Crystals of alanine N-acetic acid precursors, process to prepare them and their use

1. An alanine N-acetic acid precursor selected from the group consisting of:

(a) alanine N-monoacetonitrile of formula COOM-CH(CH3)—NH—(CH2CN), wherein M is hydrogen, said alanine N-monoacetonitrile showing X-ray diffraction reflections at 28=13.3; 20.3; 21.4; 21.9; 24.0 with an accuracy of ±0.1,

(b) alanine N,N-diacetonitrile and its partial sodium salts of formula COOM-CH(CH3)—N—(CH2CN)2, wherein greater than 0 to 50% of all M is sodium and 50 to less than 100% of all M is hydrogen comprising L-alanine N,N-diacetonitrile to D-alanine N,N-diacetonitrile, or their respective partial sodium salts, in a range of from 75:25 to 50:50 (L:D), said alanine N,N-diacetonitrile partial sodium salts showing X-ray diffraction reflections at 28=7.1; 10.8; 14.3; 14.8; 18.2; 20.7; 21.0; 23.3 with an accuracy of ±0.1, and

(c) alanine N,N-diacetamide of formula COOM-CH(CH3)—N—(CH2CONH2)2, wherein M is hydrogen,

and wherein the precursors is in the form of crystals that exhibit interference in monochromatic X-ray diffraction which fulfills the Bragg equation 2d sin θ=nλ.

2. The alanine N-monoacetonitrile or alanine N,N-diacetamide precursor of claim 1 comprising L-alanine N-monoacetonitrile to D-alanine N-monoacetonitrile, or, L-alanine N,N-diacetamide to D-alanine N,N-diacetamide, respectively, in a range of from 75:25 to 50:50 (L:D).

3. Process to prepare the precursors according to claim 1 , comprising:

a first step providing an aqueous solution of the alanine N-acetic acid precursor;

optionally for the alanine N monoacetonitrile or alanine N,N diacetamide precursor, a second step ensuring the alanine is at least partly racemized, one step after the other in random order or simultaneously, and

a third step allowing the aqueous solution to crystallize.

4. Process of claim 3 , wherein in the first step the alanine N-acetic acid precursor is made by reacting alanine or partially neutralized alanine with 0.8-2.4 molar equivalents of formaldehyde and 0.8-2.4 molar equivalents of hydrogen cyanide, wherein the reaction takes place by simultaneous dosing of both the formaldehyde and the hydrogen cyanide, or by dosing at least 40% of the amount of formaldehyde before dosing of the hydrogen cyanide is started.

5. Process according to claim 3 , wherein the second step includes a concentrating step that is carried out until the solution has a concentration of equal to or more than 15 wt % to up to or equal to 80 wt % of the precursor, based on the weight of the aqueous solution.

6. Process according to claim 3 , wherein the third step comprises crystallization by allowing the solution to stand for an extended period of time and/or cooling and/or seeding.

7. Process according to claim 3 , wherein the third step comprises crystallization by spraying the aqueous solution of the second step on seeding crystals.

8. Process according to claim 3 , wherein the third step is performed at a temperature of below 40° C.

9. Process according to claim 3 , wherein the process is a continuous process.

10. Process for preparing methylglycine N-acetic acid (MGMA) or methylglycine N,N-diacetic acid (MGDA) comprising the steps of adding together the precursors of claim 1 and an alkali metal salt in an aqueous solution and heating this solution to a temperature of at least 80° C.

11. The alanine N-acetic acid precursor in crystal form of claim 1 that is alanine N-monoacetonitrile showing X-ray diffraction reflections at 2θ=13.3; 20.3; 21.4; 21.9; 24.0 with an accuracy of ±0.1.

12. The alanine N-acetic acid precursor in crystal form of claim 1 that is alanine N,N-diacetonitrile showing X-ray diffraction reflections at 2θ=6.9; 10.2; 13.8; 14.1; 16.5; 17.3; 19.3 with an accuracy of ±0.1.

13. The alanine N-acetic acid precursor in crystal form of claim 1 that is alanine N,N-diacetonitrile sodium salt showing X-ray diffraction reflections at 2θ=7.1; 10.8; 14.3; 14.8; 18.2; 20.7; 21.0; 23.3 with an accuracy of ±0.1.

14. The alanine N-acetic acid precursor in crystal form of claim 1 that is D,L-alanine diacetonitrile having the X-ray powder diffractogram of FIG. 1 .

15. The alanine N-acetic acid precursor in crystal form of claim 1 that is D,L-alanine monoacetonitrile having the X-ray powder diffractogram of FIG. 2 .

16. The alanine N-acetic acid precursor in crystal form of claim 1 that is D,L-alanine diacetonitrile sodium salt having the X-ray powder diffractogram of FIG. 3 .