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Thiocarbonic acid

Trithiocarbonic acid
Names
IUPAC name
Carbonotrithioic acid
Systematic IUPAC name
Trithiocarbonic acid
Other names
  • Dithiocarbon sulfide
  • Sulfocarbonic acid
  • Thiocarbonic acid
  • Trisulfocarbonic acid
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.008.931 Edit this at Wikidata
EC Number
  • 209-822-6
MeSH C013321
UNII
  • InChI=1S/CH2S3/c2-1(3)4/h(H2,2,3,4) ☒N
    Key: HIZCIEIDIFGZSS-UHFFFAOYSA-N ☒N
  • C(=S)(S)S
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
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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]

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]

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.[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).

Applications

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

References

  1. ^ a b c Gattow, Gerhard; Behrendt, Werner (1977). Carbon Sulfides and their Inorganic and Complex Chemistry. Stuttgart: Georg Thieme. p. 154-6. ISBN 3135262014.
  2. ^ Berzelius, J. J. (1826). "Ueber die Schwefelsalze" [About the sulfur salts]. Annalen der Physik (in German). 82 (4): 425–458. Bibcode:1826AnP....82..425B. doi:10.1002/andp.18260820404.
  3. ^ O'Donoghue, Ida Guinevere; Kahan, Zelda (1906). "CLXXIV.—Thiocarbonic acid and some of its salts". J. Chem. Soc., Trans. 89: 1812–1818. doi:10.1039/CT9068901812.
  4. ^ Krebs, B.; Gattow, G. (1965). "Über Chalkogenocarbonate. XIV. Das Kohlenstoffsulfid-bis-(hydrogensulfid) SC(SH)2 und das System H2S−CS2 6. Die Kristallstruktur der Trithiokohlensure bei -100 ″C". Zeitschrift für anorganische und allgemeine Chemie. 340 (5–6): 294–311. doi:10.1002/zaac.19653400508.
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