Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and Thioglycolic acid: Difference between pages

{{cs1 config|name-list-style=vanc}}

| Watchedfields = changed

| verifiedrevid = 470607208

| Reference =<ref>''Merck Index'', 11th Edition, '''9265'''</ref>

| Name = Thioglycolic acid

| ImageFile_Ref = {{chemboximage|correct|??}}

| ImageFile = Thioglycolic acid.png

| ImageSize = 150px

| ImageFile1 = Thioglycolic-acid-van-der-waals.png

| ImageSize1 = 150px

| ImageName1 = Space-filling model of thioglycolic acid

| PIN = Sulfanylacetic acid <!-- the locant ‘2’ for acetic acid is not cited -->

| OtherNames = 2-Sulfanylacetic acid<br />2-Mercaptoacetic acid<br />Acetyl mercaptan<br />Mercaptoacetate<br />Mercaptoacetic acid<br />Thioglycolic acid<br />Thiovanic acid<ref>[https://www.cdc.gov/niosh/npg/npgd0610.html NIOSH Pocket Guide to Chemical Hazards]. CDC.</ref>

|Section1={{Chembox Identifiers

| PubChem = 1133

| CASNo_Ref = {{cascite|correct|CAS}}

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChEBI_Ref = {{ebicite|correct|EBI}}

|Section2={{Chembox Properties

| C=2 | H=4 | O=2 | S=1

| Density = 1.32 g/cm³

| MeltingPtC = −16

| BoilingPtC = 96

| BoilingPt_notes = at 5 mmHg

| Appearance = colorless, clear liquid<ref name=PGCH/>

| Odor = strong, disagreeable<ref name=PGCH/>

| Solubility = miscible<ref name=PGCH/>

| VaporPressure = 10 mmHg (17.8&nbsp;°C)<ref name=PGCH/>

| MagSus = −50.0·10⁻⁶ cm³/mol

}}

|Section3={{Chembox Hazards

| GHSPictograms = {{GHS05}} {{GHS06}}

| HPhrases = {{H-phrases|H301+H311+H331|314}}

| PEL = none<ref name=PGCH>{{PGCH|0610}}</ref>

| ExploLimits = 5.9%<ref name=PGCH/>

| IDLH = N.D.<ref name=PGCH/>

| REL = TWA 1 ppm (4&nbsp;mg/m³) [skin]<ref name=PGCH/>

| FlashPt = >

| FlashPtF=230

| FlashPt_ref = <ref name=PGCH/>

}}

'''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]].<ref>{{Cite web|url=https://www.independent.co.uk/news/uk/home-news/what-exactly-is-mercaptan-8462250.html |archive-url=https://ghostarchive.org/archive/20220507/https://www.independent.co.uk/news/uk/home-news/what-exactly-is-mercaptan-8462250.html |archive-date=2022-05-07 |url-access=subscription |url-status=live|title = What exactly is Mercaptan?|website = [[Independent.co.uk]]|date = 22 January 2013}}{{cbignore}}</ref><ref>{{Cite web|url=https://www.prevor.com/en/thioglycolic-acid-understanding-the-risk-of-specific-chemicals-of-interest/|title = Thioglycolic acid :Understanding the risk of specific chemicals of interest - PREVOR|date = 11 September 2014}}</ref> TGA is miscible with polar organic solvents.<ref name="Merck index">''The Merck index'', 14th ed.; O’Neil, Maryadele J., Ed.; Merck & Co., Inc.: Whitehouse Station, NJ, 2006; p.&nbsp;9342.</ref><ref name=Ullmann>Robert Rippel "Mercaptoacetic Acid and Derivatives" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2012, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a16_265}}.</ref>

==Uses==

TGA is used as a chemical [[depilatory]] and is still used as such, especially in [[salt (chemistry)|salt forms]], including calcium thioglycolate and sodium thioglycolate. TGA is the precursor to [[ammonium thioglycolate]], which is used for [[permanent wave#Cold wave|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 [[hair removal|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.<ref name=Ullmann/> Thioglycolysis reactions are used on [[condensed tannin]]s to study their structure.<ref>{{Cite journal |last1=Vernhet |first1=Aude |last2=Dubascoux |first2=Stéphane |last3=Cabane |first3=Bernard |last4=Fulcrand |first4=Hélène |last5=Dubreucq |first5=Eric |last6=Poncet-Legrand |first6=Céline |date=2011-09-01 |title=Characterization of oxidized tannins: comparison of depolymerization methods, asymmetric flow field-flow fractionation and small-angle X-ray scattering |url=https://doi.org/10.1007/s00216-011-5076-2 |journal=Analytical and Bioanalytical Chemistry |language=en |volume=401 |issue=5 |pages=1559–1569 |doi=10.1007/s00216-011-5076-2 |pmid=21573842 |s2cid=4645218 |issn=1618-2650}}</ref><ref>{{Cite journal |last1=Suc |first1=Lucas |last2=Rigou |first2=Peggy |last3=Mouls |first3=Laetitia |date=2021-03-17 |title=Detection and Identification of Oxidation Markers of the Reaction of Grape Tannins with Volatile Thiols Commonly Found in Wine |url=https://pubs.acs.org/doi/10.1021/acs.jafc.0c07163 |journal=Journal of Agricultural and Food Chemistry |language=en |volume=69 |issue=10 |pages=3199–3208 |doi=10.1021/acs.jafc.0c07163 |pmid=33657810 |s2cid=232112725 |issn=0021-8561}}</ref><ref>{{Cite journal |last1=Trivelato |first1=Priscilla |last2=Mayer |first2=Claire |last3=Barakat |first3=Abdellatif |last4=Fulcrand |first4=Hélène |last5=Aouf |first5=Chahinez |date=2016-08-01 |title=Douglas bark dry fractionation for polyphenols isolation: From forestry waste to added value products |url=https://www.sciencedirect.com/science/article/pii/S0926669016301601 |journal=Industrial Crops and Products |volume=86 |pages=12–15 |doi=10.1016/j.indcrop.2016.03.014 |issn=0926-6690}}</ref><ref>{{Cite journal |last1=Ben Aziz |first1=Mohamed |last2=Mouls |first2=Laetitia |last3=Fulcrand |first3=Hélène |last4=Douieb |first4=Hicham |last5=Hajjaj |first5=Hassan |date=2017-05-01 |title=Phenolic compounds of Moroccan red press wines: Influence of fining agents and micro-oxygenation treatments |url=https://www.sciencedirect.com/science/article/pii/S002364381630812X |journal=LWT |volume=78 |pages=143–150 |doi=10.1016/j.lwt.2016.12.034 |issn=0023-6438}}</ref>

TGA has also been used to soften nails, either to reshape [[pincer nails]] into the correct position<ref>{{Cite journal | vauthors=((Okada, K.)), ((Okada, E.)) | year=2012 | title=Novel treatment using thioglycolic acid for pincer nails | journal=The Journal of Dermatology | volume=39 | issue=12 | pages=996–999 | publisher=Wiley | doi=10.1111/j.1346-8138.2012.01670.x | pmid=22963208 | s2cid=7413716 | url=http://dx.doi.org/10.1111/j.1346-8138.2012.01670.x}}</ref> or to help [[topical antifungal]]s penetrate the nail.<ref>{{Cite journal | vauthors=((Gregorí Valdes, B. S.)), ((Serro, A. P.)), ((Gordo, P. M.)), ((Silva, A.)), ((Gonçalves, L.)), ((Salgado, A.)), ((Marto, J.)), ((Baltazar, D.)), ((Santos, R. G. dos)), ((Bordado, J. M.)), ((Ribeiro, H. M.)) | year=2017 | title=New Polyurethane Nail Lacquers for the Delivery of Terbinafine: Formulation and Antifungal Activity Evaluation | journal=Journal of Pharmaceutical Sciences | volume=106 | issue=6 | pages=1570–1577 | publisher=Elsevier BV | doi=10.1016/j.xphs.2017.02.017 | pmid=28263845 | url=http://dx.doi.org/10.1016/j.xphs.2017.02.017}}</ref>

[[Organotin]] derivatives of thioglycolic acid isooctyl esters are widely used as stabilizers for [[PVC]]. These species have the formula R₂Sn(SCH₂CO₂C₈H₁₇)₂.<ref name=Ullmann/>

Sodium thioglycolate is a component of [[thioglycolate broth]], a special bacterial growth media. It is also used in so-called "fallout remover"<ref>{{Cite web |url=http://www.detailingwiki.org/decontaminating/what-is-a-fallout-remover/ |title=What is a fallout remover |date=2016-03-17|website=DetailingWiki |language=en-GB |access-date=2016-06-14}}</ref> or "wheel cleaner" to remove [[iron oxide]] residue from [[wheels]].<ref>"SONAX Xtreme Wheel Cleaner" Safety data sheet</ref> [[Ferrous]] iron combines with thioglycolate to form red-violet<ref>{{Cite book |url=https://books.google.com/books?id=FMXU0kosXrMC |title=Encyclopedia of Chemical Processing and Design |volume=12: Corrosion to Cottonseed |last=McKetta |first=John J. Jr. |date=1981-01-01 |publisher=CRC Press |isbn=9780824724627 |page=103 |language=en}}</ref> ferric thioglycolate.<ref>{{Cite journal |last=Lyons |first=Edward |date=1927-08-01 |journal=Journal of the American Chemical Society |volume=49 |issue=8 |pages=1916–1920 |doi=10.1021/ja01407a010 |issn=0002-7863 |title=Thioglycolic Acid as a Color Test for Iron}}</ref><ref>{{Cite web |url=http://www.web-formulas.com/Formulas_of_Chemistry/Limit_Test_of_Iron.aspx |title=Limit Test of Iron |website=Web Formulas |access-date=2016-06-14}}</ref>

==Production==

Thioglycolic acid is prepared by reaction of sodium or potassium chloroacetate with alkali metal hydrosulfide in aqueous medium.<ref name="CTFA">Cosmetic, Toiletry, and Fragrance Association (CTFA). Thioglycolic Acid. 1987;(1987a). Submission of unpublished data by CTFA Code No. 3-25-2</ref> It can be also prepared via the [[Bunte salt]] obtained by reaction of [[sodium thiosulfate]] with [[chloroacetic acid]]:<ref name=Ullmann/><ref name="Saeed M">Saeed M. Hameed N. Madan V. Mansoor S. Preparation and Mechanisms studies of Thioglycolic Acid. ''Pak. J. Sci. Ind. Res.'' '''1992,''' 35: 131-132</ref>

:ClCH₂CO₂H + Na₂S₂O₃ → Na[O₃S₂CH₂CO₂H] + NaCl

:Na[O₃S₂CH₂CO₂H] + H₂O → HSCH₂CO₂H + NaHSO₄

==Reactions==

Thioglycolic acid with a [[acid dissociation constant|pK_a]] of 3.83 <ref name=Ullmann/> is an acid about 10 times stronger than [[acetic acid]] (pK_a 4.76):

:HSCH₂CO₂H → HSCH₂CO₂⁻ + H⁺

The second ionization has a pK_a of 9.3:

: HSCH₂CO₂⁻ → ⁻SCH₂CO₂⁻ + H⁺

Thioglycolic acid is a reducing agent, especially at higher pH. It oxidizes to the corresponding [[disulfide]] (2-[(carboxymethyl)disulfanyl]acetic acid or dithiodiglycolic acid):

:2 HSCH₂CO₂H + "O" → [SCH₂CO₂H]₂ + H₂O

===With metal ions===

Thioglycolic acid, usually as its dianion, forms [[complex (chemistry)|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).<ref name="Lee CW">Lee CW, Phil M. The detection of iron traces on hands by ferrozine sparys: a report on the sensitivity and interference of the method and recommended procedure in forensic science investigation. ''J Forensic Sci.'' '''1986,''' 31:920-930.</ref>

==History==

Scientist [[David R. Goddard#Inventions|David R. Goddard]], in the early 1930s, identified TGA as a useful reagent for [[redox|reducing]] the [[disulfide bond]]s in [[protein]]s, 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.<ref name="NAP">[http://www.nap.edu/readingroom.php?book=biomems&page=dgoddard.html National Academies Press:Biographical Memoirs:David Rockwell Goddard:by Ralph O. Erickson]</ref> TGA was developed in the 1940s for use as a chemical [[depilatory]].

==Safety and detection==

The [[median lethal dose|LD₅₀]] (oral, rat) is 261 mg/kg,<ref name=Ullmann/> [[Median lethal dose|LC₅₀]] inhalation for rat is 21 mg/m³ for 4 h, and LD₅₀ dermal for rabbit is 848 mg/kg.<ref name="Sigma-Aldrich">Sigma-Aldrich MSDS. http://www.sigmaaldrich.com/safety-center.html?cm_sp=Search-_-MSDS-_-MSDS1 (accessed Nov 10, 2013). Product Number – T3758</ref> Mercaptoacetic acid in hair waving and depilatory products containing other mercapto acids can be identified by using thin-layer chromatography and gas chromatography.<ref name="Goetz N1">Goetz N, Gataud P, Bore P. Determination of mercaptoacetic acid in hair waving and depilatory products. ''Analyst.'' '''1979,'''104:1062-1069</ref><ref name="Goetz N2">Goetz N, Gataud P, Bore P. Gas-chromatographic determination of mercaptoacetic acid in hair-waving and diplatory products. ''Cosmet Sci Technol Ser.'' '''1985,''' 4:65-79.</ref> MAA also has been identified by using potentiometric titration with [[silver nitrate]] solution.<ref name="Vandeputte M">Vandeputte M, Dryon L, Van Den Winkel P, Mertens J, Massart DL. Determination of thioglycolic acid using a silver sulfide single crystal electrode. ''Analysis.'' '''1975,'''3:500-504.</ref>

==See also==

*[[Ammonium thioglycolate]]

*[[Glycolic acid]]

*[[Thiolactic acid]]

==References==

{{reflist}}

==Further reading==

*Okada K, Okada E. Novel treatment using thioglycolic acid for pincer nails. ''J. Dermatol.'' '''2012,''' volume 39, pp. 996-999.

{{Authority control}}

[[Category:Thiols]]

[[Category:Acetic acids]]

[[Category:Chelating agents]]

[[Category:Foul-smelling chemicals]]