A one-step process for the preparation of nitrosamine-free dinitroaniline herbicides which involves contacting the crude dinitroaniline herbicide in the liquid state, after removal of excess amine, with an effective quantity of a hydrobromide salt of a p-amino benzoate ester, optionally in the presence of such an ester, passing a gaseous stream of air therethrough or applying a reduced pressure so as to essentially remove water present, resulting in an essentially nitrosamine-free product.
A process for the preparation of the unsaturated dinitroaniline, ethalfluralin having a level of nitrosamines lower than 0.5 ppm and essentially free from the compound of addition of halogenhydric acid on the methallyl double bond, by treatment with aqueous halogenhydric acid, wherein crude ethalfluralin is treated under agitation with an aqueous solution of hydrobromic acid in the presence of sulfamic acid and a sulfur compound selected from the group consisting of bisulfites, metabisulfites, hydrosulfites, sulfurous acid and gaseous sulfur dioxide.
A process is provided for preparing 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine from 4-chlorotrifluoromethylbenzene. The process includes a two stage nitration and an amination step. Ethylene dichloride is utilized as a diluent and solvent in the nitration steps. Spent acid from the first nitration is reconstituted with sulfur trioxide for use in the second nitration. Spent acid from the second nitration is used directly in the first nitration and evaporation is used to remove nitrosoamines from the final trifluralin product.
A simple and inexpensive process is described for reducing the concentration of N-nitroso-containing compounds. The process is applicable for compositions comprising N-nitroso-containing compounds and other desired compounds wherein the N-nitroso-containing compounds thermally decompose at a temperature below the decomposition temperature of the desired compounds. For compositions comprising N-nitroso-pendimethalin in Pendimethalin, the process requires heating the mixture to a temperature greater than about 120.degree. C., and holding the Pendimethalin at that temperature for a time effective to decompose the N-nitroso-pendimethalin present in the mixture. Volatile decomposition products are advantageously removed from the composition.
A simple and inexpensive process is described for reducing the concentration of N-nitroso-containing compounds in compositions comprising N-nitroso-containing compounds and other desired compounds wherein the N-nitroso-containing compounds thermally decompose at a temperature below the decomposition temperature of the desired compounds. For compositions comprising dinitroaniline herbicides wherein the N-nitroso compound is a N-nitroso derivative of a precursor in the manufacture of the herbicide, for example Flumetralin, N-ethyl-N-(2-chloro-6-fluorobenzyl)-2,6-dinitro-4-trifluoromethylaniline, the process requires heating the mixture to a temperature greater than about 120.degree. C., and holding the composition at that temperature for a time effective to decompose the N-nitroso compound present in the mixture. Volatile decomposition products are advantageously removed from the composition.
