RU1806131C - Method of n-methylformamide synthesis - Google Patents

Abstract

SUMMARY OF THE INVENTION: The product is N-methylformamide. 100-101 ° C / 40 mm, 20 1.4320. Reagent 1: UN-HC. Reagent 2: CHzMN. Reaction conditions: reagents in an equimolar ratio are heated with simultaneous distillation of volatiles to 180-186 ° C, then to 190-200 ° C so that the temperature of the vapor of volatiles does not exceed 100-105 ° C.

Description

The invention relates to the field of organic chemistry, specifically to a method for producing N-methylformamide.

In order to increase the purity and yield of the target product, a new method for the preparation of N-methylformamide (1) was developed, based on the interaction of equimolecular amounts of formic acid and methylamine when heated, different from the known one, which leads to the temperature being heated while the volatiles are distilled off. 180 -186 ° C, after which it is gradually heated to 190-200 ° C so that the temperature of the vapor of volatile substances does not exceed 100-105 ° C.

The yield of methylformamide is virtually independent of the order in which the reactants are mixed. The reaction rate does not increase with the addition of proton donor catalysts: p-toluenesulfonic acid, phosphoric and boric acids. Even prolonged heating without distillation of volatiles does not give positive results.

Example 1. To 144 g (120 ml, 3 mol) of 90% formic acid with vigorous stirring and cooling (ice bath) was added dropwise a 32% aqueous solution of methylamine to a strongly alkaline reaction at such a rate that the temperature of the reaction mixture did not exceed 15 ° C. After completion of the reaction, the mixture is heated under a downward refrigerator and slowly distilled, taking a fraction with a boiling point of 180-185 ° C. Get 131 g of liquid with 20 1.4305. According to the PMR spectrum, the resulting material is a 1: 1 mixture of N-methylformamide and N-methylammonium salt of formic acid.

In the PMR spectrum of the mixture in carbon tetrachloride, there are two doublets at 2.70–2.76 ppm. (J 0.8 Hz), characteristic for methylformamide, and a doublet at 273 ppm. (J 0.5 Hz) characteristic of the methyl ammonium salt of formic acid.

The mixture can be separated by thin-layer chromatography in a spiritsssse system.

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aqueous ammonia (400: 4) on the Silufol plate. After developing in iodine vapor, methyl formamide gives a spot with Rf 0.66 and a salt with RfO, 35.

Example p-2. T ($ 45 ml of a 32% methylamine solution (8.99 mol) is added dropwise with cooling and vigorous stirring 311 ml of 99% formic acid (8.16 mol) at such a rate that the temperature inside the reaction mass does not rise above 20 ° C (about 2 hours),

Upon completion of the addition, the reaction flask is connected to a top-down refrigerator and the reaction mass is heated in a silicone bath to a temperature of 185-186 ° C. At this point, the distillation of the liquid is practically stopped. Slow heating is continued until the temperature of the reaction mixture reaches 195-200 ° C. In this case, 8 ml of liquid are distilled off over 10 hours, and the vapor temperature is not higher than 100-105 ° C. Obtain 376.5 g (79.2%) of spectrally pure N-methylformamide (bp 100-101 ° / AO mm, 20 1.4320. NMR spectrum of methylformamide (in CCIo): 2.73 sq. (J 0.8 and 4.5 Hz), 2.89 d. (J 4.5 Hz), 8.05 ppm.

Literature data: bk 183-185 ° C, 83-85 ° / South O.D. mmHg, 20 1.4319; 1.4320 3.

Example 3. The reaction is carried out as described in example 1.

After distillation of water, the reaction mass, heated to 180 ° C, is gradually heated to 198 ° C so that

the temperature of the exhaust vapors did not exceed 100-105 ° С. 145 g (82%) of methyl formamide (1) are obtained, b.p., 83-85 ° C (10 mmHg), 20 1.4320.

Example 4. 14.4 g (12 ml, 0.3 mol) of 90% formic acid are neutralized with methylamine gas with vigorous stirring and cooling (ice bath) at such a rate that the temperature of the reaction mixture does not exceed 10-12 C The mixture is then converted to N-methylformamide as described in Example 2,

According to PMR, the content of N-methylformamide in the reaction mixture up to 5 distillations is 91.5%, and the methylamine salt of formic acid is 2.3%.

The yield of N-methylfbrmamide, after distillation, 82.5%, purity 99.8%, 20 1.4320.

The developed method for the preparation of M-methylformamide. it is simple and makes it possible to obtain this compound in a pure form and with a good yield.

Claims (1)

The claims  The method of producing N-methylformamide by the interaction of equimolecular amounts of formic acid and methylamine when heated, and the fact that, in order to increase the purity and yield of the target product, the heating is carried out with simultaneous distillation of volatile substances to 180- 186 ° C, then gradually heated to 190-200 ° C so that the temperature of the vapor of volatile substances does not exceed 100-105 ° C. 5 0