The Chemistry of Powder and Explosives - Sciencemadness Dot Org

188 AROMATIC NITRO COMPOUNDS
and is less sensitive to shock than the sulfide. It is a more
powerful explosive than hexanitrodiphenyl sulfide.
Hexanitro-oxanilide
NO2
J
NO2
-NH—CO—CO—NH——NO,
NOa
NO2
2,2',4,4',6,6'-Hexanitro-N,N'-diphenylurea (hexanitrocarbanilide
or sj/m-dipicrylurea) 120 may be prepared by the nitration of
carbanilide (s?/m-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 Hexanitrocarbanilide (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-
119 Fr. Pat. 391,106.
120 Davis, U. S. Pat. 1,568,502 (1926).