Hydrogen peroxide - urea

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Hydrogen peroxide - urea
Hydrogen-peroxide-2D.png
Harnstoff.svg
H2O2-urea complex, code26444.png
Names
Other names
Urea peroxide, percarbamide, UHP
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.004.275
UNII
Properties
CH6N2O3
Molar mass 94.070 g·mol−1
Appearance White solid
Density 1.50 g/cm3
Melting point 75 to 91.5 °C (167.0 to 196.7 °F; 348.1 to 364.6 K) (decomposes)
Pharmacology
D02AE01 (WHO)
Hazards
Safety data sheet External MSDS
Explosive E, Corrosive C
Flash point 60 °C (140 °F; 333 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Hydrogen peroxide - urea (also called Hyperol, artizone, urea hydrogen peroxide, and UHP) 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. Hydrogen peroxide - urea contains solid and water-free hydrogen peroxide, which offers a higher stability and better controllability than liquid hydrogen peroxide when used as an oxidizing agent. Often called carbamide peroxide in the dental office, it is used as a source of hydrogen peroxide for bleaching, disinfection, and oxidation.

Production[edit]

For the preparation of the complex, urea is dissolved in 30% hydrogen peroxide (molar ratio 2:3) at temperatures below 60 °C. upon cooling this solution, hydrogen peroxide - urea precipitates in the form of small platelets.[1]

Determination of the hydrogen peroxide content by titration with potassium permanganate solution gives a value of 35.4% which corresponds to 97.8% of the theoretical maximum value. The remaining impurity consists of urea.

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.[2] The laboratory synthesis is analogous.[3]

Structure and properties[edit]

The solid state structure of this adduct has been determined by neutron diffraction.[4]

Hydrogen peroxide-urea is a readily water-soluble, odorless, crystalline solid, which is available as white powder or colorless needles or platelets.[1] Upon dissolving in various solvents, the 1:1 complex dissociates back to urea and hydrogen peroxide. So just like hydrogen peroxide, the (erroneously) so-called adduct is an oxidizer but the release at room temperature in the presence of catalysts proceeds in a controlled manner, thus the compound is suitable as a safe substitute for the unstable aqueous solution of hydrogen peroxide. Because of the tendency for thermal decomposition, which accelerates at temperatures above 82 °C,[5] it should not be heated above 60 °C, particularly in pure form.

The solubility of commercial samples varies from 0.05 g/mL[6] to more than 0.6 g/mL.[7]

Applications[edit]

Disinfectant and bleaching agent[edit]

Hydrogen peroxide - urea is mainly used as a disinfecting and bleaching agent in cosmetics and pharmaceuticals.[2] As a drug, this compound is used in some preparations for the whitening of teeth.[2][8][9] It is also used to relieve minor inflammation of gums, oral mucosal surfaces and lips including canker sores and dental irritation,[10] and to emulsify and disperse earwax.[citation needed]

Carbamide peroxide is also suitable as a disinfectant, e.g. for germ reduction on contact lens surfaces or as an antiseptic for mouthwashes, ear drops or for superficial wounds and ulcers.

Reagent in organic synthesis[edit]

In the laboratory, it is used as a more easily handled replacement for hydrogen peroxide.[3][11][12] It has proven to be a stable, easy-to-handle and effective oxidizing agent which is readily controllable by a suitable choice of the reaction conditions. It delivers oxidation products in an environmentally friendly manner and often in high yields especially in the presence of organic catalysts such as cis-butenedioic anhydride[13] or inorganic catalysts such as sodium tungstate.[14]

Reaktionen mit Carbamidperoxid

[verification needed]

It converts thiols selectively to disulfides,[13] secondary alcohols to ketones,[14] sulfides to sulfoxides and sulfones,[15] nitriles to amides,[15][16] N-heterocycles to amine oxides.[15][17]

Reaktionen von Methoxyphenolen mit UHP

Hydroxybenzaldehyde are converted to dihydroxybenzenes (Dakin reaction)[15][18][better source needed] and gives under suitable conditions the corresponding benzoic acids.[18]

Baeyer-Villiger-Oxidation mit UHP

It oxidizes ketones to esters, in particular cyclic ketones, such as substituted cyclohexanones[19] or cyclobutanones[20] to give lactones (Baeyer-Villiger oxidation).

The epoxidation of various alkenes in the presence of benzonitrile yields oxiranes in yields of 79 to 96%.[21]

Epoxidierung von Cyclohexen mit UHP

The oxygen atom transferred to the alkene originates from the peroxoimide acid formed intermediately from benzonitrile. The resulting imidic acid tautomerizes to the benzamide.

Safety[edit]

The compound acts as a strong oxidizing agent and can cause skin irritation and severe eye damage.[22]

See also[edit]

References[edit]

  1. ^ a b C.-S. Lu, E.W. Hughes, P.A. Giguère, "The crystal structure of the urea-hydrogen peroxide addition compound CO(NH2)2 H2O2", J. Am. Chem. Soc. (in German), 63 (6), pp. 1507–1513, doi:10.1021/ja01851a007CS1 maint: multiple names: authors list (link)
  2. ^ a b c Harald Jakob, Stefan Leininger, Thomas Lehmann, Sylvia Jacobi, Sven Gutewort. "Peroxo Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_177.pub2.CS1 maint: multiple names: authors list (link)
  3. ^ a b 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. S2CID 98323467.
  4. ^ Fritchie, Jr., C. J.; McMullan, R. K. (1981). "Neutron Diffraction Study of the 1:1 Urea:Hydrogen Peroxide complex at 81 K". Acta Crystallographica Section B. 37 (5): 1086. doi:10.1107/S0567740881005116.
  5. ^ H. Heaney, F. Cardona, A. Goti, A.L. Frederick (2013). "Hydrogen Peroxide-Urea". Encyclopedia of Reagents for Organic Synthesis. E-EROS Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rh047.pub3. ISBN 978-0471936237.CS1 maint: multiple names: authors list (link)
  6. ^ Sigma-Aldrich specification sheet
  7. ^ Chemicalland data sheet
  8. ^ Mokhlis, G. R.; Matis, B. A.; Cochran, M. A.; Eckert, G. J. (2000). "A Clinical Evaluation of Carbamide Peroxide and Hydrogen Peroxide Whitening Agents during Daytime Use". Journal of the American Dental Association. 131 (9): 1269–77. doi:10.14219/jada.archive.2000.0380. PMID 10986827. Archived from the original on 2013-02-23.
  9. ^ Toothwhitening Archived 2008-03-17 at the Wayback Machine from the UMD of New Jersey website
  10. ^ Center for Integrative Medicine: Carbamide Peroxide from the University of Maryland Medical Center website Archived October 18, 2007, at the Wayback Machine
  11. ^ 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.
  12. ^ Harry Heaney, Francesca Cardona, Andrea Goti, "Hydrogen Peroxide–Urea" Encyclopedia of Reagents for Organic Synthesis 2008. doi:10.1002/047084289X.rh047.pub2
  13. ^ a b B. Karami, M. Montazerozohori, M. H. Habibi (2005), "Urea-Hydrogen Peroxide (UHP) oxidation of thiols to the corresponding disulfides promoted by maleic anhydride as mediator" (PDF), Molecules (in German), 10 (10), pp. 1358–1363, doi:10.3390/10101385, PMC 6147623, PMID 18007530CS1 maint: multiple names: authors list (link)
  14. ^ a b M. Lukasiewicz; D. Bogdal; J. Pielichowski. "Microwave-assisted oxidation of alcohols using urea hydrogen peroxide". 8th International Electronic Conference on Synthetic Organic Chemistry. ECSOC-8. Retrieved 2016-05-10.
  15. ^ a b c d R.S. Varma, K.P. Naicker, "The Urea-Hydrogen Peroxide Complex: Solid-State Oxidative Protocols for Hydroxylated Aldehydes and Ketones (Dakin Reaction), Nitriles, Sulfides, and Nitrogen Heterocycles", Org. Lett. (in German), 1 (2), pp. 189–191, doi:10.1021/ol990522n
  16. ^ US 0 
  17. ^ D. Rong, V.A. Phillips, R.S. Rubio, M.A. Castro, R.T. Wheelhouse, "A safe, convenient and efficient method for the preparation of heterocyclic N-oxides using urea-hydrogen peroxide", Tetrahedron Lett. (in German), 49 (48), pp. 6933–6935, doi:10.1016/j.tetlet.2008.09.124CS1 maint: multiple names: authors list (link)
  18. ^ a b H. Heaney, A.J. Newbold (2001), "The oxidation of aromatic aldehydes by magnesium monoperoxyphthalate and urea-hydrogen peroxide", Tetrahedron Lett. (in German), 42 (37), pp. 6607–6609, doi:10.1016/S0040-4039(01)01332-6
  19. ^ M.Y. Rios, E. Salazar, H.F. Olivo (2007), "Baeyer–Villiger oxidation of substituted cyclohexanones via lipase-mediated perhydrolysis utilizing urea–hydrogen peroxide in ethyl acetate", Green Chem. (in German), 9 (5), pp. 459–462, doi:10.1039/B618175ACS1 maint: multiple names: authors list (link)
  20. ^ A. Watanabe, T. Uchida, K. Ito, T. Katsuki (2002), "Highly enantioselective Baeyer-Villiger oxidation using Zr(salen) complex as catalyst", Tetrahedron Lett. (in German), 43 (25), pp. 4481–4485, doi:10.1016/S0040-4039(02)00831-6CS1 maint: multiple names: authors list (link)
  21. ^ L. Ji, Y.-N. Wang, C. Qian, X.-Z. Chen (2013), "Nitrile-promoted alkene epoxidation with urea-hydrogen peroxide (UHP)", Synth. Commun. (in German), 43 (16), pp. 2256–2264, doi:10.1080/00397911.2012.699578, S2CID 93770740CS1 maint: multiple names: authors list (link)
  22. ^

External links[edit]