This substance, m.p. 295-300°, results from the direct nitration of oxanilide. It is stable and about as powerful as TNT, and is reported to explode with the production of a temperature which is distinctly lower than that produced by many high explosives.
2,2',4,4',6,6'-Hexanitro-N,N,-diphenylurea (hexanitrocarbanilide or sym-dipicrylurea) may be prepared by the nitration of carbanilide (sym-diphenylurea) in one, in two, or in three stages. It is of interest because of its explosive properties and because it supplies one way in which benzene may be converted into an explosive which is valuable both for military and for civil uses. Carbanilide may be prepared by the interaction of aniline and phosgene but is most conveniently and economically procured by heating aniline and urea together at 160-165°.
Preparation of Hexamtrocarbanilide (Two Stages). Forty grams of carbanilide is dissolved in 60 cc. of concentrated sulfuric acid (d. 1.84), and the solution is added drop by drop during 4 hours to 96 cc. of nitric acid (d. 1.51) while the mixture is stirred vigorously with a mechanical stirrer and its temperature is maintained at 35° to 40°. After all has been added, the stirring is continued and the temperature is raised to
60° during half an hour and maintained at 60° for another hour. The mixture is cooled to room temperature, allowed to stand over night, then treated with cracked ice and water, and filtered. The crude tetra-
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