chemistry

Phosphorus pentasulfide

Phosphorus pentasulfide 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 pentasulfide rather than just read about it. In short: Phosphorus pentasulfide is the inorganic compound with the formula P2S5 (empirical) or P4S10 (molecular). This yellow solid is the one of two phosphorus sulfides of commercial value.

Key takeaways

Phosphorus pentasulfide 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 pentasulfide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Phosphorus pentasulfide from memory before moving on to harder problems.

Reference excerpt

Phosphorus pentasulfide is the inorganic compound with the formula P2S5 (empirical) or P4S10 (molecular). This yellow solid is the one of two phosphorus sulfides of commercial value. Samples often appear greenish-gray due to impurities. It is soluble in carbon disulfide but reacts with many other solvents such as alcohols, DMSO, and DMF.

Structure and synthesis Its tetrahedral molecular structure is similar to that of adamantane and almost identical to the structure of phosphorus pentoxide. Phosphorus pentasulfide is obtained by the reaction of liquid white phosphorus (P4) with sulfur above 300 °C. The first synthesis of P4S10 by Berzelius in 1843 was by this method. Alternatively, P4S10 can be formed by reacting elemental sulfur or pyrite, FeS2, with ferrophosphorus, a crude form of Fe2P (a byproduct of white phosphorus (P4) production from phosphate rock):

4 Fe2P + 18 S → P4S10 + 8 FeS 4 Fe2P + 18 FeS2 heat→ P4S10 + 26 FeS

Applications Approximately 150,000 tons of P4S10 are produced annually. The compound is mainly converted to other derivatives for use as lubrication additives such as zinc dithiophosphates. It is widely used in the production of sodium dithiophosphate for applications as a flotation agent in the concentration of molybdenite minerals. It is also used in the production of pesticides such as Parathion and Malathion. It is also a component of some amorphous solid electrolytes (e.g. Li2S-P2S5) for some types of lithium batteries. Phosphorus pentasulfide is a dual-use material, for the production of early insecticides such as Amiton and also for the manufacture of the related VX nerve agents. Phosphorus pentasulfide reacts with ethanol to give diethyl dithiophosphoric acid:

P2S5 + 4 C2H5OH → 2 (C2H5O)2PS2H + H2S Diorganodithiophosphoric acids are used to produce metal dithiophosphates, which are used commercially.

Reactivity Due to hydrolysis by atmospheric moisture, P4S10 evolves hydrogen sulfide H2S, thus P4S10 is associated with a rotten egg odour. Aside from H2S, hydrolysis of P4S10 eventually gives phosphoric acid:

P4S10 + 16 H2O → 4 H3PO4 + 10 H2S Other mild nucleophiles react with P4S10, including alcohols and amines. Reaction with ammonium chloride gives the polymeric (SPN)∞. Aromatic compounds such as anisole, ferrocene and 1-methoxynaphthalene react to form 1,3,2,4-dithiadiphosphetane 2,4-disulfides such as Lawesson's reagent:

P4S10 + 4 ArH → 2 [ArPS2]2 + 2 H2S (Ar = aryl)

Thionations P4S10 is used as a reagent for thionation (thiation). In doing so, P=S bonds are converted to P=O bonds, concomitant with C=O bonds converting to C=S. Some ketones, esters, and imides are converted to the corresponding thiocarbonyls. Amides give thioamides. With 1,4-diketones the reagent forms thiophenes. P4S10 is also used to deoxygenate sulfoxides. Typical conditions entail boiling organic solvents (benzene, dioxane, or acetonitrile). Hexamethyldisiloxane is an effective solvent for these thionations because the phosphorus-containing side products are more easily separated from the products. The use of P4S10 has been displaced somewhat by the aforementioned Lawesson's reagent. It is probable that thionation reactions involve dissociation of P4S10 into more reactive species, perhaps P2S5. Supporting evidence is the reaction of P4S10 with pyridine to form the complex P2S5(pyridine)2.

References

Illustrations

Worked examples

Example 1 — a first encounter with Phosphorus pentasulfide

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

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

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

Frequently asked questions

What is Phosphorus pentasulfide in simple terms?

Phosphorus pentasulfide is the inorganic compound with the formula P2S5 (empirical) or P4S10 (molecular). This yellow solid is the one of two phosphorus sulfides of commercial value.

Why does Phosphorus pentasulfide 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 pentasulfide?

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 pentasulfide.