Organic Chemistry of Explosives

248 Synthetic Routes toN-Nitro

higher performance of HMX compared to RDX is offset by its higher cost of production. Conse-

quently, HMX has been restricted to military use where it has found application as a component

of some high performance propellants and powerful explosive compositions. Octol is a cast ex-

plosive containing HMX (75 %) and TNT (25 %), whereas Octal consists of wax-desensitized

HMX (70 %) and aluminium powder (30 %) and is pressed into charges. HMX has also been in-

corporated into some high performance plastic bonded explosives (PBXs). One such explosive,

PBX-9404, contains 94 % HMX, 3 % nitrocellulose and 3 % tris(chloroethyl)phosphate.

HMX can be synthesized from hexamine by any of the routes discussed below. Both methods

5.15.2.1 and 5.15.2.2 have been used for the industrial synthesis of HMX. However, the

recent commercial availability of dinitrogen pentoxide means that method 5.15.2.3 is achieving

industrial importance.

5.15.2.1 Synthesis of HMX from the nitrolysis of hexamine

Variations in the conditions used for the nitrolysis of hexamine have a profound effect on the

nature and distribution of isolated products, including the ratio of RDX to HMX. It has been

shown that lower reaction acidity and a reduction in the amount of ammonium nitrate used in

the Bachmann process increases the amount of HMX formed at the expense of RDX.^196 ,^207

Bachmann and co-workers^208 were able to tailor the conditions of hexamine nitrolysis to

obtain an 82 % yield of a mixture containing 73 % HMX and 23 % RDX. Continued efforts

to provide a method for the industrial synthesis of HMX led Castorina and co-workers^187 to

describe a procedure which produces a 90 % yield of a product containing 85 % HMX and

15 % RDX. This procedure conducts nitrolysis at a constant reaction temperature of 44◦C

and treats hexamine, in the presence of a trace amount of paraformaldehyde, with a mixture

of acetic acid, acetic anhydride, ammonium nitrate and nitric acid. Bratia and co-workers^209

used a three stage ‘aging process’ and a boron trifluoride catalyst to obtain a similar result. A

procedure reported by Picard^210 uses formaldehyde as a catalyst and produces a 95 % yield of

a product containing 90 % HMX and 10 % RDX.

The different solubilities of HMX and RDX in organic solvents means that pure HMX is

easily isolated from RDX–HMX mixtures; the higher solubility of RDX in acetone means that

recrystallization of such mixtures from hot acetone yields pure HMX.^187 ,^207

5.15.2.2 Synthesis of HMX from the nitrolysis of DPT

CH 2

N

N

H 2 C CH 2

H 2 C CH 2

O 2 N N NO 2

N

NN

N

O 2 N NO 2

O 2 N NO 2

(CH 2 ) 6 N 4

104

239

(DPT)

see text see text

3

(HMX)

nitrolysis nitrolysis

N

Figure 5.106

HMX (3) can be synthesized from the nitrolysis of 1,5-dinitroendomethylene-1,3,5,7-

tetraazacyclooctane (DPT) (239). Wright and co-workers^189 reported that the reaction of