[...]
It has been shown previously that, while Cyclonite prepared from hexamethylenetetramine is always contaminated with
1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX), this impurity is absent when the starting material contains a single preformed
1,3,5-triazacyclohexane ring. If, then, the condensation product of formaldehyde and potassium sulfamate were actually trimeric, and composed such a
ring system, the Cyclonite produced from it ought to show by its high melting point (204-205 degrees Celsius) that it contained none of the tetramer,
HMX. This was found to be the case when the crude product obtained from treatment of the salt with nitric acid and sulfur trioxide was purified by
crystallization from nitric acid under conditions where the tetramer, HMX, would not have escaped detection if it had been present.
[...]
Experimental:
Tripotassium 1,3,5-Triazacyclohexane-1,3,5-trisulfonate. -- A solution of potassium sulfamate, prepared in the cold from sulfamic
acid and aqueous alkali, was filtered, chilled to 0 degrees Celsius and treated with 75 mL (1 mol) of 37% aqueous formaldehyde solution. The
temperature rose to 20 degrees Celsius, was recooled and neutralized to pH 5 with 20-30 mL of 35% aqueous potassium hydroxide. The precipitate (64.5
g) thus formed was filtered off from the chilled slurry. A second identical crop (8.5 g) was obtained by slight dilution of the filtrate. The
air-dried material thus represents 50% of the theoretical yield.
[analysis and crystallographic information omitted]
1,3,5-Trinitro-1,3,5-triazacyclohexane (RDX)
A. From Phosphorus Pentoxide. -- Into a 200 mL three-necked flask equipped with a wide sweep powerful stirrer was placed 34.4 mL (0.8
mol) of absolute nitric acid. The stirred acid, maintained at 0 degrees Celsius was treated with 28.4 g (0.2 mol) of phosphorus pentoxide over two
minutes. This mixture was chilled and stirred while 29.4 g (0.066 mol) of tripotassium 1,3,5-triazacyclohexane-1,3,5-trisulfonate was added over
thirty-five minutes so as to maintain a reaction temperature of 25-30 degrees Celsius. After one hundred fifty minutes more at this temperature the
whole was raked into ice (reverse dilution causes decomposition), filtered and washed with dilute ammonia. The vacuum-dried RDX (m.p. 195-197 degrees
Celsius) weighed 12.4 g, or 84% of theoretical. This was heated cautiously with 50 mL of 60% nitric acid until by-product decomposition was complete
after two minutes, then diluted with 50 mL of water, cooled and filtered. The product, washed with 3% ammonia and vacuum dried weighed 11.8 g. and
melted at 204.3-204.7 degrees Celsius.
B. From Sulfur Trioxide. -- The yield was essentially the same as that shown above when 0.01 mol of tripotassium
triazacyclohexanetrisulfonate was added to a solution of 0.0225 mol of stabilized liquid sulfur trioxide in 0.11 mol of absolute nitric acid, but the
crude (198-201 degrees C) and the refined (204.5-204.8 degrees C) melting points were slightly better. However the violence of solution of sulfur
trioxide in nitric acid (even at -40 degrees Celsius) recommends the procedure with phosphorus pentoxide for laboratory use. |