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| Names | |||
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| Systematic IUPAC name | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
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| UNII | |||
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| Properties | |||
| S2− | |||
| Molar mass | 32.06 g·mol−1 | ||
| Conjugate acid | Bisulfide | ||
| Related compounds | |||
Otheranions | oxide selenide Telluride | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Sulfide (alsosulphide inBritish English)[2] is aninorganicanion ofsulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive.Sulfide also refers to large families of inorganic andorganic compounds, e.g. lead sulfide anddimethyl sulfide.Hydrogen sulfide (H2S) andbisulfide (HS−) are the conjugate acids of sulfide.
The sulfide ion does not exist in aqueous alkaline solutions of Na2S.[3][4] Instead sulfide converts to hydrosulfide:
Upon treatment with an acid, sulfide salts convert tohydrogen sulfide:
Oxidation of sulfide is a complicated process. Depending on the conditions, the oxidation can produce elemental sulfur,polysulfides,polythionates,sulfite, orsulfate. Metal sulfides react withhalogens, formingsulfur and metal salts.
Aqueous solutions oftransition metalscations react with sulfide sources (H2S, NaHS, Na2S) to precipitate solid sulfides. Suchinorganic sulfides typically have very low solubility in water, and many are related to minerals with the same composition (see below). One famous example is the bright yellow species CdS or "cadmium yellow". The black tarnish formed on sterling silver is Ag2S. Such species are sometimes referred to as salts. In fact, the bonding in transition metal sulfides is highly covalent, which gives rise to theirsemiconductor properties, which in turn is related to the deep colors. Several have practical applications as pigments, in solar cells, and as catalysts. The fungusAspergillus niger plays a role in the solubilization of heavy metal sulfides.[5]
Many importantmetalores are sulfides.[6] Significant examples include:argentite (silver sulfide),cinnabar (mercury sulfide),galena (lead sulfide),molybdenite (molybdenum sulfide),pentlandite (nickel sulfide),realgar (arsenic sulfide), andstibnite (antimony sulfide),sphalerite (zinc sulfide), andpyrite (iron disulfide), andchalcopyrite (iron-copper sulfide). This sulfideminerals recorded information (likeisotopes) of their surrounding environment during their formation. Scientists use these minerals to study environments in the deep sea or in the Earth's past.[7]
Dissolved free sulfides (H2S, HS− and S2−) are very aggressive species for the corrosion of many metals such as steel, stainless steel, and copper. Sulfides present in aqueous solution are responsible forstress corrosion cracking (SCC) of steel, and is also known assulfide stress cracking. Corrosion is a major concern in many industrial installations processing sulfides: sulfide ore mills, deepoil wells, pipelines transporting souredoil andKraft paper factories.
Microbially-induced corrosion (MIC) orbiogenic sulfide corrosion are also caused bysulfate reducing bacteria producing sulfide that is emitted in the air and oxidized in sulfuric acid by sulfur oxidizing bacteria. Biogenic sulfuric acid reacts withsewerage materials and most generally causes mass loss, cracking of the sewer pipes and ultimately, structural collapse. This kind of deterioration is a major process affecting sewer systems worldwide and leading to very high rehabilitation costs.
Oxidation of sulfide can also formthiosulfate (S
2O2−
3), an intermediate species responsible for severe problems ofpitting corrosion of steel and stainless steel while the medium is also acidified by the production of sulfuric acid when oxidation is more advanced.
Inorganic chemistry, "sulfide" usually refers to the linkage C–S–C, although the termthioether is less ambiguous. For example, the thioetherdimethyl sulfide is CH3–S–CH3.Polyphenylene sulfide (see below) has the empirical formula C6H4S. Occasionally, the term sulfide refers to molecules containing the –SHfunctional group. For example, methyl sulfide can mean CH3–SH. The preferred descriptor for such SH-containing compounds isthiol or mercaptan, i.e. methanethiol, or methyl mercaptan.
Confusion arises from the different meanings of the term "disulfide".Molybdenum disulfide (MoS2) consists of separated sulfide centers, in association with molybdenum in the formal +4oxidation state (that is, Mo4+ and two S2−). Iron disulfide (pyrite, FeS2) on the other hand consists ofS2−
2, or−S–S− dianion, in association with divalent iron in the formal +2 oxidation state (ferrous ion: Fe2+).Dimethyldisulfide has the chemical binding CH3–S–S–CH3, whereascarbon disulfide has no S–S bond, being S=C=S (linear molecule analog to CO2). Most often in sulfur chemistry and in biochemistry, the disulfide term is commonly ascribed to the sulfur analogue of theperoxide –O–O– bond. Thedisulfide bond (–S–S–) plays a major role in the conformation ofproteins and in the catalytic activity ofenzymes.
| Formula | Melting point (°C) | Boiling point (°C) | CAS number | |
|---|---|---|---|---|
| H2S | Hydrogen sulfide is a very toxic and corrosive gas characterised by a typical odour of "rotten egg". | −85.7 | −60.20 | 7783-06-4 |
| CdS | Cadmium sulfide can be used inphotocells. | 1750 | 1306-23-6 | |
| Calcium polysulfide ("lime sulfur") is a traditionalfungicide ingardening. | ||||
| CS2 | Carbon disulfide is a precursor to organosulfur compounds. | −111.6 | 46 | 75-15-0 |
| PbS | Lead sulfide is used ininfra-red sensors. | 1114 | 1314-87-0 | |
| MoS2 | Molybdenum disulfide, the mineralmolybdenite, is used as a catalyst to remove sulfur from fossil fuels; also as lubricant for high-temperature and high-pressure applications. | 1317-33-5 | ||
| Cl–CH2CH2–S–CH2CH2–Cl | Sulfur mustard (mustard gas) is anorganosulfur compound (thioether) that was used as a chemical weapon in the First World War. | 13–14 | 217 | 505-60-2 |
| Ag2S | Silver sulfide is a component ofsilver tarnish. | 21548-73-2 | ||
| Na2S | Sodium sulfide, as the hydrate, is used in manufacture ofkraftpaper and as a precursor toorganosulfur compounds. | 920 | 1180 | 1313-82-2 |
| ZnS | Zinc sulfide is used forlenses and otheroptical devices in theinfrared part of thespectrum. ZnS-doped with silver is used in alpha detectors while zinc sulfide with traces of copper has applications inphotoluminescent strips for emergency lighting and luminous watch dials. | 1850 | 1314-98-3 | |
| C6H4S | Polyphenylene sulfide is a polymer commonly called "Sulfar". Its repeating units are bonded together by sulfide (thioether) linkages. | 26125-40-6 25212-74-2 | ||
| SeS2 | Selenium disulfide is anantifungal used in anti-dandruff preparations, such asSelsun Blue. The presence of the highly toxic selenium in healthcare and cosmetics products represents a general health and environmental concern. | <100 | 7488-56-4 | |
| FeS2 | Known as "fool's gold",pyrite, is a common mineral. | 600 | 1317-66-4 |
Sulfide compounds can be prepared in several different ways:[8]
Many metal sulfides are so insoluble in water that they are probably not very toxic. Some metal sulfides, when exposed to a strong mineralacid, includinggastric acids, will release toxichydrogen sulfide.
Organic sulfides are highly flammable. When a sulfide burns it producessulfur dioxide (SO2) gas.
Hydrogen sulfide, some of its salts, and almost all organic sulfides have a strong and putrid stench; rottingbiomass releases these.
The systematic namessulfanediide andsulfide(2−), validIUPAC names, are determined according to the substitutive and additive nomenclatures, respectively. The name sulfide is also used in compositional IUPAC nomenclature which does not take the nature of bonding involved. Examples of such naming includeselenium disulfide andtitanium sulfide, which contain no sulfide ions.
Media related toSulfides at Wikimedia Commons
