Thiocarbonic acid
Chemical compound
From Wikipedia, the free encyclopedia
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.[1]
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| Names | |
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| IUPAC name
Carbonotrithioic acid | |
| Systematic IUPAC name
Trithiocarbonic acid | |
Other names
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| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.008.931 |
| EC Number |
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| MeSH | C013321 |
PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| H2CS3 | |
| Molar mass | 110.21 g·mol−1 |
| Appearance | Red oily liquid, yellow crystalline solid |
| Density | 1.483 g/cm3 (liquid) |
| Melting point | −26.8 °C; −16.3 °F; 246.3 K |
| Boiling point | 58 °C; 136 °F; 331 K |
| Related compounds | |
Related compounds |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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,[2] in both cases it was produced by the action of carbon disulfide on a hydrosulfide salt (e.g. potassium hydrosulfide).[3]
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.[1]
- 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.[4]
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.[1]
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).
Oxalyl trithiocarbonate
Applications
Thiocarbonic acid currently has no significant applications. Its esters find use in RAFT polymerization.