Thioacetic acid
| Thioacetic acid | |
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Ethanethioic S-acid |
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Other names
Thioacetic S-acid |
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| Identifiers | |
| CAS number | 507-09-5  |
| PubChem | 10484 |
| ChemSpider | 10052 |
| UNII | PS92MLC0FQ |
| KEGG | C01857 |
| ChEBI | CHEBI:46800 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C2H4OS |
| Molar mass | 76.11756 |
| Density | 1.08 g/mL |
| Melting point |
-58 °C, 215 K, -72 °F |
| Boiling point |
93 °C, 366 K, 199 °F |
| Hazards | |
| MSDS | Fischer Scientific |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 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]
[edit] 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 75 °C lower than those for acetic acid. It is also about 15x more acidic than acetic acid.
[edit] Reactivity
The thioacetate anion and radical generated from thioacetic acid 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:
- 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[2]:
[edit] References
- ^ Jeannie R. Phillips "Thiolacetic Acid" Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley. doi:10.1002/047084289X.rt096 .
- ^ 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
