Thioacetic acid

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Thioacetic acid
Thioacetic-acid-2D-skeletal.png
Thioacetic-acid-3D-balls.png
Identifiers
CAS number 507-09-5 YesY
PubChem 10484
ChemSpider 10052 YesY
UNII PS92MLC0FQ YesY
KEGG C01857 YesY
ChEBI CHEBI:46800 YesY
Jmol-3D images Image 1
Properties
Molecular formula C2H4OS
Molar mass 76.11756
Density 1.08 g/mL
Melting point −58 °C (−72 °F; 215 K)
Boiling point 93 °C (199 °F; 366 K)
Hazards
MSDS Fischer Scientific
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Thioacetic acid is an organosulfur compound with the molecular formula CH3COSH. It is a colourless liquid with a strong thiol-like odor. It is used in organic synthesis for the introduction of thiol groups in molecules[1]

Synthesis and properties[edit]

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

(CH3C(O))2O + H2S → CH3C(O)SH + CH3CO2H

Thioacetic acid is typically contaminated by acetic acid.

The compound exists exclusively as the thiol tautomer, consistent with the strength of the C=O double bond. Reflecting the influence of hydrogen-bonding, the boiling point (93 °C) and melting points are 20 and 75K lower than those for acetic acid. It is also about 15x more acidic than acetic acid.

Reactivity[edit]

The thioacetate anion and radical generated from thioacetic acid are used to generate thioacetate esters.[2] 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:

CH3C(O)SH + NaOH → CH3C(O)SNa + H2O
CH3C(O)SNa + RX → CH3C(O)SR + NaX (X = Cl, Br, I, etc)
CH3C(O)SR + 2 NaOH → CH3CO2Na + RSNa + H2O
RSNa + HCl → RSH + NaCl

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:[3]

thioacetic acid application

References[edit]

  1. ^ Jeannie R. Phillips "Thiolacetic Acid" Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley. doi:10.1002/047084289X.rt096.
  2. ^ Ervithayasuporn, V. (2011). "Synthesis and Characterization of Octakis(3-propyl ethanethioate)octasilsesquioxane". Organometallics 30 (17): 4475–4478. doi:10.1021/om200477a. 
  3. ^ 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 Link