Both the S enantiomer and the racemic (RS) forms of 2-(2-nitro-1-phenylethyl)-1,3-diphenyl-propane-1,3-dione (1) have been obtained from the same reaction media by fractional crystallization from toluene. First, the racemic compound, (R,S)-1, was precipitated (mp. 159.7 degrees C), then, from the filtrate, (S)-1 (mp. 135.6 degrees C) was crystallized. The absolute configuration (S) and crystal structure of (S)-1 has been solved by single crystal X-ray diffraction (R=0.0377). (S)-1 crystallizes in the orthorhombic crystal system (space group P2(1)2(1)2(1) (19), a = 10.6377(2) angstrom, b = 11.4348(2) angstrom, c = 31.3543(6) angstrom, Z = 8, Z' = 2). Powder XRD pattern of the racemic crystal (R,S)-1 could be indexed in the orthorhombic space group Pbca (61) (a = 22.18(7) angstrom, b = 17.08(3)angstrom, c = 9.96(3) angstrom, z = 8, Z' = 1). Differences in secondary bonding interactions and crystal stability of both (S)-1 and (R,S)-1 were evaluated on the basis of their FTIR spectra, melting points, and enthalpies of fusion. The expected eutectic-type binary melting phase diagram of (S)-1 and (R,S)-1 crystals has been constructed based on differential scanning calorimetric (DSC) measurements and calculation of the liquidus curves according to the combination of the simplified Schroder-van Laar and Prigogine-Defay equations. (C) 2014 Elsevier B.V. All rights reserved.