A SEPARATION OF 2-HYDROXYMANDELIC AND 4-HYDROXYMANDELIC ACID

Hydroxyalkylation of phenol with glyoxylic acid, catalyzed by Al-III r esults, under neutral aqueous conditions, in ortho-rich mixtures of hy droxymandelic acids. Para-rich mixtures of hydroxymandelic acids are o btained by Zn-II catalysis under slightly alkaline conditions. A new s eparation method of these mixtures into the pure alkali salts of 2- an d 4-hydroxymandelic acid is presented. Formation of a complex between the alkali ion and three co-operating oxygen atoms of 2-hydroxymandela te explains the excellent solubility of the ortho isomer in acetone, e nabling extraction of this isomer selectively from mixtures of alkali salts of 2- and 4-hydroxymandelic acid.