Bisulfide
Inorganic anion containing one sulfur and one hydrogen atoms
From Wikipedia, the free encyclopedia
Bisulfide (or bisulphide in British English) is an inorganic anion with the chemical formula HS− (also written as SH−). It contributes no color to bisulfide salts, and its salts may have a distinctive putrid smell. It is a strong base. Bisulfide solutions are corrosive and attack the skin.
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| Names | |
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| IUPAC name
Hydrosulfide | |
| Systematic IUPAC name
Sulfanide (rarely used, not common) | |
Other names
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| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| 24766 | |
PubChem CID |
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CompTox Dashboard (EPA) |
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| Properties | |
| HS− | |
| Molar mass | 33.07 g·mol−1 |
| Conjugate acid | Hydrogen sulfide |
| Conjugate base | Sulfide |
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 an important chemical reagent and an industrial chemical, mainly used in paper pulp industry (Kraft process), textiles, synthetic flavors, coloring brasses, and iron control.
Properties
A variety of salts are known, including sodium hydrosulfide and potassium hydrosulfide. Ammonium hydrosulfide, a component of "stink bombs" has not been isolated as a pure solid. Some compounds described as salts of the sulfide dianion contain primarily hydrosulfide. For example, the hydrated form of sodium sulfide, nominally with the formula Na2S · 9 H2O, is better described as NaSH · NaOH · 8 H2O.
Aqueous bisulfide absorbs light at around 230 nm in the UV–visible spectrum.[1] Using this approach, bisulfide has been detected in the ocean[2][3] and in sewage.[4] Bisulfide should not be confused with the disulfide dianion, S2−2, or −S–S−.
Basicity
At physiological pH, hydrogen sulfide is fully ionized to bisulfide (HS−). Therefore, in biochemical settings, "hydrogen sulfide" is often used to mean, bisulfide. Hydrosulfide has been identified as the third gasotransmitter along with nitric oxide and carbon monoxide.[5]
The bisulfide anion can accept a proton:
| HS− + H+ → H2S | 1 |
Because of its affinity to accept a proton (H+), bisulfide has a basic character. In aqueous solution, it has a corresponding pKa value of 6.9. Its conjugate acid is hydrogen sulfide (H2S). However, bisulfide's basicity stems from its behavior as an Arrhenius base. A solution containing spectator-only counter ions, has a basic pH according to the following acid-base reaction:
| HS− + H2O H2S + OH− | 2 |
Chemical reactions
Upon treatment with an acid, bisulfide converts to hydrogen sulfide. With strong acids, it can be doubly protonated to give H
3S+
. Oxidation of bisulfide gives sulfate. When strongly heated, bisulfide salts decompose to produce sulfide salts and hydrogen sulfide.
| 2 HS− → H2S + S2− | 3 |
SH− is a soft anionic ligand that forms complexes with most metal ions. Examples include [Au(SH)2]− and (C5H5)2Ti(SH)2, derived from gold(I) chloride and titanocene dichloride, respectively.[6]
Safety
Bisulfide salts are corrosive, strongly alkaline and release toxic hydrogen sulfide upon acidification.