chemistry

Sodium cyanoborohydride

Sodium cyanoborohydride 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 Sodium cyanoborohydride rather than just read about it. In short: Sodium cyanoborohydride is a chemical compound with the formula Na[BH3(CN)]. It is a colourless salt used in organic synthesis for chemical reduction including that of imines and carbonyls.

Key takeaways

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

Reference excerpt

Sodium cyanoborohydride is a chemical compound with the formula Na[BH3(CN)]. It is a colourless salt used in organic synthesis for chemical reduction including that of imines and carbonyls. Sodium cyanoborohydride is a milder reductant than other conventional reducing agents.

Structure Sodium cyanoborohydride is a salt. The cationic sodium ion, [Na]+, interacts with the anionic cyanoborohydride ion, [BH3(CN)]−. The anionic component of the salt is tetrahedral at the boron atom. The electron-withdrawing cyanide substituent draws electron density away from the negatively charged boron; thus, reducing the electrophilic capabilities of the anionic component. This electronic phenomenon causes sodium cyanoborohydride to have more mild reducing qualities than other reducing agents. For example, Na[BH3(CN)] is less reducing than its counterpart sodium borohydride, containing [BH4]−.

Uses Sodium cyanoborohydride is a mild reducing agent. It is generally used for the reduction of imines. These reactions occur <pH 7 because the iminium ions are the actual substrates. Reductive amination, sometimes called the Borch reaction, is the conversion of a carbonyl into an amine through an intermediate imine. The carbonyl is first treated with ammonia to promote imine formation by nucleophilic attack. The imine is then reduced to an amine by sodium cyanoborohydride. This reaction works on both aldehydes and ketones. The carbonyl can be treated with ammonia, a primary amine, or a secondary amine to produce, respectively, 1°, 2°, and 3° amines. Aromatic ketones and aldehydes can be reductively deoxygenated using sodium cyanoborohydride. This means that the carbonyl oxygen is being removed completely from the molecule. Deoxygenation using sodium cyanoborohydride is often done in the presence of trimethylsilyl chloride, or TMSCl.

Preparation Sodium cyanoborohydride can be purchased from most chemical suppliers. It can be synthesized by combining sodium cyanide and borane tetrahydrofuran.

BH3·THF + NaCN → NaBH3CN + THF

Selectivity Since sodium cyanoborohydride is a mild reducing agent, it gives good chemoselectivity for reaction with certain functional groups in the presence of others. For example, sodium cyanoborohydride is generally incapable of reducing amides, ethers, esters and lactones, nitriles, or epoxides. Therefore, it can selectively reduce some functionalities in the presence of others. Some examples of selective reduction include:

Reduction of iminium ions in the presence of carbonyls Reduction of aldehydes in the presence of ketones and esters. Reduction of aldehydes in the presence of thioesters The selectivity of this reducing agent makes it an important tool in organic synthesis. It allows for specific modifications to be made to complex organic molecules.

History Georg Wittig was the first to synthesize a cyanoborohydride by treating lithium borohydride with hydrogen cyanide in 1951. The corresponding compound, sodium cyanoborohydride, was synthesized following a similar rationale by reacting sodium borohydride with hydrogen cyanide. The synthesis was later refined to use sodium cyanide and borane in THF making the process safer.

See also Sodium triacetoxyborohydride – a milder reductant, but unstable in water Sodium borohydride – a stronger, cheaper reductant

References

Illustrations

Worked examples

Example 1 — a first encounter with Sodium cyanoborohydride

Start with the simplest possible case. Write down what Sodium cyanoborohydride 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 Sodium cyanoborohydride 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 Sodium cyanoborohydride 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 Sodium cyanoborohydride

In research: Sodium cyanoborohydride 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 Sodium cyanoborohydride 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: Sodium cyanoborohydride is common in secondary-school and first-year university syllabi. It links to neighbouring topics Borohydrides, Cyano compounds, Inorganic carbon compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Sodium cyanoborohydride 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 Sodium cyanoborohydride in 20 minutes

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

Frequently asked questions

What is Sodium cyanoborohydride in simple terms?

Sodium cyanoborohydride is a chemical compound with the formula Na[BH3(CN)]. It is a colourless salt used in organic synthesis for chemical reduction including that of imines and carbonyls.

Why does Sodium cyanoborohydride 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 Sodium cyanoborohydride?

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 Sodium cyanoborohydride.