Organic Chemistry of Explosives

Kaplan–Shechter reaction 25

A range of primary and secondary nitroalkanes and their derivatives have been converted

to the correspondinggem-dinitroalkanes via oxidative nitration, including: the conversion of

nitroethane, 1-nitropropane, 2-nitropropane and 2-nitro-1,3-propanediol to 1,1-dinitroethane

(78 %), 1,1-dinitropropane (86 %), 2,2-dinitropropane (93 %) and 2,2-dinitro-1,3-propanediol

(77 %) respectively.^105 The silver nitrate used in these reactions can be recovered quantitatively

on a laboratory scale and this has led to a study where oxidative nitration has been considered

for the large-scale production of 2,2-dinitropropanol (25) from the nitroethane (22).^107

C

NO 2

NO 2

HOCH 2 (CH 2 )n C

NO 2

NO 2

CH 2 OH

CC

NO 2

CH 2 OH

O 2 N

2 OH HOCH 2

2 CH 2 O

(NO 2 ) 2 CH(CH 2 )nCH(NO 2 ) 2

4 AgNO 3

2 NaNO 2

1. OH


2. H
   see Table 1.8

83

86

85

84

O 2 NCH 2 (CH 2 )nCH 2 NO 2 (CH 2 )n

Figure 1.36

Feuer and co-workers^108 used oxidative nitration for the synthesis of α,α,ω,ω-

tetranitroalkanes from the correspondingα,ω-dinitroalkanes (Table 1.8). However, this fails for

α,ω-dinitroalkanes in which the nitro groups are not separated by at least three methylene units.

Accordingly, oxidative nitration fails for both 1,3-dinitropropane (n=1) and 1,4-dinitrobutane

(n=2) and gives a low yield of 1,1,5,5-tetranitropentane (n=3) from 1,5-dinitropentane

(Table 1.8). Feuer and co-workers^108 later discovered that the bis-methylol derivatives (84) of

α,ω-dinitroalkanes (83) give good yields of product (85) when the separation between nitro

groups is two methylene units or greater; the methylol groups can be removedin situvia base-

catalyzed demethylolation, with loss of formaldehyde, to yield theα,α,ω,ω-tetranitroalkane

(86) (Table 1.8). These reactions still fail for the bis-methylol derivative of 1,3-dinitropropane

(n=1) but give a 49 % yield of 1,1,4,4-tetranitrobutane (n=2) after demethylolation of the

corresponding bis-methylol derivative, namely, 2,2,5,5-tetranitro-1,6-hexanediol.

Oxidative nitration has a number of advantages over pre-existing routes to gem-

dinitroalkanes, including:

Reactions are successful for hindered compounds; 3,3-dinitro-2-butanol is obtained from

the oxidative nitration of 3-nitro-2-butanol.^105

Oxidative nitration avoids the isolation ofgem-nitronitronate salts, which are often unstable

explosives with a high sensitivity to impact and friction.

Oxidative nitration has been modified to an electrolytic process. 200

Good yields of internalgem-dinitroalkanes are attainable, whereas the Ter Meer reaction

fails for the synthesis of this class of compounds.

Oxidative nitration is a one step process from nitroalkane togem- dinitroalkane, whereas the

Ter Meer reaction requires two steps (initial halogenation followed by halide displacement

with nitrite anion).