Thioacetic acid
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Names | |||
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Preferred IUPAC name
Ethanethioic S-acid[1] | |||
Other names
Thioacetic S-acid
Thiolacetic acid | |||
Identifiers | |||
3D model (
JSmol ) |
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ChEBI | |||
ChemSpider | |||
ECHA InfoCard
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100.007.331 | ||
KEGG | |||
PubChem CID
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UNII | |||
CompTox Dashboard (EPA)
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Properties | |||
CH3C(O)SH | |||
Molar mass | 76.11756 g/mol | ||
Appearance | Transparent, colorless to light yellow liquid[2][3] | ||
Odor | Unpleasant, strong thiol-like | ||
Density | 1.08 g/mL | ||
Melting point | −58 °C (−72 °F; 215 K) | ||
Boiling point | 93 °C (199 °F; 366 K) | ||
−38.4·10−6 cm3/mol | |||
Refractive index (nD)
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1.465 | ||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards
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Severe skin burns and eye damage. Highly flammable. | ||
GHS labelling: | |||
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Danger | |||
H225, H301, H302, H314, H317 | |||
P210, P233, P240, P241, P242, P243, P260, P261, P264, P264+P265, P270, P272, P280, P301+P316, P301+P317, P301+P330+P331, P302+P352, P302+P361+P354, P303+P361+P353, P304+P340, P305+P354+P338, P316, P317, P321, P330, P333+P317, P362+P364, P363, P370+P378, P403+P235, P405, P501 | |||
Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
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75 mg/kg (mouse, intraperitoneal) | ||
Safety data sheet (SDS) | Fischer Scientific | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Thioacetic acid is an
Synthesis and properties
Thioacetic acid is prepared by the reaction of acetic anhydride with hydrogen sulfide:[5]
- (CH3C(O))2O + H2S → CH3C(O)SH + CH3C(O)OH
It has also been produced by the action of phosphorus pentasulfide on glacial acetic acid, followed by distillation.[6]
- CH3C(O)OH + P2S5 → CH3C(O)SH + P2OS4
Thioacetic acid is typically contaminated by acetic acid.
The compound exists exclusively as the thiol
Reactivity
Acidity
With a pKa near 3.4, thioacetic acid is about 15 times more acidic than acetic acid.
- CH3C(O)SH → CH3C(O)S− + H+
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.
- CH3C(O)SH + NaOH → CH3C(O)SNa + H2O
- CH3C(O)SNa + RX → CH3C(O)SR + NaX, where X = Cl, Br, I
- 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
Reductive acetylation
Salts of thioacetic acid such as 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.[10]
References
- ISBN 978-0-85404-182-4.
- ^ "Thioacetic acid".
- ^ https://www.sigmaaldrich.com/GB/en/sds/aldrich/t30805
- .
- ^ Schiff, Robert (1895-08-09). "Preparation of Thioacetic Acid and its Importance for Chemical-Legal Investigations". Chemical News and Journal of Industrial Science. 72: 64. Retrieved 2016-11-02.
- .
- ^ 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
- doi:10.1016/j.tetlet.2005.09.196. Archived from the original(PDF) on 2016-11-04. Retrieved 2016-11-02.