Bisphenol flukicides. IV. Conformational studies of two halogenated bisbenzyl phenols : 2,6-Bis(3'-bromo-5'-chloro-2'-hydroxybenzy1)-4-fluorophenol and 2,6-bis(3'-bromo-5'-chloro-4'-hydroxybenzyl)-4-fluorophenol

Abstract

Monoclinic crystals of an ethyl acetate adduct of 2,6-bis(3´-bromo-5´-chloro-2´-hydroxybenzyl)- 4-fluorophenol (l),⅓EtOAc, C₂₀H₁₃Br₂Cl₂FO₃⅓(C₄H₈O₂), belong to the space group P2₁/c with a 11.943(2), b 25.395(15), c 7.287(1) Å, β 96.56(1)º, Z 4. Crystals of the isomeric compound, 2,6-bis(3´-bromo-5´-chloro-4´-hydroxybenzy)-4-fluorophenol (2), belong to the monoclinic space group C2/c with a 8.853(4), b 14.246(3), c 15.972(4) Å, β 98.49(3)º, Z 4. The structures were refined with diffractometer data measured with Mo Kα radiation to R 0.059 (2243 terms) for (l),⅓EtOAc and R 0.060 (1119 terms) for (2). The conformation of each bisbenzylphenol molecule can be described in terms of two chemically equivalent diphenylmethane moieties with the 4-fluoro- phenol ring common to both. In the molecules of (1), the moieties adopt skew and butterfly conformations. For the former, the dihedral angles between the perpendiculars to the plane of the C-CH₂-C bridge and the bromochlorophenol and fluorophenol rings are 19.0º and 85.0º respectively, while, for the butterfly conformation, the analogous angles are 84.8º and 88.8º. Molecules of (2) have exact C₂ symmetry and the conformation of the bridged diphenyl moiety is skew, with dihedral angles between the perpendiculars to the C-CH₂-C plane and the bromochlorophenol and fluorophenol rings of 27.0º and 78.1º respectively.