2,3,4,5-tetrafluorobenzene derivatives can be obtained in a particularly
advantageous manner by reacting the corresponding chlorobenzene or
(chloro, fluoro)-benzene derivatives with a fluorinating agent in the
presence of a solvent and a catalyst at elevated temperature, which
comprises carrying out the reaction initially under temperature and
pressure conditions such that the respective 2,3,4,5-tetrafluoro-benzene
derivative continuously distills off through a column, and subsequently
setting temperature and pressure conditions such that residual fractions
of the 2,3,4,5-tetrafluorobenzene derivative distill off with the
corresponding 2,3,4-trifluoro-5-chloro compound.