GB1587925A - Manufacture of n,n-dimethylpiperidinium chloride and n,n-dimethylmorpholinium chloride - Google Patents

Abstract

N,N-dimethylpiperidinium chloride or N,N-dimethylmorpholinium chloride is prepared by reacting N-methylpiperidine or N-methylmorpholine, respectively, with methylating agents. The monomethyl compounds are reacted with methyl chloride in the presence of water as diluent. The temperature is from 0 to 100 DEG C and the pressure is from 1 to 7 bar. N,N-dimethylpiperidinium chloride and N,N-dimethylmorpholinium chloride can be used as plant growth regulators.

Description

(54)MANUFACTURE OF N,N-DIMETHYLPIPERIDINIUM CHLORIDE AND N,N-DIMETHYLMORPHOLINIUM CHLORIDE (71) We, BASF AKTIENGESELLSCHAFT, a German Joint Stock Company of 6700 Ludwigshafen, Federal Republic of Germany, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following Statement: The present invention relates to a process for the manufacture of N,Ndimethylpiperidinium chloride and N,N-dimethylmorpholinium chloride from the corresponding monomethyl compounds with a methylating agent.

It is known (German Patent Specification 1,642,215 and German Laid-Open Application DOS 2,207,575) to use N,N-dimethylpiperidinium chloride and N,N-dimethylmorpholinium chloride as agents for influencing plant growth. They are applied as an aqueous solution.

They are there said to be prepared in conventional manner by conversion of N,Ndimethylpiperidinium iodide and N,N-dimethylmorpholinium iodide into the corresponding chlorides (Helv. Chim. Acta, 39, 399, 1956; Chem. Ber., 22, 2091, 1889).

We have now found that N,N-dimethylpiperidinium chloride and N,Ndimethylmorpholinium chloride are easily obtained from N-methylpiperidine and N-methylmorpholine respectively, in excellent yields, when the corresponding N-monomethyl compound is reacted with methyl chloride in the presence of water as diluent, at a temperature of from 0 to 1000C and a pressure of from 1 to 7 bars.

This is surprising and could not have been foreseen, because methylation with methyl chloride hitherto has been carried out in non-aqueous solvents, or, when water has been used as diluent, temperatures far in excess (120"C) of room temperature and high pressures (20 to 60 bars) have been employed.

The process according to the invention has two important advantages: a) the process is very simple and thus extremely economical as a result of the use of water as diluent, because the aqueous solution of the end products can be employed directly for biological purposes; b) as the reaction takes place at atmospheric or slightly superatmospheric pressure, inexpensive standard stirred vessels may be used, as they are usually designed for safety reasons to withstand a pressure of from 4 to 7 bars, even when intended for non-pressurized reactions.

When N-methylpiperidine is used, the reaction may be represented as follows:

Compared with prior art processes, the process of the invention is able to provide, in a simpler and more economic manner, the desired quaternary ammonium chlorides in good yield and high purity. Whereas prior art processes were cumbersome because they had to be carried out in two stages, the reaction in the process according to the invention is carried out in one step.

Starting materials for the process are N-methylpiperidine, N-methylmorpholine and methyl chloride. They are used for instance in approximately equivalent amounts, optionally with a slight excess of methyl chloride.

The reaction may be carried out for instance as follows. Water and the monomethylamine are placed in the reaction vessel, and the mixture is brought to the desired reaction temperature and then treated with methyl chloride. Advantageously, the reaction components are mixed with each other, for example by stirring. After the reaction is over, the reaction solution is brought to room temperature and then diluted with water to the desired active ingredient concentration.

The monomethylamine concentration in the water upon commencement of the reaction may be varied within wide limits. It is preferred to use concentrations which, upon completion of the reaction, give end product concentrations slightly above the concentration of the aqueous solutions when marketed. However, it is also possible to start with more dilute aqueous solution and to distil off some of the water used after the reaction is over without the quality of the end products suffering. The concentration of the monomethylamines in the water may also be so high that they are not fully dissolved, either initially or during the reaction.

As methyl chloride is a gas, it is advantageous to employ a closed apparatus. The process according to the invention may be operated at atmospheric or superatmospheric pressure. In the latter case the reaction proceeds somewhat more quickly. If the process is operated at atmospheric pressure, it is expedient to free the reaction vessel substantially from air by partial evacuation; the desired pressure can now be set up by introduction of the methyl chloride.

If the pressure is constant during the reaction, the progress of the reaction can be followed by the amount of methyl chloride supplied.

The reaction is carried out at from 0 to 1000C, preferably at at least 20"C, advantageously from 30 to 800C, and especially at from 400 to 600C, and continuously or batchwise.

The duration of the reaction is without relevance for the quality of the end products. The reaction period can therefore be chosen in accordance with economic considerations. If may for instance be more favorable to operate at atmospheric pressure because only a vessel designed for atmospheric operation is available, and to accept a longer reaction period.

Upon conclusion of the reaction no more methyl chloride is taken up; the pH of the reaction solution is 6 to 7. The solution is a clear almost colorless liquid.

In the reaction according the invention, the desired end products are formed practically exclusively, i.e. no byproducts are obtained, and consequently the yield is practically quantitative.

The only byproducts which may occur are those from impurities in the starting materials. If, for example, the N-methylpiperidine still contains small amounts of unsubstituted piperidine, N-methylpiperidine hydrochloride, which is not further methylated because of the hydrochloride formation, is formed in the reaction with methyl chloride. If basic compounds which liberate the amines from amine hydrochlorides, e.g., sodium hydroxide, are added to the starting solution, the formation of the hydrochloride of the tertiary amine described above can be prevented. If the metal chloride formed from the amine hydrochloride and the basic additive is no handicap, it is possible to make the process even more economical by starting from impure amines. If a fairly large amount of metal chloride is no drawback, it is even possible to start from the secondary amines, i.e., from piperidine and morpholine, and to react them under the abovementioned reaction conditions with methyl chloride in the presence of an equivalent of a basic additive. The end product obtained is an aqueous solution of a mixture of 1 mole of quaternary ammonium chloride and an equivalent of metal chloride.

The process of the invention also represents an advance because it does not harm the environmcnt. There is absolutely no solid or liquid waste, as the reaction solution is the desired end product. Gaseous emissions can be substantially avoided if the reaction vessel is emptied and charged with the starting materials without being previously vented; this can be done without difficulty with the aid of pumps.

As the aqueous solution contains some methyl chloride upon completion of the reaction, this solution might be considered to be a source of impurities. In this case. the solution may.

after completion of the reaction, be passed through an evaporator or a distillation column to free it from methyl chloride. The aqueous distillate thus obtained can then be added to the next production batch as a diluent.

Both N.N-dimethylpiperidinium chloride and N,N-dimethylmorpholinium chloride can be produced with the same equipment, which can conceivably be of economic importance. If desired, both products may be produced together in admixture; this measure can definitely be meaningful, because both products can also be particularly successfully applied together in some crops.

If it is desired to isolate both products in the form of solid crystalline substances, this can readily be achieved by evaporating the aqueous solutions. They are obtained as coarse colorless crystals of high purity which have melting points of more than 300"C.

EXAMPLE 30 parts by volume of water and 15.6 parts by weight of N-methylpiperidine (parts by volume bear the same relationship to parts by weight as liters to kilograms) were introduced into a jacketed stirred vessel having a volume of 100 parts by volume. The apparatus was evacuated and heated to 500C. At this temperature, a maximum of 1,000 parts by volume of methyl chloride was introduced per hour through a flowmeter, and the mixture was stirred.

After about 2 hours a pressure of 2 bars had been reached, which was maintained by continuously controlled addition of methyl chloride.

During the reaction, water at 550C was passed through the jacketing, thus maintaining the internal temperature at 49 -50 C.

After 7.25 hours, the pressure remained constant without methyl chloride being passed in.

The mixture was stirred for a further 0.75 hour, and the apparatus was then emptied in such a manner that the bottom valve just stayed covered, thus preventing the pressure on the vessel from being released.

The solution thus obtained was a yellowish clear liquid having a pH of 6.9 and containing, in accordance with a test in which the N,N-dimethylpiperidinium chloride was precipitated and determined gravimetrically, 0.46 part by weight per part by volume. The yield was thus quantitative.

Methyl chloride consumption corresponded to a molar ratio of N-methylpiperidine to methyl chloride of 1:1.02.

Completely analogously, N,N-dimethylmorpholinium chloride was obtained from N-methylmorpholine and methyl chloride. In this case the reaction period was 14 hours.

WHAT WE CLAIM IS: 1. A process for the manufacture of N,N-dimethylpiperidinium chloride or N,Ndimethylmorpholinium chloride by reacting N-methylpiperidine or N-methylmorpholine, as the case may be, with a methylating agent, wherein the N-methyl compound is reacted with methyl chloride as methylating agent in the presence of water as diluent, at a temperature of from 0 to 100"C and a pressure of from 1 to 7 bars.

2. A process as claimed in claim 1 carried out at a temperature of 40 to 600C.

3. A process as claimed in claim 1 or 2 carried out in a closed apparatus.

4. A process as claimed in claim 1 carried out substantially as described in the foregoing Example.

5. N,N-dimethylpiperidinium chloride when manufactured by a process as claimed in any of claims 1 to 4.

6. N,N-dimethylmorpholinium chloride when manufactured by a process as claimed in any of claims 1 to 4.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. After about 2 hours a pressure of 2 bars had been reached, which was maintained by continuously controlled addition of methyl chloride. During the reaction, water at 550C was passed through the jacketing, thus maintaining the internal temperature at 49 -50 C. After 7.25 hours, the pressure remained constant without methyl chloride being passed in. The mixture was stirred for a further 0.75 hour, and the apparatus was then emptied in such a manner that the bottom valve just stayed covered, thus preventing the pressure on the vessel from being released. The solution thus obtained was a yellowish clear liquid having a pH of 6.9 and containing, in accordance with a test in which the N,N-dimethylpiperidinium chloride was precipitated and determined gravimetrically, 0.46 part by weight per part by volume. The yield was thus quantitative. Methyl chloride consumption corresponded to a molar ratio of N-methylpiperidine to methyl chloride of 1:1.02. Completely analogously, N,N-dimethylmorpholinium chloride was obtained from N-methylmorpholine and methyl chloride. In this case the reaction period was 14 hours. WHAT WE CLAIM IS:

1. A process for the manufacture of N,N-dimethylpiperidinium chloride or N,Ndimethylmorpholinium chloride by reacting N-methylpiperidine or N-methylmorpholine, as the case may be, with a methylating agent, wherein the N-methyl compound is reacted with methyl chloride as methylating agent in the presence of water as diluent, at a temperature of from 0 to 100"C and a pressure of from 1 to 7 bars.

2. A process as claimed in claim 1 carried out at a temperature of 40 to 600C.

3. A process as claimed in claim 1 or 2 carried out in a closed apparatus.

4. A process as claimed in claim 1 carried out substantially as described in the foregoing Example.

5. N,N-dimethylpiperidinium chloride when manufactured by a process as claimed in any of claims 1 to 4.

6. N,N-dimethylmorpholinium chloride when manufactured by a process as claimed in any of claims 1 to 4.