Organic Chemistry of Explosives

Nitration of compounds containing acidic hydrogen 31

inductive effect of three nitro groups and the increased sp^2 character of these positions as a

result of the strained cubane core. Even then, the low acidity of theβ-proton is reflected in the

need for a fairly strong base (hexamethyldisilazide in THF∼pKaof 25.8^228 ).

1.8.2 Acidic nitration

Electrophilic nitrations of aliphatic nitriles,^117 carboxylic acids,^229 carboxylic esters,^230 and

β-diketones^231 have been reported. The nitration of 2-alkyl-substituted indane-1,3-diones

with nitric acid, followed by alkaline hydrolysis, is a standard laboratory route to primary

nitroalkanes.^231

(CH 3 ) 2 C

NO 2

NO 2

HNO 3

(CH 3 ) 2 CHCOOH + CO 2

103

104

Figure 1.42

Treatment of some carboxylic acids with nitric acid is a route togem-dinitroalkanes, as in the

case ofiso-butyric acid (103), which undergoes nitration-decarboxylation on treatment with

nitric acid to give 2,2-dinitropropane (104).^232 Yields are often poor for this type of reaction.

70 % HNO 3

NO 2

C

NO 2

CO 2 EtR

H

CCO 2 Et

CO 2 H

R

105 106

R = H, 11 %

R = Me, 17 %

R = Et, 17 %

R = n-Bu, 8 %

Figure 1.43

The half esters of malonic acid (105) yieldα,α-dinitroesters (106) on nitration-decarboxyla-

tion with nitric acid, although yields are often poor.^229 Treatment of theseα,α-dinitroesters with

hydrazine hydrate or alkali metal hydroxides yields the correspondinggem-dinitroalkanes.^229

20 % red nitric acid

-5 °C to 5 °C, 60 %

KOH (aq), 70 °C

90 %

HO 2 CCH 2 CO 2 Me

107

(NO 2 ) 2 CHCO 2 Me

108

K

+ −

CH(NO 2 ) 2

18

Figure 1.44

A potential industrial route to potassium dinitromethane (18) involves treatment of methyl

malonate (107) with red fuming nitric acid to give methylα,α-dinitroacetate (108), followed by

hydrolysis-decarboxylation with aqueous potassium hydroxide.^233 Dinitromethane is a precur-

sor to 2,2-dinitroethanol and 2,2-dinitro-1,3-propanediol, both of which are useful in addition

and esterification reactions for the production of energetic oligomers and plasticizers.

CCl 4

NO 2

NO 2

CH 2 COOH + 3 HNO 3 + 3 SO 2

109

N C N C C

110

NO 2 + CO 2 + 3 H 2 SO 4

73–77 %

Figure 1.45