RU2057118C1 - Process for preparing n,n-diethylmethatoluamide - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: the product: N,N- diethylmethatoluamide. Reagent 1: m-toluic acid. Reagent 2: diethylamine. Reaction conditions: diethylamine is fed in admixture with solvent (benzene, toluene, m-xylene) in 1:1 ratio under reaction mixture layer under vigorous agitation at 200-220 C and continuous direct azeotropic distillation of mixture of solvent, water and unreacted diethylamine in the presence of complex-forming P(3) or B compound catalyst. EFFECT: more efficient preparation process.

Description

 The invention relates to methods for producing N, N-diethyl-meta-toluamide (DETA), which is one of the best repellents, and can be used in the chemical and pharmaceutical industries.

A known method of producing DETA, which consists in the interaction of m-toluic acid (MTK) with thionyl chloride or other chlorinating agents (PCl ₃ , COCl ₂ ) with the formation of m-toluic acid chloride, its isolation, distillation and further processing of the latter with diethylamine followed by vacuum distillation of the obtained DETA raw [1]
The disadvantage of this method is the use of a large number of chlorinating agents, severe corrosion of equipment due to the formation of hydrogen chloride in the reaction process, the presence of a large amount of wastewater, solid waste, including vacuum distillation of m-toluic acid chloride, and gas emissions containing Hcl and SO ₂ .

There is also a more promising method for producing DETA from m-toluic acid without intermediate formation of acid chloride in the presence of titanium compounds (0.0001-0.1 g per 1 g of MTK). Use TiCl ₄ , Ti (OAlk) ₄ , where Alk C ₃ -C ₁₈ , complex compounds of titanates with triethanolamine, tetraoctylene glycol; titanium acetylacetonate. The process is carried out in an organic solvent with azeotropic distillation of water and return of the solvent. The yield of DETA 68-74% [2]
The advantage of this method is the elimination of the stage of production of acid chloride, which leads to a reduction in aggressive waste.

A disadvantage of the method is to use as catalysts poisonous titanium compounds which may get into the final product, and the duration of the process at a fairly high temperature (220-235 ^{° C} for 40 hours). The technological design of the method using the Dean-Stark nozzle for returning the solvent to the reaction mass does not allow water to be completely removed from the reaction mass due to the formation of a triple mixture: diethylamine, water, solvent (benzene), which leads to a shift in equilibrium in the opposite direction and inhibition of the reaction ( conversion 93% yield 68-74%).

 The invention allows to reduce the duration of the process, reduce the temperature of the process, use more affordable and cheaper catalysts, and also increase the yield of diethyl toluamide.

The essence of the proposed method lies in the fact that N, N-diethyl-meta-toluamide is obtained by the interaction of meta-toluic acid with diethylamine when heated (200-220 ^about C) in the presence of a catalyst (compounds of 3-valent phosphorus and boron) and solvents, forming an azeotrope with liberated during the reaction with water, with continuous feeding of diethylamine in a solvent mixture (1: 1) under the layer of the reaction mass at a temperature of 200-230 ^C and with continuous distilling off of the solvent mixture of water and unreacted diethylamine via direct refrigerator with eflegmatorom that promotes more complete removal of water from the reaction mixture and the equilibrium shift towards the formation of diethyltoluamide.

 Condensate can then be regenerated.

PRI me R 1. 50 g (0.36 m) of m-toluic acid, 1 ml of diethylamine and 1 ml of xylene, 1.25 g of H ₃ PO ₃ (0.015 m) is loaded into a 250 ml flask equipped with a stirrer , a thermometer, a dropping funnel for feeding the reagent under the reaction mass layer, a direct refrigerator with a reflux condenser. Gradually heating the reaction mass ^to 200 ° C, is distilled off azeotropically with xylene excess moisture from m-toluic acid and phosphorous and at a temperature of 200 ^{° C} start feeding layer under the weight of the reaction mixture with xylene diethylamine (1: 1). The water formed during the reaction is azeotropically distilled off with xylene and unreacted diethylamine. The condensate is collected in a special receiver and then subjected to regeneration. The reaction time is 9 hours.

After the reaction, the mass is cooled to a temperature of 60 ^about C and washed with 50 ml of a 25% solution of sodium chloride containing 1.1 g of sodium hydroxide in 1 l. Stir at 60 ° ^C for 1 hour, transferred to a separatory funnel and the lower aqueous layer was separated, which then goes on acidification and isolation of the unreacted m-toluic acid. An upper layer comprising diethyltoluamide, washed again with 40 ml of 25% sodium chloride solution at ⁶⁰ ° C, is divided into a separatory funnel. The organic layer containing DETA is subjected to vacuum distillation. The main fraction was distilled off under a residual pressure of 5 mm at 133 ^{° C,} 10 mm at 146-148 ° ^C.

58.3 g of DEET are obtained with a main product content of 98%.
MTK conversion 96%
The yield of DETA is 83% for charged acid, 86.5% for reacted.

PRI me R 2. 50 g of m-toluic acid, 1 ml of diethylamine, 1 ml of benzene and 1.25 g of phosphorous acid are charged into a 250 ml flask, heated to 220 ^° C and under experiment conditions 1 a mixture of diethylamine with benzene (1: 1). The reaction proceeds analogously to example 1. The duration of the process is 8 hours. The yield of DETA is 81% per charged acid.

EXAMPLE EXAMPLE 3 Under the conditions of Examples 1 and 2 begin dispensing the mixture of diethylamine with toluene at 200 ° ^C. The reaction takes place analogously to Examples 1 and 2. The results of the process the same as example 1.

PRI me R 4. 30 g (0.217 m) of m-toluic acid, 2 ml of benzene, 2.35 g (0.017 g-m) of phosphorus trichloride are charged into a 100 ml flask equipped as described in examples 1 and 2 and at ²⁰⁰ ° C is fed a mixture of m-xylene / diethylamine under layer of the reaction mass. After 7 hours, the conversion of m-toluic acid is 97.5%
PRI me R 5. In a 4-necked flask with a capacity of 250 ml, equipped, as described in example 1, reflux condenser, load 50 g of m-toluic acid, 1.5 g of boric acid and 1 ml of diethylamine and m-xylene . The reaction mass is heated until the MTK is completely melted with the stirrer stopped, then the stirrer is turned on and heating is continued. At a temperature of 220 ^{° C} begin to dispense a mixture of diethylamine with m-xylene in an amount of 150 ml and a 1: 1 ratio. Load the mixture is carried out for 7 hours at a temperature of 220 ° ^C. During the reaction, a continuous removal of unreacted diethylamine, m-xylene and water of reaction. 66.3 g of the reaction mass is stirred in 120 ml of 5% NaOH solution at ⁶⁰ ° C for 15 minutes, then poured into a separatory funnel, the organic layer was separated from the water containing the unreacted Na-salt of m-toluic acid, and vacuum is performed -razgonku, selecting the main fraction at a temperature of 151 ^C and a vacuum of 10 mm Hg Get 46.8 g of commodity DETA containing 95.25% m-DETA, which is 80.6% of the loaded MTK.

PRI me R 6 (comparative). The conditions of the experiments 1 and 2 the supply of diethylamine the mixture with a solvent is carried out at 180 ^C. After 20 h the reaction mixture of 12% DEET detected.

PRI me R 7 (comparative prototype). 50 g (0.36 m) of m-toluic acid, 6.5 g of diethylamine (0.09 m) and 0.36 g of phosphorous acid are charged into a 250 ml flask with a Dean-Stark nozzle filled with benzene and reflux condenser. The reaction mixture was heated to melt the m-toluic acid and stirred for 22 hours at a temperature of ^about 220-235 C. In the first 3-4 hours is observed separation of water from the reaction mass and its sedimentation in the Dean-Stark trap, then benzene vapor, water and diethylamine form inseparable mixture.

 Diethylamine (25 g, 0.37 m) is fed under the reaction mass layer for 18 hours. After the exposure is complete, the reaction mass is treated as described in Example 1. 11.98 g of N, N-diethyltoluamide are obtained, which is 44.9% from theory.

Thus, the proposed method allows to reduce the processing time from 35-40 to 7-10 hours at a temperature decrease from 220-235 to 200-220 ^C, and to use the cheapest available catalysts (compound 3-valent phosphorus, boron and H ₃ PO _3, PCl ₃ , POCl ₃ , H ₃ BO _3. In addition, the technological design of the method with the irreversible removal of water from the reaction mass with solvent and excess diethylamine can increase the conversion of μ-toluic acid to 96-99% and, accordingly, increase the yield of diethyltoluamide.

Claims (1)

METHOD FOR PRODUCING N, N-DIETHYLMETHATOMULOAMIDE by reacting metatoluylic acid with diethylamine at 200 - 220 ^o C in the presence of a catalyst and a solvent - aromatic hydrocarbon with azeotropic distillation of the resulting water, characterized in that diethylamine is fed in a mixture with a solvent in the ratio 1: 1 under the reaction layer masses with vigorous stirring and continuous direct azeotropic distillation of the mixture of solvent, water and unreacted diethylamine, while the complexing compound is used as a catalyst trivalent phosphorus or boron, and as an aromatic solvent - benzene, or toluene, or methaxylene.