Hydrogen peroxide - urea (also called Hyperol, artizone, urea hydrogen peroxide, and UHP) is a solid composed of equal amounts of

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

and

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important ...

. 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

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. 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 In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization i ...

, 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

in excess concentrated

solution, followed by crystallization. The laboratory synthesis is analogous.

Structure and properties

The solid state structure of this adduct has been determined by

neutron diffraction Neutron diffraction or elastic neutron scattering is the application of neutron scattering to the determination of the atomic and/or magnetic structure of a material. A sample to be examined is placed in a beam of thermal or cold neutrons to o ...

. Hydrogen peroxide-urea is a readily water-soluble, odorless, crystalline solid, which is available as white powder or colorless needles or platelets. Upon dissolving in various solvents, the 1:1 complex dissociates back to urea and hydrogen peroxide. So just like

, the (erroneously) so-called

adduct An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...

is an

oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...

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, it should not be heated above 60 °C, particularly in pure form. The solubility of commercial samples varies from 0.05 g/mL to more than 0.6 g/mL.

Applications

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 sore Aphthous stomatitis, or recurrent aphthous stomatitis (RAS), is a common condition characterized by the repeated formation of benign and non-contagious mouth ulcers (aphthae) in otherwise healthy individuals. The informal term ''canker sore'' i ...

s and dental irritation,Center for Integrative Medicine: Carbamide Peroxide
from the

University of Maryland Medical Center The University of Maryland Medical Center (UMMC) is a teaching hospital with 806 beds based in Baltimore, Maryland, that provides the full range of health care to people throughout Maryland and the Mid-Atlantic region. It gets more than 26,000 inpa ...

website and to emulsify and disperse

earwax Earwax, also known by the medical term cerumen, is a brown, orange, red, yellowish or gray waxy substance secreted in the ear canal of humans and other mammals. It protects the skin of the human ear canal, assists in cleaning and lubrication, ...

. Carbamide peroxide is also suitable as a disinfectant, e.g. for germ reduction on contact lens surfaces or as an antiseptic for

mouthwash Mouthwash, mouth rinse, oral rinse, or mouth bath is a liquid which is held in the mouth passively or swilled around the mouth by contraction of the perioral muscles and/or movement of the head, and may be gargled, where the head is tilted back ...

es, ear drops or for superficial wounds and

ulcer An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caused by sloughing o ...

Reagent in organic synthesis

In the laboratory, it is used as a more easily handled replacement for

. 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 or inorganic catalysts such as

sodium tungstate Sodium tungstate is the inorganic compound with the formula Na2WO4. This white, water-soluble solid is the sodium salt of tungstic acid. It is useful as a source of tungsten for chemical synthesis. It is an intermediate in the conversion of tungs ...

It converts thiols selectively to disulfides, secondary alcohols to ketones, sulfides to sulfoxides and sulfones, nitriles to amides, and ''N''-heterocycles to

amine oxide In chemistry, an amine oxide, also known as an amine ''N''-oxide or simply ''N''-oxide, is a chemical compound that contains the functional group , a nitrogen-oxygen coordinate covalent bond with three additional hydrogen and/or substituent-grou ...

Hydroxybenzaldehydes are converted to

dihydroxybenzenes In organic chemistry, dihydroxybenzenes (benzenediols) are organic compounds in which two hydroxyl groups () are substituted onto a benzene ring (). These aromatic compounds are classed as phenols. There are three structural isomers: 1,2-dihy ...

(

Dakin reaction The Dakin oxidation (or Dakin reaction) is an organic redox reaction in which an '' ortho''- or ''para''-hydroxylated phenyl aldehyde (2-hydroxybenzaldehyde or 4-hydroxybenzaldehyde) or ketone reacts with hydrogen peroxide in base to form a ...

) and give, under suitable conditions, the corresponding benzoic acids. Baeyer-Villiger-Oxidation mit Cyclobutanonen

It oxidizes ketones to esters, in particular cyclic ketones, such as substituted cyclohexanones or cyclobutanones to give lactones ( Baeyer-Villiger oxidation). The epoxidation of various alkenes in the presence of benzonitrile yields oxiranes in yields of 79 to 96%. Epoxidierung 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

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

References

External links

* * {{cite web , url=https://www.drugs.com/monograph/carbamide-peroxide.html , title=Carbamide Peroxide Monograph , publisher=Drugs.com Bleaches Antiseptics Cleaning product components Ureas Peroxides Oxidizing agents Hydrogen peroxide