Polymorphs of herbicidal sulfonamides
Solid polymorphic forms of sulfentrazone are described. Particularly, a new polymorphic form of sulfentrazone is described herein as sulfentrazone-1, having surprising property advantages over technical sulfentrazone. Processes for the preparation of sulfentrazone-1, herbicidal compositions comprising sulfentrazone-1, and methods of its use are described.
1. A sulfentrazone composition comprising a crystalline polymorphic form of the compound N-[2,4-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl]phenyl]methanesulfonamide (sulfentrazone-1) wherein the sulfentrazone-1 has a powder X-ray diffraction profile that comprises peaks in terms of 2-theta, at 10.1±0.2°, 12.5+0.2°, 33.7+0.2° 15.9+0.2° and 37.7+0.2°, wherein at least 80 weight % of the sulfentrazone composition is present as sulfentrazone-1 and wherein the composition comprises by comprising less than 2 weight % of an organic solvent.
2. The sulfentrazone composition of claim 1 wherein the sulfentrazone-1 has an onset of melting in the range of from 119° C. to 130° C.
3. The sulfentrazone composition of claim 1 wherein the sulfentrazone-1 a single endothermic peak in the range of from 123° C. to 129° C.
4. The sulfentrazone composition of claim 1 wherein at least 95 weight % of the sulfentrazone is present as sulfentrazone-1.
5. The sulfentrazone composition of claim 1 wherein at least 99 weight % of the sulfentrazone is present as sulfentrazone-1.
6. The sulfentrazone composition of claim 5 wherein the composition comprises less than 1 weight % solvent.
7. The sulfentrazone composition of claim 6 wherein the composition comprises less than 0.5 weight % solvent.
8. The sulfentrazone composition of claim 7 wherein the composition comprises less than 0.2 weight % solvent.
9. The sulfentrazone composition of claim 5 wherein the organic solvent is an aromatic solvent.
10. The sulfentrazone composition of claim 9 wherein the aromatic solvent is toluene.
11. A process for preparing the sulfentrazone-1 of claim 1 comprising the steps of: (i) obtaining a solution comprising sulfentrazone in a polar, protic solvent selected from the group consisting of C 1-4 alcohols, water and combinations thereof; (ii) modifying conditions of solubility for sulfentrazone in the solvent to initiate crystallization of sulfentrazone-1 from the solution.
12. The process of claim 11 wherein the polar, protic solvent is isopropanol.
13. The process of claim 12 wherein the polar, protic solvent in step (a) comprises water.
14. The process of claim 11 wherein the crystallization is effected by addition of a solubility-decreasing solvent to the sulfentrazone solution.
15. The process of claim 11 wherein a saturated or near-saturated solution of sulfentrazone is obtained prior to step (ii).
16. The process of claim of any one of preceding claims 11 to 15 further comprising: (a) heating a slurry of toluene-containing sulfentrazone in a polar, protic solvent selected from the group consisting of C 1-4 alcohols, water and combinations thereof to provide a melt; and (b) removing the toluene by azeotropic co-distillation with the polar, protic solvent prior to crystallizing sulfentrazone-1 from the solvent in step (ii).
17. The process of claim 16 wherein the crystallization is promoted by seeding with crystals of sulfentrazone-1.
18. A sulfentrazone composition according to claim 1 comprising an herbicidally effective amount of sulfentrazone-1 in admixture with an agriculturally acceptable carrier.
19. The sulfentrazone composition of claim 18 wherein at least 95% of the sulfentrazone comprises sulfentrazone-1.
20. The sulfentrazone composition of claim 18 wherein at least 99% of the sulfentrazone comprises sulfentrazone-1.
21. The sulfentrazone composition of claim 1 consisting essentially of sulfentrazone-1.
22. A method for controlling undesired plant growth which comprises applying to the locus thereof where control is desired an herbicidally effective amount of the composition of any one of claim 1 - 10 , 21 .