Organic Chemistry of Explosives

Halide displacement 13

1.5.4 Displacements using nitronate salts as nucleophiles

Nitronate salts can react with alkyl halides to yield polynitroaliphatic compounds with varying

degrees of success. The main by-products of these reactions arise for competitiveO-alkylation.

Alkyl nitrates are formed as by-products when the nitroform anion is used in these reactions.^109

+ CH 3 C(NO 2 ) 3

CH 3 CN

Br

Br

+

C(NO 2 ) 3

(O 2 N) 3 C

35

dioxane

72 %

34

CH 3 I (NO 2 ) 2 CNO 2 Ag

32

(NO 2 ) 2 CNO 2 Ag

31 32 51 % 33

Figure 1.13

Methyl iodide (31) reacts with silver nitroform (32) in acetonitrile to give a 51 % yield of

1,1,1-trinitroethane (33).^109 The potassium salt of nitroform in acetone has been used for the

same reaction.^110 Yields between 28 % and 65 % have been reported for the reaction of silver

nitroform in acetonitrile with higher molecular weight alkyl iodides.^109 The choice of solvent

is important in some reactions, for example, silver nitroform reacts with 1,4-dibromo-2-butyne

(34) in solvents like dioxane^111 and acetone^111 to give 1,1,1,6,6,6-hexanitro-3-hexyne (35) in

approximately 72 % yield, whereas the same reaction in acetonitrile^109 is reported to give a

mixture of compounds.

CH 2 C(NO 2 ) 3

O 2 N NO 2

NO 2

36

NO 2 CH 2 C(NO 2 ) 3

37 38

(34 % via iodide) (8.5 % via iodide) (7.7 % via bromide)

(O 2 N) 3 CCH 2 CH 2 C(NO 2 ) 3 (O 2 N) 3 CCH 2 CH 2 C(NO 2 ) 3

Figure 1.14

Poor to modest yields of trinitromethyl compounds are reported for the reaction of silver ni-

troform with substituted benzyl iodide and bromide substrates. Compounds like (36), (37), and

(38) have been synthesized via this route; these compounds have much more favourable oxygen

balances than TNT and are probably powerful explosives.^112 The authors noted that consider-

able amounts of unstable red oils accompanied these products. The latter are attributed toO-

alkylation, a side-reaction favoured by an SN1 transition state and typical of reactions involving

benzylic substrates and silver salts. Further research showed that while silver nitroform favours

O-alkylation, the sodium, potassium and lithium salts favourC-alkylation.^113 The synthesis

and chemistry of 1,1,1-trinitromethyl compounds has been extensively reviewed.^9 ,^114 ,^115 The

alkylation of nitronate salts has been the subject of an excellent review by Nielsen.^116

H 2 C CHCH 2 Br

AgC(NO 2 ) 2 CN

35 %

NO 2

CHCH 2

NO 2

CH 2 CCN

Figure 1.15