5-Membered rings – 3N 313NHN NHONHN NHOO 2 NH 2 N NHNH2.HClO+
HCOOH 139100 °C 70 % HNO 3
or H 2 SO 4 , HNO 3140
(NTO)Figure 7.53hydrochloride with formic acid.^81 –^83 The facile synthesis of NTO from readily available start-
ing materials, coupled with its high performance (VOD∼8510 m/s,d= 1 .91 g/cm^3 ), and
properties which classify it as an insensitive high explosive (IHE), makes NTO a very attractive
explosive for use in insensitive munitions, either cast, pressed or in a plastic bonded matrix.
NTO is much less sensitive to impact than both the widely used military explosives RDX and
HMX.^84 The French first used NTO in combination with HMX in plastic bonded explosives.^85
NTO is now widely used alone or in combination with HMX or RDX for use as a filling for
insensitive munitions.^81 ,^86 AFX644 is an explosive composition based on NTO (40 %), TNT
(30 %), Wax (10 %) and Al powder (20 %) which has recently been used by the USAF as a low
vulnerability general purpose filler for bombs and is classified as an extremely insensitive deto-
nating substance (EIDS). Agrawal^87 has recently reviewed the advances made in the use of NTO
in munitions and explosive formulations. Spear and co-workers^83 have reviewed the history of
NTO and its structural, chemical, explosive and thermal properties, together with its synthesis.
NN NOO 2 NNN NHOO 2 NO 2 N NO 2NO 2O 2 N NO 2NO 2O 2 N NO 2NO 2(^141142)
Figure 7.54
The acidity of 1-H in NTO (140) has been exploited by a number of researchers in
this field. Many amine salts of NTO have been reported including the ammonium, hy-
drazinium, guanidinium, aminoguanidinium, diaminoguanidinium, triaminoguanidinium and
1,2-ethylenediammonium salts.^88 Metal salts of NTO have been prepared by the addition of
metal hydroxides or carbonates to aqueous solutions of NTO.^89 The physical properties of these
salts have been thoroughly investigated^89. Coburn and Lee^90 used NTO as a nucleophile, treat-
ment of NTO (140) with a mixture of picryl fluoride and 1-methyl-2-pyrrolidinone yielding
either (141) or (142) depending on the reaction stoichiometry.
7.4.3 Benzotriazoles
1-Picryl-5,7-dinitro-2H-benzotriazole (BTX) (145) was first synthesized by Coburn and co-
workers^91 from the reaction of benzotriazole with picryl chloride in DMF, followed by nitration
with mixed acid. Gilardi and co-workers^92 reported an alternative synthesis of BTX involving
treatment of 2-amino-4,6-dinitrodiphenylamine (143) with a solution of nitrous acid, which
leads to an intramolecular cyclisation via the diazonium salt to give (144), nitration of the