Organic sulfide

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General structure of a sulfide with the blue marked functional group. FunktionelleGruppen Thioether.svg
General structure of a sulfide with the blue marked functional group.

In organic chemistry, a sulfide (British English sulphide) or thioether is an organosulfur functional group with the connectivity R−S−R' as shown on right. Like many other sulfur-containing compounds, volatile sulfides have foul odors. [1] A sulfide is similar to an ether except that it contains a sulfur atom in place of the oxygen. The grouping of oxygen and sulfur in the periodic table suggests that the chemical properties of ethers and sulfides are somewhat similar, though the extent to which this is true in practice varies depending on the application.

Contents

Nomenclature

Sulfides are sometimes called thioethers, especially in the old literature. The two organic substituents are indicated by the prefixes. (CH3)2S is called dimethylsulfide. Some sulfides are named by modifying the common name for the corresponding ether. For example, C6H5SCH3 is methyl phenyl sulfide, but is more commonly called thioanisole, since its structure is related to that for anisole, C6H5OCH3.

The modern systematic nomenclature in chemistry for the trival name thioether is sulfane. [2]

Structure and properties

Sulfide is an angular functional group, the C–S–C angle approaching 90° The C–S bonds are about 180  pm. For the prototype, dimethylsulfide, the C-S-C angles is 99°, which is smaller than the C-O-C angle in ether (~110°). The C-S distance in dimethylsulfide is 1.81 Å. [3]

Sulfides are characterized by their strong odors, which are similar to thiol odor. This odor limits the applications of volatile sulfides. In terms of their physical properties they resemble ethers, but are less volatile, higher melting, and less hydrophilic. These properties follow from the polarizability of the divalent sulfur center, which is greater than that for oxygen in ethers.

Thiophenes

Thiophenes are a special class of sulfide-containing heterocyclic compounds. Because of their aromatic character, they are non-nucleophilic. The nonbonding electrons on sulfur are delocalized into the π-system. As a consequence, thiophene exhibits few properties expected for a sulfide – thiophene is non-nucleophilic at sulfur and, in fact, is sweet-smelling. Upon hydrogenation, thiophene gives tetrahydrothiophene, C4H8S, which indeed does behave as a typical sulfide.

Occurrence and applications

Sulfides are important in biology, notably in the amino acid methionine and the cofactor biotin. Petroleum contains many organosulfur compounds, including sulfides. Polyphenylene sulfide is a useful high temperature plastic. Coenzyme M, CH
3SCH
2CH
2SO−
3, is the precursor to methane (i.e. natural gas) via the process of methanogenesis.

Selected thioethers, from left: dimethylsulfide, coenzyme-M, the amino acid methionine, the vitamin biotin, and the engineering plastic polyphenylene sulfide. ThioetherGallery.png
Selected thioethers, from left: dimethylsulfide, coenzyme-M, the amino acid methionine, the vitamin biotin, and the engineering plastic polyphenylene sulfide.

Preparation

Sulfides are typically prepared by alkylation of thiols. Alkylating agents include not only alkyl halides, but also epoxides, aziridines, and Michael acceptors. [4]

RBr + HSR' → RSR' + HBr

Such reactions are usually conducted in the presence of a base, which converts the thiol into the more nucleophilic thiolate. [5] Analogously, the reaction of disulfides with organolithium reagents produces thioethers:

R3CLi + R1S-SR2 → R3CSR1 + R2SLi

Analogous reactions are known starting with Grignard reagents.

Alternatively, sulfides can be synthesized by the addition of a thiol to an alkene in the thiol-ene reaction:

R-CH=CH2 + H-SR' → R-CH2-CH2-S-R'

This reaction is often catalysed by free radicals produced from a photoinitiator. [6]

Sulfides can also be prepared by many other methods, such as the Pummerer rearrangement. Trialkysulfonium salts react with nucleophiles with a dialkyl sulfide as a leaving group:

Nu− + R3S+ → Nu-R + R2SR1

This reaction is exploited in biological systems as a means of transferring an alkyl group. For example, S-adenosylmethionine acts as a methylating agent in biological SN2 reactions.

An unusual but well tested method for the synthesis of thioethers involves addition of alkenes, especially ethylene across the S-Cl bond of sulfur dichloride. This method has been used in the production of bis(2-chloroethyl)sulfide, a mustard gas: [7]

SCl2 + 2 C2H4 → (ClC2H4)2S

Reactions

The Lewis basic lone pairs on sulfur dominate the sulfides' reactivity. Sulfides readily alkylate to stable sulfonium salts, such as trimethylsulfonium iodide: [8]

S(CH3)2 + CH3I → [S(CH3)3]+I−

Sulfides also oxidize easily to sulfoxides (R−S(=O)−R), which can themselves be further oxidized to sulfones (R−S(=O)2−R). Hydrogen peroxide is a typical oxidant—for example, with dimethyl sulfide (S(CH3)2): [9]

S(CH3)2 + H2O2 → OS(CH3)2 + H2O
OS(CH3)2 + H2O2 → O2S(CH3)2 + H2O

In analogy to their easy alkylation, sulfides bind to metals to form thioether complexes. Consequently Lewis acids do not decompose thioethers as they do ethers. [10] Sulfides are soft ligands, but their affinity for metals is lower than typical phosphines. Chelating thioethers are known, such as 1,4,7-trithiacyclononane.

Sulfides undergo hydrogenolysis in the presence of certain metals:

R-S-R' + 2 H2 → RH + R'H + H2S

Raney nickel is useful for stoichiometric reactions in organic synthesis [11] whereas molybdenum-based catalysts are used to "sweeten" petroleum fractions, in the process called hydrodesulfurization.

Unlike ethers, thioethers are stable in the presence of Grignard reagents. [12] The protons adjacent to the sulfur atom are labile, and can be deprotonated with strong bases. [13]

Related Research Articles

<span class="mw-page-title-main">Ether</span> Organic compounds made of alkyl/aryl groups bound to oxygen (R–O–R)

In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two organyl groups. They have the general formula R−O−R′, where R and R′ represent organyl groups. Ethers can again be classified into two varieties: if the organyl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers. A typical example of the first group is the solvent and anaesthetic diethyl ether, commonly referred to simply as "ether". Ethers are common in organic chemistry and even more prevalent in biochemistry, as they are common linkages in carbohydrates and lignin.

<span class="mw-page-title-main">Ester</span> Compound derived from an acid

In chemistry, an ester is a compound derived from an acid in which the hydrogen atom (H) of at least one acidic hydroxyl group of that acid is replaced by an organyl group. Analogues derived from oxygen replaced by other chalcogens belong to the ester category as well. According to some authors, organyl derivatives of acidic hydrogen of other acids are esters as well, but not according to the IUPAC.

<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">Alkylation</span> Transfer of an alkyl group from one molecule to another

Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene. Alkylating agents are reagents for effecting alkylation. Alkyl groups can also be removed in a process known as dealkylation. Alkylating agents are often classified according to their nucleophilic or electrophilic character. In oil refining contexts, alkylation refers to a particular alkylation of isobutane with olefins. For upgrading of petroleum, alkylation produces a premium blending stock for gasoline. In medicine, alkylation of DNA is used in chemotherapy to damage the DNA of cancer cells. Alkylation is accomplished with the class of drugs called alkylating antineoplastic agents.

The prefix thio-, when applied to a chemical, such as an ion, means that an oxygen atom in the compound has been replaced by a sulfur atom. This term is often used in organic chemistry. For example, from the word ether, referring to an oxygen-containing compound having the general chemical structure R−O−R′, where R and R′ are organic functional groups and O is an oxygen atom, comes the word thioether, which refers to an analogous compound with the general structure R−S−R′, where S is a sulfur atom covalently bonded to two organic groups. A chemical reaction involving the replacement of oxygen to sulfur is called thionation or thiation.

<span class="mw-page-title-main">Thiourea</span> Organosulfur compound (S=C(NH2)2)

Thiourea is an organosulfur compound with the formula SC(NH2)2 and the structure H2N−C(=S)−NH2. It is structurally similar to urea, except that the oxygen atom is replaced by a sulfur atom ; however, the properties of urea and thiourea differ significantly. Thiourea is a reagent in organic synthesis. Thioureas are a broad class of compounds with the general structure R2N−C(=S)−NR2.

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

Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to PPh3 or Ph3P. It is versatile compound that is widely used as a reagent in organic synthesis and as a ligand for transition metal complexes, including ones that serve as catalysts in organometallic chemistry. PPh3 exists as relatively air stable, colorless crystals at room temperature. It dissolves in non-polar organic solvents such as benzene and diethyl ether.

Organosulfur chemistry is the study of the properties and synthesis of organosulfur compounds, which are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature is abound with organosulfur compounds—sulfur is vital for life. Of the 20 common amino acids, two are organosulfur compounds, and the antibiotics penicillin and sulfa drugs both contain sulfur. While sulfur-containing antibiotics save many lives, sulfur mustard is a deadly chemical warfare agent. Fossil fuels, coal, petroleum, and natural gas, which are derived from ancient organisms, necessarily contain organosulfur compounds, the removal of which is a major focus of oil refineries.

<span class="mw-page-title-main">Sulfoxide</span> Organic compound containing a sulfinyl group (>SO)

In organic chemistry, a sulfoxide, also called a sulphoxide, is an organosulfur compound containing a sulfinyl functional group attached to two carbon atoms. It is a polar functional group. Sulfoxides are oxidized derivatives of sulfides. Examples of important sulfoxides are alliin, a precursor to the compound that gives freshly crushed garlic its aroma, and dimethyl sulfoxide (DMSO), a common solvent.

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

Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur compound with the formula (CH3)2S. The simplest thioether, it is a flammable liquid that boils at 37 °C (99 °F) and has a characteristic disagreeable odor. It is a component of the smell produced from cooking of certain vegetables, notably maize, cabbage, beetroot, and seafoods. It is also an indication of bacterial contamination in malt production and brewing. It is a breakdown product of dimethylsulfoniopropionate (DMSP), and is also produced by the bacterial metabolism of methanethiol.

<span class="mw-page-title-main">Enol ether</span> Class of chemical compounds

In organic chemistry an enol ether is an alkene with an alkoxy substituent. The general structure is R2C=CR-OR where R = H, alkyl or aryl. A common subfamily of enol ethers are vinyl ethers, with the formula ROCH=CH2. Important enol ethers include the reagent 3,4-dihydropyran and the monomers methyl vinyl ether and ethyl vinyl ether.

<span class="mw-page-title-main">Benzothiophene</span> Aromatic organic compound

Benzothiophene is an aromatic organic compound with a molecular formula C8H6S and an odor similar to naphthalene (mothballs). It occurs naturally as a constituent of petroleum-related deposits such as lignite tar. Benzothiophene has no household use. In addition to benzo[b]thiophene, a second isomer is known: benzo[c]thiophene.

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">Thiophenol</span> Chemical compound

Thiophenol is an organosulfur compound with the formula C6H5SH, sometimes abbreviated as PhSH. This foul-smelling colorless liquid is the simplest aromatic thiol. The chemical structures of thiophenol and its derivatives are analogous to phenols. An exception is the oxygen atom in the hydroxyl group (-OH) bonded to the aromatic ring is replaced by a sulfur atom. The prefix thio- implies a sulfur-containing compound and when used before a root word name for a compound which would normally contain an oxygen atom, in the case of 'thiol' that the alcohol oxygen atom is replaced by a sulfur atom.

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

Sulfur dichloride is the chemical compound with the formula SCl2. This cherry-red liquid is the simplest sulfur chloride and one of the most common, and it is used as a precursor to organosulfur compounds. It is a highly corrosive and toxic substance, and it reacts on contact with water to form chlorine-containing acids.

<span class="mw-page-title-main">Sulfenyl chloride</span> Chemical group (R–S–Cl)

In organosulfur chemistry, a sulfenyl chloride is a functional group with the connectivity R−S−Cl, where R is alkyl or aryl. Sulfenyl chlorides are reactive compounds that behave as sources of RS+. They are used in the formation of RS−N and RS−O bonds. According to IUPAC nomenclature they are named as alkyl thiohypochlorites, i.e. esters of thiohypochlorous acid.

<i>tert</i>-Butylthiol Chemical compound

tert-Butylthiol, also known as tert-butyl mercaptan (TBM), and abbreciated t-BuSH, is an organosulfur compound with the formula (CH3)3CSH. This thiol is used as an odorant for natural gas, which is otherwise odorless. It may also have been used as a flavoring agent.

In organic chemistry, thiocarboxylic acids or carbothioic acids are organosulfur compounds related to carboxylic acids by replacement of one of the oxygen atoms with a sulfur atom. Two tautomers are possible: a thione form and a thiol form. These are sometimes also referred to as "carbothioic O-acid" and "carbothioic S-acid" respectively. Of these the thiol form is most common.

Divinyl sulfide is the organosulfur compound with the formula S(CH=CH2)2. A colorless liquid with a faint odor, it is found in some species of Allium.

Chloromethyl methyl sulfide is the organosulfur compound with the formula ClCH2SCH3. In terms of functional groups, it is a thioether and an alkyl chloride. The compound is structurally related to sulfur mustards, i.e., it is a potentially hazardous alkylating agent. The compound finds some use in organic chemistry as a protecting group. In the presence of base, it converts carboxylic acids (RCO2H) to esters RCO2CH2SCH3. The compound is prepared by treatment of dimethylsulfide with sulfuryl chloride.

References

  1. ↑ Cremlyn, R. J. (1996). An Introduction to Organosulfur Chemistry. Chichester: John Wiley and Sons. ISBN   0-471-95512-4.
  2. ↑ Hellwinkel, Dieter (2012-12-06). Systematic Nomenclature of Organic Chemistry: A Directory to Comprehension and Application of its Basic Principles (1 ed.). Springer Science & Business Media. p. 131. ISBN   978-3-64256765-0. p. 131: Individual species of the genus thioether can again most uniformly be named as ...sulfane and ...sulfanyl derivatives, respectively (formerly: ...sulfides and ...thio derivatives, respectively). [...] Cyclic sulfides (thioethers) are treated as heterocycles, in the same way as their ether counterparts. Polysulfides substituted at both ends are named substitutively as ...polysulfanes (formerly: ...polysulfides). (230 pages)
  3. ↑ Iijima, T.; Tsuchiy, S.; Kimura, M. (1977). "The Molecular Structure of Dimethyl Sulfide". Bull. Chem. Soc. Jpn. 50 (10): 2564. doi: 10.1246/bcsj.50.2564 .
  4. ↑ Chauhan, Pankaj; Mahajan, Suruchi; Enders, Dieter (2014). "Organocatalytic Carbon–Sulfur Bond-Forming Reactions". Chemical Reviews. 114 (18): 8807–8864. doi:10.1021/cr500235v.
  5. ↑ D. Landini; F. Rolla (1978). "Sulfide Synthesis In Preparation Of Dialkyl And Alkyl Aryl Sulfides: Neopentyl Phenyl Sulfide". Org. Synth. 58: 143. doi:10.15227/orgsyn.058.0143.
  6. ↑ Hoyle, Charles E.; Bowman, Christopher N. (2010-02-22). "Thiol-Ene Click Chemistry". Angewandte Chemie International Edition. 49 (9): 1540–1573. doi:10.1002/anie.200903924. PMID   20166107.
  7. ↑ Stewart, Charles D. (2006). Weapons of mass casualties and terrorism response handbook. Boston: Jones and Bartlett. p. 47. ISBN   0-7637-2425-4.
  8. ↑ Brendsma & Arens 1967, p. 596.
  9. ↑ Brendsma & Arens 1967, p. 601.
  10. ↑ Brendsma & Arens 1967, p. 587.
  11. ↑ Brendsma & Arens 1967, pp. 576–578.
  12. ↑ Brendsma & Arens 1967, p. 581.
  13. ↑ Brendsma & Arens 1967, pp. 555–559.
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