Names | |
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Preferred IUPAC name Sulfanylacetic acid | |
Other names 2-Sulfanylacetic acid 2-Mercaptoacetic acid Acetyl mercaptan Mercaptoacetate Mercaptoacetic acid Thioglycolic acid Thiovanic acid [2] | |
Identifiers | |
3D model (JSmol) | |
ChEBI | |
ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.000.616 |
KEGG | |
PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
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Properties | |
C2H4O2S | |
Molar mass | 92.11 g·mol−1 |
Appearance | colorless, clear liquid [3] |
Odor | strong, disagreeable [3] |
Density | 1.32 g/cm3 |
Melting point | −16 °C (3 °F; 257 K) |
Boiling point | 96 °C (205 °F; 369 K) at 5 mmHg |
miscible [3] | |
Vapor pressure | 10 mmHg (17.8 °C) [3] |
−50.0·10−6 cm3/mol | |
Hazards | |
GHS labelling: | |
H301+H311+H331, H314 | |
Flash point | >110 °C; 230 °F; 383 K [3] |
Explosive limits | 5.9% [3] |
NIOSH (US health exposure limits): | |
PEL (Permissible) | none [3] |
REL (Recommended) | TWA 1 ppm (4 mg/m3) [skin] [3] |
IDLH (Immediate danger) | N.D. [3] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Thioglycolic acid (TGA) is the organic compound HSCH2CO2H. TGA is often called mercaptoacetic acid (MAA). It contains both a thiol (mercaptan) and carboxylic acid functional groups. It is a colorless liquid with a strongly unpleasant odor. [4] [5] TGA is miscible with polar organic solvents. [6] [7]
TGA is used as a chemical depilatory and is still used as such, especially in salt forms, including calcium thioglycolate and sodium thioglycolate. TGA is the precursor to ammonium thioglycolate, which is used for permanents. TGA and its derivatives break the disulfide bonds in the cortex of hair. One reforms these broken bonds in giving hair a "perm". Alternatively and more commonly, the process leads to depilation, as is done commonly in leather processing. It is also used as an acidity indicator, manufacturing of thioglycolates, and in bacteriology for preparation of thioglycolate media. [7] Thioglycolysis reactions are used on condensed tannins to study their structure. [8] [9] [10] [11]
TGA has also been used to soften nails, either to reshape pincer nails into the correct position [12] or to help topical antifungals penetrate the nail. [13]
Organotin derivatives of thioglycolic acid isooctyl esters are widely used as stabilizers for PVC. These species have the formula R2Sn(SCH2CO2C8H17)2. [7]
Sodium thioglycolate is a component of thioglycolate broth, a special bacterial growth media. It is also used in so-called "fallout remover" [14] or "wheel cleaner" to remove iron oxide residue from wheels. [15] Ferrous iron combines with thioglycolate to form red-violet [16] ferric thioglycolate. [17] [18]
Thioglycolic acid is prepared by reaction of sodium or potassium chloroacetate with alkali metal hydrosulfide in aqueous medium. [19] It can be also prepared via the Bunte salt obtained by reaction of sodium thiosulfate with chloroacetic acid: [7] [20]
Thioglycolic acid with a pKa of 3.83 [7] is an acid about 8.5 times stronger than acetic acid (pKa 4.76):
The second ionization has a pKa of 9.3:
Thioglycolic acid is a reducing agent, especially at higher pH. It oxidizes to the corresponding disulfide (2-[(carboxymethyl)disulfanyl]acetic acid or dithiodiglycolic acid):
Thioglycolic acid, usually as its dianion, forms complexes with metal ions. Such complexes have been used for the detection of iron, molybdenum, silver, and tin. Thioglycolic acid reacts with diethyl acetylmalonate to form acetylmercaptoacetic acid and diethyl malonate, the reducing agent in the conversion of Fe(III) to Fe(II). [21]
Scientist David R. Goddard, in the early 1930s, identified TGA as a useful reagent for reducing the disulfide bonds in proteins, including keratin (hair protein), while studying why protease enzymes could not easily digest hair, nails, feathers, and such. He realized that while the disulfide bonds, which stabilize proteins by cross-linking, were broken, the structures containing these proteins could be reshaped easily, and that they would retain this shape after the disulfide bonds were allowed to re-form. [22] TGA was developed in the 1940s for use as a chemical depilatory.
The LD50 (oral, rat) is 261 mg/kg, [7] LC50 inhalation for rat is 21 mg/m3 for 4 h, and LD50 dermal for rabbit is 848 mg/kg. [23] Mercaptoacetic acid in hair waving and depilatory products containing other mercapto acids can be identified by using thin-layer chromatography and gas chromatography. [24] [25] MAA also has been identified by using potentiometric titration with silver nitrate solution. [26]
Hydrolysis is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Cysteine is a semiessential proteinogenic amino acid with the formula HOOC−CH(−NH2)−CH2−SH. The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. Cysteine is chiral, but both D and L-cysteine are found in nature. L‑Cysteine is a protein monomer in all biota, and D-cysteine acts as a signaling molecule in mammalian nervous systems. Cysteine is named after its discovery in urine, which comes from the urinary bladder or cyst, from Greek κύστη kýsti, "bladder".
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations Na+ and hydroxide anions OH−.
In chemistry, a disulfide is a compound containing a R−S−S−R′ functional group or the S2−
2 anion. The linkage is also called an SS-bond or sometimes a disulfide bridge and usually derived from two thiol groups.
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".
A permanent wave, commonly called a perm or permanent, is a hairstyle consisting of waves or curls set into the hair. The curls may last a number of months, hence the name.
In chemistry and biology, a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural polymers.
Methylamine is an organic compound with a formula of CH3NH2. This colorless gas is a derivative of ammonia, but with one hydrogen atom being replaced by a methyl group. It is the simplest primary amine.
Methyl acetate, also known as MeOAc, acetic acid methyl ester or methyl ethanoate, is a carboxylate ester with the formula CH3COOCH3. It is a flammable liquid with a characteristically pleasant smell reminiscent of some glues and nail polish removers. Methyl acetate is occasionally used as a solvent, being weakly polar and lipophilic, but its close relative ethyl acetate is a more common solvent being less toxic and less soluble in water. Methyl acetate has a solubility of 25% in water at room temperature. At elevated temperature its solubility in water is much higher. Methyl acetate is not stable in the presence of strong aqueous bases or aqueous acids. Methyl acetate is not considered a VOC in the USA.
A relaxer is a type of lotion or cream generally used by people with tight curls or very curly hair which makes hair easier to straighten by chemically "relaxing" the natural curls. The active agent is usually a strong alkali, although some formulations are based on ammonium thioglycolate or formaldehyde.
Ammonium thioglycolate, also known as perm salt, is the salt of thioglycolic acid and ammonia. It has the formula HSCH2CO2NH4 and has use in perming hair.
Dithiothreitol (DTT) is an organosulfur compound with the formula (CH CH2SH)2. A colorless compound, it is classified as a dithiol and a diol. DTT is redox reagent also known as Cleland's reagent, after W. Wallace Cleland. The reagent is commonly used in its racemic form. Its name derives from the four-carbon sugar, threose. DTT has an epimeric ('sister') compound, dithioerythritol (DTE).
Thiophenol is an organosulfur compound with the formula C6H5SH, sometimes abbreviated as PhSH. This foul-smelling colorless liquid is the simplest aromatic thiol. The chemical structures of thiophenol and its derivatives are analogous to phenols, where the oxygen atom in the hydroxyl group (-OH) bonded to the aromatic ring in phenol is replaced by a sulfur atom. The prefix thio- implies a sulfur-containing compound and when used before a root word name for a compound which would normally contain an oxygen atom, in the case of 'thiol' that the alcohol oxygen atom is replaced by a sulfur atom.
A chemical depilatory is a cosmetic preparation used to remove hair from the skin. Common active ingredients are salts of thioglycolic acid and thiolactic acids. These compounds break the disulfide bonds in keratin and also hydrolyze the hair so that it is easily removed. Formerly, sulfides such as strontium sulfide were used, but due to their unpleasant odor, they have been replaced by thiols.
Proanthocyanidins are a class of polyphenols found in many plants, such as cranberry, blueberry, and grape seeds. Chemically, they are oligomeric flavonoids. Many are oligomers of catechin and epicatechin and their gallic acid esters. More complex polyphenols, having the same polymeric building block, form the group of condensed tannins.
Iron(III) nitrate, or ferric nitrate, is the name used for a series of inorganic compounds with the formula Fe(NO3)3.(H2O)n. Most common is the nonahydrate Fe(NO3)3.(H2O)9. The hydrates are all pale colored, water-soluble paramagnetic salts.
Procyanidins are members of the proanthocyanidin class of flavonoids. They are oligomeric compounds, formed from catechin and epicatechin molecules. They yield cyanidin when depolymerized under oxidative conditions.
Veet, formerly called Neet and Immac, is a Canadian brand of chemical depilatory products manufactured by the British-Dutch company Reckitt Benckiser. Hair removal cream, Lotions, gel, mousse, and wax products are produced under this brand, with differing variants being sold internationally. Previous products produced under the Neet and Immac brands were similar to those produced today.
Nair is a hair-removal product manufactured by Church & Dwight.
Condensed tannins are polymers formed by the condensation of flavans. They do not contain sugar residues.