Racemic Structure and Optical Resolution by Preferential Crystallization of (+/-)-Organic Ammonium Hydrogen Malates

Article abstract of DOI:10.1246/bcsj.61.899

Gibbs energies of formation of racemate, binary melting point diagrams, and ternary solubility diagrams indicate that (+/-)-propylammonium ((+/-)-PA salt) and (+/-)-1,1,3,3-tetramethylbutylammonium ((+/-)-TMB salt) hydrogen malates are conglomerates at room temperature, whereas (+/-)-TMB salt forms a racemic compound at its melting point.Free energies of critical nucleation in supersaturated solutions were examined to resolve (+/-)-PA and -TMB salts efficiently by preferential crystallization.Successive preferential crystallization of (+/-)-PA salt in methanol at 10 deg C and that of (+/-)-TMB salt in water give (+)- and (-)-PA and -TMB salts with about 90percent optical purity.Optically pure (+)- and (-)-malic acids are obtained from purified (-)- and (+)-salts.