242 Synthetic Routes toN-Nitro
acid.^177 This route is favoured on both industrial and laboratory scales – the two nitro groups of
2,4-dinitro-N-methylaniline make this substrate less susceptible to oxidative side-reactions and
so yields of tetryl are considerably higher than for the direct nitration ofN, N-dimethylaniline.
Tetryl has been synthesized by treating picryl chloride with the potassium salt of methyl-
nitramine but the reaction is of theoretical interest only.^178
NO 2 NO 2 NNO 2NO 2
152
(pentryl)NO 2 NNO 2NO 2O 2 NR232, R = Et (ethyltetryl)
233, R = n-Bu (butyltetryl)CH 2 CH 2 ONO 2Figure 5.95Pentryl (152) is obtained from the action of fuming nitric acid or mixed acid onN-(2,4-
dinitrophenyl)ethanolamine, itself obtained from the reaction of 2,4-dinitrochlorobenzene with
ethanolamine.^179 Another route to pentryl (152) involves the nitration ofN-phenylethanol-
amine, which is obtained from the reaction of aniline with ethylene oxide.^74
Other aromatic nitramines have not found use as practical explosives. Ethyltetryl (232)
is prepared from the nitration of 2,4-dinitro-N-ethylaniline, N, N-diethylaniline or N-
ethylaniline.^178 Butyltetryl (233) can be synthesized from the nitration of 2,4-dinitro-N-
butylaniline, which is attainable from the reaction ofn-butylamine with 2,4-dinitrochloro-
benzene.^178
NO 2NO 2N NNO 2 NO 2 NNO CH^3O 2 N NO 2H 3 C234 235N
N
NO 2NO 2 NO 2O 2 N NO 2NO 2O 2 N NO 2Figure 5.96The aromatic nitramine (234) can be prepared by nitratingN, N′-diphenylethylenediamine^180
or 2,2′,4,4′-tetranitro-N, N′-diphenylethylenediamine with mixed acid,^181 the latter synthe-
sized from 2,4-dinitrochlorobenzene. The azoxy-nitramine (235) is prepared by nitrating 4,4′-
bis(dimethylamino)azoxybenzene with mixed acid.^182 ,^183
OH OH
CH 2 NMe 2CH 2 NMe 2
236Me 2 NCH 2OH
CH 2 NNO 2
237NCH 2
70 % HNO 340 °C3 CH 2 O3 Me 2 NHNO 2MeO 2 NMeFigure 5.97