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 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 is obtained by a process comprising the steps: (i) obtaining a solution, suspension, or dispersion of technical grade sulfentrazone; (ii) crystallizing sulfentrazone-1 from the technical grade sulfentrazone from a polar, protic solvent; and (iii) isolating the crystallized sulfentrazone-1 to obtain the sulfentrazone composition, wherein the sulfentrazone-1 has a powder X-ray diffraction profile that comprises peaks in terms of 2-theta at 15.9±0.2°, 10.1±0.2°, 12.5±0.2°, 33.7±0.2°, and 37.7±0.2°, wherein at least 80 weight % of the sulfentrazone composition present is sulfentrazone-1, and wherein the composition is further characterized by comprising less than 2 weight % of an organic solvent.
2. The composition of claim 1 wherein sulfentrazone-1 is crystallized from the polar, protic solvent selected from the group consisting of C 1-4 alcohols, water and combinations thereof.
3. The composition of claim 2 wherein the polar, protic solvent is isopropanol.
4. The composition of claim 3 wherein the polar, protic solvent further comprises water.
5. The composition of claim 2 wherein a saturated or near-saturated solution of sulfentrazone is obtained.
6. The composition of claim 2 wherein the technical grade sulfentrazone comprises entrapped solvent, the process further comprising: (a) heating a slurry of technical grade sulfentrazone in the polar, protic solvent selected from the group consisting of C1-4 alcohols, water and combinations thereof to provide a melt; and (b) removing the entrapped solvent by azeotropic co-distillation with the polar, protic solvent prior to crystallizing sulfentrazone.
7. The composition of claim 2 wherein crystallization is promoted by seeding with crystals of sulfentrazone-1.
8. The composition of claim 1 further comprising at least one agriculturally acceptable carrier or diluent, wherein the composition is an agrochemical composition comprising a herbicidally effective amount of sulfentrazone-1.
9. The agrochemical of claim 8 wherein at least 95% of the sulfentrazone is sulfentrazone-1.
10. The agrochemical composition of claim 8 wherein the sulfentrazone-1 is characterized by having an onset of melting in the range of from about 123° C. to about 129° C.
11. The agrochemical composition of claim 8 wherein the sulfentrazone-1 is characterized by having a single endothermic peak at about 126° C.
12. The agrochemical composition of claim 8 wherein at least about 80 weight % of sulfentrazone is present as sulfentrazone-1.
13. The agrochemical composition of claim 8 wherein at least about 95 weight % of sulfentrazone is present as sulfentrazone-1.
14. The agrochemical composition of claim 8 wherein at least about 99 weight % of sulfentrazone is present as sulfentrazone-1.
15. A method for controlling undesired plant growth which comprises applying to the locus of crop and/or undesired plant where control is desired an herbicidally effective amount of the agrochemical composition of claim 8 .