Mandelic acid

Mandelic acid^[1]

Names
IUPAC name 2-Hydroxy-2-phenylacetic acid
Other names Mandelic acid Phenylglycolic acid α-Hydroxyphenylacetic acid
Identifiers
CAS Number	90-64-2 611-71-2 (R) 17199-29-0 (S)
ChEBI	CHEBI:35825
ChEMBL	ChEMBL1609
ChemSpider	1253
EC Number	202-007-6
Jmol interactive 3D	Image
PubChem	1292
RTECS number	OO6300000
UNII	NH496X0UJX
InChI InChI=1S/C8H8O3/c9-7(8(10)11)6-4-2-1-3-5-6/h1-5,7,9H,(H,10,11) Key: IWYDHOAUDWTVEP-UHFFFAOYSA-N InChI=1/C8H8O3/c9-7(8(10)11)6-4-2-1-3-5-6/h1-5,7,9H,(H,10,11) Key: IWYDHOAUDWTVEP-UHFFFAOYAD
SMILES O=C(O)C(O)c1ccccc1
Properties
Chemical formula	C8H8O3
Molar mass	152.15 g·mol^−1
Appearance	White crystalline powder
Density	1.30 g/cm^3
Melting point	119 °C (246 °F; 392 K) optically pure: 132 to 135 °C (270 to 275 °F; 405 to 408 K)
Boiling point	321.8 °C (611.2 °F; 595.0 K)
Solubility in water	15.87 g/100 mL
Solubility	soluble in diethyl ether, ethanol, isopropanol
Acidity (pKa)	3.41[2]
Refractive index (nD)	1.5204
Thermochemistry
Std enthalpy of formation (ΔfH^o298)	0.1761 kJ/g
Pharmacology
ATC code	B05CA06 (WHO) J01XX06
Hazards
Flash point	162.6 °C (324.7 °F; 435.8 K)
Related compounds
Related compounds	mandelonitrile, phenylacetic acid, vanillylmandelic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Mandelic acid is an aromatic alpha hydroxy acid with the molecular formula C₆H₅CH(OH)CO₂H. It is a white crystalline solid that is soluble in water and polar organic solvents. It is a useful precursor to various drugs. The molecule is chiral. The racemic mixture is known as paramandelic acid.

Isolation, synthesis, occurrence

Mandelic acid was discovered while heating amygdalin, an extract of bitter almonds, with diluted hydrochloric acid. The name is derived from the German "Mandel" for "almond". Derivatives of mandelic acid are formed as a result of metabolism of adrenaline and noradrenaline by monoamine oxidase and catechol-O-methyl transferase.

Mandelic acid is usually prepared by the acid-catalysed hydrolysis of mandelonitrile,^[3] which is the cyanohydrin of benzaldehyde. Mandelonitrile can also be prepared by reacting benzaldehyde with sodium bisulfite to give the corresponding adduct, forming mandelonitrile with sodium cyanide, which is hydrolyzed:^[4]

Alternatively, it can be prepared by base hydrolysis of phenylchloroacetic acid and dibromacetophenone.^[5] It also arises by heating phenylglyoxal with alkalis.

It arises from the biodegradation of styrene, as detected in urine.^[6]

Uses

Mandelic acid has a long history of use in the medical community as an antibacterial, particularly in the treatment of urinary tract infections.^[7] It has also been used as an oral antibiotic, and as a component of "chemical face peels", along with other alpha-hydroxy acids (AHAs).

The drugs cyclandelate and homatropine are esters of mandelic acid.

References

1. Merck Index, 11th Edition, 5599.
2. Bjerrum, J., et al. Stability Constants, Chemical Society, London, 1958.
3. Edwin Ritzer and Rudolf Sundermann "Hydroxycarboxylic Acids, Aromatic" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi: 10.1002/14356007.a13_519
4. Corson, B. B.; Dodge, R. A.; Harris, S. A.; Yeaw, J. S. (1941). "Mandelic Acid". Org. Synth.; Coll. Vol. 1, p. 336
5. J. G. Aston, J. D. Newkirk, D. M. Jenkins, and Julian Dorsky (1952). "Mandelic Acid". Org. Synth.; Coll. Vol. 3, p. 538
6. Engström K, Härkönen H, Kalliokoski P, Rantanen J. "Urinary mandelic acid concentration after occupational exposure to styrene and its use as a biological exposure test" Scand. J. Work Environ. Health. 1976, volume 2, pp. 21-6.
7. Putten, P. L. (1979). "Mandelic acid and urinary tract infections". Antonie van Leeuwenhoek 45 (4): 622. doi:10.1007/BF00403669.

•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "^{article name needed}". Encyclopædia Britannica (11th ed.). Cambridge University Press.