PREPARATION OF DICARBOXYLIC ACID OR ESTER THEREOF

PURPOSE:To prepare the titled compound in high yield, by reacting an alpha,omega- bis(phenoxy)alkane-4,4'-dicarboxylic acid which is a raw material for a polyester as a starting material with chlorine in a 2-6C halogenated lower fatty acid as a solvent. CONSTITUTION:An alpha,omega-bis(phenoxy)alkane-4,4'-dicarboxylic acid or an ester thereof is reacted with chlorine in a 2-6C halogenated lower fatty acid, e.g. monochloroacetic acid, dichloroacetic acid or trichloroacetic acid, as a slovent to give an alpha,omega-bis(2,6-dichlorophenoxy)alkane-4,4'-dicarboxylic acid which is an aromatic dicarboxylic acid containing four chlorine atoms linked to the given positions of the benzene nucleus or an ester thereof. USE:A raw material for fiber-forming polyesters having a high elasticity and self-extinguishing characteristics.