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NITRATION AGENTS AND METHODS MORE RARELY USED 129

OTHER NITRATION REACTIONS BY SUBSTITUTION
An alkyl group is sometimes replaced by a nitro group. This happens particularly
when nitrating amines to nitramines. As a classical example, the formation of

trinitrophenylmethylnitramine (tetryl) from dimethylaniline can be mentioned:

(Vol. III)

(92)

Some branched alkyl groups, especially the isopropyl group, can readily be

replaced by a nitro group, even when they are attached to an aromatic ring. For

example, under certain nitration conditions thymol ethers can yield the corre-

sponding trinitro-m-cresol ethers (Giua [198]). Similarly, the nitration of p- cymene

may lead to dinitrotoluene (Alfthan [199]):

(93)

The nitration reaction that consists in replacing a hydroxyl group by a nitro

group is not often used. It is usually applied to tertiary alcohols. For example,

tert-butyl alcohol (trimethylcarbinol) reacted with nitric acid to yield tert-nitro-

butane in 10% yield in relation to the alcohol weight (Haitinger [4]):

(CH 3 ) 3 COH (CH 3 ) 3 CNO 2 (94)

In the aliphatic series the substitution of a carboxyl group by a nitro group

can only be accomplished with a small yield. gem-Dinitropropane, for example, is

obtained from isobutyric acid (Bredt [200]):

(CH 3 ) 2 CHCOOH (CH 3 ) 2 C(NO 2 ) 2 (95)

In the aromatic series such a reaction is more often observed. For example,

p- dimethylaminobenzoic acid can be nitrated to 2,4-dinitrodimethylaniline (Re-

verdin [201]) :