Chemistry:Hydrogen disulfide

Short description: Chemical compound

Hydrogen disulfide

Sulfur, S   Hydrogen, H
Names
IUPAC name Dihydrogen disulfide
Systematic IUPAC name Disulfane
Other names Dithioperoxol Hydrogen disulphide Hydrogen persulfide Hydrogen persulphide Thiosulfenic acid
Identifiers
CAS Number	13465-07-1 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:33114 Y
ChemSpider	97274 Y
PubChem CID	108196
InChI InChI=1S/H2S2/c1-2/h1-2H Y Key: BWGNESOTFCXPMA-UHFFFAOYSA-N Y InChI=1/H2S2/c1-2/h1-2H Key: BWGNESOTFCXPMA-UHFFFAOYAV
SMILES SS
Properties
Chemical formula	H2S2
Molar mass	66.14 g·mol−1
Appearance	Pale yellow liquid
Density	1.334 g/cm3
Melting point	−89.6 °C (−129.3 °F; 183.6 K)
Boiling point	70.7 °C (159.3 °F; 343.8 K)
Hazards
Flash point	flammable
Related compounds
Related compounds	Hydrogen sulfide Hydrogen peroxide Hydrogen diselenide Hydrogen ditelluride Disulfur dichloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Hydrogen disulfide is the inorganic compound with the formula H
2S
2. This hydrogen chalcogenide is a pale yellow volatile liquid with a camphor-like odor. It decomposes readily to hydrogen sulfide (H
2S) and elemental sulfur.

Structure

The connection of atoms in the hydrogen disulfide molecule is H–S–S–H. The structure of hydrogen disulfide is similar to that of hydrogen peroxide, with C₂ point group symmetry. Both molecules are distinctly nonplanar. The dihedral angle between the Ha
–S–S and S–S–Hb
planes is 90.6°, compared with 111.5° in H
2O
2. The H–S–S bond angle is 92°, close to 90° for unhybridized divalent sulfur.

Synthesis

Hydrogen disulfide can be synthesised by cracking polysulfanes (H
2S
n) according to this idealized equation:

H
2S
n → H
2S
2 + S
n-2

The main impurity is trisulfane (H
2S
3). The precursor polysulfane is produced by the reaction of hydrochloric acid with aqueous sodium polysulfide. The polysulfane precipitates as an oil.

Reactions

Upon contact with water or alcohols, hydrogen disulfide readily decomposes under ambient conditions to hydrogen sulfide and sulfur.

It is more acidic than hydrogen sulfide, but the pK_a has not been reported.

In organosulfur chemistry, hydrogen disulfide adds to alkenes to give disulfides and thiols.

Quantum tunneling and its suppression in deuterium disulfide

The deuterated form of hydrogen disulfide, deuterium disulfide D–S–S–D (dideuterodisulfane), has a similar geometry to H–S–S–H, but its tunneling time is slower, making it a convenient test case for the quantum Zeno effect, in which frequent observation of a quantum system suppresses its normal evolution. Trost and Hornberger have calculated that while an isolated D–S–S–D molecule would spontaneously oscillate between left and right chiral forms with a period of 5.6 milliseconds, the presence of a small amount of inert helium gas should stabilize the chiral states, the collisions of the helium atoms in effect "observing" the molecule's momentary chirality and so suppressing spontaneous evolution to the other chiral state.

Health effects

In high concentrations, it can cause dizziness, disorientation and ultimately unconsciousness.

Historic literature

• Walton, James H.; Parsons, Llewellyn B. (1921-12-01). "Preparation and Properties of the Persulfides of Hydrogen". J. Am. Chem. Soc. 43 (12): 2539–48. doi:10.1021/ja01445a008. https://zenodo.org/record/1428820. 
• Georg Brauer: Handbook of Preparative Inorganic Chemistry Volume I, page 391, Wiley, 1963.
• von Richter, Victor: Translated by Edgar F Smith, "A Text-Book of Inorganic Chemistry", Page 111, P. Blakiston, Son & Co., 1893