View source for Chemistry:Organosulfur chemistry

{{Short description|Organic compounds that contain sulfur}}
'''Organosulfur chemistry''' is the study of the properties and synthesis of '''organosulfur compounds''', which are [[Chemistry:Organic compound|organic compound]]s that contain [[Chemistry:Sulfur|sulfur]].<ref>{{cite book|last=Block|first=E.|title=Reactions of Organosulfur Compounds|publisher=Academic Press|year=1978|isbn=0-12-107050-6}}</ref> They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., [[Chemistry:Saccharin|saccharin]]. Nature is abound with organosulfur compounds—sulfur is vital for life. Of the 20 common amino acids, two ([[Chemistry:Cysteine|cysteine]] and [[Chemistry:Methionine|methionine]]) are organosulfur compounds, and the antibiotics [[Chemistry:Penicillin|penicillin]] and sulfa drugs both contain sulfur. While sulfur-containing antibiotics save many lives, [[Chemistry:Sulfur mustard|sulfur mustard]] is a deadly chemical warfare agent. Fossil fuels, [[Earth:Coal|coal]], [[Chemistry:Petroleum|petroleum]], and [[Chemistry:Natural gas|natural gas]], which are derived from ancient organisms, necessarily contain organosulfur compounds, [[Chemistry:Desulfurization|the removal]] of which is a [[Chemistry:Claus process|major focus]] of oil refineries.

Sulfur shares the [[Chemistry:Chalcogen|chalcogen]] group with [[Chemistry:Oxygen|oxygen]], [[Chemistry:Selenium|selenium]], and [[Chemistry:Tellurium|tellurium]], and it is expected that organosulfur compounds have similarities with carbon–oxygen, carbon–selenium, and carbon–tellurium compounds.

A classical [[Chemistry:Chemical test|chemical test]] for the detection of sulfur compounds is the [[Chemistry:Carius halogen method|Carius halogen method]].

==Structural classes==
Organosulfur compounds can be classified according to the sulfur-containing [[Chemistry:Functional group|functional group]]s, which are listed (approximately) in decreasing order of their occurrence.
<gallery caption="Illustrative organosulfur compounds" perrow="6">
Image:R-allicin-2D-skeletal.svg|[[Chemistry:Allicin|Allicin]], the active flavor compound in crushed garlic
Image:Cysteine.svg| (''R'')-[[Chemistry:Cysteine|Cysteine]], an [[Chemistry:Amino acid|amino acid]] containing a thiol group
Image:Methionin - Methionine.svg|[[Chemistry:Methionine|Methionine]], an [[Chemistry:Amino acid|amino acid]] containing a sulfide
Image:Diphenyl disulfide.svg|[[Chemistry:Diphenyl disulfide|Diphenyl disulfide]], a representative disulfide
Image:Dibenzothiophen - Dibenzothiophene.svg|[[Chemistry:Dibenzothiophene|Dibenzothiophene]], a component of crude oil 
Image:Perfluorooctanesulfonic acid structure.svg|[[Chemistry:Perfluorooctanesulfonic acid|Perfluorooctanesulfonic acid]], a controversial surfactant
Image:Lipoic_acid.svg|[[Chemistry:Lipoic acid|Lipoic acid]], an essential cofactor of four mitochondrial enzyme complexes.
Image:Penicillin core.svg|[[Chemistry:Penicillin|Penicillin]] core structure, where "R" is the variable group.
image:Sulfanilamide-skeletal.svg|[[Chemistry:Sulfanilamide|Sulfanilamide]], a sulfonamide antibacterial, called a sulfa drug.
Image:Sulfur-mustard-2D-skeletal.svg|[[Chemistry:Sulfur mustard|Sulfur mustard]], a type of sulfide used as a chemical warfare agent.
Image:MartinSulfurane.svg|[[Chemistry:Martin's sulfurane|Martin's sulfurane]] with a see-saw structure, like that of SF<sub>4</sub><ref name = bis>{{OrgSynth|first1=J. C. |last1=Martin |first2= R. J. |last2=Arhart |first3=J. A. |last3=Franz |first4=E. F. |last4=Perozzi |first5=L. J. |last5=Kaplan|title= Bis[2,2,2-trifluoro-1-phenyl-1-(trifluoromethyl)ethoxy]diphenyl sulfurane|volume=57|page=22|date=1977|doi=10.15227/orgsyn.057.0022}}</ref></gallery>
===Sulfides===
{{main|Chemistry:Sulfide (organic)}}
Sulfides, formerly known as thioethers, are characterized by C−S−C [[Chemistry:Chemical bond|bond]]s<ref>Organic chemistry IUPAC Blue Book. Rules C-5: Compounds Containing Bivalent Sulfur http://www.acdlabs.com/iupac/nomenclature/79/r79_25.htm</ref><ref>Organic chemistry IUPAC Blue Book. Recommendation R-5.7.1.3.4 Thiocarboxylic and thiocarbonic acids.[https://web.archive.org/web/19980202070846/http://www.acdlabs.com/iupac/nomenclature/93/r93_480.htm]</ref> Relative to C−C bonds, C−S bonds are both longer, because sulfur atoms are larger than carbon atoms, and about 10% weaker. Representative [[Bond length|bond length]]s in sulfur compounds are 183&nbsp;pm for the S−C single bond in [[Chemistry:Methanethiol|methanethiol]] and 173&nbsp;pm in [[Chemistry:Thiophene|thiophene]]. The C−S bond dissociation energy for thiomethane is 89&nbsp;kcal/mol (370&nbsp;kJ/mol) compared to methane's 100&nbsp;kcal/mol (420&nbsp;kJ/mol) and when hydrogen is replaced by a methyl group the energy decreases to 73&nbsp;kcal/mol (305&nbsp;kJ/mol).<ref>{{cite book|title=Handbook of Chemistry and Physics|date=June 2000 |edition=81st|publisher=CRC Press|isbn=0-8493-0481-4}}</ref> The single [[Chemistry:Carbon–oxygen bond|carbon to oxygen bond]] is shorter than that of the C−C bond. The bond dissociation energies for [[Chemistry:Dimethyl sulfide|dimethyl sulfide]] and [[Chemistry:Dimethyl ether|dimethyl ether]] are respectively 73 and 77&nbsp;kcal/mol (305 and 322&nbsp;kJ/mol).

Sulfides are typically prepared by [[Chemistry:Alkylation|alkylation]] of thiols. Alkylating agents include not only alkyl halides, but also epoxides, aziridines, and Michael acceptors.<ref name=Enders>{{cite journal |doi=10.1021/cr500235v |title=Organocatalytic Carbon–Sulfur Bond-Forming Reactions |year=2014 |last1=Chauhan |first1=Pankaj |last2=Mahajan |first2=Suruchi |last3=Enders |first3=Dieter |journal=Chemical Reviews |volume=114 |issue=18 |pages=8807–8864 |pmid=25144663 }}</ref>

They can also be prepared via the [[Chemistry:Pummerer rearrangement|Pummerer rearrangement]]. 

In the Ferrario reaction, phenyl ether is converted to ''phenoxathiin'' by action of elemental sulfur and [[Chemistry:Aluminium chloride|aluminium chloride]].<ref>{{OrgSynth|title=Phenoxthin [Phenoxathiin]|last1=Suter|first1=C. M.|last2=Maxwell|first2=Charles E.|volume=18|page=64|year=1938|doi=10.15227/orgsyn.018.0064}}</ref>

:[[File:Ferrario reaction.svg|400px|Ferrario reaction]]

[[Chemistry:Thioacetal|Thioacetal]]s and [[Chemistry:Thioketal|thioketal]]s feature C−S−C−S−C bond sequence. They represent a subclass of sulfides. The thioacetals are useful in "[[Chemistry:Umpolung|umpolung]]" of carbonyl groups. Thioacetals and thioketals can also be used to protect a carbonyl group in organic syntheses.

The above classes of sulfur compounds also exist in saturated and unsaturated heterocyclic structures, often in combination with other heteroatoms, as illustrated by [[Chemistry:Thiirane|thiirane]]s, [[Chemistry:Thiirene|thiirene]]s, [[Chemistry:Thietane|thietane]]s, [[Chemistry:Thiete|thiete]]s, [[Chemistry:Dithietane|dithietane]]s, thiolanes, [[Chemistry:Thiane|thiane]]s, [[Chemistry:Dithiane|dithiane]]s, [[Chemistry:Thiepane|thiepane]]s, [[Chemistry:Thiepine|thiepine]]s, [[Chemistry:Thiazole|thiazole]]s, [[Chemistry:Isothiazole|isothiazole]]s, and [[Chemistry:Thiophene|thiophene]]s, among others. The latter three compounds represent a special class of sulfur-containing heterocycles that are aromatic. The resonance stabilization of [[Chemistry:Thiophene|thiophene]] is 29&nbsp;kcal/mol (121&nbsp;kJ/mol) compared to 20&nbsp;kcal/mol (84&nbsp;kJ/mol) for the oxygen analogue [[Chemistry:Furan|furan]]. The reason for this difference is the higher [[Chemistry:Electronegativity|electronegativity]] for oxygen drawing away electrons to itself at the expense of the aromatic ring current. Yet as an aromatic [[Chemistry:Substituent|substituent]] the thio group is less electron-releasing than the alkoxy group. [[Chemistry:Dibenzothiophene|Dibenzothiophene]]s (see drawing), tricyclic heterocycles consisting of two benzene rings fused to a central thiophene ring, occurs widely in heavier fractions of petroleum.

===Thiols, disulfides, polysulfides===
[[Chemistry:Thiol|Thiol]] groups contain the functionality R−SH. Thiols are structurally similar to the [[Chemistry:Alcohol|alcohol]] group, but these functionalities are very different in their chemical properties. Thiols are more [[Chemistry:Nucleophile|nucleophilic]], more acidic, and more readily oxidized. This acidity can differ by 5 p''K''<sub>a</sub> units.<ref>{{cite book|first=R. J.|last=Cremlyn|title=An Introduction to Organosulfur Chemistry|publisher=John Wiley and Sons|location=Chichester|date=1996|isbn=0-471-95512-4}}</ref>

The difference in [[Chemistry:Electronegativity|electronegativity]] between sulfur (2.58) and hydrogen (2.20) is small and therefore hydrogen bonding in thiols is not prominent. Aliphatic thiols form [[Physics:Monolayer|monolayer]]s on [[Chemistry:Gold|gold]], which are topical in [[Engineering:Nanotechnology|nanotechnology]].

Certain aromatic thiols can be accessed through a [[Chemistry:Herz reaction|Herz reaction]].

Disulfides R−S−S−R with a covalent sulfur to sulfur bond are important for [[Chemistry:Cross-link|crosslinking]]: in [[Biology:Biochemistry|biochemistry]] for the folding and stability of some proteins and in [[Chemistry:Polymer chemistry|polymer chemistry]] for the crosslinking of rubber.

Longer sulfur chains are also known, such as in the natural product [[Chemistry:Varacin|varacin]] which contains an unusual pentathiepin ring (5-sulfur chain cyclised onto a benzene ring).

===Thioesters===
[[Biology:Thioester|Thioester]]s have general structure R−C(O)−S−R. They are related to regular esters (R−C(O)−O−R) but are more susceptible to hydrolysis and related reactions.  Thioesters are prominent in biochemistry, especially in [[Chemistry:Fatty acid|fatty acid]] synthesis.

===Sulfoxides, sulfones and thiosulfinates===
A [[Chemistry:Sulfoxide|sulfoxide]], R−S(O)−R, is the ''S''-oxide of a sulfide ("sulfide oxide"), a [[Chemistry:Sulfone|sulfone]], R−S(O)<sub>2</sub>−R, is the ''S'',''S''-dioxide of a sulfide, a [[Chemistry:Thiosulfinate|thiosulfinate]], R−S(O)−S−R, is the ''S''-oxide of a disulfide, and a thiosulfonate, R−S(O)<sub>2</sub>−S−R, is the ''S'',''S''-dioxide of a disulfide. All of these compounds are well known with extensive chemistry, e.g., [[Chemistry:Dimethyl sulfoxide|dimethyl sulfoxide]], dimethyl sulfone, and [[Chemistry:Allicin|allicin]] (see drawing).

===Sulfimides, sulfoximides, sulfonediimines===
[[Chemistry:Sulfilimine|Sulfimides]] (also called a sulfilimines) are sulfur–nitrogen compounds of structure R<sub>2</sub>S=NR′, the nitrogen analog of sulfoxides. They are of interest in part due to their pharmacological properties. When two different R groups are attached to sulfur, sulfimides are chiral. Sulfimides form stable α-carbanions.<ref>{{cite encyclopedia|last1=García Ruano |first1=J. L. |last2=Cid |first2=M. B. |last3=Martín Castro |first3=A. M. |last4= Alemán|first4= J. | editor-last = Kambe|editor-first= N. |title=Acyclic ''S'',''S''-Dialkylsulfimides |encyclopedia=Science of Synthesis|publisher=Thieme |year=2008 |volume=39 |pages=352–375|isbn = 978-1-58890-530-7}}</ref>

Sulfoximides (also called sulfoximines) are tetracoordinate sulfur–nitrogen compounds, isoelectronic with sulfones, in which one oxygen atom of the sulfone is replaced by a substituted nitrogen atom, e.g., R<sub>2</sub>S(O)=NR′. When two different R groups are attached to sulfur, sulfoximides are chiral. Much of the interest in this class of compounds is derived from the discovery that methionine sulfoximide (methionine sulfoximine) is an inhibitor of [[Biology:Glutamine synthetase|glutamine synthetase]].<ref>{{cite encyclopedia|last1=Drabowicz |first1=J. |last2=Lewkowski|first2= J. |last3=Kudelska|first3= W. |last4= Girek|first4= T. | editor-last = Kambe|editor-first= N. |title=''S'',''S''-Dialkylsulfoximides |encyclopedia=Science of Synthesis|publisher=Thieme |year=2008 |volume=39 |pages=154–173|isbn = 978-1-58890-530-7}}</ref>

[[Chemistry:Sulfur diimide|Sulfonediimines]] (also called sulfodiimines, sulfodiimides or sulfonediimides) are tetracoordinate sulfur–nitrogen compounds, isoelectronic with sulfones, in which both oxygen atoms of the sulfone are replaced by a substituted nitrogen atom, e.g., R<sub>2</sub>S(=NR′)<sub>2</sub>. They are of interest because of their biological activity and as building blocks for heterocycle synthesis.<ref>{{cite encyclopedia|last1=Drabowicz |first1=J. |last2=Lewkowski|first2= J. |last3=Kudelska|first3= W. |last4= Girek|first4= T. | editor-last = Kambe|editor-first= N. |title=''S'',''S''-Dialkylsulfonediimines |encyclopedia=Science of Synthesis|publisher=Thieme |year=2008 |volume=39 |pages=173–180|isbn = 978-1-58890-530-7}}</ref>

===''S''-Nitrosothiols===
[[Chemistry:S-Nitrosothiol|''S''-Nitrosothiols]], also known as thionitrites, are compounds containing a nitroso group attached to the sulfur atom of a thiol, e.g. R−S−N=O. They have received considerable attention in biochemistry because they serve as donors of the nitrosonium ion, NO<sup>+</sup>, and nitric oxide, NO, which may serve as signaling molecules in living systems, especially related to vasodilation.<ref>{{Cite journal|last1=Zhang |first1=Y. |last2=Hogg |first2=N. |title=''S''-Nitrosothiols: cellular formation and transport|journal=Free Radic. Biol. Med.|year= 2005| volume =38|pages=831–838|doi=10.1016/j.freeradbiomed.2004.12.016|issue=7|pmid=15749378}}</ref>

===Sulfur halides===
A wide range of organosulfur compounds are known which contain one or more [[Chemistry:Halogen|halogen]] atom ("X" in the chemical formulas that follow) bonded to a single sulfur atom, e.g.: sulfenyl halides, RSX; [[Chemistry:Sulfinyl halide|sulfinyl halide]]s, RS(O)X; [[Chemistry:Sulfonyl halide|sulfonyl halide]]s, RSO<sub>2</sub>X; alkyl and arylsulfur trichlorides, RSCl<sub>3</sub> and trifluorides, RSF<sub>3</sub>;<ref>{{cite encyclopedia|last1=Braverman |first1=S. |last2=Cherkinsky|first2= M. |last3=Levinger|first3= S.| editor-last = Kambe|editor-first= N. |title=Alkylsulfur Trihalides |encyclopedia=Science of Synthesis|publisher=Thieme |year=2008 |volume=39 |pages=187–188|isbn = 978-1-58890-530-7}}</ref> and alkyl and arylsulfur pentafluorides, RSF<sub>5</sub>.<ref>{{cite journal|title=Arylsulfur Pentafluorides|last=Sheppard|first=W. A.|journal=J. Am. Chem. Soc.|date=1962|volume=84|issue=16|pages=3064–3072|doi=10.1021/ja00875a006}}</ref> Less well known are dialkylsulfur tetrahalides, mainly represented by the tetrafluorides, e.g., R<sub>2</sub>SF<sub>4</sub>.<ref>{{cite encyclopedia|last1=Drabowicz |first1=J. |last2=Lewkowski|first2 =J. |last3=Kudelska|first3= W. |last4= Girek|first4= T.| editor-last = Kambe|editor-first= N. |title=Dialkylsulfur Tetrahalides |encyclopedia=Science of Synthesis|publisher=Thieme |year=2008 |volume=39 |pages=123–124|isbn = 978-1-58890-530-7}}</ref>

===Thioketones, thioaldehydes, and related compounds===
Compounds with [[Chemistry:Double bond|double bond]]s between carbon and sulfur are relatively uncommon, but include the important compounds [[Chemistry:Carbon disulfide|carbon disulfide]], [[Chemistry:Carbonyl sulfide|carbonyl sulfide]], and [[Chemistry:Thiophosgene|thiophosgene]]. [[Chemistry:Thioketone|Thioketone]]s (RC(=S)R′) are uncommon with alkyl substituents, but one example is [[Chemistry:Thiobenzophenone|thiobenzophenone]]. Thioaldehydes are rarer still, reflecting their lack of steric protection ("thioformaldehyde" exists as a cyclic trimer). [[Chemistry:Thioamide|Thioamide]]s, with the formula R<sub>1</sub>C(=S)N(R<sub>2</sub>)R<sub>3</sub> are more common. They are typically prepared by the reaction of amides with [[Chemistry:Lawesson's reagent|Lawesson's reagent]]. [[Chemistry:Isothiocyanate|Isothiocyanate]]s, with formula R−N=C=S, are found naturally. Vegetable foods with characteristic flavors due to isothiocyanates include [[Biology:Wasabi|wasabi]], [[Biology:Horseradish|horseradish]], mustard, [[Biology:Radish|radish]], [[Biology:Brussels sprout|Brussels sprout]]s, [[Biology:Watercress|watercress]], [[Biology:Tropaeolum|nasturtiums]], and [[Biology:Caper|caper]]s.

====''S''-Oxides and ''S'',''S''-dioxides of thiocarbonyl compounds====
The ''S''-oxides of thiocarbonyl compounds are known as thiocarbonyl ''S''-oxides: (R<sub>2</sub>C=S=O, and thiocarbonyl ''S'',''S''-dioxides or [[Chemistry:Sulfene|sulfene]]s, R<sub>2</sub>C=SO<sub>2</sub>). The thione ''S''-oxides have also been known as [[Chemistry:Sulfine|sulfine]]s, and while IUPAC considers this term obsolete,<ref>{{GoldBookRef|title=sulfines| file = S06108}}</ref> the name persists in the literature.<ref>{{cite journal |last1=McCaw |first1=Patrick G. |last2=Buckley |first2=Naomi M. |last3=Collins |first3=Stuart G. |last4=Maguire |first4=Anita R. |title=Generation, Reactivity and Uses of Sulfines in Organic Synthesis |journal=European Journal of Organic Chemistry |date=March 2016 |volume=2016 |issue=9 |pages=1630–1650 |doi=10.1002/ejoc.201501538}}</ref> These compounds are well known with extensive chemistry.<ref>{{cite journal |last1=Opitz |first1=G. |title=Sulfines and Sulfenes– theS-Oxides andS,S-Dioxides of Thioaldehydes and Thioketones |journal=Angewandte Chemie International Edition in English |date=February 1967 |volume=6 |issue=2 |pages=107–123 |doi=10.1002/anie.196701071}}</ref><ref>{{cite journal |last1=Zwanenburg |first1=Binne |title=Sulfine Chemistry |journal=Phosphorus, Sulfur, and Silicon and the Related Elements |date=May 1989 |volume=43 |issue=1–2 |pages=1–24 |doi=10.1080/10426508908040276}}</ref> Examples include ''syn''-propanethial-''S''-oxide and [[Chemistry:Sulfene|sulfene]].

====Triple bonds between carbon and sulfur====
Triple bonds between sulfur and carbon in sulfaalkynes are rare and can be found in [[Chemistry:Carbon monosulfide|carbon monosulfide]] (CS) <ref>{{Cite journal| doi = 10.1021/cr00084a003| title = Carbon monosulfide: a review| year = 1988| last1 = Moltzen | first1 = E. K.| last2 = Klabunde | first2 = K. J.| last3 = Senning | first3 = A.| journal = Chem. Rev.| volume = 88| issue = 2| page = 391 }}</ref> and have been suggested for the compounds F<sub>3</sub>CCSF<sub>3</sub><ref>{{Cite journal| doi = 10.1002/anie.198401501| title = Trifluoroethylidynesulfur Trifluoride, F<sub>3</sub>C−C≡SF<sub>3</sub>| year = 1984| last1 = Pötter | first1 = B.| last2 = Seppelt | first2 = K.| journal = Angew. Chem. Int. Ed. Engl.| volume = 23| issue = 2| page = 150 }}</ref><ref>{{Cite journal| doi = 10.1021/ja00050a027| title = (Trifluoroethylidyne)sulfur trifluoride, F<sub>3</sub>CC≡SF<sub>3</sub>: two solid-state structures and reactivity as a carbene| year = 1992| last1 = Buschmann | first1 = J.| last2 = Damerius | first2 = R.| last3 = Gerhardt | first3 = R.| last4 = Lentz | first4 = D.| last5 = Luger | first5 = P.| last6 = Marschall | first6 = R.| last7 = Preugschat | first7 = D.| last8 = Seppelt | first8 = K.| last9 = Simon | first9 = A.| journal = J. Am. Chem. Soc.| volume = 114| issue = 24| page = 9465}}</ref> and F<sub>5</sub>SCSF<sub>3</sub>.<ref>{{Cite journal| doi = 10.1002/anie.198815341| title = The SF<sub>5</sub>-Unit as Steric Protecting Group; Synthesis and Structure of F<sub>5</sub>S−C≡SF<sub>3</sub>| year = 1988| last1 = Gerhardt | first1 = R.| last2 = Gerlbig | first2 = T.| last3 = Buschamann | first3 = J.| last4 = Luger | first4 = P.| last5 = Seppelt | first5 = K.| journal = Angew. Chem. Int. Ed. Engl.| volume = 27| issue = 11| page = 1534 }}</ref> The compound HCSOH is also represented as having a formal triple bond.<ref>{{Cite journal| title = A formal carbon–sulfur triple bond: H−C≡S−O−H. | first4 = G.| last4 = Mloston| volume = 48| issue = 43| journal = Angew. Chem. Int. Ed. Engl.| pages = 8133–8136 | first3 = J.| last3 = Romanski| year = 2009| pmid = 19768827| last1 = Schreiner | first1 = P. | first2 = H.| last2 = Reisenauer| doi = 10.1002/anie.200903969 }}</ref>

===Thiocarboxylic acids and thioamides===
[[Chemistry:Thiocarboxylic acid|Thiocarboxylic acid]]s (RC(O)SH) and dithiocarboxylic acids (RC(S)SH) are well known. They are structurally similar to carboxylic acids but more acidic. Thioamides are analogous to amides.

===Sulfonic, sulfinic and sulfenic acids, esters, amides, and related compounds===
[[Chemistry:Sulfonic acid|Sulfonic acid]]s have functionality R−S(=O)<sub>2</sub>−OH.<ref>Organic chemistry IUPAC Blue Book. C-6 Sulfur Halides, Sulfoxides, Sulfones, and Sulfur Acids and Their Derivatives http://www.acdlabs.com/iupac/nomenclature/79/r79_26.htm</ref> They are strong acids that are typically soluble in organic solvents. Sulfonic acids like trifluoromethanesulfonic acid is a frequently used reagent in [[Chemistry:Organic chemistry|organic chemistry]]. [[Chemistry:Sulfinic acid|Sulfinic acid]]s have functionality R−S(O)−OH while [[Chemistry:Sulfenic acid|sulfenic acid]]s have functionality R−S−OH. In the series sulfonic—sulfinic—sulfenic acids, both the acid strength and stability diminish in that order.<ref>{{cite encyclopedia|last1=Braverman |first1=S. |last2=Cherkinsky|first2= M.| editor-last = Kambe|editor-first= N. |last3=Levinger|first3= S. |title=Alkanesulfinic Acids and Salts |encyclopedia=Science of Synthesis|publisher=Thieme |year=2008 |volume=39 |pages=196–211|isbn = 978-1-58890-530-7}}</ref><ref>{{cite encyclopedia|last1=Drabowicz|first1= J. |last2=Kiełbasiński|first2= P. |last3=Łyżwa|first3= P. |last4=Zając|first4= A. |last5=Mikołajczyk|first5= M. | editor-last = Kambe|editor-first= N. | year = 2008 | title = Alkanesulfenic Acids | encyclopedia=Science of Synthesis|publisher=Thieme | volume = 39 | pages = 550–557 | isbn = 978-1-58890-530-7}}</ref> Sulfonamides, [[Chemistry:Sulfinamide|sulfinamide]]s and [[Chemistry:Sulfenamide|sulfenamide]]s, with formulas R−SO<sub>2</sub>NR′<sub>2</sub>, R−S(O)NR′<sub>2</sub>, and R−SNR′<sub>2</sub>, respectively, each have a rich chemistry. For example, sulfa drugs are sulfonamides derived from [[Chemistry:Aromatic sulfonation|aromatic sulfonation]]. Chiral sulfinamides are used in asymmetric synthesis, while sulfenamides are used extensively in the vulcanization process to assist cross-linking. [[Chemistry:Thiocyanate|Thiocyanate]]s, R−S−CN, are related to sulfenyl halides and esters in terms of reactivity.

===Sulfonium, oxosulfonium and related salts===
A sulfonium ion is a positively charged ion featuring three organic substituents attached to sulfur, with the formula [R<sub>3</sub>S]<sup>+</sup>. Together with their negatively charged counterpart, the anion, the compounds are called sulfonium salts. An oxosulfonium ion is a positively charged ion featuring three organic substituents and an oxygen attached to sulfur, with the formula [R<sub>3</sub>S=O]<sup>+</sup>. Together with their negatively charged counterpart, the anion, the compounds are called oxosulfonium salts. Related species include alkoxysulfonium and chlorosulfonium ions, [R<sub>2</sub>SOR]<sup>+</sup> and [R<sub>2</sub>SCl]<sup>+</sup>, respectively.

===Sulfonium, oxosulfonium and thiocarbonyl ylides===
Deprotonation of sulfonium and oxosulfonium salts affords [[Chemistry:Ylide|ylide]]s, of structure R<sub>2</sub>S<sup>+</sup>−C<sup>−</sup>−R′<sub>2</sub> and R<sub>2</sub>S(O)<sup>+</sup>−C<sup>−</sup>−R′<sub>2</sub>. While sulfonium ylides, for instance in the [[Chemistry:Johnson–Corey–Chaykovsky reaction|Johnson–Corey–Chaykovsky reaction]] used to synthesize [[Chemistry:Epoxide|epoxide]]s, are sometimes drawn with a C=S double bond, e.g., R<sub>2</sub>S=CR′<sub>2</sub>, the ylidic carbon–sulfur bond is highly polarized and is better described as being ionic. Sulfonium ylides are key intermediates in the synthetically useful [[Chemistry:Stevens rearrangement|Stevens rearrangement]]. Thiocarbonyl ylides (RR′C=S<sup>+</sup>−C<sup>−</sup>−RR′) can form by ring-opening of [[Chemistry:Thiirane|thiirane]]s, photocyclization of aryl vinyl sulfides,<ref>{{cite journal|title=Thiocarbonyl ylides. Photogeneration, rearrangement, and cycloaddition reactions|last1=Schultz|first1=A. G.|last2=DeTar|first2=M. B.|journal=J. Am. Chem. Soc.|date=1976|volume=98|issue=12|pages=3564–3572|doi=10.1021/ja00428a029}}</ref> as well as by other processes.

===Sulfuranes and persulfuranes===
'''Sulfuranes''' are relatively specialized functional group that feature tetravalent sulfur, with the formula SR<sub>4</sub><ref name="bis" /> Likewise, '''persulfuranes''' feature hexavalent SR<sub>6</sub>.

One of the few all-carbon persulfuranes has two methyl and two [[Chemistry:Biphenyl|biphenyl]]ene [[Chemistry:Ligand|ligand]]s:<ref>{{cite journal|title=Isolation and Molecular Structure of the Organo-persulfuranes [12-S-6(C6)]|last1=Sato|first1=S.|last2=Matsunaga|first2=K.|last3=Horn|first3=E.|last4=Furukawa|first4=N.|last5=Nabeshima|first5=T.|journal=J. Am. Chem. Soc.|date=2006|volume=128|issue=21|pages=6778–6779|doi=10.1021/ja060497y|pmid=16719444}}</ref>
:[[File:AllCarbonPersulfurane.svg|500px|All-carbon persulfurane]]

It is prepared from the corresponding sulfurane '''1''' with [[Chemistry:Xenon difluoride|xenon difluoride]] / [[Chemistry:Boron trifluoride|boron trifluoride]] in [[Chemistry:Acetonitrile|acetonitrile]] to the sulfuranyl dication '''2''' followed by reaction with [[Chemistry:Methyllithium|methyllithium]] in [[Chemistry:Tetrahydrofuran|tetrahydrofuran]] to (a stable) persulfurane '''3''' as the cis isomer. X-ray diffraction shows C−S [[Bond length|bond length]]s ranging between 189 and 193&nbsp;pm (longer than the standard bond length) with the central sulfur atom in a distorted [[Physics:Octahedral molecular geometry|octahedral molecular geometry]].

==Organosulfur compounds in nature==
A variety or organosulfur compounds occur in nature.  Most abundant are the amino acids [[Chemistry:Methionine|methionine]], [[Chemistry:Cysteine|cysteine]], and [[Chemistry:Cystine|cystine]].  The vitamins [[Chemistry:Biotin|biotin]] and [[Chemistry:Lipoic acid|lipoic acid]] contain sulfur heterocycles.  [[Chemistry:Glutathione|Glutathione]] is a pervasive [[Biology:Antioxidant|antioxidant]].<ref name=Enders/> [[Chemistry:Penicillin|Penicillin]] and [[Chemistry:Cephalosporin|cephalosporin]] are life-saving [[Chemistry:Antibiotic|antibiotic]]s, derived from fungi. [[Chemistry:Gliotoxin|Gliotoxin]] is a sulfur-containing [[Chemistry:Mycotoxin|mycotoxin]] produced by several species of fungi under investigation as an [[Biology:Antiviral drug|antiviral]] agent. 

===In fossil fuels===
Common organosulfur compounds present in petroleum fractions at the level of 200–500&nbsp;ppm. Common compounds are [[Chemistry:Thiophene|thiophene]]s, especially [[Chemistry:Dibenzothiophene|dibenzothiophene]]s. By the process of [[Chemistry:Hydrodesulfurization|hydrodesulfurization]] (HDS) in refineries, these compounds are removed as illustrated by the hydrogenolysis of thiophene:
{{chem2|C4H4S  +  8 H2  ->  C4H10  +  H2S}}

===Flavor and odor===
Compounds like [[Chemistry:Allicin|allicin]] and [[Chemistry:Ajoene|ajoene]] are responsible for the odor of [[Biology:Garlic|garlic]]. [[Chemistry:Lenthionine|Lenthionine]] contributes to the flavor of shiitake mushrooms. Volatile organosulfur compounds also contribute subtle flavor characteristics to wine, nuts, cheddar cheese, chocolate, coffee, and tropical fruit flavors.<ref>{{cite book|editor1-last=Qian|editor1-first= M. C.|editor2-last= Fan|editor2-first= X.|editor3-last= Mahattanatawee|editor3-first= K.|title=Volatile Sulfur Compounds in Food|series=ACS Symposium Series 1068|publisher=American Chemical Society |year=2011 |volume= 1068|isbn=978-0-8412-2616-6|doi=10.1021/bk-2011-1068}}</ref> Many of these natural products also have important medicinal properties such as preventing [[Biology:Platelet|platelet]] aggregation or fighting cancer.

Humans and other animals have an exquisitely sensitive sense of smell toward the [[Chemistry:Odor|odor]] of low-valent organosulfur compounds such as thiols, sulfides, and disulfides. Malodorous volatile thiols are protein-degradation products found in putrid food, so sensitive identification of these compounds is crucial to avoiding intoxication. Low-valent volatile sulfur compounds are also found in areas where oxygen levels in the air are low, posing a risk of suffocation. 

Copper is required for the highly sensitive detection of certain volatile thiols and related organosulfur compounds by olfactory receptors in mice. Whether humans, too, require copper for sensitive detection of thiols is not yet known.<ref>{{cite journal | last1 = Duan | first1 = X. | last2 = Block | first2 = E. | last3 = Li | first3 = Z. | last4 = Connelly | first4 = T. | last5 = Zhang | first5 = J. | last6 = Huang | first6 = Z. | last7 = Su | first7 = X. | last8 = Pan | first8 = Y. | last9 = Wu | first9 = L. | last10 = Chi | first10 = Q. | last11 = Thomas | first11 = S. | last12 = Zhang | first12 = S. | last13 = Ma | first13 = M. | last14 = Matsunami | first14 = H. | last15 = Chen | first15 = G.-Q. | last16 = Zhang | first16 = H. | title = Crucial role of copper in detection of metal-coordinating odorants. | journal = Proc. Natl. Acad. Sci. USA | date = 2012 | volume = 109 | issue = 9 | pages = 3492–3497 | doi=10.1073/pnas.1111297109|bibcode = 2012PNAS..109.3492D | pmid=22328155 | pmc=3295281| doi-access = free }}</ref>

== References ==
{{reflist|30em}}
{{ChemicalBondsToCarbon}}

[[Category:Organosulfur compounds| ]]
[[Category:Soil chemistry]]
[[Category:Foul-smelling chemicals]]

{{Sourceattribution|Organosulfur chemistry}}