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| Names | |||
|---|---|---|---|
| Preferred IUPAC name Hydroxyacetic acid | |||
| Other names Hydroacetic acid 2-Hydroxyethanoic acid | |||
| Identifiers | |||
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3D model (JSmol) | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider |
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| DrugBank |
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| ECHA InfoCard | 100.001.073 | ||
| EC Number |
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| KEGG |
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| RTECS number |
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| UNII | |||
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| Properties | |||
| C2H4O3 | |||
| Molar mass | 76.05 g/mol | ||
| Appearance | White powder or colorless crystals | ||
| Density | 1.49 g/cm3[1] | ||
| Melting point | 75 °C (167 °F; 348 K) | ||
| Boiling point | 100 °C (212 °F; 373 K) Decomposes above 100 °C | ||
| 70% solution | |||
| Solubility in other solvents | Alcohols,acetone, acetic acid and ethyl acetate[2] | ||
| logP | −1.05[3] | ||
| Vapor pressure | 1.051 kPa (80 °C) | ||
| Acidity (pKa) | 3.83 | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | Corrosive | ||
| GHS labelling: | |||
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| Danger | |||
| H302,H314,H332 | |||
| P260,P264,P270,P271,P280,P301+P312,P301+P330+P331,P303+P361+P353,P304+P312,P304+P340,P305+P351+P338,P310,P312,P321,P330,P363,P405,P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | 300 °C (572 °F; 573 K)[4] | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 1950 mg/kg (rat, oral) 2040 mg/kg (rat, oral) | ||
LC50 (median concentration) | 7.7 ppm (rat, 4h) 3.6 ppm (rat, 4h) | ||
| Related compounds | |||
Relatedα-hydroxy acids | Lactic acid | ||
Related compounds | Glycolaldehyde Acetic acid Glycerol | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Glycolic acid (orhydroxyacetic acid; chemical formulaHOCH2CO2H) is a colorless, odorless andhygroscopiccrystalline solid that is highlysoluble in water. It is used in variousskin-care products. Glycolic acid is widespread in nature. Aglycolate (sometimes spelled "glycollate") is asalt orester of glycolic acid.
The name "glycolic acid" was coined in 1848 by French chemistAuguste Laurent (1807–1853). He proposed that theamino acidglycine—which was then calledglycocolle—might be theamine of a hypothetical acid, which he called "glycolic acid" (acide glycolique).[5]
Glycolic acid was first prepared in 1851 by German chemistAdolph Strecker (1822–1871) and Russian chemist Nikolai Nikolaevich Sokolov (1826–1877). They produced it by treatinghippuric acid withnitric acid andnitrogen dioxide[contradictory] to form anester ofbenzoic acid and glycolic acid (C6H5C(=O)OCH2COOH), which they called "benzoglycolic acid" (Benzoglykolsäure; also benzoyl glycolic acid). They boiled the ester for days with dilutesulfuric acid, thereby obtaining benzoic acid and glycolic acid (Glykolsäure).[6][7]
Glycolic acid can be synthesized in various ways. The predominant approaches use a catalyzed reaction offormaldehyde withsynthesis gas (carbonylation of formaldehyde), for its low cost.[8]
It is also prepared by the reaction ofchloroacetic acid withsodium hydroxide followed by re-acidification.
Other methods, not noticeably in use, includehydrogenation ofoxalic acid, andhydrolysis of thecyanohydrin derived fromformaldehyde.[9] Some of today's glycolic acids areformic acid-free. Glycolic acid can be isolated from natural sources, such assugarcane,sugar beets,pineapple,cantaloupe and unripegrapes.[10]
Glycolic acid can also be prepared using an enzymatic biochemical process that may require less energy.[11][unreliable source?]
Glycolic acid is slightly stronger than acetic acid due to the electron-withdrawing power of the terminal hydroxyl group. The carboxylate group can coordinate to metal ions, forming coordination complexes. Of particular note are the complexes with Pb2+ and Cu2+ which are significantly stronger than complexes with other carboxylic acids. This indicates that the hydroxyl group is involved in complex formation, possibly with the loss of its proton.[12]
Glycolic acid is used in the textile industry as adyeing andtanning agent.[13]
Glycolic acid is a useful intermediate for organic synthesis, in a range of reactions including:oxidation-reduction,esterification and long chainpolymerization. It is used as amonomer in the preparation ofpolyglycolic acid and otherbiocompatiblecopolymers (e.g.PLGA). Commercially, important derivatives include the methyl (CAS# 96-35-5) and ethyl (CAS# 623-50-7) esters which are readily distillable (boiling points 147–149 °C and 158–159 °C, respectively), unlike the parent acid. The butyl ester (b.p. 178–186 °C) is a component of somevarnishes, being desirable because it is nonvolatile and has good dissolving properties.[9]
Glycolide is the cyclic dimer, abislactone, which is used in some of the polymerization processes.
Plants produce glycolic acid duringphotorespiration. It is recycled by conversion to glycine within the peroxisomes and totartronic acid semialdehyde within the chloroplasts.[14]
Because photorespiration is a wasteful side reaction in regard tophotosynthesis, much effort has been devoted to suppressing its formation. One process converts glycolate intoglycerate without using the conventional BASS6 and PLGG1 route; seeglycerate pathway.[15][16]
Glycolic acid is an irritant to the skin.[17] It occurs in all green plants.[9]
