In organic chemistry, a sulfoxide, also called a sulphoxide, is an organosulfur compound containing a sulfinyl (>SO) 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. [1]
Sulfoxides feature relatively short S–O distances. In DMSO, the S–O distance is 1.531 Å. The sulfur center is pyramidal; the sum of the angles at sulfur is about 306°. [3] Sulfoxides are generally represented with the structural formula R−S(=O)−R', where R and R' are organic groups. The bond between the sulfur and oxygen atoms is intermediate of a dative bond and a polarized double bond. [4] The double-bond resonance form implies 10 electrons around sulfur (10-S-3 in N-X-L notation). The double-bond character of the S−O bond may be accounted for by donation of electron density into C−S antibonding orbitals ("no-bond" resonance forms in valence-bond language). Nevertheless, due to its simplicity and lack of ambiguity, the IUPAC recommends use of the expanded octet double-bond structure to depict sulfoxides, rather than the dipolar structure or structures that invoke "no-bond" resonance contributors. [5] The S–O interaction has an electrostatic aspect, resulting in significant dipolar character, with negative charge centered on oxygen.
A lone pair of electrons resides on the sulfur atom, giving it tetrahedral electron-pair geometry and trigonal pyramidal shape (steric number 4 with one lone pair; see VSEPR theory). When the two organic residues are dissimilar, the sulfur atom is a chiral center, for example, in methyl phenyl sulfoxide. The energy barrier required to invert this stereocenter is sufficiently high that sulfoxides are optically stable near room temperature. That is, the rate of racemization is slow at room temperature. The enthalpy of activation for racemization is in the range 35 - 42 kcal/mol and the corresponding entropy of activation is -8 - +4 cal/mol-K. The barriers are lower for allylic and benzylic substituents. [6]
Sulfoxides are typically prepared by oxidation of sulfides, sometimes referred to as sulfoxidation. [7] hydrogen peroxide is a typical oxidant, but periodate has also been used. [8] In these oxidations, care is required to avoid over oxidation to form the sulfone. For example, dimethyl sulfide is oxidized to dimethyl sulfoxide and then further to dimethyl sulfone. Unsymmetrical sulfides are prochiral, thus their oxidation gives chiral sulfoxides. This process can be performed enantioselectively. [9] [10]
Symmetrical sulfoxides can be formed from a diorganylzinc compound and liquid sulfur dioxide. [11]
In addition to the oxidation routes, diaryl sulfoxides can be prepared by two Friedel–Crafts arylations of sulfur dioxide using an acid catalyst:
Both aryl sulfinyl chlorides and diaryl sulfoxides can be also prepared from arenes through reaction with thionyl chloride in the presence of Lewis acid catalysts such as BiCl3, Bi(OTf)3, LiClO4, or NaClO4. [12] [13]
Sulfoxides undergo deoxygenation to give sulfides. Typically metal complexes are used to catalyze the reaction, using hydrosilanes as the stoichiometric reductant. [14] The deoxygenation of dimethylsulfoxide is catalyzed by DMSO reductase, a molybdoenzyme: [15]
The α-CH groups of alkyl sulfoxides are susceptible to deprotonation by strong bases, such as sodium hydride: [16]
In the Pummerer rearrangement, alkyl sulfoxides react with acetic anhydride to give migration of the oxygen from sulfur to the adjacent carbon as an acetate ester. The first step of the reaction sequence involves the sulfoxide oxygen acting as a nucleophile:
Sulfoxide undergo thermal elimination via an Ei mechanism to yield vinyl alkenes and sulfenic acids. [17] [18]
The acids are powerful antioxidants, but lack long-term stability. [19] Some parent sulfoxides are therefore marketed as antioxidant polymer stabilisers. [20] Structures based on thiodipropionate esters are popular. [21] The reverse reaction is possible.
Sulfoxides, especially DMSO, form coordination complexes with transition metals. Depending on the hard-soft properties of the metal, the sulfoxide binds through either the sulfur or the oxygen atom. The latter is particularly common. [22]
DMSO is a widely used solvent.
The sulfoxide functional group occurs in several drugs. Notable is esomeprazole, the optically pure form of the proton-pump inhibitor omeprazole. Another commercially important sulfoxides include armodafinil.
Methionine sulfoxide forms from the amino acid methionine and its accumulation is associated with aging. The enzyme DMSO reductase catalyzes the interconversion of DMSO and dimethylsulfide.
Naturally-occurring chiral sulfoxides include alliin and ajoene.
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. These compounds contain a distinctive functional 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.
In organic chemistry, the Swern oxidation, named after Daniel Swern, is a chemical reaction whereby a primary or secondary alcohol is oxidized to an aldehyde or ketone using oxalyl chloride, dimethyl sulfoxide (DMSO) and an organic base, such as triethylamine. It is one of the many oxidation reactions commonly referred to as 'activated DMSO' oxidations. The reaction is known for its mild character and wide tolerance of functional groups.
Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula (CH3)2SO. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds and is miscible in a wide range of organic solvents as well as water. It has a relatively high boiling point. DMSO is metabolised to compounds that leave a garlic-like taste in the mouth after DMSO is absorbed by skin.
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.
In organic chemistry, a sulfone is a organosulfur compound containing a sulfonyl functional group attached to two carbon atoms. The central hexavalent sulfur atom is double-bonded to each of two oxygen atoms and has a single bond to each of two carbon atoms, usually in two separate hydrocarbon substituents.
Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur compound with the formula (CH3)2S. It is the simplest thioether and has a characteristic disagreeable odor. It is a flammable liquid that boils at 37 °C (99 °F). It is a component of the smell produced from cooking of certain vegetables 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.
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.
Organoselenium chemistry is the science exploring the properties and reactivity of organoselenium compounds, chemical compounds containing carbon-to-selenium chemical bonds. Selenium belongs with oxygen and sulfur to the group 16 elements or chalcogens, and similarities in chemistry are to be expected. Organoselenium compounds are found at trace levels in ambient waters, soils and sediments.
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, where the oxygen atom in the hydroxyl group (-OH) bonded to the aromatic ring in phenol 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.
The Corey–Kim oxidation is an oxidation reaction used to synthesize aldehydes and ketones from primary and secondary alcohols. It is named for American chemist and Nobel Laureate Elias James Corey and Korean-American chemist Choung Un Kim.
DMSO reductase is a molybdenum-containing enzyme that catalyzes reduction of dimethyl sulfoxide (DMSO) to dimethyl sulfide (DMS). This enzyme serves as the terminal reductase under anaerobic conditions in some bacteria, with DMSO being the terminal electron acceptor. During the course of the reaction, the oxygen atom in DMSO is transferred to molybdenum, and then reduced to water.
Sulfinic acids are oxoacids of sulfur with the structure RSO(OH). In these organosulfur compounds, sulfur is pyramidal.
Sodium methylsulfinylmethylide is the sodium salt of the conjugate base of dimethyl sulfoxide. This unusual salt has some uses in organic chemistry as a base and nucleophile.
In organosulfur chemistry, thiosulfinate is a functional group consisting of the linkage R-S(O)-S-R. Thiolsulfinates are also named as alkanethiosulfinic acid esters.
In organosulfur chemistry, sulfinamide is a functional group with the structure R−S(O)−NR2. This functionality is composed of a sulfur-carbon single bond, a sulfur-nitrogen single bond, and a sulfur-oxygen (S-O) bond. As a non-bonding electron pair is present on the sulfur, the sulfur atom is a stable stereogenic centre, and so these compounds are chiral. They are sometimes referred to as S-chiral sulfinamides. Sulfinamides are amides of sulfinic acid.
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, thermolabile, moisture-sensitive compounds, which are useful intermediates for preparation of other sufinyl derivatives such as sulfinamides, sulfinates, sulfoxides, and thiosulfinates. Unlike the sulfur atom in sulfonyl halides and sulfenyl halides, the sulfur atom in sulfinyl halides is chiral, as shown for methanesulfinyl chloride.
N-Sulfinyl imines are a class of imines bearing a sulfinyl group attached to nitrogen. These imines display useful stereoselectivity reactivity and due to the presence of the chiral electron withdrawing N-sulfinyl group. They allow 1,2-addition of organometallic reagents to imines. The N-sulfinyl group exerts powerful and predictable stereodirecting effects resulting in high levels of asymmetric induction. Racemization of the newly created carbon-nitrogen stereo center is prevented because anions are stabilized at nitrogen. The sulfinyl chiral auxiliary is readily removed by simple acid hydrolysis. The addition of organometallic reagents to N-sulfinyl imines is the most reliable and versatile method for the asymmetric synthesis of amine derivatives. These building blocks have been employed in the asymmetric synthesis of numerous biologically active compounds.
Sulfoxylic acid (H2SO2) (also known as hyposulfurous acid or sulfur dihydroxide) is an unstable oxoacid of sulfur in an intermediate oxidation state between hydrogen sulfide and dithionous acid. It consists of two hydroxy groups attached to a sulfur atom. Sulfoxylic acid contains sulfur in an oxidation state of +2. Sulfur monoxide (SO) can be considered as a theoretical anhydride for sulfoxylic acid, but it is not actually known to react with water.
A transition metal sulfoxide complex is a coordination complex containing one or more sulfoxide ligands. The inventory is large.
Diphenyl sulfide is an organosulfur compound with the chemical formula (C6H5)2S, often abbreviated as Ph2S, where Ph stands for phenyl. It is a colorless liquid with an unpleasant odor. Diphenyl sulfide is an aromatic sulfide. The molecule consists of two phenyl groups attached to a sulfur atom.
{{cite journal}}: CS1 maint: multiple names: authors list (link)| Authority control databases: National |
|---|
