of N-hydroxymethylphthalimide used to prepare the mixture in step aj. 5. The process of claim 1 wherein the organic solvent is benzene in an amount of 0.42 to 0.58 m ^{&lt; 3 &gt;} per kgmol of N-hydroxymethylphthalimide used to prepare the mixture in step aj; and the reaction mixture of step bj is thoroughly contacted with anhydrous hydrogen chloride at a rate of 45 to 65 kg of hydrogen chloride per hour per kgmol of N-hydroxymethylphthalimide used to prepare the mixture of step a).