Mandelic acid is an aromatic alpha hydroxy acid with the molecular formula C₈H₈O₃. It is a white crystalline solid that is soluble in water and most common organic solvents.

Discovery and name

Mandelic acid was discovered while heating amygdalin, an extract of bitter almonds, with diluted hydrochloric acid. It was first reported in 1909 by J. W. Walker and V. K. Krieble. The name is derived from the German "Mandel" for "almond".

Chemistry

It is an isomer of cresotinic acid (2-hydroxy-3-methylbenzoic acid) and oxymethylbenzoic acid (2-methoxybenzoic acid). Derivatives of mandelic acid are formed as a result of metabolism of adrenaline and noradrenaline by monoamine oxidase and catechol-o-methyl transferase. It is also present in certain skin care products, is an intermediate molecule in the production of other biochemicals, may be used as an analytical reagent and is a precursor in the manufacture of dyes.

Since the molecule contains a chiral carbon atom, the acid exists in either of two optically active forms. The racemic mixture of the two is known as paramandelic acid.

It may be prepared by the action of hydrochloric acid on mandelonitrile, the addition compound of benzaldehyde and hydrocyanic acid; by boiling phenylchloracetic acid with alkalis; by heating benzoyl formaldehyde with alkalis; or by the action of dilute alkalis on ω-dibromacetophenone.

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