Manufacture of substituted glycinonitriles

R²

in the R¹ and R² may be the same or different and each represents an optionally substituted by alkoxy groups having 1 to 4 carbon atoms substituted alkyl group having 1 to 10 carbon atoms and R² also may denote a hydrogen atom, by reacting amines of the general formula

R¹

R²

Ν-Η

(II)

in the R¹ and R² have the abovementioned meanings, with formaldehyde and hydrocyanic acid in the presence of water, characterized in that the reaction for 0.1 to 4 hours at a temperature of 0 to 40⁰C is carried out while the concentration of hydrogen cyanide during the reaction to not more than. 0.1 weight percent, based on the reaction mixture, holds.

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

It is known from DE-PS 6 56 350 that glycolic acid nitrile can be reacted with an excess of methylamine in aqueous solution 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 (DE-PS 6 56 350). When stoichiometric amounts are used, the difficult to remove nitrile of methyl diglycolamide acid is produced in considerable quantities.

Another way to prepare 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 environmental problems by technical means for the formation of alkali salts which may contain residual cyanides as by-products. It is also known that the amines used in the form of salts, for. B. Chlorides, use (Jean M a thieu and Jean Weil Raynal, Formation of CC bonds, Vol. I, pages 442 to 446 [Georg Thieme Verlag Stuttgart 1973]).

All of 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 general formula

R¹

R²

N-CH, -CN

in the R¹ and R² may be the same or different and each represents an optionally substituted by alkoxy groups having 1 to 4 carbon atoms Aikylgruppe having 1 to 10 carbon atoms and R² also may denote a hydrogen atom, by reacting amines of the general formula

R¹

Ν-Η

R²

in the R¹ and R² have the meanings mentioned above, with formaldehyde and hydrocyanic acid in the presence of water, mentioned advantageous if the reaction is carried out for 0.1 to 4 hours at a temperature of 0 to 40 ° C while the concentration of hydrogen cyanide during the reaction to not more as 0.1 weight percent, based on the reaction mixture.

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

H, CO Η

Ν-Η + HCN

CH,

- -> N-CH₂-CN + H₂O CH,

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 method is comparatively straightforward for large-scale operation and suitable for continuous operation, offers no significant wastewater issues and is environmentally friendly. By-products, eg. B. Nitriles of alkyl diglycolamic acids or methylamines due to the presence of formaldehyde do not occur to any appreciable extent. All these advantageous properties are surprising in view of the prior art.

Formaldehyde can be used in liquid form or as a gas, generally in the form of its aqueous, suitably from 10 to 50, preferably from 30 to 40gewichtsprozentigen solution. Hydrocyanic acid is suitable as a gas or expediently in liquid form. The starting amine II can be used alone or expediently in solution, preferably in aqueous solution; are appropriate 40 to 60gewichtsprozentige

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 hydrogen cyanide per mole of formaldehyde (calculated 100%). , Preferred starting materials II and correspondingly preferred end products I are those in whose formulas R¹ and R² may be the same or different and each represents an alkyl radical having 1 to 8, in particular 1 to 4, carbon atoms, R² in addition, can also denote a hydrogen atom. It come z. B. as starting materials II into consideration: Methyl, ethyl, n-propyl, isopropyl, η-butyl, isobutyl, selc-butyl, tert-butyl, pentyl, pentyl (2), pentyl (3), n -Hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, 2-ethylhexyl, 2, 6-trimethyl-n-pentyl, 2-ethylpentyl, J-ethylpentyl- Dimethyl-n-butyl, 2,2-dimethyl-n-butyl, 2-methylpentyl, 3-methylpentyl, 2,2,4-trimethylpentyl, 2-methylheptyl, 3-methylheptyl, 4- Methylheptyl, 3-ethylhexyl, ^ -dimethylhexyl- ^ -dimethylhexyl, 2,4-dimethylhexyl, 2,5-dimethylhexyl, Dimethyldimethylhexyl-dimethyldimethylhexyl, 2-methyl-3-ethylpentyl, 3-methyl-3-ethylpentyl, 2,2,3-trimethylpentyl,

pentyl, 2,3,4-trimethylpentyl,

2,2,3,3-tetramethylbutyl-amine; Di (methyl), di (ethyl), di (n-propyl), di (isopropyl), di (n-butyl), di (isobutyl),

Di- (sec-butyl), di (tert-bmyl), di (pentyl), di (pentyl) - (2) -,

Di- (pentyl) - (3) -, 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- (3-ethylpentyl) -, di- (2,3-dimethyl-n-butyl) -, di- (2,2-dimethyln-butyl) -, di- (2 -methylpentyl) -,

Di (3-methylpentyl), di (2,2,4-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), di (2,5-dimethylhexyl) -, di- (3,3-dimethylhexyl) -,

Di- (3,4-dimethyl-hexyl) -,

Di- (2-methyl-3-ethyl-pentyl) -,

Di- (3-methyl-3-äthylpentyl) -,

Di- (2,2,3-trimethylpentyl) -,

Di- (2,2,4-trimethylpentyl) -,

Di (2,3,3-trimethylpentyl) -,

Di- (2,3,4-trimethylpentyl) -,

Di- (2,2,3,3-tetramethylbutyl) -amine; corresponding amines with 2 aforementioned, but different radicals, for. 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 is formed in the reaction itself; total is a total of 1 to 6, preferably from 3 to 4 moles of water, based on formaldehyde, into consideration prussic 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 ■ j from 0.01 to 0.1, in particular from 0.05 to 0.1 wt .-% 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. Preferably, water is used alone as a solution

K) medium, optionally 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; aliphatisehe or cycloaliphatic hydrocarbons, eg. B. heptane, 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, 2,2,3-trimethylpentane, octane; and corresponding mixtures. The solvent is expediently used in an amount of from 40 to 10 000% by weight, preferably from 50 to 1500% by weight, based on starting materials 11.

2^rThe reaction can be carried out as follows: A mixture of formaldehyde, water, hydrocyanic acid and starting amine II, if appropriate together with an organic solvent, is kept at the reaction temperature during the reaction time. you

»Ι are shares 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 concentration

R> 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 The obtainable by the process of the invention N-alkylglycinnitriles are valuable starting materials for the production of dyes, fungicides, bactericides, Texülhilfsmitteln, aids in the field of dental cosmetics, gas cleaning and hydrophobic

4-, beer. 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

-, ο mean parts by weight.

example 1

Into a stirred tank at 18 ° C. hourly 196 parts of a 30gewichtsprozentigen aqueous formaldehyde

v, hyd, 54 parts of liquid hydrogen cyanide and 214 parts of a 42gewichtsprozentigen dimethylamine slowly added, during the reaction, the cyanide concentration does not exceed 0.1 percent by weight, based on the total mixture. The hydrocyanic acid

average concentration is 0.08 to 0.09 percent by weight. Then the reaction mixture is distilled. Obtained every hour 330 parts (98% of theory) Ν, Ν-dimethylglycinnitrile Kp₄, 63 ° C, η 1.4107.

Example 2

In a stirred tank are analogously to Examples 1 at 18 ° C per hour 400 parts 30gewichtsprozentiger molding

aldehyde, 108 parts of liquid hydrogen cyanide and 458 parts 40gewichtsprozentige methylamine solution was added, wherein in the reaction space, the hydrocyanic acid concentration is not exceeded 0.1 percent by weight. After a mean residence time of 30 minutes, the reaction mixture is passed into a reactor whose temperature at 20⁰Here, the cyanide concentration drops below 500 ppm, based on the total mixture. The hydrocyanic acid concentration is an average of 0.04 percent by weight is obtained hourly 966 parts of a reaction mixture, from which hourly by azeotropic dehydration with toluene 270 parts (96.4% of theory) of N-methylglycinnitrile from b.p.₂O 65 ° C receives