Thioacetic acid

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Organosulfur compound (CH3C(O)SH)

title: "Thioacetic acid" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["thiocarboxylic-acids", "reagents-for-organic-chemistry", "foul-smelling-chemicals"] description: "Organosulfur compound (CH3C(O)SH)" topic_path: "science/chemistry" source: "https://en.wikipedia.org/wiki/Thioacetic_acid" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Organosulfur compound (CH3C(O)SH) ::

| verifiedrevid = 470606827 | ImageFileL1= AcSH.svg | ImageSizeL1=120 | ImageClassL1 = skin-invert | ImageAltL1=Skeletal formula of thioacetic acid | ImageFileR1= Thioacetic acid 3D ball.png | ImageSizeR1=120 | ImageAltR1=Ball-and-stick model of the thioacetic acid molecule | PIN=Ethanethioic S-acid | OtherNames=Thioacetic S-acid Thiolacetic acid |Section1={{Chembox Identifiers | ChemSpiderID_Ref = | ChemSpiderID = 10052 | UNII_Ref = | UNII = PS92MLC0FQ | KEGG_Ref = | KEGG = C01857 | InChI = 1/C2H4OS/c1-2(3)4/h1H3,(H,3,4) | InChIKey = DUYAAUVXQSMXQP-UHFFFAOYAO | StdInChI_Ref = | StdInChI = 1S/C2H4OS/c1-2(3)4/h1H3,(H,3,4) | StdInChIKey_Ref = | StdInChIKey = DUYAAUVXQSMXQP-UHFFFAOYSA-N | CASNo_Ref = | CASNo=507-09-5 | PubChem=10484 | ChEBI_Ref = | ChEBI = 46800 | SMILES = O=C(S)C |Section2={{Chembox Properties | Formula= | MolarMass=76.11756 g/mol | Density=1.08 g/mL | MeltingPtC=-58 | BoilingPtC=93 | Appearance = Transparent, colorless to light yellow liquid | Odor = Unpleasant, strong thiol-like | RefractIndex = 1.465 | MagSus = −38.4·10−6 cm3/mol |Section7={{Chembox Hazards | LD50 = 75 mg/kg (mouse, intraperitoneal) | MainHazards = May cause severe skin and eye burns. Highly flammable liquid. | GHSPictograms = | GHSSignalWord = Danger | HPhrases = | PPhrases = | ExternalSDS = Fischer Scientific Thioacetic acid is an organosulfur compound with the molecular formula . 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.

Synthesis and properties

Thioacetic acid is prepared by the reaction of acetic anhydride with hydrogen sulfide: :

It has also been produced by the action of phosphorus pentasulfide on glacial acetic acid, followed by distillation. :

Thioacetic acid is typically contaminated by acetic acid.

The compound exists exclusively as the thiol tautomer, consistent with the strength of the double bond. Reflecting the influence of hydrogen-bonding, the boiling point (93 °C) and melting points are 20 and 75 K lower than those for acetic acid.

Reactivity

Acidity

With a pKa near 3.4, thioacetic acid is about 15 times more acidic than acetic acid. The conjugate base is thioacetate: : In neutral water, thioacetic acid is fully ionized.

Reactivity of thioacetate

Most of the reactivity of thioacetic acid arises from the conjugate base, thioacetate. Salts of this anion, e.g. potassium thioacetate, are used to generate thioacetate esters. Thioacetate esters undergo hydrolysis to give thiols. A typical method for preparing a thiol from an alkyl halide using thioacetic acid proceeds in four discrete steps, some of which can be conducted sequentially in the same flask: : :, where X = Cl, Br, I : :

In an application that illustrates the use of its radical behavior, thioacetic acid is used with AIBN in a free radical mediated nucleophilic addition to an exocyclic alkene forming a thioester: :[[File:Thioacetic acid application.svg|class=skin-invert-image|center|500px|thioacetic acid application]]

Reductive acetylation

Potassium thioacetate can be used convert nitroarenes to aryl acetamides in one step. This is particularly useful in the preparation of pharmaceuticals, e.g., paracetamol from 4-nitrophenol or 4-nitroanisole.

References

References

  1. [[International Union of Pure and Applied Chemistry]]. (2014). "Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013". [[Royal Society of Chemistry.
  2. "Thioacetic acid".
  3. "Identification of the substance/mixture and of the company/undertaking - Thioacetic acid".
  4. Jeannie R. Phillips "Thiolacetic Acid" Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley. {{doi. 10.1002/047084289X.rt096
  5. (1951). "Thiolacetic acid". Organic Syntheses.
  6. Schiff, Robert. (1895-08-09). "Preparation of Thioacetic Acid and its Importance for Chemical-Legal Investigations". Chemical News and Journal of Industrial Science.
  7. Matthys J. Janssen "Carboxylic Acids and Esters" in PATAI'S Chemistry of Functional Groups: Carboxylic Acids and Esters, Saul Patai, Ed. pp. 705–764, 1969. {{doi. 10.1002/9780470771099.ch15
  8. Ervithayasuporn, V.. (2011). "Synthesis and Characterization of Octakis(3-propyl ethanethioate)octasilsesquioxane". [[Organometallics]].
  9. ''Synthesis of methyl 6-deoxy-4-O-(sodium sulfonato)-α-L-talopyranoside, its C-4 epimer and both isosteric [4-C-(potassium sulfonatomethyl)] derivatives ''László Lázár, Magdolna Csávás, Anikó Borbás, Gyöngyi Gyémánt, and András Lipták ''[[Arkivoc]]'' '''2004''' (vii) 196-207 [http://www.arkat-usa.org/ARKIVOC/JOURNAL_CONTENT/manuscripts/2004/SA-1033BP%20as%20published%20mainmanuscript.pdf Link]
  10. Bhattacharya, Apurba. (2006). "One-step reductive amidation of nitro arenes: application in the synthesis of Acetaminophen". Tetrahedron Letters.

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