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Hydrogen disulfide

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Title: Hydrogen disulfide  
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Hydrogen disulfide

Hydrogen disulfide
CAS number
ChemSpider  YesY
Jmol-3D images Image 1
Molecular formula H2S2
Molar mass 66.15 g mol−1
Appearance yellow liquid
Density 1.334 g cm-3
Melting point −89.6 °C (−129.3 °F; 183.6 K)
Boiling point 70.7 °C (159.3 °F; 343.8 K)
Flash point flammable
Related compounds
Related compounds Hydrogen peroxide
Hydrogen sulfide
Hydrogen diselenide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY   YesY/N?)

Hydrogen disulfide (H2S2) is an hydrogen sulfide (H2S) and elemental sulfur.


The structure of hydrogen disulfide is similar to that of hydrogen peroxide, with two central sulfur atoms and two outer hydrogen atoms. However, the skew angle of the molecule is different, as the H-S-S bond in hydrogen disulfide has a near-standard 90° torsion angle of the syn conformer.

Skew angle in the H2S2 molecule is 90.6°, compared with 113.7° in H2O2. Molecular dimensions in these two molecules are: O-O, O-H, S-S and S-H bonds have lengths of 1.490, 0.970, 2.055 and 1.352 ångströms respectively.[1][2]

Synthesis and reactions

Hydrogen disulfide can be synthesised by dissolving alkali or alkali earth metal polysulfides in water. When the solution is mixed with concentrated hydrochloric acid at −15 °C, a yellow oil consisting a mixture of polysulfanes (H2Sn) will pool below the aqueous layer. Fractional distillation of this oil gives hydrogen disulfide separate from any other polysulfides (mostly trisulfide).[3][4][5]

Hydrogen disulfide readily decomposes under ambient conditions to alkenes to give disulfides and thiols.[6]

Quantum tunneling and its suppression in Deuterium disulfide

The deuterated form of hydrogen disulfide DSSD, has a similar geometry to HSSH, 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[7] have calculated that while an isolated DSSD 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[1].

Health effects

Hydrogen disulfide has been described as "having a severe and irritating odour" that is similar to camphor or sulfur chloride, causing "tears and a smarting sensation in the nostrils".[4] If it is present in high concentrations, it can cause dizziness, disorientation and ultimately unconsciousness.[8]


  1. ^ Davies, D. W. (1974). "Photoelectron spectra of hydrogen peroxide and hydrogen disulfide: ab initio calculations". Chemical Physics Letters 28 (4): 520–522.  
  2. ^ P. Lazzeretti and R. Zanasi (1997). "On the calculation of parity-violating energies in hydrogen peroxide and hydrogen disulfide molecules within the random-phase approximation". Chemical Physics Letters 279 (5-6): 349–354.  
  3. ^ De, A. K. (2001-01-15). A Text Book of Inorganic Chemistry.  
  4. ^ a b c Walton and Parson; Parsons, Llewellyn B. (1921). "Preparation and Properties of the Persulfides of Hydrogen". J. Amer. Chem. Soc. 43: 2539–48.  
  5. ^ Georg Brauer: Handbook of Preparative Inorganic Chemistry Volume I, page 391, Wiley, 1963.
  6. ^ Hazardous Reagents, Robinson Brothers
  7. ^ J. Trost and K. Hornberger, "Hund's Paradox and the Collisional Stabilization of Chiral Molecules", Phys. Rev. Lett. 103, 023202 (2009)
  8. ^ Stein, Wilkinson, G (2007). Seminars in general adult psychiatry. Royal College of Psychiatrists.  
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