Manuscript draft to Thermochimica Acta, 1 Solid state structural relation and binary melting phase diagram of (S-) and racemic 2-(2-nitro-1-phenylethyl)-1,3-diphenyl-propane-1,3-dione. Katalin Gönczi a , Veronika Kudar b , Zsuzsa Jászay c , Petra Bombicz b , Ferenc Faigl a,c , János Madarász d,* a Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, H-1521 Budapest, Hungary. b Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1525 Budapest, Hungary. c MTA-BME Organic Chemical Technology Research Group, Hungarian Academy of Sciences, 1521 Budapest, Hungary. d Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, H-1521 Budapest, Hungary Abstract Both enantiomeric (S-) and 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 has been precipitated (mp. 159.7°C), then, from the filtrate, its chiral form, (S)-1 (mp. 135.6°C) has crystallized. The absolute molecular configuration (S) and crystal structure of the latter one, which crystallizes in the orthorhombic crystal system (space group P2 1 2 1 2 1 (19), a = 10.6377(2) Å, b = 11.4348(2) Å, c = 31.3543(6) Å, Z = 8, Z’ = 2), has been solved by single crystal X-ray diffraction (R = 0.0377). Powder XRD pattern of the racemic precipitation, (R,S)-1 could be indexed in the orthorhombic space group Pbca (61) (a = 22.18(7) Å, b = 17.08(3) Å, c = 9.96(3) Å, Z = 8, Z’ = 1). Differences in the secondary bonding interactions and in crystal stability of the chiral and racemic compound are evaluated on the basis of their FT-IR spectrum, melting point and enthalpy of fusion. The eutectic type binary melting phase diagram of enantiomeric and racemic compounds are constructed based on the Differential Scanning Calorimetric (DSC) measurements and calculation of the liquidus curves according to the combination of the simplified Schröder-van Laar and Prigogine-Defay equations. Keywords Enantioselective Michael addition, dibenzoylmethane, trans-2-nitrostyrene, single crystal and powder X-ray diffraction (XRD), crystal structure determination, FT-IR spectroscopy, Differential Scanning Calorimetry (DSC), binary melting phase diagrams, eutectic compositions and temperatures, structure-property relationship * Corresponding author. Fax: +36-1-463-3408; e-mail: madarasz@mail.bme.hu (J. Madarász)