Organic Chemistry of Explosives

5-Membered rings – 2N 297

alternative to TNT for mass use in ordnance. At present, chemists at Lawrence Livermore

National Laboratory (LLNL) are working with ARDEC and LANL on optimizing synthesis

and lowering production costs.^14 The ammonium salt of 2,4,5-trinitroimidazole (ATNI) (16)

has received some interest but its inability to form a useful eutectic with ammonium nitrate

means that it is unlikely to find application.^13

7.3.3 1,3,4-Oxadiazoles

COOH

NO 2

NO 2

O 2 N H

N

N

H

O

O

NO 2

NO 2

O 2 N

NO 2

O 2 N NO 2

NN

O

NO 2 NO 2

O 2 N NO 2 O 2 N NO 2

17 18

PCl 5 ,

ClCH 2 CH 2 Cl

1. PCl 5 , PhH


2. N 2 H 4 .H 2 O, MeOH

19

(DPO)

Figure 7.7

The dehydration ofN,N′-diacylhydrazines is a standard method for the formation of the

1,3,4-oxadiazole ring. 2,5-Dipicryl-1,3,4-oxadiazole (DPO) (19) is synthesized by treating

2,4,6-trinitrobenzoic acid (17) with phosphorous pentachloride, followed by treatment with hy-

drazine to give theN,N′-diacylhydrazine (18) which undergoes dehydration on further reaction

with phosphorous pentachloride in 1,2-dichloroethane.^15 DPO exhibits high thermal stability

but is very sensitive to impact and shock, making it useful in detonation transfer compositions.

NN

NN

CF 2 NF 2

Na+

NN

OO

NN

F 2 NF 2 C CF 2 NF 2

(COCl) 2

CF 2 NF 2

20 22

21

NN

Figure 7.8

The energetic 1,3,4-oxadiazole (22) is synthesized from the reaction of the tetrazole (20)

with oxalyl chloride.^16 In this reaction the tetrazole (20) undergoes a reverse cycloaddition

with the expulsion of nitrogen and the formation of the 1,3-dipolar diazoalkane (21) which

reacts with the carbonyl groups of oxalyl chloride to form the 1,3,4-oxadiazole rings.

7.3.4 1,2,5-Oxadiazoles (furazans)

Nitro and amino derivatives of the furazan ring (1,2,5-oxadiazole) are nitrogen-rich en-

ergetic materials with potential use in both propellant and explosive formulations. Some