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
CAS Number	594-08-1 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:36967 ;
ChemSpider	62204 ;
ECHA InfoCard	100.008.931
EC Number	209-822-6;
MeSH	C013321
PubChem CID	68982;
UNII	O27JHO40J8 ;
CompTox Dashboard (EPA)	DTXSID00862140 ;
	InChI InChI=1S/CH2S3/c2-1(3)4/h(H2,2,3,4) Key: HIZCIEIDIFGZSS-UHFFFAOYSA-N ;
	SMILES C(=S)(S)S;
Properties
Chemical formula	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	Carbonic acid; Thiosulfuric acid; Thiocarbonate; Xanthic acid; Thioxanthate; Ethyl xanthic acid; Thiocyanic acid; Thiocyanate; Potassium trithiocarbonate; Dimethyl trithiocarbonate; Ethylene trithiocarbonate; Thiourea; Thiocarbamate; Thiophosphoric acid;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

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 pK_a being around 2. The second pK_a 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).

Some of the organic trithiocarbonates

Applications

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

References

^ ^a ^b ^c Gattow, Gerhard; Behrendt, Werner (1977). Carbon Sulfides and their Inorganic and Complex Chemistry. Stuttgart: Georg Thieme. p. 154-6. ISBN 3135262014.
^ 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.
^ 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.
^ 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.

[Gattow-1] 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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