Urea nitrate
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Urea nitrate is produced in one step by reaction of urea with nitric acid. This is an exothermic reaction, so steps must be taken to control the temperature.
It was discovered in 1797 by William Cruickshank, inventor of the Chloralkali process.
Urea nitrate explosions may be initiated using a blasting cap.
Chemistry
Urea contains a carbonyl group. The more electronegative oxygen atom pulls electrons away from the carbon atom, forming a polar bond with greater electron density around the oxygen atom, giving it a partial negative charge. In a simplistic sense, nitric acid dissociates in aqueous solution into protons (hydrogen cations) and nitrate anions. The electrophilic proton contributed by the acid is attracted to the negatively charged oxygen atom on the urea molecule and the two form a covalent bond. The formed O-H bond is stabilized into a hydroxyl group when the oxygen abstracts an electron pair away from the central carbon atom, which leads to bond resonance between it and the two amino groups. As such, the urea cation can be thought of as a amidinium species. Paired with the spectator nitrate counteranion, it forms urea nitrate.
- (NH2)2CO (aq) + HNO3 (aq) → [(NH2)2COH]+[NO3]− (s)
The compound is favored by many amateur explosive enthusiasts as a principal explosive for use in larger charges. In this role it acts as a substitute for ammonium nitrate based explosives. This is due to the ease of acquiring the materials necessary to synthesize it, and its greater sensitivity to initiation compared to ammonium nitrate based explosives.