Mandelic acid

Mandelic acid[1]
IUPAC name	2-Hydroxy-2-phenylacetic acid
Other names	Mandelic acid Phenylglycolic acid
Identifiers
CAS number	90-64-2 Y
SMILES	OC(C(O)c1ccccc1)=O
ChemSpider ID	1253
Properties
Molecular formula	C8H8O3
Molar mass	152.14 g/mol
Density	1.30 g/cm3
Melting point	119 °C
Solubility in water	1 g per 6.3 mL
Solubility in chloroform, diethyl ether, methanol	chloroform 0.12 M, diethyl ether 0.77 M, methanol 3.54 M [2]
Acidity (pKa)	3.37
Related compounds
Related compounds	mandelonitrile, phenylacetic acid, vanillylmandelic acid
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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 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 phenylchloroacetic acid with alkalis; by heating benzoyl formaldehyde with alkalis; or by the action of dilute alkalis on ω-dibromacetophenone.

Preparation

Mandelonitrile may be prepared by reacting benzaldehyde with sodium bisulfite to give the corresponding adduct, forming mandelonitrile with sodium cyanide, which is hydrolyzed:^[3]

Uses

Mandelic acid has a long history of use in the medical community as an antibacterial, particularly in the treatment of urinary tract infections.^[4] It has also been used as an oral antibiotic. Lately, Mandelic acid has gained popularity as a topical skin care treatment for adult acne. It is also used as an alternative to glycolic acid in skin care products. Mandelic acid is a larger molecule than glycolic acid which makes it better tolerated on the skin. Mandelic acid is also advantageous in that it possesses antibacterial properties, whereas glycolic acid does not.

Its use as a skincare modality was pioneered by Dr James E. Fulton, who developed vitamin A acid (tretinoin, Retin A) in 1969.^[5] On the basis of this research, dermatologists now suggest mandelic acid as an appropriate treatment for a wide variety of skin concerns, from acne to wrinkles; it is especially good in the treatment of adult acne as it addresses both of these concerns. Mandelic acid is also recommended is a pre- and post-laser treatment, reducing the amount and length of irritation caused by laser resurfacing.

References

• This article incorporates text from the Encyclopædia Britannica, Eleventh Edition, a publication now in the public domain.