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Organosulfur compounds are
organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
s that contain
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g.,
saccharin Saccharin (''aka'' saccharine, Sodium sacchari) is an artificial sweetener with effectively no nutritional value. It is about 550 times as sweet as sucrose but has a bitter or metallic aftertaste, especially at high concentrations. Saccharin ...
. Nature abounds with organosulfur compounds—sulfur is vital for life. Of the 20 common amino acids, two (
cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, s ...
and methionine) are organosulfur compounds, and the antibiotics
penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...
and
sulfa drugs Sulfonamide is a functional group (a part of a molecule) that is the basis of several groups of drugs, which are called sulphonamides, sulfa drugs or sulpha drugs. The original antibacterial sulfonamides are synthetic (nonantibiotic) antim ...
both contain sulfur. While sulfur-containing antibiotics save many lives,
sulfur mustard Mustard gas or sulfur mustard is a chemical compound belonging to a family of cytotoxic and blister agents known as mustard agents. The name ''mustard gas'' is technically incorrect: the substance, when dispersed, is often not actually a gas, b ...
is a deadly chemical warfare agent. Fossil fuels,
coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...
,
petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crude ...
, and
natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon ...
, which are derived from ancient organisms, necessarily contain organosulfur compounds,
the removal Cherokee removal, part of the Trail of Tears, refers to the forced relocation between 1836 and 1839 of an estimated 16,000 members of the Cherokee Nation (1794–1907), Cherokee Nation and 1,000–2,000 of Slavery among Native Americans in the Uni ...
of which is a major focus of
oil refineries An oil refinery or petroleum refinery is an industrial process plant where petroleum (crude oil) is transformed and refined into useful products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquef ...
. Sulfur shares the
chalcogen The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioa ...
group with
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...
,
selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and telluriu ...
, and
tellurium Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fo ...
, and it is expected that organosulfur compounds have similarities with carbon–oxygen, carbon–selenium, and carbon–tellurium compounds. A classical chemical test for the detection of sulfur compounds is the Carius halogen method.


Classes

Organosulfur compounds can be classified according to the sulfur-containing
functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the res ...
s, which are listed (approximately) in decreasing order of their occurrence. Image:R-allicin-2D-skeletal.svg, Allicin, the active flavor compound in crushed garlic Image:Cysteine.svg, (''R'')-
Cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, s ...
, an
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...
containing a thiol group Image:Methionin - Methionine.svg, Methionine, an
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...
containing a sulfide Image:Diphenyl disulfide.svg, Diphenyl disulfide, a representative disulfide Image:Dibenzothiophen - Dibenzothiophene.svg, Dibenzothiophene, a component of crude oil Image:Perfluorooctanesulfonic acid structure.svg,
Perfluorooctanesulfonic acid Perfluorooctanesulfonic acid (PFOS) ( conjugate base perfluorooctanesulfonate) is a chemical compound having an eight-carbon fluorocarbon chain and a sulfonic acid functional group and thus a perfluorosulfonic acid. It is an anthropogenic (man ...
, a controversial surfactant Image:Lipoic_acid.svg, Lipoic acid, an essential cofactor of four mitochondrial enzyme complexes. Image:Penicillin core.svg,
Penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...
core structure, where "R" is the variable group. image:Sulfanilamide-skeletal.svg,
Sulfanilamide Sulfanilamide (also spelled sulphanilamide) is a sulfonamide antibacterial drug. Chemically, it is an organic compound consisting of an aniline derivatized with a sulfonamide group. Powdered sulfanilamide was used by the Allies in World War II to ...
, a
sulfonamide In organic chemistry, the sulfonamide functional group (also spelled sulphonamide) is an organosulfur group with the structure . It consists of a sulfonyl group () connected to an amine group (). Relatively speaking this group is unreactiv ...
antibacterial An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...
, called a
sulfa drug Sulfonamide is a functional group (a part of a molecule) that is the basis of several groups of drugs, which are called sulphonamides, sulfa drugs or sulpha drugs. The original antibacterial sulfonamides are synthetic (nonantibiotic) antimi ...
. Image:Sulfur-mustard-2D-skeletal.svg,
Sulfur mustard Mustard gas or sulfur mustard is a chemical compound belonging to a family of cytotoxic and blister agents known as mustard agents. The name ''mustard gas'' is technically incorrect: the substance, when dispersed, is often not actually a gas, b ...
, a type of sulfide used as a chemical warfare agent. Image:MartinSulfurane.svg, Martin's sulfurane with a see-saw structure, like that of SF4


Sulfides

Sulfides, formerly known as thioethers, are characterized by C−S−C bonds 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 In molecular geometry, bond length or bond distance is defined as the average distance between nuclei of two bonded atoms in a molecule. It is a transferable property of a bond between atoms of fixed types, relatively independent of the rest ...
s in sulfur compounds are 183  pm for the S−C single bond in
methanethiol Methanethiol (also known as methyl mercaptan) is an organosulfur compound with the chemical formula . It is a colorless gas with a distinctive putrid smell. It is a natural substance found in the blood, brain and feces of animals (including huma ...
and 173 pm in thiophene. The C−S bond dissociation energy for thiomethane is 89 kcal/mol (370 kJ/mol) compared to methane's 100 kcal/mol (420 kJ/mol) and when hydrogen is replaced by a methyl group the energy decreases to 73 kcal/mol (305 kJ/mol). The single carbon to oxygen bond is shorter than that of the C−C bond. The bond dissociation energies for dimethyl sulfide and
dimethyl ether Dimethyl ether (DME; also known as methoxymethane) is the organic compound with the formula CH3OCH3, (sometimes ambiguously simplified to C2H6O as it is an isomer of ethanol). The simplest ether, it is a colorless gas that is a useful precurs ...
are respectively 73 and 77 kcal/mol (305 and 322 kJ/mol). Sulfides are typically prepared by
alkylation Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effectin ...
of thiols. They can also be prepared via the Pummerer rearrangement. In one named reaction called the Ferrario reaction
phenyl ether Diphenyl ether is the organic compound with the formula ( C6 H5)2 O. It is a colorless solid. This, the simplest diaryl ether, has a variety of niche applications. Synthesis and reactions Diphenyl ether and many of its properties were first rep ...
is converted to ''phenoxathiin'' by action of elemental sulfur and aluminium chloride. : Thioacetals and thioketals feature C−S−C−S−C bond sequence. They represent a subclass of sulfides. The thioacetals are useful in " 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 thiiranes, thiirenes, thietanes, thietes, dithietanes, thiolanes,
thiane Thiane is a heterocyclic compound and an organosulfur compound Organosulfur compounds are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, ...
s, dithianes,
thiepane Thiepane is the organosulfur compound with the formula (CH2)6S. Thiepanes are seven-membered ring heterocycles that contains sulfide. The parent thiepane has seldom been studied. A variety of derivatives are known. Hexathiathiepane (CAS RN 172 ...
s, thiepines,
thiazole Thiazole, or 1,3-thiazole, is a heterocyclic compound that contains both sulfur and nitrogen. The term 'thiazole' also refers to a large family of derivatives. Thiazole itself is a pale yellow liquid with a pyridine-like odor and the molecular fo ...
s, isothiazoles, and thiophenes, among others. The latter three compounds represent a special class of sulfur-containing heterocycles that are
aromatic In chemistry, aromaticity is a chemical property of cyclic (ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to sat ...
. The resonance stabilization of thiophene is 29 kcal/mol (121 kJ/mol) compared to 20 kcal/mol (84 kJ/mol) for the oxygen analogue furan. The reason for this difference is the higher
electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...
for oxygen drawing away electrons to itself at the expense of the aromatic ring current. Yet as an aromatic
substituent A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and '' functional group'', as well as '' ...
the thio group is less electron-releasing than the alkoxy group. Dibenzothiophenes (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

Thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl gro ...
groups contain the functionality R−SH. Thiols are structurally similar to the alcohol group, but these functionalities are very different in their chemical properties. Thiols are more
nucleophilic In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they a ...
, more acidic, and more readily oxidized. This acidity can differ by 5 p''K''a units. The difference in
electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...
between sulfur (2.58) and hydrogen (2.20) is small and therefore
hydrogen bonding In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing ...
in thiols is not prominent. Aliphatic thiols form monolayers on
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
, which are topical in
nanotechnology Nanotechnology, also shortened to nanotech, is the use of matter on an atomic, molecular, and supramolecular scale for industrial purposes. The earliest, widespread description of nanotechnology referred to the particular technological goal o ...
. Certain aromatic thiols can be accessed through a
Herz reaction The Herz reaction, named after the chemist Richard Herz, is the chemical conversion of an aniline-derivative (1) to a so-called Herz salt (2) with disulfur dichloride, followed by hydrolysis of this Herz salt (2) to the corresponding sodium thio ...
. Disulfides R−S−S−R with a covalent sulfur to sulfur bond are important for crosslinking: in
biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology ...
for the folding and stability of some proteins and in
polymer chemistry Polymer chemistry is a sub-discipline of chemistry that focuses on the structures of chemicals, chemical synthesis, and chemical and physical properties of polymers and macromolecules. The principles and methods used within polymer chemistry are ...
for the crosslinking of rubber. Longer sulfur chains are also known, such as in the natural product
varacin Varacin is a bicyclic organosulfur compound originally found in marine Ascidiacea from the ''Polycitor'' genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as we ...
which contains an unusual pentathiepin ring (5-sulfur chain cyclised onto a benzene ring).


Thioesters

Thioester In organic chemistry, thioesters are organosulfur compounds with the functional group . They are analogous to carboxylate esters () with the sulfur in the thioester playing the role of the linking oxygen in the carboxylate ester, as implied by ...
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
fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...
synthesis.


Sulfoxides, sulfones and thiosulfinates

A sulfoxide, R−S(O)−R, is the ''S''-oxide of a sulfide ("sulfide oxide"), a sulfone, R−S(O)2−R, is the ''S'',''S''-dioxide of a sulfide, a thiosulfinate, R−S(O)−S−R, is the ''S''-oxide of a disulfide, and a thiosulfonate, R−S(O)2−S−R, is the ''S'',''S''-dioxide of a disulfide. All of these compounds are well known with extensive chemistry, e.g.,
dimethyl sulfoxide Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula ( CH3)2. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds ...
, dimethyl sulfone, and allicin (see drawing).


Sulfimides, sulfoximides, sulfonediimines

Sulfimides (also called a sulfilimines) are sulfur–nitrogen compounds of structure R2S=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. 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., R2S(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 glutamine synthetase. 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., R2S(=NR′)2. They are of interest because of their biological activity and as building blocks for heterocycle synthesis.


''S''-Nitrosothiols

''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+, and nitric oxide, NO, which may serve as signaling molecules in living systems, especially related to vasodilation.


Sulfur halides

A wide range of organosulfur compounds are known which contain one or more halogen atom ("X" in the chemical formulas that follow) bonded to a single sulfur atom, e.g.: sulfenyl halides, RSX;
sulfinyl halide Sulfinyl halide have the general formula R−S(O)−X, where X is a halogen. They are intermediate in oxidation level between sulfenyl halides, R−S−X, and sulfonyl halides, R−SO2−X. The best known examples are sulfinyl chlorides, thermola ...
s, RS(O)X;
sulfonyl halide In inorganic chemistry, sulfonyl halide groups occur when a sulfonyl () functional group is singly bonded to a halogen atom. They have the general formula , where X is a halogen. The stability of sulfonyl halides decreases in the order fluorides ...
s, RSO2X; alkyl and arylsulfur trichlorides, RSCl3 and trifluorides, RSF3; and alkyl and arylsulfur pentafluorides, RSF5. Less well known are dialkylsulfur tetrahalides, mainly represented by the tetrafluorides, e.g., R2SF4.


Thioketones, thioaldehydes, and related compounds

Compounds with
double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...
s between carbon and sulfur are relatively uncommon, but include the important compounds
carbon disulfide Carbon disulfide (also spelled as carbon disulphide) is a neurotoxic, colorless, volatile liquid with the formula and structure . The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical ...
,
carbonyl sulfide 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 group double bonded to a sulfur atom. Carbonyl sulfide can be consid ...
, and
thiophosgene Thiophosgene is a red liquid with the formula . It is a molecule with trigonal planar geometry. There are two reactive C–Cl bonds that allow it to be used in diverse organic syntheses. Preparation is prepared in a two-step process from carbo ...
. Thioketones (RC(=S)R′) are uncommon with alkyl substituents, but one example is
thiobenzophenone Thiobenzophenone is an organosulfur compound with the formula (C6H5)2CS. It is the prototypical thioketone. Unlike other thioketones that tend to dimerize to form rings and polymers, thiobenzophenone is quite stable, although it photoxidizes in ...
.
Thioaldehyde In organic chemistry, a thial or thioaldehyde is a functional group which is similar to an aldehyde, , in which a sulfur (S) atom replaces the oxygen (O) atom of the aldehyde (R represents an alkyl or aryl group). Thioaldehydes are even m ...
s are rarer still, reflecting their lack of steric protection (" thioformaldehyde" exists as a cyclic trimer). Thioamides, with the formula R1C(=S)N(R2)R3 are more common. They are typically prepared by the reaction of amides with
Lawesson's reagent Lawesson's reagent (LR) is a chemical compound used in organic synthesis as a thiation agent. Lawesson's reagent was first made popular by Sven-Olov Lawesson, who did not, however, invent it. Lawesson's reagent was first made in 1956 during a sy ...
. Isothiocyanates, with formula R−N=C=S, are found naturally. Vegetable foods with characteristic flavors due to isothiocyanates include wasabi, horseradish, mustard, radish, Brussels sprouts, watercress, nasturtiums, and
caper ''Capparis spinosa'', the caper bush, also called Flinders rose, is a perennial plant that bears rounded, fleshy leaves and large white to pinkish-white flowers. The plant is best known for the edible flower buds (capers), used as a seasoning ...
s.


''S''-Oxides and ''S'',''S''-dioxides of thiocarbonyl compounds

The ''S''-oxides of thiocarbonyl compounds are known as thiocarbonyl ''S''-oxides: (R2C=S=O, and thiocarbonyl ''S'',''S''-dioxides or sulfenes, R2C=SO2). The thione ''S''-oxides have also been known as
sulfine Sulfinylmethane or sulfine is an organic compound with molecular formula H2CSO. It is the simplest sulfine. Sulfines are chemical compounds with the general structure XY=SO. IUPAC considers the term 'sulfine' obsolete, preferring instead thiocarb ...
s, and while
IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
considers this term obsolete, the name persists in the literature. These compounds are well known with extensive chemistry. Examples include ''syn''-propanethial-''S''-oxide and sulfene.


Triple bonds between carbon and sulfur

Triple bonds between sulfur and carbon in sulfaalkynes are rare and can be found in
carbon monosulfide Carbon monosulfide is a chemical compound with the formula CS. This diatomic molecule is the sulfur analogue of carbon monoxide, and is unstable as a solid or a liquid, but it has been observed as a gas both in the laboratory and in the interste ...
(CS) and have been suggested for the compounds F3CCSF3 and F5SCSF3. The compound HCSOH is also represented as having a formal triple bond.


Thiocarboxylic acids and thioamides

Thiocarboxylic acids (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

Sulfonic acids have functionality R−S(=O)2−OH. They are strong acids that are typically soluble in organic solvents. Sulfonic acids like trifluoromethanesulfonic acid is a frequently used reagent in
organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clay ...
. Sulfinic acids have functionality R−S(O)−OH while sulfenic acids have functionality R−S−OH. In the series sulfonic—sulfinic—sulfenic acids, both the acid strength and stability diminish in that order. Sulfonamides, sulfinamides and sulfenamides, with formulas R−SO2NR′2, R−S(O)NR′2, and R−SNR′2, respectively, each have a rich chemistry. For example,
sulfa drug Sulfonamide is a functional group (a part of a molecule) that is the basis of several groups of drugs, which are called sulphonamides, sulfa drugs or sulpha drugs. The original antibacterial sulfonamides are synthetic (nonantibiotic) antimi ...
s are sulfonamides derived from aromatic sulfonation. Chiral sulfinamides are used in asymmetric synthesis, while sulfenamides are used extensively in the vulcanization process to assist cross-linking. Thiocyanates, R−S−CN, are related to sulfenyl halides and esters in terms of reactivity.


Sulfonium, oxosulfonium and related salts

A
sulfonium ion In organic chemistry, a sulfonium ion, also known as sulphonium ion or sulfanium ion, is a positively-charged ion (a " cation") featuring three organic substituents attached to sulfur. These organosulfur compounds have the formula . Together wi ...
is a positively charged ion featuring three organic substituents attached to sulfur, with the formula 3Ssup>+. 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 3S=Osup>+. Together with their negatively charged counterpart, the anion, the compounds are called oxosulfonium salts. Related species include alkoxysulfonium and chlorosulfonium ions, 2SORsup>+ and 2SClsup>+, respectively.


Sulfonium, oxosulfonium and thiocarbonyl ylides

Deprotonation of sulfonium and oxosulfonium salts affords ylides, of structure R2S+−C−R′2 and R2S(O)+−C−R′2. While sulfonium ylides, for instance in the Johnson–Corey–Chaykovsky reaction used to synthesize
epoxide In organic chemistry, an epoxide is a cyclic ether () with a three-atom ring. This ring approximates an equilateral triangle, which makes it strained, and hence highly reactive, more so than other ethers. They are produced on a large scale ...
s, are sometimes drawn with a C=S double bond, e.g., R2S=CR′2, the ylidic carbon–sulfur bond is highly polarized and is better described as being ionic. Sulfonium ylides are key intermediates in the synthetically useful Stevens rearrangement. Thiocarbonyl ylides (RR′C=S+−C−RR′) can form by ring-opening of thiiranes, photocyclization of aryl vinyl sulfides, as well as by other processes.


Sulfuranes and persulfuranes

Sulfuranes are relatively specialized functional group that are tetravalent, hypervalent sulfur compounds, with the formula SR4 and likewise persulfuranes are
hexavalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Description The combining capacity, or affinity of an ...
SR6. All-carbon hexavalent complexes have been known for the heavier representatives of the
chalcogen The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioa ...
group, for instance the compound hexamethylpertellurane (Te(Me)6) was discovered in 1990 by reaction of tetramethyltellurium with xenon difluoride to TeF2(CH3)4 followed by reaction with dimethylzinc. The sulfur analogue hexamethylpersulfurane (S(CH3)6) has been predicted to be stable but has not been synthesized yet. The first ever all-carbon persulfurane actually synthesized in a laboratory has two methyl and two biphenyl
ligand In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ele ...
s: : It is prepared from the corresponding sulfurane 1 with xenon difluoride /
boron trifluoride Boron trifluoride is the inorganic compound with the formula BF3. This pungent, colourless, and toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds. Structure and bondin ...
in acetonitrile to the sulfuranyl dication 2 followed by reaction with methyllithium in
tetrahydrofuran Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water- miscible organic liquid with low viscosity. It is ...
to (a stable) persulfurane 3 as the cis isomer. X-ray diffraction shows C−S
bond length In molecular geometry, bond length or bond distance is defined as the average distance between nuclei of two bonded atoms in a molecule. It is a transferable property of a bond between atoms of fixed types, relatively independent of the rest ...
s ranging between 189 and 193 pm (longer than the standard bond length) with the central sulfur atom in a distorted
octahedral molecular geometry In chemistry, octahedral molecular geometry, also called square bipyramidal, describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. The ...
. Computer simulation suggests that these bonds are very polar with the negative charges residing on carbon.


Naturally occurring organosulfur compounds

Not all organosulfur compounds are foul-smelling pollutants.
Penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...
and
cephalosporin The cephalosporins (sg. ) are a class of β-lactam antibiotics originally derived from the fungus '' Acremonium'', which was previously known as ''Cephalosporium''. Together with cephamycins, they constitute a subgroup of β-lactam antibioti ...
are life-saving
antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, ...
s, derived from fungi. Gliotoxin is a sulfur-containing mycotoxin produced by several species of fungi under investigation as an antiviral agent. Compounds like allicin and ajoene are responsible for the odor of
garlic Garlic (''Allium sativum'') is a species of bulbous flowering plant in the genus ''Allium''. Its close relatives include the onion, shallot, leek, chive, Welsh onion and Chinese onion. It is native to South Asia, Central Asia and northe ...
, and lenthionine contributes to the flavor of shiitake mushrooms. Volatile organosulfur compounds also contribute subtle flavor characteristics to
wine Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different varieties of grapes and strains of yeasts are ...
, nuts,
cheddar cheese Cheddar cheese (or simply cheddar) is a natural cheese that is relatively hard, off-white (or orange if colourings such as annatto are added), and sometimes sharp-tasting. Cheddar originates from the English village of Cheddar in Somerset. C ...
,
chocolate Chocolate is a food made from roasted and ground cacao seed kernels that is available as a liquid, solid, or paste, either on its own or as a flavoring agent in other foods. Cacao has been consumed in some form since at least the Olmec civil ...
,
coffee Coffee is a drink prepared from roasted coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content. It is the most popular hot drink in the world. Seeds of ...
, and tropical fruit flavors. Many of these natural products also have important medicinal properties such as preventing
platelet Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby i ...
aggregation or fighting cancer.


In pollution

Most organic sulfur compounds in the environment are naturally occurring, as a consequence of the fact that sulfur is essential for life and two amino acids (cysteine and methionine) contain this element. Some organosulfur compounds in the environment, are generated as minor by-products of industrial processes such as the manufacture of plastics and tires. Selected smell-producing processes are organosulfur compounds produced by the coking of coal designed to drive out sulfurous compounds and other volatile impurities in order to produce 'clean carbon' ( coke), which is primarily used for steel production.


In fossil fuels

Odours An odor (American English) or odour (Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their sense ...
occur as well in
chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wit ...
processing of
coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...
or crude oil into precursor chemicals (feedstocks) for downstream industrial uses (e.g.
plastics Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
or pharmaceutical production) and the ubiquitous needs of petroleum distillation for
gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic ...
s, diesel, and other grades of
fuel oil Fuel oil is any of various fractions obtained from the distillation of petroleum (crude oil). Such oils include distillates (the lighter fractions) and residues (the heavier fractions). Fuel oils include heavy fuel oil, marine fuel oil (MFO), bu ...
s production. Organosulfur compounds might be understood as aromatic contaminants that need to be removed from natural gas before commercial uses, from exhaust stacks and exhaust vents before discharge. In this latter context, organosulfur compounds may be said to account for the pollutants in sulfurous acid rain, or equivalently, said to be pollutants within most common fossil fuels, especially
coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...
. The most common organosulfur compound present in all petroleum fractions is thiophene (C4H4S), a cyclic and aromatic liquid. In addition, the heavy fractions of oil contain benzothiophene (C8H6S, thianaphtene) and dibenzothiophene. Most of the last compounds are solids and smell like naphthalene. Many methylated, dimethyl, diethyl benzothiophene derivatives are present in diesel and fuel oils which make fuel oils very difficult to clean. All these heterocyclic sulfides account for 200–500 ppm of natural fuel, the heavily substituted dibenzothiophenes remain after HDS and account for 10–20 ppm. These molecules are also found in coals and they must be eliminated before consumption. Reduced molybdenum together with nickel is currently used to eliminate thiophenes from petroleum (HDS) due to its great affinity towards sulfur. In addition tungsten together with nickel and cobalt is used for hydrodesulfurization (HDS) in large refineries. The adsorption mechanism of thiophene to transition metals is proposed to occur through the π system, where the organosulfur compound lies almost parallel to the metal surface. Many researchers focus their efforts in optimizing the oxidation state of the transition metals for HDS, like Cu(I) and Ag(II) which together with Pd(0) have proven to be more specific for π bonding with thiophenes of all kinds.


Basis for odor

Humans and other animals have an exquisitely sensitive sense of smell toward the
odor An odor (American English) or odour (Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their sense ...
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. It has been found that 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.


References

{{Authority control Soil chemistry Foul-smelling chemicals