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Bible Encyclopedias
Mandelic Acid
1911 Encyclopedia Britannica
or MANDELIC ACID (Phenylglycollic Acid), C 8 H 8 O 3 or C 6 H 5
CH(OH)
COOH, an isomer of the cresotinic and the oxymethylbenzoic acids. Since the molecule contains an asymmetric carbon atom, the acid exists in three forms, one being an inactive "racemic" mixture, and the other two being optically active forms. The inactive variety is known as paramandelic acid. It may be prepared by the action of hydrochloric acid on the addition compound of benzaldehyde and hydrocyanic acid: C 6 H 5 CHO-HCN+HC1+2H 2 O= C6H5
[[Choh
000h+Nh4c1, (F. L]]. Winckler, Ann., 1836, 18, 3 10), by boiling phenylchloracetic acid with alkalis (A. Spiegel, Ber., 1881, 14, 23 9), by heating benzoylformaldehyde with alkalis (H. v. Pechmann, Ber., 1887, 20, 2905), and by the action of dilute alkalies on w-dibromacetophenone (C. Engler, Ber., 1887, 20, 2202): C6HS000HBr2 -13KH0 = 2KBr+ H 2 O + C6H5
[[Choh
C02k]].
It crystallizes from water in large rhombic crystals, which melt at 118° C. Oxidizing agents convert it into benzaldehyde. When heated with hydriodic acid and phosphorus it forms phenylacetic acid; whilst concentrated hydrobromic acid and hydrochloric acid at moderate temperatures convert it into phenylbromand phenylchlor-acetic acids. The inactive mixture may be resolved into its active components by fractional crystallization of the cinchonine salt, when the salt of the dextro modification separates first; or the ammonium salt may be fermented by Penicillium glaucum, when the laevo form is destroyed and the dextro form remains untouched; on the other' hand, Saccharomyces ellipsoideus destroys the dextro form, but does not touch the laevo form. A mixture of the two forms in equivalent quantities produces the inactive variety, which is also obtained when either form is heated for some hours to 160° C.
These files are public domain.
Chisholm, Hugh, General Editor. Entry for 'Mandelic Acid'. 1911 Encyclopedia Britanica. https://www.studylight.org/encyclopedias/eng/bri/m/mandelic-acid.html. 1910.
