2,6-Diphenylphenol: a structure containing an intramolecular O–H⋯π hydrogen bond

C~sH~40, orthorhombic, P2~2~21, a = 11.165 (1), b = 18.399 (2), c = 6.368 (1) A, Z = 4, D x = 1.251 gcm -a, #(Mo Ka) = 0.89 cm-k The stereochemistry of the intramolecular O-H...Tt hydrogen bond in the title molecule has been estab- fished by single-crystal X-ray analysis. The hydroxyl H atom is favourably located in the proximity of two of the 2-phenyl C atoms, at distances of 2.43 (4) and 2.40 (4) A, to interact with their 7t electrons. The 2- and 6-phenyl rings are twisted from the phenol ring by 52 and 44 ° respectively. Introduction. Hitherto many spectroscopic studies have been carried out on hydrogen bonds in which 7r electrons are involved as the acceptor base. However, only a few unequivocal X-ray studies on such hydrogen bonds have been reported (Hardy & MacNicol, 1976; Aubry, Protas, Moreno-Gonzalez & Marraud, 1977). To elucidate the stereochemistry of the intramolecular O-H... 7t bond the structure of the present compound was studied by X-ray diffraction. Spectroscopic studies on CC14 solutions of the compound (0ki, Hosoya & Iwamura, 1961; Ueji, Ueda & Kinugasa, 1976) showed an intramo!ecular interaction between the hydroxyl group and the 7t electrons of the o-phenyl group. The IR spectrum of the crystals (CsI disc) indicated a single hydroxyl stretching band at 3524 cm -~, which was red- shifted by 88 cm -~ from that of phenol in a dilute CCI 4 solution. This strongly suggests the presence of an