mathematics

Hydrazone

Hydrazone is a mathematics 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 Hydrazone rather than just read about it. In short: Hydrazones are a class of organic compounds with the structure R1R2C=N−NH2. They are related to ketones and aldehydes by the replacement of the oxygen =O with the =N−NH2 functional group.

Key takeaways

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

Reference excerpt

Hydrazones are a class of organic compounds with the structure R1R2C=N−NH2. They are related to ketones and aldehydes by the replacement of the oxygen =O with the =N−NH2 functional group. They are formed usually by the action of hydrazine on ketones or aldehydes.

Synthesis Hydrazine, its hydrate, and various organohydrazines react with aldehydes and ketones to give hydrazones:

Phenylhydrazine reacts with reducing sugars to form hydrazones known as osazones, which was developed by German chemist Emil Fischer as a test to differentiate monosaccharides. Hydrazones having 1,3-diketomoiety are also known in literature. More generally, diazonium ions react with carbon acids in the Japp-Klingemann reaction to give hydrazones via tautomeric rearrangement of a diazo intermediate.

Uses

Hydrazones are the basis for various analyses of ketones and aldehydes. For example, dinitrophenylhydrazine coated onto a silica sorbent is the basis of an adsorption cartridge. The hydrazones are then eluted and analyzed by high-performance liquid chromatography (HPLC) using a UV detector. The compound carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (abbreviated as FCCP) is used to uncouple ATP synthesis and reduction of oxygen in oxidative phosphorylation in molecular biology. Hydrazones are the basis of bioconjugation strategies. Hydrazone-based coupling methods are used in medical biotechnology to couple drugs to targeted antibodies (see ADC), e.g. antibodies against a certain type of cancer cell. The hydrazone-based bond is stable at neutral pH (in the blood), but is rapidly destroyed in the acidic environment of lysosomes of the cell. The drug is thereby released in the cell, where it exerts its function.

Reactions Hydrazones carry two heteroatoms: a double-bonded "imine nitrogen", and a single-bonded "amine nitrogen". Reactivity arises predominantly from the amine nitrogen, which is basic and nucleophilic. When the amine nitrogen is unsubstituted, the hydrazone can condense with a second equivalent of a carbonyl to give azines, e.g.:

The nitrogen atom also stabilizes the development of negative charge at the double-bonded carbon atom, umpoling the carbonyl. Aldehydic hydrazones undergo electrophilic substitution there; for example benzylium cations react to give the corresponding ketonic hydrazone. In base, they simply deprotonate: similar to oxime dehydration, they eliminate the amine nitrogen to give a nitrile. The behavior of ketonic hydrazones in base is more complicated, as they have no aldehydic proton to lose. If the amine nitrogen is unsubstituted, then the molecule can undergo the Wolff–Kishner reduction: first, it deprotonates at the amine nitrogen and then reprotonates at the carbon. The resulting hydrazo compound is unstable and decomposes to an alkane, but can be intercepted to perform a Grignard-like addition.

If the amine nitrogen is instead fully substituted, then the next proton to leave is α to the double-bonded carbon, restoring conventional carbonyl polarity. As such, the amine nitrogen is a convenient location for a chiral auxiliary. This idea is the Enders SAMP/RAMP alkylation and its descendants. Hydrolysis, which would require another umpolung, is generally a difficult reaction for hydrazones. Nevertheless, alkyl hydrazones are 102- to 103-fold more susceptible to hydrolysis than analogous oximes. The reaction can be performed reliably with BiCl3 acid catalysis. Alternatively, acylation of the amine nitrogen, which reduces its basicity, makes hydrolysis possible with tosylic acid. Other reactions exploit hydrazones' similarity to the diazo and alkene functionalities. In the Shapiro reaction and descendants (hydrazone iodination and the Bamford–Stevens reaction), α elimination converts a sulfonamidrazone to the diazo, which then decomposes to vinyl compounds. In variants on the Lemieux–Johnson oxidation, strong oxidants peroxidize the imine nitrogen's double-bond to carbon, recovering the carbonyl and a nitrosamine. Some reductants cleave the nitrogen-nitrogen bond.

Gallery

See also Azo compound Imine Nitrosamine Hydrogenation of carbon–nitrogen double bonds

References

Illustrations

Worked examples

Example 1 — a first encounter with Hydrazone

Start with the simplest possible case. Write down what Hydrazone claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In mathematics, 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 Hydrazone 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 Hydrazone 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 Hydrazone

In research: Hydrazone appears in mathematics 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 Hydrazone 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: Hydrazone is common in secondary-school and first-year university syllabi. It links to neighbouring topics Functional groups, Hydrazones, so understanding it makes those chapters shorter.
In everyday life: Look for Hydrazone 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 Hydrazone in 20 minutes

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

Frequently asked questions

What is Hydrazone in simple terms?

Hydrazones are a class of organic compounds with the structure R1R2C=N−NH2. They are related to ketones and aldehydes by the replacement of the oxygen =O with the =N−NH2 functional group.

Why does Hydrazone matter?

Because it connects several mathematics 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 Hydrazone?

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 Hydrazone.