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Silicon tetraazide

Silicon tetraazide 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 Silicon tetraazide rather than just read about it. In short: Silicon tetraazide is a thermally unstable binary compound of silicon and nitrogen with a nitrogen content of 85.7% (by molar mass). This high-energy compound combusts spontaneously and can only be studied in a solution.

Silicon tetraazide — main illustration
Silicon tetraazide — illustration

Key takeaways

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

Reference excerpt

Silicon tetraazide is a thermally unstable binary compound of silicon and nitrogen with a nitrogen content of 85.7% (by molar mass). This high-energy compound combusts spontaneously and can only be studied in a solution. A further coordination to a six-fold coordinated structure such as a hexaazidosilicate ion [Si(N3)6]2− or as an adduct with bidentate ligands Si(N3)4·L2 will result in relatively stable, crystalline solids that can be handled at room temperature.

Preparation Silicon tetraazide is synthesized by conversion of silicon tetrachloride with sodium azide in benzene.

The reaction of silicon tetrachloride with an excess of sodium azide at room temperature in acetonitrile will result in the formation of sodium hexaazidosilicate (Na2[Si(N3)6]) which by adding ligands such as 2,2′-bipyridine and 1,10-phenanthroline will result in stable silicon tetraazide adducts. Other bases such as pyridine and tetramethylethylenediamine will not react with the hexaazidosilicate ion.

Another preparation of a bis(triphenylphosphine)iminium hexaazidosilicate salt [(Ph3P)2N]2[Si(N3)6] is possible by conversion of bis(triphenylphosphine)iminium azide [(Ph3P)2N]N3 with silicon tetrachloride in acetonitrile, where Ph is phenyl.

Properties Silicon tetraazide is a white crystalline compound that will detonate at even 0 °C. The pure compound, and also silicon chloride triazide SiCl(N3)3 and silicon dichloride diazide SiCl2(N3)2 contaminated samples, can detonate spontaneously without clear cause. The compound is susceptible to hydrolysis. It is soluble in diethylether and benzene. The addition compound with 2,2′-bipyridine is much more stable. A melting point of 212 °C with a melting enthalpy of 110 J/g is recorded. The DSC measurement shows at 265 °C a sharp exothermic reaction with an enthalpy of −2400 J/g. Similar results are found for the addition compound with 1,10-phenanthroline. As the hemiacetonitrile solvatated isolated compound expels solvent at 100 °C, and shows then in the DSC measurement from 240 °C onwards a strong exothermic reaction with a generated heat of 2300 J/g. The enthalpies are higher than that of sodium azide with −800 J/g, but still lower than the values encountered with classic explosives such as RDX with −4500 J/g. The addition compounds are stable in solution. It can be concluded from IR-spectroscopy and proton NMR data that no dissociation occurs in silicon tetraazide and 2,2'-bipyridine or for example 1,10-phenanthroline. The bis(triphenylphosphino)iminium hexaazidosilicate salt [(Ph3P)2N]2[Si(N3)6] on the other hand is relatively stable. The compound melts at 214 °C and shows in the DSC measurement at 250 °C a reaction. One mass spectrometry coupled thermogravimetric analysis investigation indicated as reaction products nitrogen, silicon tetraazide and hydrazoic acid.

Applications A practical application of free silicon tetraazide is unlikely due to the high instability. In solution the compound has potential uses as raw material for nitrogen-rich materials. One application as reagent in the manufacture of polyolefins has been patented. The stabilized adducts can serve as energetic compounds as a replacement for lead azide.

References

Illustrations

Silicon tetraazide illustration
Silicon tetraazide illustration
Silicon tetraazide illustration
Silicon tetraazide illustration

Worked examples

Example 1 — a first encounter with Silicon tetraazide

Start with the simplest possible case. Write down what Silicon tetraazide 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 Silicon tetraazide 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 Silicon tetraazide 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 Silicon tetraazide

In research
Silicon tetraazide 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 Silicon tetraazide 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
Silicon tetraazide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Azido compounds, Explosive chemicals, Inorganic silicon compounds, so understanding it makes those chapters shorter.
In everyday life
Look for Silicon tetraazide 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 Silicon tetraazide in 20 minutes

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

Frequently asked questions

What is Silicon tetraazide in simple terms?

Silicon tetraazide is a thermally unstable binary compound of silicon and nitrogen with a nitrogen content of 85.7% (by molar mass). This high-energy compound combusts spontaneously and can only be studied in a solution.

Why does Silicon tetraazide 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 Silicon tetraazide?

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 Silicon tetraazide.

Tags

  • Azido compounds
  • Explosive chemicals
  • Inorganic silicon compounds

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