CONFORMATIONAL AND SOLID-STATE STUDIES OF DIPHENYL 1-HYDROXY-1-PHENYLETHYLPHOSPHONATE

The crystal structure of the title compound, diphenyl 1-hydroxy-1-phen ylethylphosphonate (1), was determined by the single-crystal X-ray dif fraction method. The crystallographic data for 1 are as follow: C20H19 O4P, M-r = 354.34, monoclinic, P2(1)/n, a = 9.787(1) Angstrom, b = 20. 235(1) Angstrom, c = 9.797(1) Angstrom, beta = 106.18(3)degrees, V = 1 863.3(4) Angstrom(3), Z = 4, D-calc = 1.26 g/cm(3), lambda(Mo-K alpha) = 0.71073 Angstrom, mu = 1.6 cm(-1), F(000) = 744, R = 0.018, and R-w = 0.032 for 2258 observed reflections. The solid-state structure in a dimeric packing mode exhibits intermolecular hydrogen bonding of the type P=O ... H-O. Infrared solution studies (CCl4) indicate that upon high dilution (10(-4) M) the dimers completely dissociate to give conf ormers with and without intramolecular hydrogen bonds. Theoretical stu dies (PM3) were undertaken to determine the energy profile about the P -C torsional angle, which exhibited low energy barriers to rotation wi th no clear minimum energy conformation. (C) 1996 John Wiley & Sons, I nc.