chemistry

Hydrogen peroxide–urea

Hydrogen peroxide–urea is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hydrogen peroxide–urea rather than just read about it. In short: Hydrogen peroxide–urea (also called Hyperol, artizone, urea hydrogen peroxide, and UHP) is a white crystalline solid chemical compound composed of equimolar amounts of hydrogen peroxide and urea. It 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.

Key takeaways

Hydrogen peroxide–urea belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hydrogen peroxide–urea to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hydrogen peroxide–urea from memory before moving on to harder problems.

Reference excerpt

Hydrogen peroxide–urea (also called Hyperol, artizone, urea hydrogen peroxide, and UHP) is a white crystalline solid chemical compound composed of equimolar amounts of hydrogen peroxide and urea. It 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 dentistry and when used in over-the-counter ear drops, it is used as a source of hydrogen peroxide when dissolved in water 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 (140 °F). upon cooling this solution, hydrogen peroxide–urea precipitates out in the form of small platelets. 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.

Structure and properties The solid state structure of this adduct has been determined by neutron diffraction. 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 hydrogen peroxide, the 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 safer substitute for the unstable aqueous solution of hydrogen peroxide. Because of the tendency for thermal decomposition, which accelerates at temperatures above 82 °C (180 °F), it should not be heated above 60 °C (140 °F), particularly in pure form.

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 sores and dental irritation, and to emulsify and disperse earwax. 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 In the laboratory, it is used as a more easily handled replacement for hydrogen peroxide. Its effectiveness is enhanced by organic catalysts cis-butenedioic anhydride or inorganic catalysts such as sodium tungstate.

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

Hydroxybenzaldehydes are converted to dihydroxybenzenes (Dakin reaction) and give, under suitable conditions, the corresponding benzoic acids.

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%.

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. Urea–hydrogen peroxide was also found to be an insensitive but moderately powerful secondary explosive.

See also Sodium percarbonate Peroxide-based bleach

References

External links "Hydrogen peroxide urea adduct, UHP". Organic Chemistry Portal. "Carbamide Peroxide Monograph". Drugs.com.

Illustrations

Worked examples

Example 1 — a first encounter with Hydrogen peroxide–urea

Start with the simplest possible case. Write down what Hydrogen peroxide–urea claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hydrogen peroxide–urea before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hydrogen peroxide–urea ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hydrogen peroxide–urea

In research: Hydrogen peroxide–urea appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hydrogen peroxide–urea in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hydrogen peroxide–urea is common in secondary-school and first-year university syllabi. It links to neighbouring topics Antiseptics, Bleaches, Cleaning product components, so understanding it makes those chapters shorter.
In everyday life: Look for Hydrogen peroxide–urea outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Hydrogen peroxide–urea in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hydrogen peroxide–urea means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hydrogen peroxide–urea out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hydrogen peroxide–urea in simple terms?

Why does Hydrogen peroxide–urea matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hydrogen peroxide–urea?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hydrogen peroxide–urea.