chemistry

Thiocarbonic acid

Thiocarbonic acid 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 Thiocarbonic acid rather than just read about it. In short: Thiocarbonic acid is an acid with the chemical formula H2CS3 (or S=C(SH)2). It is an analog of carbonic acid H2CO3 (or O=C(OH)2), in which all oxygen atoms are replaced with sulfur atoms.

Key takeaways

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

Reference excerpt

Thiocarbonic acid is an acid with the chemical formula H2CS3 (or S=C(SH)2). It is an analog of carbonic acid H2CO3 (or O=C(OH)2), in which all oxygen atoms are replaced with sulfur atoms. It is an unstable, hydrophobic, red oily liquid. It is often referred to as trithiocarbonic acid so as to differentiate it from other carbonic acids containing sulfur, such as monothiocarbonic O,O-acid S=C(OH)2, monothiocarbonic O,S-acid O=C(OH)(SH), dithiocarbonic O,S-acid S=C(OH)(SH) and dithiocarbonic S,S-acid O=C(SH)2 (see thiocarbonates).

Discovery and synthesis It was first reported in brief by Zeise in 1824 and later in more detail by Berzelius in 1826, in both cases it was produced by the action of carbon disulfide on a hydrosulfide salt (e.g. potassium hydrosulfide).

CS2 + 2 KSH → K2CS3 + H2S Treatment with acids liberates the thiocarbonic acid as a red oil:

K2CS3 + 2 HX → H2CS3 + 2 KX Both the acid and many of its salts are unstable and decompose via the release of carbon disulfide, particularly upon heating:

H2CS3 → CS2 + H2S An improved synthesis involves addition of barium trithiocarbonate to hydrochloric acid at 0 °C. This method provided samples with which many measurement have been made.

BaCS3 + 2 HCl → H2CS3 + BaCl2 Despite its lability, crystals of thiocarbonic acid have been examined by X-ray crystallography, which confirms the anticipated molecular structure of a trigonal planar molecular geometry at the central carbon atom. The C-S bond lengths range from 1.69 to 1.77 Å.

Reactions and derivatives Thiocarbonic acid is acidic, with the first pKa being around 2. The second pKa is near 7. It dissolves S8, but does not react with it. Salts and esters of trithiocarbonic acid are called trithiocarbonates, and they are sometimes called thioxanthates. Thiocarbonic acid reacts with bifunctional reagents to give rings. 1,2-Dichloroethane gives ethylene trithiocarbonate (S=CS2(CH2)2). Oxalyl chloride gives oxalyl trithiocarbonate (S=CS2(C=O)2).

Applications Thiocarbonic acid currently has no significant applications. Its esters find use in RAFT polymerization.

References

Illustrations

Worked examples

Example 1 — a first encounter with Thiocarbonic acid

Start with the simplest possible case. Write down what Thiocarbonic acid 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 Thiocarbonic acid 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 Thiocarbonic acid 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 Thiocarbonic acid

In research: Thiocarbonic acid 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 Thiocarbonic acid 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: Thiocarbonic acid is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hydrogen compounds, Inorganic carbon compounds, Sulfur(−II) compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Thiocarbonic acid 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 Thiocarbonic acid in 20 minutes

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

Frequently asked questions

What is Thiocarbonic acid in simple terms?

Thiocarbonic acid is an acid with the chemical formula H2CS3 (or S=C(SH)2). It is an analog of carbonic acid H2CO3 (or O=C(OH)2), in which all oxygen atoms are replaced with sulfur atoms.

Why does Thiocarbonic acid 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 Thiocarbonic acid?

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 Thiocarbonic acid.