Organic Chemistry of Explosives

The nitrolysis of hexamine 249

DPT (239) with a mixture of acetic anhydride, ammonium nitrate and nitric acid at 65–70◦C

furnishes HMX in 65 % yield after purification. Bachmann and co-workers^196 repeated the

method of Wright and co-workers but obtained a slightly lower yield of HMX (59 %) after

purification of the crude product from both RDX (16 % total of the crude) and linearN-acetyl

nitramine by-products. Another procedure treated DPT (239) with 1.6 mole equivalents of

ammonium nitrate and 3.2 equivalents of fuming nitric acid at 60–65◦C and is reported to

furnish HMX in 75 % yield after purification.^211

1,5-Dinitroendomethylene-1,3,5,7-tetraazacyclooctane (DPT) (239) was first isolated from

the partial nitrolysis of hexamine; the reaction of hexamine with acetic acid, acetic anhy-

dride and nitric acid at 15–30◦C, followed by quenching with water and neutralization of the

liquors with aqueous ammonia to pH 5.5–6.5, leads to the precipitation of DPT (239).^187 ,^188 ,^196

However, the yield of DPT from such reactions is often poor (15–25 %). DPT has also been

synthesized from the reaction of hexamine dinitrate with acetic anhydride or cold 90 % aqueous

sulphuric acid. Both methods under optimum conditions give yields of DPT of approximately

31 %.^188 The reaction of nitramine (NH 2 NO 2 ) with aqueous formaldehyde, followed by neu-

tralization of the reaction mixture with ammonia to pH 5.5–6.5, gives DPT in 73 % yield based

on the nitramine starting material.^188 This last reaction presumably involves the formation of

dimethylolnitramine as an intermediate (Section 5.15.4.2).

5.15.2.3 Other synthetic routes to HMX

Gilbert and co-workers^97 showed that the nitrolysis of 1,3,5-triacyl-1,3,5-triazacyclohexanes

offered little benefit over the conventional synthesis of RDX via the nitrolysis of hexamine. This

is not the case for HMX where its synthesis via the Bachmann process is far from perfect.

This process and its modifications are expensive, requiring large amounts of acetic anhydride.

The rate of production is slow and the maximum attainable yield is 75 %. In fact, HMX is five

times as expensive as RDX to produce by this process and this prevents the widespread use

of this high performance explosive. Many efforts have focused on finding more economical

routes to HMX.

The nitrolysis of cyclic polyamides offers a possible alternative industrial synthesis of HMX.

The nitrolysis of 1,3,5,7-tetraacetyl-1,3,5,7-tetraazacyclooctane (TAT) (79) and 1,5-diacetyl-

3,7-dinitro-1,3,5,7-tetraazacyclooctane (DADN) (80) with a solution of dinitrogen pentoxide

in anhydrous nitric acid gives HMX in 79 % and 98 % yields, respectively.^96 Interestingly, the

same reactions with nitric acid–acetic anhydride fail at room temperature.

N

NN

N

AcAc

AcAc

N

NN

N

Ac

Ac

AcCl, Ac 2 O/AcOH

NaOAc, 10 °C

96 % HNO 3

P 2 O 5 , 75 °C

240

(DAPT)

79

(TAT)

N

NN

N

O 2 N NO 2

O 2 N NO 2

3

(HMX)

Figure 5.107

The acetolysis of hexamine has been extensively studied^96 ,^206 ,^212 −^216 and reviewed^217 and

the synthesis of two key intermediates optimized. 3,7-Diacetyl-1,3,5,7-tetraazabicyclo