Nitrotriazolone

Nitrotriazolone (NTO) is a heterocyclic semicarbazide-derived high explosive first identified in 1905, but research into its explosive properties was not conducted until the 1980s.^[2] NTO is currently being used by the US Army in munitions, specifically Insensitive munitions replacing those made with legacy explosives.^[3]

Nitrotriazolone^[1]

Names
Preferred IUPAC name 5-nitro-1,2-dihydro-3H-1,2,4-triazol-3-one
Identifiers
CAS Number	932-64-9 Y
3D model (JSmol)	Interactive image
Abbreviations	NTO
ChemSpider	2696109
ECHA InfoCard	100.012.050
EC Number	213-254-4
MeSH	C420648
PubChem CID	3453883
UNII	43WPQ5QCE3 Y
UN number	0490
CompTox Dashboard (EPA)	DTXSID80883616
InChI InChI=1S/C2H2N4O3/c7-2-3-1(4-5-2)6(8)9/h(H2,3,4,5,7) Key: QJTIRVUEVSKJTK-UHFFFAOYSA-N
SMILES C1(=NC(=O)NN1)[N+](=O)[O-]
Properties
Chemical formula	C2H2N4O3
Molar mass	130.063 g·mol−1
Appearance	Off white, yellowish beige color to light yellow powder, crystals, or prills
Odor	Odourless
Density	1.9 g/cm3 (20 °C)
Melting point	268–271 °C (514–520 °F; 541–544 K)
Solubility in water	17,200 mg/L
Solubility	Soluble in acetone, ethyl acetate Slightly soluble in dichloromethane
log P	−1.699 (22 °C)
Acidity (pKa)	3.76 (20 °C)
Explosive data
Shock sensitivity	Very low
Friction sensitivity	Very low
Detonation velocity	8,500 m/s
Thermochemistry
Heat capacity (C)	124.5 J/K at (47 °C)
Std enthalpy of combustion (ΔcH⦵298)	−934.4 kJ/mol
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H209, H223, H242, H301, H313, H315, H319, H333, H335
Precautionary statements	P210, P220, P260, P262, P270, P280
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Nitrotriazolone is getting progressively adopted in novel explosive formulations, such as IMX-101, a new, safer alternative to TNT specially devised in 2010 by BAE Systems, where it is combined with 2,4-dinitroanisole (DNAN) and nitroguanidine. As such, NTO is found in the vast majority of IMX formulations. The Picatinny Arsenal has also adopted the implementation of NTO and DNAN in many of their likewise newly developed insensitive explosive mixtures, which share many of the same applications of the IMXs. ^[4]

Properties

Nitrotriazolone shows keto–enol tautomerism through proton transfer reactions. The keto form shows significantly different stability to heat, friction, and impact.^[5]

Nitrotriazolone can form either a mono or dihydrate.^[5]

Preparation

NTO was first made in 1905^[6] in a two step process. Semicarbazide hydrochloride is condensed with formic acid to produce 1,2,4-triazol-3-one, which is nitrated with nitric acid to form nitrotriazolone.^[7][5]

Toxicity

In vivo studies showed the nitrotriazolone is absorbed through the skin and gastrointestinal tract. In the kidneys, NTO is broken down into 5-amino-1,2,4-triazol-3-one, which undergoes oxidative denitrification and forms urazoles and nitrites in rats.^[8]