Thioacetic acid

Thioacetic acid

Names
IUPAC name Ethanethioic S-acid
Other names Thioacetic S-acid Thiolacetic acid
Identifiers
CAS Number	507-09-5 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:46800 Y
ChemSpider	10052 Y
ECHA InfoCard	100.007.331
KEGG	C01857 Y
PubChem	10484
UNII	PS92MLC0FQ Y
InChI InChI=1S/C2H4OS/c1-2(3)4/h1H3,(H,3,4) Y Key: DUYAAUVXQSMXQP-UHFFFAOYSA-N Y InChI=1/C2H4OS/c1-2(3)4/h1H3,(H,3,4) Key: DUYAAUVXQSMXQP-UHFFFAOYAO
SMILES O=C(S)C
Properties
Chemical 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)
Magnetic susceptibility (χ)	-38.4·10−6 cm3/mol
Hazards
Safety data sheet	Fischer Scientific
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

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

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 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.

With a pK_a near 3.4, thioacetic acid is about 15x more acidic than acetic acid. The conjugate base is thioacetate:

In neutral water, thioacetic acid is fully ionized.

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:

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: