Mandelic acid

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Mandelic acid[1]
Kwas migdałowy.svg
CAS number 90-64-2 YesY, 611-71-2 (R), 17199-29-0 (S)
PubChem 1292
ChemSpider 1253 YesY
EC number 202-007-6
ChEBI CHEBI:35825 YesY
RTECS number OO6300000
ATC code B05CA06,J01XX06
Jmol-3D images Image 1
Molecular formula C8H8O3
Molar mass 152.15 g mol−1
Appearance White crystalline powder
Density 1.30 g/cm3
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]
0.1761 kJ/g
Flash point 162.6 °C (324.7 °F; 435.8 K)
Related compounds
Related compounds mandelonitrile, phenylacetic acid, vanillylmandelic acid
Except where noted otherwise, 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. Since the molecule is chiral, it exists in either of two enantiomers as well as the racemic mixture, known as paramandelic acid.

Isolation and synthesis[edit]

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]

Preparation of mandelic acid.png

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


Mandelic acid has a long history of use in the medical community as an antibacterial, particularly in the treatment of urinary tract infections.[6] 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.


  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: 336 
  5. ^ J. G. Aston, J. D. Newkirk, D. M. Jenkins, and Julian Dorsky (1952), "Mandelic Acid", Org. Synth. ; Coll. Vol. 3: 538 
  6. ^ Putten, P. L. (1979). "Mandelic acid and urinary tract infections". Antonie van Leeuwenhoek 45 (4): 622. doi:10.1007/BF00403669.