硫化物（りゅうかぶつ、英: sulfide/sulphide）とは、硫黄化合物のうち硫黄原子が最低酸化数である-2を持つものの総称。言い換えると、硫化水素 (H-S-H) の H を他の原子に置換した構造を持つ化合物である。普通は特に、硫黄の2価の陰イオン（硫化物イオン）と各種陽イオンから構成された塩の形をとる化合物、もしくは他の元素との無機化合物（硫化水素、二硫化炭素など）を指す。
目次
- 1 硫化物イオンとその塩
- 2 その他の硫化物
- 3 硫化鉱物
- 4 脚注
- 5 参考文献
- 6 関連項目
- 7 外部リンク
硫化物イオンとその塩
硫化物イオン S2- は硫化水素を水酸化アルカリなどの塩基性水溶液に溶解すると発生し、Na2S、K2S などの塩を形成する。しかし硫化物イオンは非常に塩基性が強く（pKa は14以上）、pH 14以下の普通の水溶液ではほとんどが加水分解して硫化水素イオン HS- となる（加水分解によって水分子は水酸化物イオンとなるため、硫化アルカリの水溶液は塩基性を示す）。pH 7以下ではさらに変化して硫化水素となる。ゆえに金属硫化物塩を水に溶かして実際に何の化学種が生成するかは、水溶液の最終的な pH によって異なる。金属硫化物塩は水溶液では酸化されやすく、還元剤となる。
遷移金属塩の水溶液は硫化物 (H2S, NaSH, Na2S 等) と反応して固体の塩を沈澱する。このような硫化物塩は水溶解度が非常に低く、また半導体の性質をもつものも多い。有名な例は硫化カドミウム (CdS) で、鮮やかな黄色の顔料としてカドミウムイエローとも呼ばれるが、半導体としても光センサー（光により電気抵抗が変化する）などに用いられる。また硫化亜鉛 (ZnS) なども半導体として用いられる。これらの化合物は塩と呼ばれるものの、その結合は共有結合性が強く、半導体の性質もこれによる。
硫化鉄（黄鉄鉱、磁硫鉄鉱など）や二硫化モリブデン（輝水鉛鉱）など、鉱物として天然に存在するもの（硫化鉱物）も多い。
その他の硫化物
その他の硫化物としては、例えば非金属元素である炭素との化合物である二硫化炭素 (CS2, S=C=S) などがある。これらは完全な共有結合化合物である。また広義には、複数の硫黄原子が直接結合した構造を持つ二硫化物、多硫化物も含める。
さらに有機化合物でも C-S-C または H-S-C という構造をもつ個々の化合物は「硫化〜」という名で呼ばれることもある。例としては硫化メチル（硫化ジメチル、ジメチルスルフィド）、硫化アリル（ジアリルスルフィド）などがある。これらの総称は英語では硫化物と同じく sulfide (sulphide) と呼ばれるが、日本語では硫化物ではなくスルフィドと呼ぶ。
硫化鉱物
「鉱物の一覧#硫化鉱物」も参照
鉱物学において、金属元素が硫黄と結合している鉱物を硫化鉱物（りゅうかこうぶつ、英: sulfide mineral[1]）という。黄鉄鉱 (FeS2)、輝水鉛鉱 (MoS2)、黄銅鉱 (CuFeS2)、方鉛鉱 (PbS)、辰砂 (HgS) などがある。
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シュツルンツ分類 |
| ケイ酸塩鉱物以外 |
01 元素鉱物 · 02 硫化鉱物と硫塩鉱物（英語版） · 03 ハロゲン化鉱物 · 04 酸化鉱物（水酸化鉱物 · 亜ヒ酸塩鉱物（英語版）） · 05 炭酸塩鉱物（硝酸塩鉱物） · 06 ホウ酸塩鉱物 · 07 硫酸塩鉱物（クロム酸塩鉱物 · モリブデン酸塩鉱物 · タングステン酸塩鉱物） · 08 リン酸塩鉱物 · ヒ酸塩鉱物 · バナジン酸塩鉱物 · 10 有機鉱物
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| ケイ酸塩鉱物 |
09.A ネソケイ酸塩鉱物 · 09.B ソロケイ酸塩鉱物 · 09.C シクロケイ酸塩鉱物 · 09.D イノケイ酸塩鉱物 · 09.E フィロケイ酸塩鉱物 · 09.F テクトケイ酸塩鉱物（沸石類を除く） · 09.G テクトケイ酸塩鉱物（沸石類を含む） · 09.H 未分類のケイ酸塩鉱物 · 09.J ゲルマニウム酸塩鉱物（英語版）
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脚注
- ^ 文部省編 『学術用語集 地学編』 日本学術振興会、1984年、115頁。ISBN 4-8181-8401-2。
参考文献
関連項目
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ウィキメディア・コモンズには、硫化物に関連するカテゴリがあります。 |
外部リンク
For other uses, see Sulphide (disambiguation).
Sulfide
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| Names |
Systematic IUPAC name
Sulfanediide[1] (substitutive)
Sulfide(2−)[1] (additive)
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| Identifiers |
|
CAS Number
|
18496-25-8 Y |
| ChEBI |
CHEBI:15138 |
| ChemSpider |
27079 Y |
| Jmol 3D model |
Interactive image |
| PubChem |
29109 |
InChI
-
InChI=1S/S/q-2 Y
Key: UCKMPCXJQFINFW-UHFFFAOYSA-N Y
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|
|
| Properties |
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Chemical formula
|
S2−
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| Molar mass |
32.06 g·mol−1 |
| Related compounds |
|
Other anions
|
Telluride |
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 |
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Sulfide (systematically named sulfanediide, and sulfide(2−)) is an inorganic anion of sulfur with the chemical formula S2−. It contributes no color to sulfide salts. As it is classified as a strong base, even dilute solutions of salts such as sodium sulfide (Na2S) are corrosive and can attack the skin. Sulfide is the simplest sulfur anion.
Contents
- 1 Nomenclature
- 2 Chemical properties
- 2.1 Basicity
- 2.2 Chemical reactions
- 3 Metal derivatives
- 4 Geology
- 5 Corrosion induced by sulfide
- 6 Organic chemistry
- 7 Disulfides
- 8 Examples
- 9 Preparation
- 10 Safety
- 11 See also
- 12 References
Nomenclature
The systematic names sulfanediide and sulfide(2−), valid IUPAC names, are determined according to the substitutive and additive nomenclatures, respectively. However, the name sulfide is also used in compositional IUPAC nomenclature which does not take the nature of bonding involved. Examples of such naming are selenium disulfide and titanium sulfide, which contains no sulfide ions whatsoever.
Sulfide is also used non-systematically, to describe compounds which release hydrogen sulfide upon acidification, or a compound that otherwise incorporates sulfur in some form, such as dimethyl sulfide. "Hydrogen sulfide" is itself an example of a non-systematic name of this nature. However, it is also a trivial name, and the preferred IUPAC name for sulfane.
Chemical properties
Sulfide does not exist in appreciable concentrations even in highly alkaline water, being undetectable at pH < ~15 (8 M NaOH).[2]
Basicity
The sulfide anion can assimilate a proton by recombination:
- S2− + H+ → SH−
Because of this capture of a proton (H+), sulfide has basic character. In aqueous solution, it has a pKb value of less than 0. Its conjugate acid is bisulfide (SH−). In aqueous solution, most sulfide ions are neutralized.
- S2− + H2O SH− + OH−
Chemical reactions
Upon treatment with a standard acid, sulfide converts to hydrogen sulfide (H2S) and a metal salt. Oxidation of sulfide gives sulfur or sulfate. Metal sulfides react with nonmetals including iodine, bromine, and chlorine forming sulfur and metal salts.
- 8 MgS + 8 I2 → S8 + 8 MgI2
Sulfur can also be prepared from a sulfide and an appropriate oxidizer:
- 16 HNO3 + 24 H2S → 16 NO + 3 S8 + 32 H2O
Metal derivatives
Aqueous solutions of transition metals cations react with sulfide sources (H2S, NaHS, Na2S) to precipitate solid sulfides. Such inorganic 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 their semiconductor properties, which in turn is related to the deep colors. Several have practical applications as pigments, in solar cells, and as catalysts. Aspergillus niger plays a role in the solubilization of heavy metal sulfides. [3]
Geology
Main article: sulfide mineral
Many important metal ores are sulfides.[4] Significant examples include: argentite (silver sulfide), cinnabar (mercury), galena (lead sulfide), molybdenite (molybdenum sulfide), pentlandite (nickel sulfide]), realgar (arsenic sulfide), and stibnite (antimony), sphalerite (zinc sulfide), and pyrite (iron disulfide), and chalcopyrite (iron-copper sulfide).
Corrosion induced by sulfide
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 for stress corrosion cracking (SCC) of steel, and is also known as sulfide stress cracking. Corrosion is a major concern in many industrial installations processing sulfides: sulfide ore mills, deep oil wells, pipelines transporting soured oil, Kraft paper factories.
Microbially-induced corrosion (MIC) or biogenic sulfide corrosion are also caused by sulfate reducing bacteria producing sulfide that is emitted in the air and oxidized in sulfuric acid by sulfur oxidizing bacteria. Biogenic sulfuric acid reacts with sewerage 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 form thiosulfate (S
2O2−
3) an intermediate species responsible for severe problems of pitting corrosion of steel and stainless steel while the medium is also acidified by the production of sulfuric acid when oxidation is more advanced.
Organic chemistry
In organic chemistry, "sulfide" usually refers to the linkage C–S–C, although the term thioether is less ambiguous. For example, the thioether dimethyl sulfide is CH3–S–CH3. Polyphenylene sulfide (see below) has the empirical formula C6H4S. Occasionally, the term sulfide refers to molecules containing the –SH functional group. For example, methyl sulfide can mean CH3–SH. The preferred descriptor for such SH-containing compounds is thiol or mercaptan, i.e. methanethiol, or methyl mercaptan.
Disulfides
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 +4 oxidation state (Mo4+). Iron disulfide (pyrite, FeS2) on the other hand consists of S22−, 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, whereas carbon 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 the peroxide –O–O– bond. The disulfide bond (–S–S–) plays a major role in the conformation of proteins and in the catalytic activity of enzymes.
Examples
| Formula |
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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 in photocells. |
1750 |
|
1306-23-6 |
|
Calcium polysulfide ("lime sulfur") is a traditional fungicide in gardening. |
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| CS2 |
Carbon disulfide is sometimes used as a solvent in industrial chemistry. |
−111.6 |
46 |
75-15-0 |
| PbS |
Lead sulfide is used in infra-red sensors. |
1114 |
|
1314-87-0 |
| MoS2 |
Molybdenum disulfide, the mineral molybdenite, 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 an organosulfide (thioether) that has been used as a chemical weapon in the First World War, the chloride on the molecule acts as a leaving group when in the presence of water and forms a thioether-alcohol and HCl. |
13–14 |
217 |
505-60-2 |
| Ag2S |
Silver sulfide is formed on silver electrical contacts operating in an atmosphere rich in hydrogen sulfide. |
|
|
21548-73-2 |
| Na2S |
Sodium sulfide is an important industrial chemical, used in manufacture of kraft paper, dyes, leather tanning, crude petroleum processing, treatment of heavy metal pollution, and others. |
920 |
1180 |
1313-82-2 |
| ZnS |
Zinc sulfide is used for lenses and other optical devices in the infrared part of the spectrum. Zinc sulfide doped with silver is used in alpha detectors while zinc sulfide with traces of copper has applications in photoluminescent strips for emergency lighting and luminous watch dials. |
|
1185 |
1314-98-3 |
| MeS |
Several metal sulfides are used as pigments in art, although their use has declined somewhat due to their toxicity. Sulfide pigments include cadmium, mercury, and arsenic. |
|
|
|
| C6H4S |
Polyphenylene sulfide is a polymer commonly called "Sulfar". Its repeating units are bonded together by sulfide (thioether) linkages. |
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26125-40-6
25212-74-2 |
| SeS2 |
Selenium disulfide is an antifungal used in anti-dandruff preparations, such as Selsun 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 |
The crystal lattice of pyrite is made of iron disulfide, in which iron is divalent and present as ferrous ion (Fe2+). |
600 |
|
1317-66-4 |
Preparation
Sulfide compounds can be prepared in several different ways:[5]
- Direct combination of elements:
- Example: Fe(s) + S(s) → FeS(s)
- Reduction of a sulfate:
- Example: MgSO4(s) + 4C(s) → MgS(s) + 4CO(g)
- Precipitation of an insoluble sulfide:
- Example: M2+ + H2S(g) → MS(s) + 2H+(aq)
Safety
Many metal sulfides are so insoluble in water that they are probably not very toxic. Some metal sulfides, when exposed to a strong mineral acid, including gastric acids, will release toxic hydrogen sulfide.
Organic sulfides are highly flammable. When a sulfide burns it produces sulfur dioxide (SO2) gas.
Hydrogen sulfide, some of its salts, and almost all organic sulfides have a strong and putrid stench; rotting biomass releases these.
See also
- Dithionite
- Sulfate
- Sulfide stress cracking
- Sulfite
- Tetrathionate
- Thioether
- Thiosulfate
References
- ^ a b "sulfide(2−) (CHEBI:15138)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.
- ^ Meyer, B; Ward, K; Koshlap, K; Peter, L (1983). "Second dissociation constant of hydrogen sulfide". Inorganic Chemistry. 22: 2345. doi:10.1021/ic00158a027.
- ^ Harbhajan Singh. Mycoremediation: Fungal Bioremediation. p. 509.
- ^ Vaughan, D. J.; Craig, J. R. “Mineral chemistry of metal sulfides" Cambridge University Press, Cambridge: 1978. ISBN 0-521-21489-0.
- ^ Atkins; Shriver (2010). Inorganic Chemistry (5th ed.). New York: W. H. Freeman & Co. p. 413.
