Samples of all three of the expected bisphenols, 4,4′,5,5′-tetrachloro-2,2′-methylenebisphenol (1) and the 3,4,4′,5′-(2) and 3,3′,4,4′-tetrachloro (3) isomers, and of a minor by-product, 5,5′,6,6′-tetrachloro-8,8′-methylenebis(4H-benzo-1,3-dioxin) (4), have been isolated from the mixture formed by acid-catalyzed condensation of 3,4-dichlorophenol with one half of a molar equivalent of formaldehyde. In addition, the structures and solid state conformations of all four compounds, and of an ethanol solvate of 1, have been revealed by X-ray crystallographic studies. The three bisphenols (1, 2, 3) all crystallize in space group [Formula: see text], as centrosymmetric hydrogen-bonded dimers, while the solvate, 1•EtOH, although it also belongs to space group [Formula: see text], forms relatively open infinite bands of hydrogen-bonded molecules. Crystals of 4 belong to space group Fdd2 and the molecules have twofold crystallographic symmetry. Keywords: X-ray crystallography, bisphenols, tetrachloro-2,2′-methylenebisphenols, tetrachloro-8,8′-methylenebis(4H-benzo-1,3-dioxin).
