DD201140A1 - PROCESS FOR THE PREPARATION OF 3- (HALOGENPHENYL) -1.1-DIMETHYL HARVES - Google Patents

Abstract

The invention relates to a process for the preparation of 3- (halophenyl) -1.1-dimethylureas (halogen = preferably chlorine or bromine), which are used as herbicides. The invention has for its object to avoid the disadvantages of the known methods which consist either in the necessary drying and consequent solvent loss or in quality reductions or work under amine pressure. In the process according to the invention, the reaction is carried out in the final stage at temperatures above the melting point of the urea which forms, excess liquid or gaseous dimethylamine being introduced into the halophenyl isocyanates and working without application of pressure. In another embodiment, an indifferent solvent is added initially, which boils between 100 ° C. and below the melting point of the urea which forms and which is distilled off again using the reaction heat before the product is scummed off. Very high yields and active substance contents are achieved.

Description

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Title of the invention:

Process for the preparation of 3- (halophenyl) -1,1-dimethylureas

Field of application of the invention:

The invention is used in the production of herbicides.

Characteristic of the known technical solutions:

To prepare the herbicidally active 3-aryl-1,1-dimethy! Ureas, it is known to react aryl isocyanates with dimethylamine. The reaction is usually carried out in an inert organic solvent, and the urea formed precipitates as a voluminous precipitate. The recovery of the adherent solvent is problematic. In order to circumvent the loss associated use of toxic or flammable solvents, it has been proposed to bring aryl isocyanates with aqueous dimethylamine solution in the presence of surfactants to implement. However, the thus obtained crude ₇ products have an unsatisfactory purity. They contain more than 5 % diphenylurea, which results from the unavoidable reaction of the phenyl isocyanate with water.

Now, a solvent-free process for the preparation of 3- (halophenyl) -1 * 1-dialkyl ureas has become known, in which the dimethylamine and the isocyanate are combined simultaneously and with stirring, whereby one works to form an excess of amine under pressure and the temperature the reactant is above the melting point of the forming urea.

-7.MIG.1981 * 9f) 2L9

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Although this so-called melting process yields a high-percentage product with considerable space-time yield, it is difficult to practice in the technical implementation. These difficulties result from the fact that the current guarantee of an excess of amine is expressly carried out under pressure. The deeper reason for this is obviously to be seen in the fact that an immediate reaction of the added halophenyl isocyanate should take place in order to remove it from the thermal decomposition. According to the literature, the halophenyl isocyanates are in fact much more reactive and more decomposable than the phenyl isocyanate itself. On the other hand, the use of pressure makes the addition and metering of the reactants and other operations extremely difficult.

A later known unpressurized execution of the melting process is limited to the preparation of 3-phenyl-1 · 1-dimethylurea. However, this product has less significance as a herbicide than the 3- (halophenyl) -1,1-dimethylureas used. Compared with the 3- (halophenyl) -1.1-dimethylureas such as monuron and diuron, the 3-phenyl-i. 1-dimetliylurea is expected to be easier to produce by a melt process because the melting point is lower and the thermal load is correspondingly smaller. In addition, the phenyl isocyanate is known to be more stable than its halogen-substituted derivatives.

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Object of the invention:

The aim of the invention is a process for the preparation of herbicidally active 3 ~ (halophenyl) -1.1-dimethylureas of the general formula

CH ₃

- C - JSf ^

Il X "X _n 0 ^CH 3

X j = halogen, preferably Cl, Br

η = 1 - 3

to develop, which avoids the described disadvantages of the known technische.Lösungen.

Exposition of the essence ^; deri invention:

It was felt that the production of the '- ^; 3- (halophenyl) -1'.1-dimethylureas in the melt process in a simpler manner; Weise''aüc-h. without; In the case of this non-pressurized operation, mixtures of the halophenyl isocyanates with the 3- (halophenyl) -1,1-dimethylureas formed are present in the process. these proportions of isocyanate are not expected to be appreciably reduced under the reaction conditions. "The desired 3-halophenyl-1,1-dimethylureas are obtained in high yields and active ingredients. The interferences and apparatuses occurring when working under amine autogenous pressure Difficulties are thus eliminated.

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Of course, it is necessary for sufficiently pure halophenyl isocyanates to be used. The dimethylamine can be introduced gaseous or liquid in the process according to the invention. In the latter case, the heat of reaction is reduced by the amount of heat of vaporization of the dimethylamine Excess dimethylamine introduced. The reaction temperature is expediently to be chosen so that clogging of the inlet tube is prevented without, on the other hand, placing too much thermal stress on the mixture. In the final stage but the temperature must be at least 5 ⁰ C above the melting point of the corresponding urea. After the reaction has ended, the product is discharged via a flaking roller or a cooling belt during industrial recovery.

In another embodiment of the method according to the invention can also be used with a quantitative and temporary addition of a suitable solvent · It is initially such indifferent solvent whose boiling point is between 100 ⁰ C and below the melting point of the corresponding urea derivative. It is then removed again before the coating of the active substance. Expediently, the resulting heat of reaction is used immediately to distill off the solvent which is used in the next batch. As such a solvent, for example, chlorobenzene is considered.

The method variant described makes it possible to carry out the synthesis under somewhat milder conditions, which can be advantageous for achieving higher qualities and lighter products. It is, of course, somewhat more complicated and is preferably suitable for active ingredients with a higher melting point, such as monuron (m.p. 176-177 ⁰⁾ ,

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The described methods can in principle also be designed continuously by suitable measures. The solutions according to the invention are illustrated by the following examples:

Example 1:

3- (3 ^f .4 ^f -Dichlo: rphenyl) -1,1-dimethylurea (Diuron) 94 g (0.5 mol) of 3,4-dichlorophenyl isocyanate (bp ₃₅ 132 133 ⁰ G) are dissolved in a 250 ml three-necked flask equipped with a wide inlet tube , Stirrer, thermometer and reflux condenser, initially charged and heated to 13O ⁰ G. A vigorous stream of dimethylamine is introduced, with the temperature rising to 150 ° C. By throttling the supply or by cooling the temperature is initially held in this area. To S _c STATEMENTS of the reaction the temperature is increased to 170 ⁰ C. The recorded dimethylamine amount is 22.5 g · The melt is drained and solidified to a light yellow product, further lightening during crushing. - Larger approaches can be shed well.

Yield: 114.7 g (98.4% of theory..) Melting point: 153-156 ⁰ C Active ingredient content: 98.0%

Example 2 ·:

3- (3 ».4 ^f -Dichlorophenyl) -1,1-dimethylurea (Diuron) 94 g (0.5 mol) of 3,4-dichlorophenyl isocyanate (bp ₂₅ 132-133 ⁰ C) are dissolved together with 30 ml of chlorobenzene in a 250 ml three-necked flask ( with stirrer, wide inlet tube, thermometer and distillation device) and heated to at least 100 ⁰ C '.

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Man "begins now with the introduction of dimethylamine, the reaction temperature quickly. 140 - rises 150 ⁰ C. At this temperature, the chlorobenzene begins to distill, and you can control with the dimethylamine offer the distillation rate is chosen, the reaction procedure so that. Finally, an internal temperature of 170 ⁰ C prevails and removes the last residue of the Ghlorbenzens by applying a slight vacuum.The Diuron melt is drained and comminuted after cooling.This procedure results in a nearly white Diuron.The total time required is about 2 1 /2 hours.

Yield: 115.2 g (98.8 % of theory )

Melting point: 155 to 157 ⁰ C Active ingredient: 98.9%

Example 3:

3- (4-chlorophenyl) -1,1-dimethylurea (monuron) Following the procedure described in Example 1, 76.8 g (0.5 mol) of 4-chlorophenyl isocyanate (bp _{1 Q} 93-95 ⁰ C) in the same apparatus reacted with 22.5 g of dimethylamine. The initial temperature was 130-140 ° (Due to the released heat of reaction is a constant rise in temperature was noted, the tests were carried out so that at the end a temperature of 190 ⁰ C was reached The resulting Monuron was colored yellowish...

Yield: 97.9 g (98.5 % of theory ) Melting point: 167-171 ° C. Active substance content: 97.4 %

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Example 4:

3- (4-chlorophenyl ^f) -1.1-dimethylurea (Monuron) Analogously to the procedure "described in Example 2 were reacted 0.5 mol of 4-chlorophenyl isocyanate, and up to 16O ⁰ C started the dimethylamine and then to 190 ⁰ C, the chlorobenzene The resulting monuron was almost white.

Yield: 98 g (98.6 % of theory )

Melting point: 170 to 173 ⁰ C Active ingredient: 99.2%

Claims (2)

Pat claims 1 · Process for the preparation of herbicidally active 3- (halophenyl) -1 · 1-dimethylureas of the general formula CH ₃ X = halogen, preferred /, Cl, Br -NH-C-N l | ^ η = 1 - 3 X 0 CH ₃ by reaction of halophenyl isocyanates of. general formula X = halogen, preferably Cl, Br η = 1 - 3 with excess dimethylamine at temperatures in the final stage above the melting point of the forming 3 - * (halophenyl) -1.1-dimethylharnstof s, characterized in that liquid or gaseous dimethylamine is introduced into the halophenyl isocyanates and thereby worked without the application of pressure. 2. The method according to claim 1, characterized in that the reaction of the halophenyl isocyanate with dimethylamine is carried out with the addition of an indifferent solvent boiling between 100 ⁰ C and below the melting point of the urea forming and before the scumming of the product using the heat of reaction again is distilled off.