| abstract |
A process for the preparation of bisphenols, which comprises condensing an aliphatic or cycloaliphatic ketone with a phenol having a free p-position in the presence, as a condensing agent, of from 0.3 to 3 mols, per mol of ketone, of an aromatic sulphonic acid of the formula (III) or (IV): <IMAGE> wherein R3 is an inert organic radical, o represents an integer from 1 to 4, and p represents 0 or an integer from 1 to 4, and in the presence of an organic solvent, in which the aromatic sulphonic acid is effectively soluble and the bisphenol or the phenol adduct which is produced is as slightly soluble as possible, the reaction being carried out at a temperature at which the produced diphenol crystallises as extensively as possible as such or as a phenol adduct during or at the end of the reaction; isolating the crystalline separated bisphenol or its adduct; and removing the adhering phenol or solvent. |