chemistry

Phosphorus sulfides

Phosphorus sulfides 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 Phosphorus sulfides rather than just read about it. In short: Phosphorus sulfides comprise a family of inorganic compounds containing only phosphorus and sulfur. These compounds have the formula P4Sn with n ≤ 10.

Key takeaways

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

Reference excerpt

Phosphorus sulfides comprise a family of inorganic compounds containing only phosphorus and sulfur. These compounds have the formula P4Sn with n ≤ 10. Two are of commercial significance, phosphorus pentasulfide (P4S10), which is made on a kiloton scale for the production of other organosulfur compounds, and phosphorus sesquisulfide (P4S3), used in the production of "strike anywhere matches". There are several other phosphorus sulfides in addition to P4S3 and P4S10. Six of these phosphorus sulfides exist as isomers: P4S4, P4S5, P4S6, P4S7, P4S8, and P4S9. These isomers are distinguished by Greek letter prefixes. The prefix is based on the order of the discovery of the isomers, not their structure. All known molecular phosphorus sulfides contain a tetrahedral array of four phosphorus atoms. P4S2 is also known but is unstable above −30 °C. Phosphorus monosulfide monomer, PS, is highly unstable and only exists at elevated temperatures. Its bond, worth about 55 kcal/mol, is about 2.4 angstroms long.

Preparation The main method for preparing these compounds is thermolysis of mixtures of phosphorus and sulfur. The product distributions can be analyzed by 31P-NMR spectroscopy. More selective syntheses entail:

desulfurization, e.g. using triphenylphosphine and, complementarily, sulfidation using triphenylarsine sulfide.

P4S3 Phosphorus sesquisulfide is prepared by treating red phosphorus with sulfur above 450 K, followed by careful recrystallization with carbon disulfide and benzene. An alternative method involves the controlled fusion of white phosphorus with sulfur in an inert, non-flammable solvent.

P4S4 The α- and β- forms of P4S4 can be prepared by treating the corresponding isomers of P4S3I2 with ((CH3)3Sn)2S:

P4S3I2 can be synthesized by the reaction of stoichiometric amounts of phosphorus, sulfur, and iodine.

P4S5 P4S5 can be prepared by treating stoichiometric amounts of P4S3 with sulfur in carbon disulfide solution, in the presence of light and a catalytic amount of iodine. The respective product distribution is then analyzed by using 31P-NMR spectroscopy. In particular, α-P4S5 can be easily made by the photochemical reaction of P4S10 with red phosphorus. Note that P4S5 is unstable when heated, tending to disproportionate to P4S3 and P4S7 before reaching its melting point.

P4S6 P4S6 can be made by abstracting a sulfur atom from P4S7 using triphenylphosphine:

P4S7 + Ph3P → P4S6 + Ph3PS Treating α-P4S5 with Ph3AsS in CS2 also yields α-P4S6. The two new polymorphs δ-P4S6 and ε-P4S6 can be made by treating α-P4S4 with Ph3SbS in CS2.

P4S7 P4S7 is most conveniently made by direct union of the corresponding elements, and is one of the most easily purified binary phosphorus sulfides.

P4 + 7 S → P4S7

P4S8 β-P4S8 can be made by treating α-P4S7 with Ph3AsS in CS2, which yields a mixture between α-P4S7 and β-P4S8.

P4S9 P4S9 can be made by two methods. One method involves the heating of P4S3 in excess sulfur. Another method involves the heating of P4S7 and P4S10 in 1:2 mole ratio, where P4S9 is reversibly formed:

P4S7 + 2 P4S10 ⇌ 3 P4S9

P4S10 P4S10 is one of the most stable phosphorus sulfides. It is most easily made by heating white phosphorus with sulfur above 570 K in an evacuated tube.

P4 + 10 S → P4S10

See also Diphosphorus heptasulfide ((P2S7)n) Diphosphorus trisulfide (P2S3)

References

Illustrations

Worked examples

Example 1 — a first encounter with Phosphorus sulfides

Start with the simplest possible case. Write down what Phosphorus sulfides 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 Phosphorus sulfides 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 Phosphorus sulfides 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 Phosphorus sulfides

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

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

Frequently asked questions

What is Phosphorus sulfides in simple terms?

Phosphorus sulfides comprise a family of inorganic compounds containing only phosphorus and sulfur. These compounds have the formula P4Sn with n ≤ 10.

Why does Phosphorus sulfides 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 Phosphorus sulfides?

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 Phosphorus sulfides.