1,2-DIPHENYLETHANE-1,2-DIAMINE - AN EFFECTIVE NMR CHIRAL SOLVATING AGENT FOR CHIRAL CARBOXYLIC-ACIDS

(1R,2R)-1,2-diphenylethane-1,2-diamine, 1, acts as an effective chiral solvating agent (CSA) in the H-1 NMR analysis of the enantiomeric purity of chiral carboxylic acids. In the 2:1 salt complexes with a range of acids including alpha-arylpropanoic, alpha-halo carboxylic acid and primary carboxylic acids, RCH2CO2H, the diastereotopic resonances in H-1 NMR were typically more than 0.05 ppm shift non-equivalent. The effect of temperature, stoichiometry, acid enantiomeric purity, concentration and solvent on the observed shift non-equivalence was studied. The structure of the CSA was varied systematically and the observed non-equivalence with 1, may be attributed to the anisotropy of the second aryl ring which is proximate to the substituents alpha to the carboxylic acid group.