Organic Chemistry of Explosives

Nitration of the parent alcohol 93

treatment with reagents like mixed acid, nitric acid in chloroform, and 98 % nitric acid in acetic

anhydride.^22 The tetranitrate ester (16) is a shock sensitive compound of little use as a practical

explosive. Treatment of 1,4-dideoxy-1,4-dinitro-neo-inositol (15) with a less powerful nitrat-

ing agent, namely, a solution of 90 % nitric acid in acetic anhydride, yields the dinitrate ester

(17) (LLM-101), a compound with significantly better properties.^22

3.2.2O-Nitration with dinitrogen tetroxide

R OH + N 2 O 4 ONOR + HNO 3

or CH 2 Cl 2 ,

0 °C to 5 °C

Neat

-170 °C to 20 °C

(Eq. 3.4)

Figure 3.8

Dinitrogen tetroxide reacts with simple alcohols in the gas and liquid phase to yield the corre-

sponding nitrite ester as the major product together with trace amounts of oxidation products

(Equation 3.4).^23 −^26 This is the case for neat reactions and those conducted in methylene

chloride between subambient and ambient temperatures.

RRO Na ONO 2 NaNO 2 (Eq. 3.5)

-75 °C

N 2 O 4

ROH, CH 2 Cl 2

++

Figure 3.9

In the presence of strong base, i.e. the alkali metal salt of the alcohol, and at low temperatures,

dinitrogen tetroxide behaves as a nitrating agent and the corresponding nitrate ester can be

obtained in high yield (Equation 3.5).^25 ,^26 Reactions need to be conducted at temperatures

of− 75 ◦C or lower and a solution of the nitrogen oxide in methylene chloride is used. The

alkali metal salts of higher alcohols (above C 4 ) are not completely homogeneous in methylene

chloride at these low temperatures and so reactions do not proceed satisfactorily.^26

3.2.3O-Nitration with dinitrogen pentoxide

Dinitrogen pentoxide is a universal nitrating agent with many advantages over conventional

nitrations using mixed acid (see Chapter 9). Amongst the advantages are: (1) faster reactions,

(2) easier temperature control, (3) easier product isolation, (4) higher purity products, and (5)

absence of large amounts of acid waste for disposal.O-Nitrations with dinitrogen pentoxide

(Equation 3.6) are noted to be clean with an absence of oxidation by-products.^26 −^28

R OH + N 2 O 5 R ONO 2 + HNO 3 (Eq. 3.6)

Figure 3.10

New and improved routes for the industrial synthesis of dinitrogen pentoxide mean that its

use is increasing and for many applications it may replace the use of mixed acid in the near

future.^27 ,^28 Dinitrogen pentoxide can be prepared by: (1) ozonolysis of dinitrogen tetroxide,^29

(2) electrolysis of nitric acid–dinitrogen tetroxide solutions,^30 and (3) dehydration of nitric

acid.^31 ,^32