Urea peroxide

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Urea peroxide
Names
Other names
Carbamide Peroxide
Properties
CH6N2O3
(NH2)2CO·H2O2
Molar mass 94.07 g/mol
Appearance White solid
Odor Odorless
Melting point 75 to 91.5 °C (167.0 to 196.7 °F; 348.1 to 364.6 K) (decomposes)
50 g/100 ml
Solubility Reacts with acids
Vapor pressure 23.3 mmHg (at 30 °C)
Hazards
Safety data sheet ReagentWorld
Related compounds
Related compounds
Urea
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Urea peroxide is a crystalline adduct composed of equal amounts of urea and hydrogen peroxide. It is used in commercial tooth-whiteners, and to loosen impacted earwax. It is also used to make plastics.

Properties

Chemical

Urea peroxide is a convenient replacement for 90% hydrogen peroxide in oxidation reactions.

In aqueous solution it behaves identically to a solution of urea and hydrogen peroxide added separately to water. Urea can be separated from this adduct by dissolving it in water and adding manganese dioxide which catalyses the decomposition of hydrogen peroxide; this way you can obtain high grade urea, but the peroxide is lost. Separating the two compounds without losing either is more tricky; one method involves using calcium or barium hydroxides to precipitate peroxide, leaving urea dissolved, and, after filtering out the alkaline earth metal peroxide, recovering hydrogen peroxide from it with sulfuric acid. This, however, requires a very concentrated solution of the adduct, decanted or vacuum-filtered from a sludge of wet powdered percarbamide.

When mixed with powdered metamizole (an over-the-counter analgesic drug), urea peroxide forms a mixture that spontaneously ignites and starts to emit noxious smoke. If the mixture does not ignite, it can be ignited manually. This mixture is widely known in Russia, where both components are OTC, among adolescent pranksters, under the name "Analgin-Hydroperit", after the local names of the components.

Physical

Urea peroxide is a free flowing white powder. Commercial forms of it often come pressed into tablets.

Availability

97% urea peroxide is available from Sigma Aldrich. In various countries it is also available in drugstores, under the names "Percarbamide" or "Hydroperite".

Preparation

Urea peroxide is prepared by combining 3:2 molar quantities of hydrogen peroxide and urea.

Projects

  • Oxidizing organic compounds
  • Separating the adduct into its constituent substances without losing either
  • Metamizole-percarbamide smoke bomb

Handling

Safety

Inhalation of dust causes irritation of nose from hydrogen peroxide formed when heated. Contact with eyes causes severe damage. Contact with moist skin causes temporary itching or burning sensation. Ingestion causes irritation of mouth and stomach.

Forms dangerous peroxides with ethers and ketones.

Can be made to explode.

Storage

Urea hydrogen peroxide is an oxidizing agent. Liable to spontaneous combustion when heated or in contact with organic materials. The contents of a screw-capped brown glass bottle spontaneously erupted after four years storage at ambient temperature. [MCA Case History No. 719]. Combustion may release Irritating ammonia gas.

Disposal

Hydrolysis of urea peroxide gives urea and hydrogen peroxide.

References

Relevant Sciencemadness threads