Sulfanyl (HS•), also known as themercapto radical,hydrosulfide radical, orhydridosulfur, is a simpleradical molecule consisting of one hydrogen and one sulfur atom. The S-H distance in the radical is 0.134 nm.[4] The radical is also proposed to be formed by the action ofultraviolet radiation on hydrogen sulfide. Awavelength of 190 nm gives maximum absorption.[5]
Sulfanyl is one of the top three sulfur-containing gasses ingas giants such asJupiter and is very likely to be found inbrown dwarfs and cool stars. It was originally discovered by Margaret N. Lewis and John U. White at theUniversity of California in 1939.[6] They observed molecular absorption bands around 325 nm belonging to the system designated by2Σ+ ←2Πi. They generated the radical by means of a radio frequency discharge inhydrogen sulfide.[7] 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.[8]
Absorption lines of sulfanyl in space were first detected in theinfrared by Yamamura (2000) in a starR And. In the sun•SH was detected at severalultravioletwavelengths: 326.0459, 327.5468, 328.9749, 330.0892 and 330.1112 nm.[9]
Various theoretical studies have examined HS• in atmospheres. In Earth's atmosphereHS• reacts with NO2 to make two products HSNO2 and HSONO. HSONO decomposes to HSO and NO.HS• also reacts with O2 and N2O.[12] HS• can also react with Cl2 producing HSCl and a Cl• atom.[13] HS• destroysozone producing HSO• and oxygen.[14] HS• is formed in the Earth's atmosphere by the reaction of HO•, thehydroxyl radical, oncarbon disulfide,carbon oxysulfide andhydrogen sulfide with side products ofcarbon dioxide and water. Photodissociation of hydrogen sulfide also produces the radical in air.[15]
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:
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 ingas giants orbrown dwarfs.[16]
Theorganic analogue of sulfanyl isthiyl radical with the formulaRS•, where R is some organic group (e.g.,alkyl oraryl). Thermal decomposition of mercaptans, such asethyl mercaptan has been proposed to involveHS•.[17]
In humanssuperoxide dismutase [Cu-Zn] is proposed to convert the hydrosulfide ion (HS−) toHS•. In the proposed mechanism Cu2+ is convert to Cu+.[18]
Sulfide dehydrogenase as found insulfur bacteria catalyses the oxidation of HS−. It has been proposed that this reaction proceeds viaHS•, by removing a single electron.[19]
When some sulfur minerals are leached with ferric ions, HS• is proposed to proceed as follows:
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.[20] This has potential forbioleaching in metallic ore extraction.
The ionization energy of HS is 10.4219 eV.[24] The reduction potential to go to HS− is 0.92 eV.[25] HS• in water can ionize to S•− and H+. The S•− can catalyze acis-trans conversion inlipids.[26]
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 commonhydrosulfide 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.
^"Mercapto radical – Compound summary".PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and related records. Retrieved12 October 2011.
^ab"sulfanyl (CHEBI:29312)".Chemical entities of biological interest. UK: European Bioinformatics Institute. 6 November 2006. Main. Retrieved8 October 2011.
^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. Retrieved20 October 2011.
^Sehon, A. H.; B. deB. Darwent (October 1954). "The thermal decomposition of mercaptans".Journal of the American Chemical Society.76 (19): 4806.Bibcode:1954JAChS..76.4806S.doi:10.1021/ja01648a011.
^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.
^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.PMID17450618.
