chemistry

Polythiazyl

Polythiazyl 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 Polythiazyl rather than just read about it. In short: Polythiazyl (polymeric sulfur nitride), (SN)x, is an electrically conductive, gold- or bronze-colored polymer with metallic luster. It was the first conductive inorganic polymer discovered and was also found to be a superconductor at very low temperatures (below 0.26 K).

Key takeaways

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

Reference excerpt

Polythiazyl (polymeric sulfur nitride), (SN)x, is an electrically conductive, gold- or bronze-colored polymer with metallic luster. It was the first conductive inorganic polymer discovered and was also found to be a superconductor at very low temperatures (below 0.26 K). It is a fibrous solid, described as "lustrous golden on the faces and dark blue-black", depending on the orientation of the sample. It is air stable and insoluble in all solvents.

History The compound was first reported as early as 1910 by F.P. Burt, who obtained it by heating tetrasulfur tetranitride in vacuum over silver wool. The compound was the first compound with only non-metallic elements in which superconductivity could be demonstrated.

Properties Polythiazyl is a metallic-golden and shiny, crystalline but fibrous material with anisotropic electrical conductivity. It has at least two crystal polymorphs, which are usually intermixed after chemical synthesis. About 90% is the monoclinic form I, while the remainder is an orthorhombic form II. The orthorhombic portion can be increased mechanically through e.g. grinding, "although full conversion is unlikely." Along the fibres (SN chains), polythiazyl is electrically conductive; perpendicular, an insulator. The one-dimensional conductivity arises from bonding conditions in the S-N chain, where each sulfur atom provides two π electrons and each nitrogen atom provides one π electron to form two-center 3π electron bonding units. At temperatures below 0.3 K, it becomes a electrical superconductor. The Peierls distortion is inhibited by weak inter-chain interactions, which resist the characteristic bond alternation. Polythiazyl is "completely insoluble"; and mostly inert to oxygen and water. But it decomposes rapidly in alkaline solutions, and slowly in air to a grey powder after months of exposure. Halogens intercalate between the strands. At temperatures above 240 °C explosive decomposition can occur. The compound also explodes on impact. Explosion generally proceeds via decomposition to the elements. Vapor sublimed from polythiazyl is actually a cracked form of the polymer, the six-membered radical ring (SN)3. Condensation reverts it back to the chain form.

Molecular structure and bonding The material is a polymer, containing trivalent nitrogen and divalent and tetravalent sulfur. The S and N atoms on adjacent chains align. Several resonance structures can be written.

The structure of the crystalline compound was resolved by X-ray diffraction. This showed alternating S–N bond lengths of 159 pm and 163 pm and S–N–S bond angles of 120 ° and N–S–N bond angles of 106 °.

Synthesis The oldest-known polythiazyl synthesis is the polymerization of the cyclic formal dimer disulfur dinitride (S2N2), which is in turn synthesized from the formal tetramer tetrasulfur tetranitride (S4N4), in the presence of hot silver wool. The reaction begins when silver abstracts sulfur from S4N4 to produce a Ag2S catalyst; the resulting gaseous S2N2 is then isolated through sublimation onto a cold surface:

S4N4 + 8 Ag → 4 Ag2S + 2 N2 S4N4 (low-pressure gas at 250-300 °C; Ag2S catalyst) → 2 S2N2 (gas) → 2 S2N2 (stable solid at 77 K) When warmed to room temperature, the additional heat induces impurity-catalyzed polymerization:

S2N2 (0 °C) → (SN)x An alternative is the azide reduction of thiazyl chloride trimer, itself made from thiazyl fluoride:

(NSF)3 + Cl2 → (SNCl)3 + ClF (SNCl)3 + NaN3 → NaCl + N2 + (SN)∞ To eschew explosive reagents entirely, iron filings in nitromethane reduce the thiazyl chloride trimer to [(SN)5]+[FeCl4]−, which a platinum cathode reduces to polythiazyl.

Uses Due to its electrical conductivity, polythiazyl is used in LEDs, transistors, battery cathodes, and solar cells.

References

Illustrations

Worked examples

Example 1 — a first encounter with Polythiazyl

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

In research: Polythiazyl 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 Polythiazyl 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: Polythiazyl is common in secondary-school and first-year university syllabi. It links to neighbouring topics Conductive polymers, Inorganic polymers, Nitrides, so understanding it makes those chapters shorter.
In everyday life: Look for Polythiazyl 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 Polythiazyl in 20 minutes

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

Frequently asked questions

What is Polythiazyl in simple terms?

Why does Polythiazyl 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 Polythiazyl?

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 Polythiazyl.