Organic Chemistry of Explosives

68 Polynitropolycycloalkanes

more of a science than a balancing act. Correlations between structure and properties such

as thermal, chemical and impact sensitivity have advanced significantly as a result of such

databases. Target compounds are increasingly chosen for synthesis as a result of theoretical

performance calculations and computer-aided design. Such calculations allow the prediction

of density, detonation velocity and pressure, and heat of formation.

Preliminary evaluations of polynitropolycyclic compounds reveal that this class of energetic

materials is relatively powerful and shock insensitive, and so, well suited for use in future

explosive and propellant formulations.

Energetic materials with strained or caged structures are often much more difficult to synthe-

size compared to their open chain counterparts. This presents a further challenge to researchers

of new energetic materials – while new compounds can be synthesized on a laboratory scale,

and their properties and performance tested, the complexity of the synthetic routes may render

their use as explosives nonfeasible. This particularly applies to polynitropolycyclic hydrocar-

bons because the direct nitration of these hydrocarbons is not a feasible route of introducing

nitro groups without considerable decomposition.

2.2 Cyclopropanes and spirocyclopropanes

O 2 N NO 2

O 2 N

(^1) H
2
H

1. NaH, DMSO


2. I 2 , DMSO

24 %

NO 2

Figure 2.1

CH 3 CH 2 NO 2

CH 3

NO 2 NO 2

NO 2

O 2 N

H 3 C

CH 3

NO 2

LiOCH 3 ,

MeOH

[CH 3 CH=NO 2 Li]

1.

2. AcOH
   71 %^5

6

1. NaH, DMSO


2. I 2 , DMSO
   36 % (2 steps)

3 4

Figure 2.2

The heat of formation of cyclopropane is approximately 276 KJ/mol with a correspond-

ing bond strain energy of 230 KJ/mol. Consequently, polynitro derivatives of cyclopropane

and spirocyclopropane constitute a class of low molecular weight energetic materials. Wade

and co-workers^1 synthesized some of these compounds using an oxidative cyclization of

the corresponding open chain 1,3-dinitronate dianions with iodine in dimethyl sulfoxide.

In this way,trans-1,2-dinitrocyclopropane (2),trans-1,2-dimethyl-1,2-dinitrocyclopropane

(6), andtrans-1,2-diethyl-1,2-dinitrocyclopropane were prepared from 1,3-dinitropropane

(1), 2,4-dinitropentane (5), and 3,5-dinitroheptane respectively. Of the compounds investi-

gated, only thetrans-isomers were isolated, possibly as a result of thermodynamic control