STRUCTURE OF 3-(P-CHLOROPHENYL)-1-PHENYL-1,3-PROPANEDIONE ENOL

1-(4-Chlorophenyl)-3-hydroxy-3-phenyl-2-propen-1-one, C15H11ClO2, M(r) = 258.7, C2/c, a = 24.324 (4), b = 6.537 (2), c = 15.598 (2) angstrom, beta = 93.52 (1)-degrees, V = 2475.5 (9) angstrom3, Z = 8, D(x) = 1.382 g cm-3, lambda(Mo Kalpha) = 0.71069 angstrom, mu = 2.95 cm-1, F(000) = 1072, T = 298 K, final R = 0.043 for 1192 observed reflections. The compound displays a strong intramolecular asymmetric hydrogen bond [O...O = 2.471 (4), O-H = 1.09 angstrom, IR nu(OH) stretching frequency = 2577 cm-1, H-1 NMR chemical shift of the enolic proton = 16.8 p.p.m.] which can be interpreted in terms of resonance-assisted hydrogen bonding. The proton localization, that is, the preference displayed by the proton for settling on an O atom of the beta-diketone fragment rather than on the other O atom, is discussed and related to the different environments of the two O atoms in the crystal packing and, in particular, to the asymmetry of their C-H...O short contacts.