STRUCTURAL ASPECTS OF OPTICAL RESOLUTIONS - OPTICAL RESOLUTION OF (R,S)-MANDELIC ACID - DSC AND X-RAY STUDIES OF THE DIASTEREOISOMERIC SALTS

The diastereoisomeric salt pair formed during the resolution of mandelic acid (MA) using (R)-2-tert-butyl-3-methylimidazolidin-4-one (BMI) has been studied by DSC and X-ray crystallographic methods. Both diastereoisomers crystallize in a monoclinic system with space group P2(1); unit cell parameters for the less soluble R-R isomer: a = 11.484(1), b = 6.027(1), c = 11.951 (1) angstrom, beta = 98.77 (1)-degrees, V = 817.5 (3) angstrom3; for the more soluble R-S diastereoisomer a = 11.170(1), b = 5.975(1), c = 13.327(1) angstrom, beta = 111.95(1)-degrees, V = 825.0(3) angstrom3. The structures were solved by direct methods and refined to a final R value of 0.044 and 0.057, respectively.