Last updated
  Sulfur, S
  Hydrogen, H
Systematic IUPAC name
Sulfanyl [1] (substitutive)
Hydridosulfur(•) [1] (additive)
Other names
λ1-Sulfane [2]
3D model (JSmol)
PubChem CID
  • InChI=1S/HS/h1H Yes check.svgY
  • [SH]
Molar mass 33.073 g mol−1
AppearanceYellow gas [3]
Std molar
195.63 J K−1 mol−1
139.33 kJ mol−1
Related compounds
Related radicals
Related compounds
Hydrogen sulfide

Hydrogen disulfide

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Sulfanyl (HS), also known as the mercapto radical, hydrosulfide radical, or hydridosulfur, is a simple radical molecule consisting of one hydrogen and one sulfur atom. The radical appears in metabolism in organisms as H2S is detoxified. Sulfanyl is one of the top three sulfur-containing gasses in gas giants such as Jupiter and is very likely to be found in brown dwarfs and cool stars. It was originally discovered by Margaret N. Lewis and John U. White at the University of California in 1939. [4] They observed molecular absorption bands around 325 nm belonging to the system designated by 2Σ+2Πi. They generated the radical by means of a radio frequency discharge in hydrogen sulfide. [5] HS is formed during the degradation of hydrogen sulfide in the atmosphere of the Earth. This may be a deliberate action to destroy odours or a natural phenomenon. [6]


The organic analogue of sulfanyl is thiyl radical with the formula RS, where R is some organic group (e.g., alkyl or aryl).

Natural occurrence

Absorption lines of sulfanyl in space were first detected in the infrared by Yamamura (2000) in a star R And. In the sun SH was detected at several ultraviolet wavelengths: 326.0459, 327.5468, 328.9749, 330.0892 and 330.1112 nm. [7]

Sulfanyl has been detected in interstellar gas, [8] and it is possibly present in comets. [9]

Various theoretical studies have examined HS in atmospheres. In Earth's atmosphere HS reacts with NO2 to make two products HSNO2 and HSONO. HSONO decomposes to HSO and NO. HS also reacts with O2 and N2O. [10] HS can also react with Cl2 producing HSCl and a Cl atom. [11] HS destroys ozone producing HSO and oxygen. [12] HS is formed in the Earth's atmosphere by the reaction of HO, the hydroxyl radical, on carbon disulfide, carbon oxysulfide and hydrogen sulfide with side products of carbon dioxide and water. Photodissociation of hydrogen sulfide also produces the radical in air. [13]

In a planetary atmosphere that contains H2S, HS will be formed if the temperature and pressure are high enough. The ratio of H2S and HS is given by:

log(XH2S/XHS) = 3.37 + 8785/T + 0.5 log PT + 0.5 log XH2

For a hydrogen dominated atmosphere in a gas giant or star: H2S has the same level as HS at


At higher temperatures HS breaks up into sulfur vapour and H2. The line of equal S and HS concentration follows the line


The lines of equal concentration cross at 1509 K and 1.51 Pa, with HS being left out of the mix at lower temperatures and pressures. SH is expected to be the second or third most common sulfur containing gas in gas giants or brown dwarfs. [14]


Thermal decomposition of mercaptans, such as ethyl mercaptan yields HS. [15]

The radical can be formed by the action of ultraviolet radiation on hydrogen sulfide, which splits off a hydrogen atom. A wavelength of 190 nm gives maximum absorption. [16]

In humans superoxide dismutase [Cu-Zn] converts the hydrosulfide ion (HS) to HS. This happens as the Cu2+ ion in the enzyme is converted to Cu+. [17]

Sulfide dehydrogenase as found in sulfur bacteria catalyses the oxidation of HS to HS, by removing a single electron. [18]

When sulfur minerals are leached with ferric ions HS is formed in this way:

MS + Fe3+ + 2H+ → M2+ + Fe2+ + H2S•+

with the H2S•+ radical then passing a proton to water to make the HS radical. M is a metal such as zinc or copper. [19] This has potential for bioleaching in metallic ore extraction.

The hydrosulfide ion HS can be oxidized to HS with cerium (IV) sulfate. [20]


Being a radical, HS is quite reactive. In water HS can react with O2 producing SO2 and H+. SO2 reacts further with O2 to make SO2 and superoxide O2. In water HS has an equilibrium with S− • and H+. The hydroxyl radical OH combines with H2S to form HS and water. [21] Other reactions investigated by Tiee (1981) are HS + ethylene, HS + O2 → HO + SO, and reactions with itself HS + HSH2S2 or H2 and S. [22] The disulfide can further react with HS to make the disulfide radical HS–S and H2S. [19]


The ionization energy of HS is 10.4219 eV. [23] The reduction potential to go to HS is 0.92 eV. [24] HS in water can ionize to S•− and H+. The S•− can catalyze a cis-trans conversion in lipids. [25]

The interatomic distance between sulfur and hydrogen in the radical is 0.134 nm. [26]

HS reacts with carboxylic acids to make carbonyl sulfide (COS) and probably is the main source of this substance in the atmosphere of Earth. [20]

HS—S is called disufanyl with lengthening chains as trisulfanyl, tetrasulfanyl and pentasulfanyl HSSSSS. S* is termed sulfanidyl. HS+ is known as sulfanylium, and the common hydrosulfide ion HS is also known as sulfanido for a ligand or sulfanide as an anion. Further down the periodic table, HSe is known as selanyl, and HTe is termed tellanyl.

Related Research Articles

<span class="mw-page-title-main">Sulfur</span> Chemical element, symbol S and atomic number 16

Sulfur (also spelled sulphur in British English) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with the chemical formula S8. Elemental sulfur is a bright yellow, crystalline solid at room temperature.

<span class="mw-page-title-main">Thiol</span> Any organic compound having a sulfanyl group (–SH)

In organic chemistry, a thiol, or thiol derivative, is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The −SH functional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols, and the word is a blend of "thio-" with "alcohol".

<span class="mw-page-title-main">Hydrogen sulfide</span> Poisonous, corrosive and flammable gas

Hydrogen sulfide is a chemical compound with the formula H2S. It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.

<span class="mw-page-title-main">Methanethiol</span> Chemical compound

Methanethiol is an organosulfur compound with the chemical formula CH
. It is a colorless gas with a distinctive putrid smell. It is a natural substance found in the blood, brain and feces of animals, as well as in plant tissues. It also occurs naturally in certain foods, such as some nuts and cheese. It is one of the chemical compounds responsible for bad breath and the smell of flatus. Methanethiol is the simplest thiol and is sometimes abbreviated as MeSH. It is very flammable.

Sulfide (British English also sulphide) is an inorganic anion of sulfur 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 and organic compounds, e.g. lead sulfide and dimethyl sulfide. Hydrogen sulfide (H2S) and bisulfide (SH) are the conjugate acids of sulfide.

<span class="mw-page-title-main">Bisulfide</span> Inorganic anion containing one sulfur and one hydrogen atoms

Bisulfide is an inorganic anion with the chemical formula HS. 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.

In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states. The reverse of disproportionation, such as when a compound in an intermediate oxidation state is formed from precursors of lower and higher oxidation states, is called comproportionation, also known as synproportionation.

<span class="mw-page-title-main">Carbonyl sulfide</span> Chemical compound

Carbonyl sulfide is the chemical compound with the linear formula OCS. It is a colorless flammable gas with an unpleasant odor. It is a linear molecule consisting of a carbonyl double bonded to a sulfur atom. Carbonyl sulfide can be considered to be intermediate between carbon dioxide and carbon disulfide, both of which are valence isoelectronic with it.

<span class="mw-page-title-main">Ammonium hydrosulfide</span> Chemical compound

Ammonium hydrosulfide is the chemical compound with the formula [NH4]SH.

<span class="mw-page-title-main">Sulfur cycle</span> Biogeochemical cycle of sulfur

The important sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (CHNOPS), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes. Steps of the sulfur cycle are:

<span class="mw-page-title-main">Sodium sulfide</span> Chemical compound

Sodium sulfide is a chemical compound with the formula Na2S, or more commonly its hydrate Na2S·9H2O. Both the anhydrous and the hydrated salts in pure crystalline form are colorless solids, although technical grades of sodium sulfide are generally yellow to brick red owing to the presence of polysulfides and commonly supplied as a crystalline mass, in flake form, or as a fused solid. They are water-soluble, giving strongly alkaline solutions. When exposed to moist air, Na2S and its hydrates emit hydrogen sulfide, an extremely toxic, flammable and corrosive gas which smells like rotten eggs.

Sulfur compounds are chemical compounds formed the element sulfur (S). Common oxidation states of sulfur range from −2 to +6. Sulfur forms stable compounds with all elements except the noble gases.

<span class="mw-page-title-main">Sodium hydrosulfide</span> Chemical compound

Sodium hydrosulfide is the chemical compound with the formula NaSH. This compound is the product of the half-neutralization of hydrogen sulfide with sodium hydroxide (NaOH). NaSH and sodium sulfide are used industrially, often for similar purposes. Solid NaSH is colorless. The solid has an odor of H2S owing to hydrolysis by atmospheric moisture. In contrast with sodium sulfide, which is insoluble in organic solvents, NaSH, being a 1:1 electrolyte, is more soluble.

A polysulfane is a chemical compound of formula H2Sn, where n > 1. Compounds containing 2 – 8 sulfur atoms have been isolated, longer chain compounds have been detected, but only in solution. H2S2 is colourless, higher members are yellow with the colour increasing with the sulfur content. In the chemical literature the term polysulfanes is sometimes used for compounds containing −(S)n, e.g. organic polysulfanes R1−(S)n−R2.

<span class="mw-page-title-main">Potassium hydrosulfide</span> Chemical compound

Potassium hydrosulfide is the inorganic compound with the formula KSH. This colourless salt consists of the cation K+ and the bisulfide anion [SH]. It is the product of the half-neutralization of hydrogen sulfide with potassium hydroxide. The compound is used in the synthesis of some organosulfur compounds. Aqueous solutions of potassium sulfide consist of a mixture of potassium hydrosulfide and potassium hydroxide.

Sulfur mononitride is an inorganic compound with the molecular formula SN. It is the sulfur analogue of and isoelectronic to the radical nitric oxide, NO. It was initially detected in 1975, in outer space in giant molecular clouds and later the coma of comets. This spurred further laboratory studies of the compound. Synthetically, it is produced by electric discharge in mixtures of nitrogen and sulfur compounds, or combustion in the gas phase and by photolysis in solution.

<span class="mw-page-title-main">Polythionic acid</span>

Polythionic acid is an oxoacid which has a straight chain of sulfur atoms and has the chemical formula Sn(SO3H)2 (n > 2). Trithionic acid (H2S3O6), tetrathionic acid (H2S4O6) are simple examples. They are the conjugate acids of polythionates. The compounds of n < 80 are expected to exist, and those of n < 20 have already been synthesized. Dithionic acid (H2S2O6) does not belong to the polythionic acids due to strongly different properties.

Hydrogen thioperoxide, also called oxadisulfane or sulfanol, is the chemical with the structure H–S–O–H. It can be considered as the simple sulfur-substituted analog of the common hydrogen peroxide (H–O–O–H) chemical, and as the simplest hydrogen chalcogenide containing more than one type of chalcogen. The chemical has been described as the "missing link" between hydrogen peroxide and hydrogen disulfide (H–S–S–H), though it is substantially less stable than either of the other two. It is the inorganic parent structure of the sulfenic acid class of organic compounds (R–S–O–H) and also the oxadisulfide linkage (R1–S–O–R2), where "R" is any organic structure. Sulfur is present in oxidation state 0.

Hydrogen chalcogenides are binary compounds of hydrogen with chalcogen atoms. Water, the first chemical compound in this series, contains one oxygen atom and two hydrogen atoms, and is the most common compound on the Earth's surface.

<span class="mw-page-title-main">Sulfoxylic acid</span> Chemical compound

Sulfoxylic acid (H2SO2) (also known as hyposulfurous acid or sulfur dihydroxide) is an unstable oxoacid of sulfur in an intermediate oxidation state between hydrogen sulfide and dithionous acid. It consists of two hydroxy groups attached to a sulfur atom. Sulfoxylic acid contains sulfur in an oxidation state of +2. Sulfur monoxide (SO) can be considered as a theoretical anhydride for sulfoxylic acid, but it is not actually known to react with water.


  1. 1 2 "sulfanyl (CHEBI:29312)". Chemical entities of biological interest. UK: European Bioinformatics Institute. 6 November 2006. Main. Retrieved 8 October 2011.
  2. "Mercapto radical – Compound summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and related records. Retrieved 12 October 2011.
  3. Zahnle, Kevin; Mark S. Marley; R. S. Freedman; K. Lodders; J. J. Fortney (26 June 2009). "Atmospheric sulfur photochemistry on hot Jupiters". The Astrophysical Journal. 701 (1): L20–L24. arXiv: 0903.1663v2 . Bibcode:2009ApJ...701L..20Z. doi:10.1088/0004-637X/701/1/L20. S2CID   16431314.
  4. Lewis, Margaret; John U. White (1939). "The band spectrum of HS". Physical Review. 55 (10): 894–898. Bibcode:1939PhRv...55..894L. doi:10.1103/PhysRev.55.894.
  5. Harrison, Jeremy J.; Bryce E. Williamson (November 2005). "Magnetic circular dichroism of the mercapto radical in noble-gas matrices" (PDF). Journal of the Indian Institute of Science. 85: 391–402.
  6. Mercado-Cabrera, Antonio; B. Jaramillo-Sierra; S.R. Barocio; R. Valencia-Alvarado; M. Pacheco-Pacheco; R. Peña-Eguiluz; R. Lopez-Callejas; A. Muñoz-Castro; A. De la Piedad-Beneitez (29 April 2009). "Environmental odour control by atmospheric dielectric barrier discharge" (PDF). ISPC. Retrieved 20 October 2011.
  7. Sveta V. Berdyugina; W.C. Livingston (May 2002). "Detection of the mercapto radical SH in the solar atmosphere". Astronomy and Astrophysics. 387: L6–L9. Bibcode:2002A&A...387L...6B. doi: 10.1051/0004-6361:20020364 .
  8. Palca, Joe (1 October 2011). "Flying telescope makes an out-of-this-world find". NPR. Retrieved 8 October 2011.
  9. "The cosmic ice laboratory – Cometary molecules".
  10. Resende, Stella M. (2007). "The atmospheric oxidation of the HS radical: Reaction with NO2". Journal of Atmospheric Chemistry. 56 (1): 21–32. Bibcode:2006JAtC...56...21R. doi:10.1007/s10874-006-9040-z. S2CID   95081477.
  11. Resende, Stella M.; Fernando R Ornellas (25 February 2000). "Atmospheric reaction between the HS radical and chlorine". Chemical Physics Letters. 318 (4–5): 340–344. Bibcode:2000CPL...318..340R. doi:10.1016/S0009-2614(00)00019-1.
  12. Yoshimura, Yasunori; Toshio Kasai, Hiroshi Ohoyama and Keiji Kuwata; Ohoyama, Hiroshi; Kuwata, Keiji (1995). "Nascent HF + and HSO(2A') formations in the elementary reactions of F + H2S and HS + O3 and the internal energy distributions". Canadian Journal of Chemistry. 73 (2): 204–221. doi: 10.1139/v95-029 .
  13. Furones, Maikel Yusat Ballester (2008). "A theoretical study on the HSO2 molecular system" (PDF). Coimbra: Universidade de Coimbra. pp. 1, 37. Retrieved 20 October 2011.
  14. Visscher, Channon; Lodders, Katharina; Fegley, Bruce Jr. (10 September 2006). "Atmospheric chemistry in giant planets, brown dwarfs, and low-mass dwarf stars. II. Sulfur and phosphorus". The Astrophysical Journal. 648 (2): 1181–1195. arXiv: astro-ph/0511136 . Bibcode:2006ApJ...648.1181V. doi:10.1086/506245. S2CID   17874854.
  15. Sehon, A. H.; B. deB. Darwent (October 1954). "The thermal decomposition of mercaptans". Journal of the American Chemical Society. 76 (19): 4806. doi:10.1021/ja01648a011.
  16. Hollaender, Alexander; Livingston, Robert (1955). "1". Radiation Biology. McGraw Hill. p. 27.
  17. Lyons, Thomas J.; Edith Butler Gralla; Joan Selverstone Valentine (1999). Biological chemistry of copper-zinc superoxide dismutase and its link to amyotrophic lateral sclerosis (PDF). Vol. 36. Basel, Switzerland: Marcel Decker Inc. p. 139. ISBN   978-0-8247-1956-2. PMID   10093924 . Retrieved 10 October 2011.{{cite book}}: |journal= ignored (help)
  18. Sorokina, Dimitry Yu; Govardus A.H de Jong; Lesley A. Robertson; Gijs J. Kuenen (1 May 1998). "Purification and characterization of sulfide dehydrogenase from alkaliphilic chemolithoautotrophic sulfur-oxidizing bacteria". FEBS Letters. 427 (1): 11–14. doi: 10.1016/S0014-5793(98)00379-2 . PMID   9613590. S2CID   2818096.
  19. 1 2 Schippers, Axel; Wolfgang Sand (January 1999). "Bacterial leaching of metal sulfides proceeds by two indirect mechanisms via thiosulfate or via polysulfides and sulfur". Applied and Environmental Microbiology. 65 (1): 319–321. Bibcode:1999ApEnM..65..319S. doi:10.1128/AEM.65.1.319-321.1999. PMC   91023 . PMID   9872800.
  20. 1 2 Pos, Willer H.; Daniel D. Riemer; Rod G. Zika (1998). "Carbonyl sulfide (OCS) and carbon monoxide (CO) in natural waters: evidence of a coupled production pathway". Marine Chemistry. 62 (1–2): 89–101. Bibcode:1998MarCh..62...89P. doi: 10.1016/S0304-4203(98)00025-5 .
  21. Fang, Hao Jie; Dong Wen Bo; Zhang Ren Xi; Hou, Hui Qi (June 2006). "水相中·HS 的光谱表征及其与氧气的反应研究" [Spectrum ofHS and its reactions with oxygen in aqueous solution]. Acta Physico-Chimica Sinica (in Chinese). 22 (6): 761–763. doi:10.3866/PKU.WHXB20060623 . Retrieved 12 October 2011.
  22. Tiee, J.J. (1981). "Spectroscopy and reaction kinetics of HS radicals" . Kinetics Database. NIST. 82 (1): 80–84. Bibcode:1981CPL....82...80T. doi:10.1016/0009-2614(81)85111-1 . Retrieved 13 October 2011.
  23. Cheng, B. M.; Chew, E. P.; Hung, Wen-Ching; Eberhard, Jürg; Lee, Yuan-Pern (May 1998). "Photoionization studies of sulfur radicals and products of their reactions" (PDF). Journal of Synchrotron Radiation. 5 (3): 1041–3. Bibcode:1998JSynR...5.1041C. doi:10.1107/S0909049597016075. PMID   15263738.
  24. Das, T. N.; R. E. Huie; P. Neta; S. Padmaja (11 June 1999). "Reduction potential of the sulfhydryl radical: pulse radiolysis and laser flash photolysis studies of the formation and reactions of SH and HS–SH•− in aqueous solutions". The Journal of Physical Chemistry A. 103 (27): 5221–5226. Bibcode:1999JPCA..103.5221D. doi:10.1021/jp9907544.
  25. Lykakis, Ioannis N.; Carla Ferreri; Chryssostomos Chatgilialoglu (19 January 2007). "The sulfhydryl radical (HS/S•−): A contender for the isomerization of double bonds in membrane lipids". Angewandte Chemie. 46 (11): 1914–1916. doi:10.1002/anie.200604525. PMID   17450618.
  26. Ellingson, Benjamin A.; Donald G. Truhlar (1 August 2007). "Explanation of the unusual temperature dependence of the atmospheric important OH + H2S → H2O + SH reaction and prediction of the rate constant at combustion temperatures" (reprint). J. Am. Chem. Soc. 129 (42): 12765–12771 [12769]. doi:10.1021/ja072538b. PMID   17910447 . Retrieved 20 October 2011.