Thiocarboxylic acid

Last updated
Thioic O-acid.svg
Thione form (carbothioic O-acid)
Thioic acid.svg
Thiol form (carbothioic S-acid)

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 (RC(S)OH) and a thiol form (RC(O)SH). [1] [2] These are sometimes also referred to as "carbothioic O-acid" and "carbothioic S-acid" respectively. Of these the thiol form is most common (e.g. thioacetic acid).

Contents

Thiocarboxylic acids are rare in nature, however the biosynthetic components for producing them appear widespread in bacteria. [3] Examples include pyridine-2,6-dicarbothioic acid, [4] and thioquinolobactin. [3]

Synthesis

Thiocarboxylic acids are typically prepared by salt metathesis from the acid chloride, as in the following conversion of benzoyl chloride to thiobenzoic acid using potassium hydrosulfide according to the following idealized equation: [5]

C6H5C(O)Cl + KSH → C6H5C(O)SH + KCl

Covalent sulfides, such as P2S5, generally give poor yields unless catalyzed with triphenylstibine oxide. [6]

2,6-Pyridinedicarbothioic acid is synthesized by treating the diacid dichloride with a solution of H2S in pyridine:

NC5H3(COCl)2 + 2 H2S + 2 C5H5N → [C5H5NH+][HNC5H3(COS)−2] + [C5H5NH]Cl

This reaction produces the orange pyridinium salt of pyridinium-2,6-dicarbothioate. Treatment of this salt with sulfuric acid gives colorless the bis(thiocarboxylic acid), which can then be extracted with dichloromethane. [7]

Reactions

At neutral pH, thiocarboxylic acids are fully ionized. Thiocarboxylic acids are about 100 times more acidic than the analogous carboxylic acids. Thiobenzoic acid has a pKa of 2.48 compared with 4.20 for benzoic acid, and thioacetic acid has a pKa near 3.4 compared with 4.72 for acetic acid. [8] Alkylation of the corresponding thioate ion gives a thioester. [9]

The conjugate base of thioacetic acid, thioacetate, is a reagent used for installing thiol groups via the displacement of alkyl halides by a two-step process. The halide is displaced to give a thioester intermedate, which is then hydrolyzed:

R−X + CH3COS− → R−SC(O)CH3 + X−
R−SC(O)CH3 + H2O → R−SH + CH3CO2H

Thiocarboxylic acids react with various nitrogen functional groups, such as organic azide, nitro, and isocyanate compounds, to give amides under mild conditions. [10] [11] This method avoids needing the amine to initiate an amide-forming acyl substitution but does requires synthesis and handling of the unstable thiocarboxylic acid. [11] Unlike the Schmidt reaction or other nucleophilic-attack pathways, reaction with an aryl or alkyl azide begins with a [3+2] cycloaddition. The resulting heterocycle expels N2 and the sulfur atom to give the monosubstituted amide. [10] [12]


Halogens or their equivalents (e.g. sulfuryl chloride) oxidize thiocarboxylic acids to acylsulfenyl halides. The latter are unstable, and decay over the course of several hours to the free halogen and the diacyl disulfide. [13]

See also

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—a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group. They have the general formula R−O−R′, where R and R′ represent the 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">Ketene</span> Organic compound of the form >C=C=O

In organic chemistry, a ketene is an organic compound of the form RR'C=C=O, where R and R' are two arbitrary monovalent chemical groups. The name may also refer to the specific compound ethenone H2C=C=O, the simplest ketene.

The following outline is provided as an overview of and topical guide to organic chemistry:

<span class="mw-page-title-main">Thioester</span> Organosulfur compounds of the form R–SC(=O)–R’

In organic chemistry, thioesters are organosulfur compounds with the molecular structure R−C(=O)−S−R’. They are analogous to carboxylate esters with the sulfur in the thioester replacing oxygen in the carboxylate ester, as implied by the thio- prefix. They are the product of esterification of a carboxylic acid with a thiol. In biochemistry, the best-known thioesters are derivatives of coenzyme A, e.g., acetyl-CoA. The R and R' represent organyl groups, or H in the case of R.

In chemistry, halogenation is a chemical reaction which introduces one or more halogens into a chemical compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. This kind of conversion is in fact so common that a comprehensive overview is challenging. This article mainly deals with halogenation using elemental halogens. Halides are also commonly introduced using salts of the halides and halogen acids. Many specialized reagents exist for and introducing halogens into diverse substrates, e.g. thionyl chloride.

<span class="mw-page-title-main">Acyl halide</span> Oxoacid compound with an –OH group replaced by a halogen

In organic chemistry, an acyl halide is a chemical compound derived from an oxoacid by replacing a hydroxyl group with a halide group.

<span class="mw-page-title-main">Sulfonic acid</span> Organic compounds with the structure R−S(=O)2−OH

In organic chemistry, sulfonic acid refers to a member of the class of organosulfur compounds with the general formula R−S(=O)2−OH, where R is an organic alkyl or aryl group and the S(=O)2(OH) group a sulfonyl hydroxide. As a substituent, it is known as a sulfo group. A sulfonic acid can be thought of as sulfuric acid with one hydroxyl group replaced by an organic substituent. The parent compound is the parent sulfonic acid, HS(=O)2(OH), a tautomer of sulfurous acid, S(=O)(OH)2. Salts or esters of sulfonic acids are called sulfonates.

<span class="mw-page-title-main">Thionyl chloride</span> Inorganic compound (SOCl2)

Thionyl chloride is an inorganic compound with the chemical formula SOCl2. It is a moderately volatile, colourless liquid with an unpleasant acrid odour. Thionyl chloride is primarily used as a chlorinating reagent, with approximately 45,000 tonnes per year being produced during the early 1990s, but is occasionally also used as a solvent. It is toxic, reacts with water, and is also listed under the Chemical Weapons Convention as it may be used for the production of chemical weapons.

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">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, 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.

<span class="mw-page-title-main">Thioacetic acid</span> Organosulfur compound (CH3C(O)SH)

Thioacetic acid is an organosulfur compound with the molecular formula CH3C(O)SH. It is a thioic acid: the sulfur analogue of acetic acid, as implied by the thio- prefix. It is a yellow liquid with a strong thiol-like odor. It is used in organic synthesis for the introduction of thiol groups in molecules.

<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.

<span class="mw-page-title-main">2,6-Pyridinedicarbothioic acid</span> Chemical compound

2,6-Pyridinedicarbothioic acid (PDTC) is an organosulfur compound that is produced by some bacteria. It functions as a, a low molecular weight compound that scavenges iron. Siderophores solubilize compounds by forming strong complexes. PDTC is secreted by the soil bacteria Pseudomonas stutzeri and Pseudomonas putida.

Dithiocarboxylic acids are organosulfur compounds with the formula RCS2H. They are the dithia analogues of carboxylic acids. A closely related and better studied family of compounds are the monothiocarboxylic acids, with the formula RCOSH.

<span class="mw-page-title-main">Sulfenamide</span> Molecules of the form >N–S–

In organosulfur chemistry, sulfenamides are a class of organosulfur compounds characterized by the general formula R−S−N(−R)2, where the R groups are hydrogen, alkyl, or aryl. Sulfenamides have been used extensively in the vulcanization of rubber using sulfur. They are related to the oxidized compounds known as sulfinamides and sulfonamides.

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

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.

Decarboxylative cross coupling reactions are chemical reactions in which a carboxylic acid is reacted with an organic halide to form a new carbon-carbon bond, concomitant with loss of CO2. Aryl and alkyl halides participate. Metal catalyst, base, and oxidant are required.

<span class="mw-page-title-main">Acyl azide</span> Carboxylic acid derivative

Acyl azides are carboxylic acid derivatives with the general formula RCON3. These compounds, which are a subclass of organic azides, are generally colorless.

<span class="mw-page-title-main">Sulfonamide</span> Organosulfur compounds containing –S(=O)2–N< functional group

In organic chemistry, the sulfonamide functional group is an organosulfur group with the structure R−S(=O)2−NR2. It consists of a sulfonyl group connected to an amine group. Relatively speaking this group is unreactive. Because of the rigidity of the functional group, sulfonamides are typically crystalline; for this reason, the formation of a sulfonamide is a classic method to convert an amine into a crystalline derivative which can be identified by its melting point. Many important drugs contain the sulfonamide group.

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

Thiobenzoic acid is an organosulfur compound with molecular formula C6H5COSH. It is the parent of aryl thiocarboxylic acids. It is a pale yellow liquid that freezes just below room temperature.

References

  1. ↑ Cremlyn, R.J. (1996). An introduction to organosulfur chemistry. Chichester: Wiley. ISBN   0-471-95512-4.
  2. ↑ Matthys J. Janssen (1969). "Thiolo, Thiono and Dithio Acids and Esters". In Saul Patai (ed.). Carboxylic Acids and Esters. PATAI'S Chemistry of Functional Groups. pp. 705–764. doi:10.1002/9780470771099.ch15. ISBN   978-0-470-77109-9.
  3. 1 2 Dong, Liao-Bin; Rudolf, Jeffrey D.; Kang, Dingding; Wang, Nan; He, Cyndi Qixin; Deng, Youchao; Huang, Yong; Houk, K. N.; Duan, Yanwen; Shen, Ben (2018). "Biosynthesis of thiocarboxylic acid-containing natural products". Nature Communications. 9: 2362. Bibcode:2018NatCo...9.2362D. doi:10.1038/s41467-018-04747-y. PMC   6006322 . PMID   29915173.
  4. ↑ Budzikiewicz, Herbert (2010). "Microbial Siderophores". In Kinghorn, A. Douglas; Falk, Heinz; Kobayashi, Junichi (eds.). Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products, Vol. 92[Progress in the Chemistry of Organic Natural Products]. Vol. 92. pp. 1–75. doi:10.1007/978-3-211-99661-4_1. ISBN   978-3-211-99660-7. PMID   20198464.
  5. ↑ Noble, Jr., Paul; Tarbell, D. S. (1952). "Thiobenzoic Acid". Organic Syntheses. 32: 101. doi:10.15227/orgsyn.032.0101.
  6. ↑ Collier, S. J. (2007). "Product class 8: Thiocarboxylic S-acids, selenocarboxylic Se-acids, tellurocarboxylic Te-acids, and derivatives". In Panek, J. S. (ed.). Category 3, Compounds with Four and Three Carbon Heteroatom Bonds: Three Carbon—Heteroatom Bonds: Esters, and Lactones; Peroxy Acids and R(CO)OX Compounds; R(CO)X, X=S, Se, Te. Science of Synthesis. Stuttgart: Georg Thieme Verlag. p. 1600. doi:10.1055/sos-sd-020-01480. ISBN   978-3-13-144691-6.
  7. ↑ Hildebrand, U.; Ockels, W.; Lex, J.; Budzikiewicz, H. (1983). "Zur Struktur Eines 1:1-Adduktes von Pyridin-2,6-Dicarbothiosäure und Pyridin". Phosphorus and Sulfur and the Related Elements. 16 (3): 361–364. doi:10.1080/03086648308080490.
  8. ↑ M. R. Crampton (1974). "Acidity and hydrogen-bonding". In Saul Patai (ed.). The Chemistry of the Thiol Group. Chichester: John Wiley & Sons Ltd. p. 402.
  9. ↑ Matthys J. Janssen "Carboxylic Acids and Esters" in PATAI's Chemistry of Functional Groups: Carboxylic Acids and Esters, Saul Patai, Ed. John Wiley, 1969, New York: pp. 705–764. doi : 10.1002/9780470771099.ch15
  10. 1 2 "21.1.2.6.1: Variation 1: From Thiocarboxylic Acids". Science of Synthesis: Houben–Weyl Methods of Molecular Transformations. Vol. 21: Three Carbon-Heteroatom Bonds: Amides and Derivatives, Peptides, Lactams. Georg Thieme Verlag. 2005. pp. 52–54. ISBN   978-3-13-171951-5.
  11. 1 2 Xie, Sheng; Zhang, Yang; Ramström, Olof; Yan, Mingdi (2016). "Base-catalyzed synthesis of aryl amides from aryl azides and aldehydes". Chem. Sci. 7 (1): 713–718. doi:10.1039/C5SC03510D. PMC   5952891 . PMID   29896355.
  12. ↑ Shangguan, Ning; Katukojvala, Sreenivas; Greenberg, Rachel; Williams, Lawrence J. (2003). "The Reaction of Thio Acids with Azides: A New Mechanism and New Synthetic Applications". Journal of the American Chemical Society. 125 (26): 7754–7755. Bibcode:2003JAChS.125.7754S. doi:10.1021/ja0294919. PMID   12822965.
  13. ↑ Ogawa Akiya; Sonoda Noboru (1995). "Acylsulfur, -selenium, or -tellurium functions". In Moody, Christopher J. (ed.). Comprehensive Organic Functional Group Transformations. Vol. 5. Oxford, UK: Pergamon. pp. 244–246. ISBN   0-08-042326-4. LCCN   95-31088.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.