Thioacetic acid
| Skeletal formula of thioacetic acid | |
| Ball-and-stick model of the thioacetic acid molecule | |
| Names | |
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| IUPAC name
Ethanethioic S-acid
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| Other names
Thioacetic S-acid
Thiolacetic acid |
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| Identifiers | |
507-09-5  |
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| ChEBI | CHEBI:46800 |
| ChemSpider | 10052 |
| Jmol 3D model | Interactive image |
| KEGG | C01857 |
| PubChem | 10484 |
| UNII | PS92MLC0FQ |
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| Properties | |
| 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) |
| Vapor pressure | {{{value}}} |
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Except where otherwise noted, 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
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
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]
References
- ↑ Jeannie R. Phillips "Thiolacetic Acid" Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley. doi:10.1002/047084289X.rt096.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 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
