chemistry

Peroxynitrite

Peroxynitrite 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 Peroxynitrite rather than just read about it. In short: Peroxynitrite (sometimes called peroxonitrite) is an ion with the formula ONOO−. It is a structural isomer of nitrate, NO−3.

Key takeaways

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

Reference excerpt

Peroxynitrite (sometimes called peroxonitrite) is an ion with the formula ONOO−. It is a structural isomer of nitrate, NO−3. Peroxynitrite is a potent reactive nitrogen species and is highly cytotoxic.

Preparation Peroxynitrite can be prepared by the reaction of superoxide with nitric oxide:

NO + O−2 → NO(O2)− It is prepared by the reaction of hydrogen peroxide with nitrite:

H2O2 + NO−2 → ONOO− + H2O Its presence is indicated by the absorbance at 302 nm (pH 12, ε302 = 1670 M−1 cm−1).

Reactions Peroxynitrite is weakly basic with a pKa of ~6.8. It is reactive toward DNA and proteins. ONOO− reacts nucleophilically with carbon dioxide. In vivo, the concentration of carbon dioxide is about 1 mM, and its reaction with ONOO− occurs quickly. Thus, under physiological conditions, the reaction of ONOO− with carbon dioxide to form nitrosoperoxycarbonate (ONOOCO−2) is by far the predominant pathway for ONOO−. ONOOCO−2 homolyzes to form carbonate radical and nitrogen dioxide, again as a pair of caged radicals. Approximately 66% of the time, these two radicals recombine to form carbon dioxide and nitrate. The other 33% of the time, these two radicals escape the solvent cage and become free radicals. It is these radicals (carbonate radical and nitrogen dioxide) that are believed to cause peroxynitrite-related cellular damage.

Peroxynitrous acid

Its conjugate acid peroxynitrous acid is highly reactive, although peroxynitrite is stable in basic solutions.

See also Nitrotyrosine Reactive nitrogen species

References

Illustrations

Worked examples

Example 1 — a first encounter with Peroxynitrite

Start with the simplest possible case. Write down what Peroxynitrite 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 Peroxynitrite 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 Peroxynitrite 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 Peroxynitrite

In research: Peroxynitrite 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 Peroxynitrite 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: Peroxynitrite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Atmospheric chemistry, Nitrogen(III) compounds, Nitrogen oxyanions, so understanding it makes those chapters shorter.
In everyday life: Look for Peroxynitrite 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Peroxynitrite in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Peroxynitrite 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 Peroxynitrite out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Peroxynitrite in simple terms?

Peroxynitrite (sometimes called peroxonitrite) is an ion with the formula ONOO−. It is a structural isomer of nitrate, NO−3.

Why does Peroxynitrite 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 Peroxynitrite?

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 Peroxynitrite.