Manufacture of substituted glycinonitriles

BASF Aktiengesellschaft

2503582 Our sign: OZ 31 125 WB / Wil

6700 Ludwigshafen, 27.1.1975

Process for the preparation of N-alkylglycinnitriles

The invention relates to a process for the preparation of N-alkylglycinnitriles by reacting N-alkylamines with formaldehyde and hydrogen cyanide under certain reaction conditions with respect to temperature, reaction time and hydrogen cyanide concentration.

It is known from the German Reich Patent 656 35O, that glycolic acid nitrile with an excess of. Methylamine in aqueous solution can convert under pressure to sarcosine nitrile. In order to achieve good yields of sarcosine nitrile, an excess of up to 10 moles of methylamine per mole of oxyacetonitrile is recommended (DRP 656 350). When stoichiometric amounts are used, the difficult to remove nitrile of methyl diglycolamide acid is produced in considerable quantities.

Another way of preparing N-alkyl substituted glycine nitriles is from formaldehyde in the presence of sodium bisulfite compounds and reacting the aldehyde with sodium cyanide and aliphatic amines. The procedure with sodium cyanide and sodium bisulfite provides for technical implementation environmental problems by the formation of alkali metal salts, which may contain residual cyanides, as by-products. It is also known that the amines used in the form of salts, eg. B. Chlorides, use (Jean Mathieu and Jean Weil Raynal, Formation of C - C-- Bonds, Vol. I, pages 442 to 446 (Georg Thieme Verlag Stuttgart I973)).

All these methods are unsatisfactory in terms of simple and economical operation, good yield of end product and easy workup, especially with regard to environmental protection and wastewater treatment.

It has now been found that N-alkylglycinnitriles of the formula ^557/74 609832/0894 ^{/ 2}

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1 P wherein R and R may be the same or different and each

an aliphatic radical, R² furthermore can also denote a hydrogen atom, advantageously obtained by reacting formaldehyde with amines and cyano compounds, if N-alkylamines of the formula

JH II,

1 P

wherein R and R have the abovementioned meaning, with formaldehyde and hydrocyanic acid in the presence of water for 0.1 to 4 hours at a temperature of 0 to 40 ° C, wherein the concentration of hydrogen cyanide during the reaction not more than 0.1 wt . ^, Based on the reaction mixture is.

The reaction can be represented by the following formulas in the case of using dimethylamine:

₃ H₂CO + 'JBt-K + HCN

In comparison with the known processes, the process according to the invention provides in a simpler and more economical way N-alkylglycinnitriles in better yield and purity. The process is relatively straightforward for large-scale operation and suitable for continuous operation, does not provide significant wastewater issues, and is more environmentally friendly. By-products, eg. B. Nitriles of alkyl diglycolamide acids or methylol amines due to the presence of formaldehyde do not occur to any significant degree. All these advantageous properties are surprising in view of the prior art.

Formaldehyde may be in liquid form or as a gas, generally in the form of its aqueous, suitably from 10,. up to 50, preferably

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white from j50 to 40 weight percent solution can be used. Hydrocyanic acid is suitable as a gas or expediently in liquid form. The starting amine II can be used alone or expedient in solution, preferably in aqueous solution; useful are 40 ~ to 60 weight percent solutions. The three starting materials can be reacted in stoichiometric amount or each of the components in each case in excess, preferably in an amount of 0.1 to 2 moles of amine and / or from 0.01 to 0.1 moles of hydrocyanic acid per mole of formaldehyde (calculated 100%). , Preferred starting materials II and accordingly preferred end products I are sol-

1 2, in whose formulas R and R may be the same or different and each have an alkyl radical having 1 to 8, in particular

2 *

In addition, R may denote a hydrogen atom. The aforementioned radicals can still by inert under the reaction conditions groups, for. As alkyl groups, alkoxy groups each having 1 to 4 carbon atoms, be substituted.

It come z. B. as starting materials II into consideration: Methyl, x-butyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, pentyl (2), pentyl (3) , n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, 2-ethylhexyl, 2,2,6-trimethyl-n-penty ^ -, 2-ethylpentyl-, 3-ethylpentyl, 2,3-dimethyl-n-butyl, 2,2-dimethyl-n-butyl, 2-methylpentyl, 3-methylpentyl, 2,2,4-trimethylpentyl, 2-methylheptyl , 3-methylheptyl, 4-methylheptyl, 3-ethylhexyl, 2,2-dimethylhexyl, 2,3-dimethylhexyl, 2,4-dimethylhexyl, 2,5-dimethylhexyl, J>, 3-dimethylhexyl, 2,4-dimethylhexyl, 2-methyl-3-ethylpentyl, 3-methyl-3-ethylpentyl, 2,2,3-trimethylpentyl, 2,2,4-trimethylpentyl- 2,3,3-trimethylpentyl-, 2,3,4-trimethylpentyl-, 2,2,3- (3-tetramethylbutyl-amine; Dl- (methyl) -, di- (ethyl) -, di- (n-propyl) -, di- (isopropyl) -, di (n-butyl) -, di- (isobutyl) -, di- (sec .-butyl) -, di- (tert-butyl) -, di- (pentyl) -, di- (pentyl) - (2) -, di- (pentyl) -t5) - * di- (n-hexyl ), Di (n-heptyl), di (n-octyl), di (n-nonyl), di (n-decyl), di (2-ethylhexyl), di - (2,2,6-trimethyl-n-pentyl) -, di- (2-ethylpentyl) -, di- (> ethylpentyl) -, di (2,> dimethyl-n-butyl) -, di- ( 2,2-dimethyl-η-butyl) -, di- (2-methylpentyl) -, di (3-methylpentyl) -, di- (2,2,4-)

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trimethylpentyl), di (2-methylheptyl), di (3-methylheptyl), di (4-methylheptyl), di (3-ethylhexyl), di (2,2-dimethylhexyl) - , Di- (2,3-dimethylhexyl) -, di- (2,4-dimethylhexyl) -, Dl- (2,5-dlmethylhexyl) -, di- (3,3-dimethylhexyl) -, di- (3, 4-dimethylhexyl) -, di- (2-methyl-3-ethylpentyl) -, di- (3-methyl-3-ethylpentyl) -, di- (2,2,3-trimethylpentyl) -, di- ( 2,2,4-trimethylpentyl), di (2,3,3-trimethylpentyl), di- (2,3,4-trimethylpentyl), di- (2,2,3-tetramethylbutyl) amine; corresponding amines with 2 aforementioned, but different radicals, ζ. B. methylethylamine.

The reaction is carried out at a temperature of 0 to 40, preferably 15 to 25⁰C, under reduced pressure or overpressure or preferably without pressure, discontinuously or preferably carried out continuously. Water is used, expediently in the form of aqueous formaldehyde solution and / or amine solutions; in addition, water itself forms in the reaction; in total, a total amount of 1 to 6, preferably from 3 to 4 moles of water, based on formaldehyde, into consideration. Hydrocyanic acid is added to the starting mixture before and during the reaction in such an amount that the concentration during the reaction is not more than 0.1, preferably from 0.01 to 0.1, in particular from 0.05 to 0.1,% by weight. Hydrocyanic acid, based on the reaction mixture is. The reaction time (in continuous operation residence time) is 0.1 to 4, preferably 1 to 2 hours. Water is preferably used alone as solvent, if appropriate also inert under the reaction conditions, organic solvents. As a solvent come z. B. in question: aromatic hydrocarbons, eg. Toluene, benzene, ethylbenzene, o-, m-, p-xylene, isopropylbenzene, methylnaphthalene; aliphatic or cycloaliphatic hydrocarbons, e.g. As heptane, a-pinene, pinane, nonane, o-, m-, p-cymene, gasoline fractions within a boiling point interval of 70 to 190⁰C, cyclohexane, methylcyclohexane, petroleum ether, decalin, hexane, ligroin, 2,2,4-trimethylpentane, 2,2,3-trimethylpentane, 2,3,3-trimethylpentane, octane; and corresponding mixtures. It is expedient to use the solvent in an amount of 40 to 10 000% by weight, preferably from 50 to 15% by weight, based on starting material II.

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The reaction can be carried out as follows? A mixture of formaldehyde, water, hydrocyanic acid and starting amine II, optionally together with an organic solvent, is maintained at the reaction temperature during the reaction time. It gives proportions of hydrogen cyanide in the starting mixture and during the reaction in portions or continuously so that the aforementioned hydrocyanic acid concentration is maintained throughout the reaction time. The ongoing measurement of hydrocyanic acid concentrations is expediently carried out via a silver calomel electrode. Then from the reaction mixture of the end product in a conventional manner, for. B. by distillation or extraction with z. As cyclohexane and distillation of the solvent ,, isolated.

In a preferred embodiment, the end product is fed directly to the saponification without separation in the reaction mixture. The saponification of the end product I is carried out by known methods, usually in an alkaline medium, preferably in aqueous ^ solutions of alkaline earth or alkali metal hydroxides or expedient alkali metal salts such as sodium or potassium carbonate, bicarbonate, acetate, formate. Preference is given to sodium hydroxide and potassium hydroxide. One uses z, B. 30 to 40 weight percent mixtures of the end product in such solutions and suitably saponifies at a pH of 9 to 14 and at a temperature of 0 to 150⁰C, in particular from 45 to 115 ° C, for 2 to 30 hours. For example, alkali metal salts or aqueous solutions of these substances are added to the mixture and saponified the end product I in a mixture in the aforementioned manner. It is advantageous to use 1 to 2 equivalents of alkali or alkali salt in the saponification, based on the isolated end product I, and 1 to β equivalents of alkali or Alkali salt, based on the non-isolated, contained in the reaction mixture in the aforementioned manner end product In an advantageous procedure, the reaction mixture goes through various, preferably 2 or 3 * saponification stages of increasing temperature, eg. B. the stirred tank a stirred tank cascade. In a two-stage saponification, temperatures of from 55 to H 2 are preferred⁰C and a residence time of 3 to hours in the first stage (first stirred tank), temperatures of 45 to 70⁰C and a residence time of 3 to 10 hours in

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the second stage (second stirred tank); in a three-stage saponification temperatures of 55 to 60⁰C and a residence time of 2 to 3 hours in the first stage, temperatures of 90 to 95 ° C and a residence time of 6 to 8 hours in the second stage, temperatures of 110 to 115⁰C and a residence time of 6 to 8 hours in the third stage. This gradual saponification surprisingly discolorations and deterioration of yield are avoided. From the saponification mixture then the salt of the end product I corresponding N-Alkylglyclns in a conventional manner, for. B. by evaporation, isolated.

The N-alkylglycinnitriles obtainable by the process of the invention are valuable starting materials for the preparation of dyes, fungicides, bactericides, textile auxiliaries, auxiliaries₍ in the field of dental cosmetics, gas purification and hydrophobing. With respect to the use of the aforementioned publications and Ullmann's Encyclopedia of Industrial Chemistry, Volume 8, pages 212 and 213 * referenced.

The parts listed in the following examples mean parts by weight,

example 1

a) In a stirred tank at 18⁰C every hour 196 parts of a 30% by weight aqueous formaldehyde solution, 5²Y parts of liquid hydrogen cyanide and 214 parts of a 42 weight percent dimethylamine slowly added, during the reaction, the cyanide concentration does not exceed 0.1 wt., Based on the total mixture. The hydrocyanic acid concentration is on average 0.08 to 0.09 wt. ^. Then the reaction mixture is distilled. Obtained every hour 330 parts (98% of theory) of N-dimethylglycinnitrile Kp₂J_-1 63⁰C.,

n ^ ° = 1.4107.

b) The reaction is carried out analogously to Example la), but the end product I not isolated, but processed directly. After a residence time of 2 hours, 464 flow hourly

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Parts of the reaction mixture in the saponification vessel, in the hourly 378 parts of potassium hydroxide solution (jSO weight percent) at 50 to 55⁰C are added. After a residence time of 2 1/2 hours, the saponification solution is heated to 90 to 95 ° C in the first boiler with cooler and exhaust gas device of a cascade. After a residence time of 8 hours, the saponification solution is transferred to a second saponification vessel with condenser, where a temperature of 110 to 115 ° C is maintained. At the same time, 200 parts of water and 550 parts of steam (170⁰C) introduced hourly, 54 parts of gaseous ammonia and 1000 parts of a »3 weight percent ammonia solution are discharged hourly via a heated column with overhead reflux. Each hour 558 parts of a 42 weight percent, aqueous, colorless solution of Dirnethylglycinkaliumsalzes.

Example 2

a) 400 parts of 30 weight percent formaldehyde, IO8 parts of liquid hydrocyanic acid and 458 parts of 40 weight percent methylamine solution are added analogously to Example 1 at l8 ° C hourly, wherein the hydrocyanic acid concentration 0.1% by weight is not exceeded in the reaction chamber. After a mean residence time of 50 minutes, the reaction mixture is passed into a reactor whose temperature is at 20⁰C is. Here, the cyanide concentration drops below 5OO ppm, based on the total mixture. On average, the hydrocyanic acid concentration is 0.04% by weight. 966 parts of a reaction mixture are obtained per hour from which 270 parts (96.4% of theory) of N-methylglycine nitrile of the bp are obtained by azeotropic dehydration with toluene₂₀ = 65⁰C receives.

b) The reaction is carried out analogously to Example 2a), but the end product I is not isolated, but further processed directly. After a mean residence time of one hour 966 parts of reaction mixture per hour flow in a saponification vessel, where hourly 200 parts of water and 548 parts 30 weight percent sodium hydroxide are introduced at 45 ° C per hour. After a residence time of 2 1/2 hours comes

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the saponification solution in another saponification vessel whose temperature at 10O⁰C is. After a mean residence time of 4 hours, the mixture flows into a post-reactor, where it is at a residence time of 3 hours at 110⁰C reacted. With simultaneous evaporation of ammonia, methylamine and water is obtained per hour 1034 parts of a 38 weight percent sarcosine sodium solution of density 1.2.

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