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212 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

with an 0.1 N solution of sodium colamate. The nitro compound behaves as a

Lewis acid:

m- Dinitrobenzene and α− trinitrotoluene require two and three equivalents of

colamate respectively. On reaction of polynitrocompounds with diazomethane-

see [160].

FREE RADICAL REACTIONS

Nitro groups also enable free radical reactions to occur with aromatic rings.

As Fieser’s investigations [71a] have shown, aromatic nitro compounds can be

methylated when reacted with lead tetraacetate:

(31)

(32)

The reactions probably involve free radicals. The lead tetraacetate liberates the

methyl radical, which reacts with the aromatic free radical.

It is characteristic that the new entrant methyl group assumes the ortho position

to the nitro group and thus a substitution occurs which is similar to nucleophilic

attack. Recently it has been found by Jackson and Waters [72] that higher nitra-

ted benzene derivatives such as m- dinitrobenzene, or 1,3,5-trinitrobenzene, become

homolytic hydrogen acceptors at temperatures of 80-100°C especially in the
presence of the 2-cyano-2-propyl radical, which is formed by thermal decomposi-
tion of a,a’-azo-bis-isobutyronitrile