Names | |||
---|---|---|---|
Preferred IUPAC name Ethanethioic S-acid [1] | |||
Other names Thioacetic S-acid Thiolacetic acid | |||
Identifiers | |||
3D model (JSmol) | |||
ChEBI | |||
ChemSpider | |||
ECHA InfoCard | 100.007.331 | ||
KEGG | |||
PubChem CID | |||
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) | 1.465 | ||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards | May cause severe skin and eye burns. Highly flammable liquid. | ||
GHS labelling: | |||
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) | 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). |
Thioacetic acid is an organosulfur compound with the molecular formula CH3C(O)SH. It is a thioic acid: the sulfur analogue of acetic acid (CH3C(O)OH), as implied by the thio- prefix. It is a yellow liquid with a strong thiol-like odor. It is used in organic synthesis for the introduction of thiol groups (−SH) in molecules. [4]
Thioacetic acid is prepared by the reaction of acetic anhydride with hydrogen sulfide: [5]
It has also been produced by the action of phosphorus pentasulfide on glacial acetic acid, followed by distillation. [6]
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 K lower than those for acetic acid.
With a pKa near 3.4, thioacetic acid is about 15 times more acidic than acetic acid. [7] 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. [8] 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: [9]
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 from 4-nitrophenol or 4-nitroanisole. [10]
An acid is a molecule or ion capable of either donating a proton (i.e. hydrogen ion, H+), known as a Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid.
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group attached to an R-group. The general formula of a carboxylic acid is often written as R−COOH or R−CO2H, sometimes as R−C(O)OH with R referring to an organyl group, or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion.
In chemistry, an ester is a compound derived from an acid in which the hydrogen atom (H) of at least one acidic hydroxyl group of that acid is replaced by an organyl group. These compounds contain a distinctive functional group. Analogues derived from oxygen replaced by other chalcogens belong to the ester category as well. According to some authors, organyl derivatives of acidic hydrogen of other acids are esters as well, but not according to the IUPAC.
In organic chemistry, a ketone is an organic compound with the structure R−C(=O)−R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group −C(=O)−. The simplest ketone is acetone, with the formula (CH3)2CO. Many ketones are of great importance in biology and industry. Examples include many sugars (ketoses), many steroids, and the solvent acetone.
In organic chemistry, a thiol, or thiol derivative, is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The −SH functional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols, and the word is a blend of "thio-" with "alcohol".
In organic chemistry, thioesters are organosulfur compounds with the molecular structure R−C(=O)−S−R’. They are analogous to carboxylate esters with the sulfur in the thioester replacing oxygen in the carboxylate ester, as implied by the thio- prefix. They are the product of esterification of a carboxylic acid with a thiol. In biochemistry, the best-known thioesters are derivatives of coenzyme A, e.g., acetyl-CoA. The R and R' represent organyl groups, or H in the case of R.
Diethyl malonate, also known as DEM, is the diethyl ester of malonic acid. It occurs naturally in grapes and strawberries as a colourless liquid with an apple-like odour, and is used in perfumes. It is also used to synthesize other compounds such as barbiturates, artificial flavourings, vitamin B1, and vitamin B6.
In organic chemistry, an acyl chloride is an organic compound with the functional group −C(=O)Cl. Their formula is usually written R−COCl, where R is a side chain. They are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH3COCl. Acyl chlorides are the most important subset of acyl halides.
In organic chemistry, an acyl halide is a chemical compound derived from an oxoacid by replacing a hydroxyl group with a halide group.
Thiourea is an organosulfur compound with the formula SC(NH2)2 and the structure H2N−C(=S)−NH2. It is structurally similar to urea, except that the oxygen atom is replaced by a sulfur atom ; however, the properties of urea and thiourea differ significantly. Thiourea is a reagent in organic synthesis. Thioureas are a broad class of compounds with the general structure R2N−C(=S)−NR2.
In organic chemistry, sulfonic acid refers to a member of the class of organosulfur compounds with the general formula R−S(=O)2−OH, where R is an organic alkyl or aryl group and the S(=O)2(OH) group a sulfonyl hydroxide. As a substituent, it is known as a sulfo group. A sulfonic acid can be thought of as sulfuric acid with one hydroxyl group replaced by an organic substituent. The parent compound is the parent sulfonic acid, HS(=O)2(OH), a tautomer of sulfurous acid, S(=O)(OH)2. Salts or esters of sulfonic acids are called sulfonates.
Phosphorus trichloride is an inorganic compound with the chemical formula PCl3. A colorless liquid when pure, it is an important industrial chemical, being used for the manufacture of phosphites and other organophosphorus compounds. It is toxic and reacts readily with water to release hydrogen chloride.
In organic chemistry, a carboxylate is the conjugate base of a carboxylic acid, RCOO−. It is an anion, an ion with negative charge.
In organic chemistry, an ortho ester is a functional group containing three alkoxy groups attached to one carbon atom, i.e. with the general formula RC(OR')3. Orthoesters may be considered as products of exhaustive alkylation of unstable orthocarboxylic acids and it is from these that the name 'ortho ester' is derived. An example is ethyl orthoacetate, CH3C(OCH2CH3)3, more correctly known as 1,1,1-triethoxyethane.
Triethyl orthoformate is an organic compound with the formula HC(OC2H5)3. This colorless volatile liquid, the ortho ester of formic acid, is commercially available. The industrial synthesis is from hydrogen cyanide and ethanol.
Mercury(II) acetate, also known as mercuric acetate is a chemical compound, the mercury(II) salt of acetic acid, with the formula Hg(O2CCH3)2. Commonly abbreviated Hg(OAc)2, this compound is employed as a reagent to generate organomercury compounds from unsaturated organic precursors. It is a white, water-soluble solid, but some samples can appear yellowish with time owing to decomposition.
In organic chemistry, carbonyl reduction is the conversion of any carbonyl group, usually to an alcohol. It is a common transformation that is practiced in many ways. Ketones, aldehydes, carboxylic acids, esters, amides, and acid halides - some of the most pervasive functional groups, -comprise carbonyl compounds. Carboxylic acids, esters, and acid halides can be reduced to either aldehydes or a step further to primary alcohols, depending on the strength of the reducing agent. Aldehydes and ketones can be reduced respectively to primary and secondary alcohols. In deoxygenation, the alcohol group can be further reduced and removed altogether by replacement with H.
In organic chemistry, thiocarboxylic acids or carbothioic acids are organosulfur compounds related to carboxylic acids by replacement of one of the oxygen atoms with a sulfur atom. Two tautomers are possible: a thione form and a thiol form. These are sometimes also referred to as "carbothioic O-acid" and "carbothioic S-acid" respectively. Of these the thiol form is most common.
Thiobenzoic acid is an organosulfur compound with molecular formula C6H5COSH. It is the parent of aryl thiocarboxylic acids. It is a pale yellow liquid that freezes just below room temperature.
Potassium thioacetate is an organosulfur compound and a salt with the formula CH3COS−K+. This white, water-soluble solid is used as a reagent for preparing thioacetate esters and other derivatives.