Hydrogen peroxide - urea
Carbamide peroxide, urea peroxide, percarbamide, UHP
|Molar mass||94.07 g·mol−1|
|Melting point||75 °C (167 °F; 348 K) (decomposes)|
|EU classification||Explosive, C|
|Flash point||60 °C (140 °F; 333 K)|
|Legal status||US: ?|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Hydrogen peroxide - urea is a solid composed of equal amounts of hydrogen peroxide and urea. This compound is a white crystalline solid, which dissolves in water to give free hydrogen peroxide. Often called carbamide peroxide in the dental applications, it is used as a source of hydrogen peroxide for bleaching, disinfection, and oxidation.
Structure, properties, production
Akin to water of crystallization, hydrogen peroxide cocrystallizes with urea with the stoichiometry of 1:1. The compound is simply produced (on a scale of several hundred tonnes a year) by the dissolution of urea in excess concentrated hydrogen peroxide solution, followed by crystallization. The laboratory synthesis is analogous. Upon dissolving in various solvents, this 1:1 complex dissociates back to urea and hydrogen peroxide. So just like hydrogen peroxide, the adduct is an oxidizer. The solubility of commercial samples varies from 0.05 g/mL to more than 0.6 g/mL. The solid state structure of this adduct at the right has been determined by neutron diffraction.
Disinfectant and bleaching agent
Hydrogen peroxide - urea is mainly used as a disinfecting and bleaching agent in cosmetics and pharmaceuticals. As a drug, this compound is used in some preparations for the whitening of teeth. It is also used to relieve minor inflammation of gums, oral mucosal surfaces and lips including canker sores and dental irritation, and to emulsify and disperse ear wax.
In tooth bleaching, the hydrogen peroxide produced acts to oxidise interprismatic extrinsic staining within tooth enamel. There are several methods of applying the peroxide gel to the tooth ranging from night-guard application at home to in-surgery application. The bleaching obtained is proportional to the length of time the peroxide is applied to the tooth, and the concentration used. Concentrations used for tooth whitening purposes range between 10% and 44%. Higher concentrations carry a higher risk of side effects such as chemical burns. 10% is widely regarded as safe.
Reagent in organic synthesis
As an oxidizer, this compound is a skin, eye and respiratory irritant. At higher concentrations, it is corrosive and may cause burns if not used properly. If too much gel is used and left in contact with skin or gums, there is a risk of white chemical burns called blanching.
- Harald Jakob, Stefan Leininger, Thomas Lehmann, Sylvia Jacobi, Sven Gutewort (2005), "Peroxo Compounds, Inorganic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a19_177.pub2
- Yu, Lei; Meng, Bo; Huang, Xian (2008). "Urea-Hydrogen Peroxide Complex: A Selective Oxidant in the Synthesis of 2-Phenylselenyl-1,3-butadienes". Synthetic Communications 38 (18): 3142. doi:10.1080/00397910802109224.
- Sigma-Aldrich specification sheet
- Chemicalland data sheet
- C.J. Fritchie, Jr.; R.K. McMullan; McMullan, R. K. (1981). "Neutron diffraction study of the 1:1 urea:hydrogen peroxide complex at 81 K". Acta Crystallogr., Sect. B 37 (5): 1086. doi:10.1107/S0567740881005116.
- Mokhlis, GR; Matis, BA; Cochran, MA; Eckert, GJ (2000). "A Clinical Evaluation of Carbamide Peroxide and Hydrogen Peroxide Whitening Agents during Daytime Use". Journal of the American Dental Association (1939) 131 (9): 1269–77. doi:10.14219/jada.archive.2000.0380. PMID 10986827.
- Toothwhitening from the UMD of New Jersey website
- Center for Integrative Medicine: Carbamide Peroxide from the University of Maryland Medical Center website
- Elorac Announces Clinical Results of Carbamide Peroxide Studies for the Treatment of Acne website
- Varma, Rajender S.; Naicker, Kannan P. (1999). "The Urea−Hydrogen Peroxide Complex: Solid-State Oxidative Protocols for Hydroxylated Aldehydes and Ketones (Dakin Reaction), Nitriles, Sulfides, and Nitrogen Heterocycles". Organic Letters 1 (2): 189. doi:10.1021/ol990522n.
- Harry Heaney, Francesca Cardona, Andrea Goti, "Hydrogen Peroxide–Urea" Encyclopedia of Reagents for Organic Synthesis 2008. doi:10.1002/047084289X.rh047.pub2