Abstract: Process for the preparation of biaryls of the formula (1)R.sup.1.sub.m --Ar--Ar--R.sup.1.sub.m (1)wherein Ar is a phenylene or naphthylene radical, R.sup.1 is a hydrogen, fluorine or chlorine atom or an unbranched or branched alkyl(C.sub.1 -C.sub.6)--, alkyl(C.sub.1 -C.sub.6)--O--, alkyl(C.sub.1 -C.sub.6)--CO-- or alkyl(C.sub.1 -C.sub.6)--SO.sub.2 -- radical and m is the number of still unsubstituted ##STR1## positions on the Ar radical, in which a compound of the formula (2)R.sup.1.sub.m --Ar--X (2)wherein Ar, R.sup.1 and m have the meanings cited above and X is a chlorine or bromine atom, is dehalogenated and dimerized in the presence of a palladium catalyst on a support material, of a reducing agent, a hydrogen halide acceptor, a polyether or polyether mixture and of water at temperatures of about 50.degree. to about 120.degree. C.

Abstract: According to a process for producing isomer-free 2,3-difluoro-6-nitrophenol, 2,3,4-trifluoronitrobenzene is reacted with an aqueous solution of alkali metal or alkaline earth metal hydroxide in the absence of organic solvent, at temperatures between about 20.degree. C. and 100.degree. C., the pH value of the reaction mixture is set at about 1 to 6 by acid addition, the resulting product is stream distilled and the 2,3-difluoro-6-nitrophenol is isolated after cooling. No organic solvents are used during any of the steps of the process.

Abstract: A process for the preparation of 1,4-bis(4-hydroxybenzoyl)benzene of the formula (I) ##STR1## by rearranging diphenyl terephthalate of the formula (II) ##STR2## in about 3 to about 50 parts, relative to the diphenyl terephthalate, of an anhydrous organic solvent which is inert to the reactants, in the presence of about 30 to about 500 mol-% of a haloalkanesulfonic acid (catalyst) of the general formula (III) or (IV)Y(C.sub.n X.sub.2n)SO.sub.3 H (III)Y(C.sub.n F.sub.2n)SO.sub.3 H (IV)in which Y is a fluorine or hydrogen atom, and X is a fluorine and/or chlorine atom, with the proviso that at least one X is a fluorine atom, and n is an integer from 1 to 10, at temperatures of about 10.degree. to about 200.degree. C.

Abstract: A process for the preparation of 1,4-bis(4-hydroxybenzoyl)benzene of the formula (I) ##STR1## by reacting a 1,4-bis(4-halobenzoyl)benzene of the formula (II) ##STR2## in which X is a fluorine, chlorine or bromine atom, with an alkali metal hydroxide or alkaline earth metal hydroxide or with mixtures of these hydroxides in a solvent which is inert to the reaction components under the reaction conditions at temperatures of about 100.degree. C. to about 250.degree. C., if appropriate in the presence of a phase transfer catalyst.

Abstract: A process for the preparation of halogen-containing aromatic compounds of the formula ##STR1## wherein Hal represents fluorine, chlorine or bromine and Z represents an aromatic group which comprises reacting a halobenzene of the formula C.sub.6 H.sub.5 Hal (II) under anhydrous conditions with a halide of a bisacid having the formula Hal-CO-Z-CO-Hal (III) in a molar ratio of at least 2:1 in the presence of a haloalkane sulfonic acid of the formula Y(C.sub.n X.sub.2n)SO.sub.3 H (IV), in formulae II and III Hal and Z having the afore-mentioned meaning and Y representing fluorine or hydrogen, X at least one of fluorine and chlorine, but at least one X being fluorine, and n being an integer of from 1 to 10.The said bis-(4-halobenzoyl) compounds being useful monomers for chemically resistant plastics which are still resistant even at high temperatures.