Nitroguanidine - sometimes abbreviated NGu - is a colorless, crystalline solid that melts at 257 °C and decomposes at 254 °C. Nitroguanidine is an extremely insensitive but powerful high explosive. Wetting it with > 20 wt.-% water effects desensitization from HD 1.1 down to HD 4.1 (flammable solid). Nitroguanidine is used as an energetic material, i.e., propellant or high explosive, precursor for insecticides, and for other purposes.

Manufacture

Nitroguanidine is produced worldwide on a large scale starting with the reaction of dicyandiamide (DCD) with ammonium nitrate to afford the salt guanidinium nitrate, which is then nitrated by treatment with concentrated sulfuric acid at low temperature. The guanidinium nitrate intermediate may also be produced via the Boatright–Mackay–Roberts (BMR) process, in which molten urea is reacted with molten ammonium nitrate in the presence of silica gel. This process had been commercialized because of its attractive economic features.

Uses

Explosives

Nitroguanidine has been in use since the 1930s as an ingredient in triple-base gun propellants in which it reduces flame temperature, muzzle flash, and erosion of the gun barrel but preserves chamber pressure due to high nitrogen content. Its extreme insensitivity combined with low cost has made it a popular ingredient in insensitive high explosive formulations (e.g AFX-453, AFX-760, IMX-101, AL-IMX-101, IMX-103, etc.). The first triple-base propellant, featuring 20-25% of nitroguanidine and 30-45% nitroglycerine, was developed at the Dynami Nobel factory at Avigliana and patented by its director Dr. Modesto Abelli (1859-1911) in 1905. Nitroguanidine's explosive decomposition is given by the following equation: H4N4CO2 (s) → 2 H2O(g) + 2 N2 (g) + C(s)

Pesticides

Nitroguanidine derivatives are used as insecticides, having a comparable effect to nicotine. Derivatives include clothianidin, dinotefuran, imidacloprid, and thiamethoxam.

Biochemistry

The nitrosoylated derivative, nitrosoguanidine, is often used to mutagenize bacterial cells for biochemical studies.

Structure

Following several decades of debate, it could be confirmed by NMR spectroscopy, and both x-ray and neutron diffraction that nitroguanidine exclusively exists as the nitroimine tautomer both in solid state and solution.