HU199854B - Process for producing ethylenediamino-n,n'-bis(alkylphosphonic acid)s - Google Patents

Abstract

Field of the Invention The present invention relates to a process for the preparation of ethylenediamino-N, N'-bis (alkylphosphonic acid) compounds of formula (I) R H O R R O, OH P - C - NH - CH 2 - CH 2 - NH - O - P ((I) HO 'R 2 k 2 OH - wherein R 1 is hydrogen or C 1-4 alkyl and R 2 is C 1 -C 4 alkyl or phenyl - ethylenediamine and C 1 -C 2 carbonyl compound - According to the invention, diethylphosphite, which is prepared from phosphorus trichloride and ethanol in a manner known per se, is added to the mixture of ethylene diamine for cooling and stirring, followed by the reaction mixture for 1-2 hours. 100-140'C, the ester is hydrolyzed with hydrochloric acid and the product is isolated in a manner known per se HO, P - C - CH - CH - 0H -, 1ΠΙ - CP IS OH 'OH (I) 10 CO Φ Φ 3 Scope of the description: 4 pages without figure -1-

Description

The present invention relates to a process for the conversion of ethylenediamino-N, N'-bis (alkylphosphonic acid) of formula (I)

HO p Rt Rt O OH

P - C - NH - CH ₂ - CH ₂ - NH - C - ξ '(I) HO R ₂ R ₂ OH

wherein R 1 is hydrogen or C 1 -C 4 alkyl and R ₂ is C 1 -C 4 alkyl or phenyl.

The compounds of formula (I) have excellent complexing properties, are accordingly effective water treatment agents and can be used as ion exchangers. In contact with metal in aqueous solution, it forms an adsorption protective layer and thus exhibits corrosion inhibitory activity. Some of their agents also have fungicidal or herbicidal activity or may be used as intermediates in the preparation of compounds having such activity.

A general procedure for the preparation of aminoalkylene phosphonic acids, including compounds of formula I, is described in U.S. Pat. No. 3,288,846. U.S. Pat. According to the process described therein, ethylenediamine is reacted with a carbonyl compound of the formula R 1 -CO-R _{2 in} which R 1 and R ₂ are as defined above and orthophosphoric acid in the presence of a halide ion source (e.g. aqueous hydrochloric acid). The advantage of the process is its simplicity. However, the disadvantage of the industrial realization is that the carbonyl compound has to be used in significant (usually 100%) excess. Further disadvantages result from the fact that orthophosphoric acid is a well-known unstable compound, which is easily oxidized to the corresponding phosphoric acid even when standing up to air. This oxidation also takes place under the reaction conditions. The phosphoric acid present also reacts with the carbonyl compound and ethylenediamine to form a by-product which can be easily removed by multiple crystallization from the target product. No. 3,288,846. U.S. Pat. No. 5,123,115, discloses the use of a halide ion source to suppress orthophosphoric acid oxidation during reaction. However, the halide ion source cannot completely suppress the oxidation of orthophosphoric acid during the reaction, and the halide ion source is not suitable for reducing the orthophosphoric acid present in the initial orthophosphoric acid to a smaller or greater extent. Because orthophosphoric acid always contains impurities depending on the origin and age of the orthophosphoric acid, the process necessarily entails the presence of contaminating phosphoric acid derivatives in the product, the removal of which requires a cumbersome, energy consuming and substantial purification process.

It is an object of the present invention to provide a process for the preparation of compounds of formula (I) in a sufficiently pure state without the need for a complex purification process.

It has been found that these goals can be fully achieved by using diethyl phosphite as a reagent instead of orthophosphoric acid, and by subsequent hydrolysis of the ester formed as an intermediate,

A further advantage is that when diethyl phosphite is used as the reagent, there is no need for excess carbonyl compound and no use of a halide ion source. The hydrolysis of the ester does not require isolation of the intermediate which improves the economics of the process.

The present invention therefore relates to a process for the preparation of ethylenediamino-N, N'-bis (alkylphosphonic acid) of the general formula (I) wherein R 1 and R ₂ are as defined above, ethylenediamine and R 1 -CO-R ₂ using a carbonyl compound of the formula wherein R 1 and R ₂ are as defined above. According to the present invention, diethyl phosphite, prepared from phosphorus trichloride and ethanol in a known manner, is added to the ethylenediamine mixture under cooling and stirring, and the reaction mixture is then heated at 100-140 ° C for 1-2 hours. hydrolyzing the ester with hydrochloric acid and isolating the product in a known manner.

If the compounds of formula (I) are to be isolated as the free acid, after hydrolysis, the reaction mixture can be evaporated, the residue taken up in water and the product crystallized at below 0 ° C. However, given that the compounds of formula (I) are relatively soluble in water, a large proportion of the product remains dissolved in the mother liquor of the crystallization. Therefore, it is preferable to isolate the product in the form of its alkali metal salt. In this case, the evaporation product is dissolved in an aqueous solution containing half an equivalent of an alkali metal hydroxide (preferably sodium hydroxide), ethanol is added to the aqueous solution until the crystallization begins, and the mixture is refrigerated. The precipitated crystals are filtered off and washed with ethanol. Thus, the yield is improved to 74-83% compared to 27-2% obtained by aqueous crystallization of the free acid.

The invention is illustrated in detail by the following non-limiting Examples.

Example 1

Acetone (36.7 ml, 0.5 mol) was added dropwise to a mixture of 64.5 ml (0.5 mol) of diethyl phosphite (17 mol, 0.25 mol) in ethylene diamine prepared from phosphorus trichloride and ethanol. The temperature of the reaction mixture rose rapidly to 120 ° C even with external cooling. After the addition was complete, the reaction mixture was heated at 120 ° C for an additional hour. To the still hot solution was added 400 ml concentrated hydrochloric acid solution and 80 ml water and refluxed for 8 hours. The solution was then treated with charcoal, evaporated in vacuo to constant weight and evaporated three times with 100 ml of water to remove traces of hydrochloric acid. The initially oily material gradually crystallized during evaporation. Finally, after the addition of 30 ml of water, ethylenediaminobis (isopropylphosphonic acid) precipitated in a refrigerator. Yield: 34 g (24%). The product crystallized with two crystalline water. M.p. 231'C (literature m.p. 230-231'C).

Result analysis:

Calculated: C, 28.23; H, 7.64; P, 18.23; Found: C, 27.95; H, 8.00; P, 18.11.

Example 2

The procedure described in Example 1 was followed except that 13.8 g (0.1 mol) of diethyl phosphite

HU 199854 Β g (0.05 mole) of ethylenediamine and 5.8 g (0.1 mole) of propionaldehyde and the ester was hydrolyzed with 80 ml of concentrated aqueous hydrochloric acid and 15 ml of water. Ethylenediaminobis (propylphosphonic acid), m.p. 243-245 'C (240 ° C in literature). 3.6 g (42%) of product are obtained.

Analysis Results: ^v: C 31.57%, H 7.20%, P: 20.39%; Found: C, 32.01; H, 7.11; P, 20.19.

Example 3

The procedure of Example 1 was followed, but starting from 11.5 g (0.08 mol) of diethyl phosphite, 2.5 g (0.04 mol) of ethylenediamine and 8.8 g (0.08 mol) of benzaldehyde. and the ester was hydrolysed with 70 ml of concentrated aqueous hydrochloric acid and 10 ml of water.

4.5 g (27%) of ethylenediaminobis (benzylphosphonic acid) are obtained, m.p. 244-246'C (literature m.p. 236'C).

Result analysis:

Calculated: C, 48.00; H, 5.50; P, 15.50;

Found: C, 47.95; H, 5.35; P, 15.70.

Claims (1)

Process for the preparation of ethylenediamino-Ν, Ν'bis (alkylphosphonic acid) of the formula (I) HO p Ri Ri O OH 'P - C - NH - CH2 - CH2 - NH - ς - Ρ (I) HO' R2 R2 OH - wherein R1 is hydrogen or C1 -C4 alkyl and R2 is C1 -C4 alkyl or phenyl-ethylenediamine and the RCO-R2 carbonyl compound wherein R1 and R2 are as defined above, that dimethyl phosphite, prepared from phosphorus trichloride and ethanol in a known manner, is added to the ethylenediamine mixture under cooling and stirring, and then the reaction mixture is kept at 100-140 ° C for 1-2 hours, hydrolyzing the ester with hydrochloric acid and isolating the product in a known manner.