Abstract: Process for the preparation of fluorobenzenes having at least one hydrogen atom as ring substituent and, optionally, further substituents, which, independently of each other, can be chlorine, bromine, nitro, hydroxyl, C.sub.1 -C.sub.3 -alkoxy or C.sub.1 -C.sub.3 -alkyl, the number of nitro groups being not more than 2 and the number of hydroxyl groups and alkoxy groups being not more than 3 in each case, by heating the corresponding benzaldehydes, substituted by at least one flourine atom, in the presence of a catalyst, characterized in that the reaction product is immediately removed from the reaction zone.

Abstract: Selectively dehalogenated thiophene derivatives are obtained from compounds of the formula II ##STR1## by an electrochemical reaction in a divided electrolysis cell in the presence of a suitable solvent, an onium compound or a compound which is converted into an onium compound in the electrolyte, and a conducting salt. Thiophene derivatives are important intermediates in the production of pharmaceuticals and plant protection agents.

Abstract: A process for the preparation of fluorobenzenes of the formula I ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 are equal or different and represent H, F, Cl or alkyl having from 1 to 3 carbon atoms, at least one of these radicals being fluorine, and S.sup.1 and S.sup.2 being equal or different and represent H or a group reducing the electron density at the benzene nucleus, which comprises subjecting a compound of the formula II ##STR2## in which R.sup.1, R.sup.2, R.sup.3, S.sup.1 and S.sup.2 have the aforementioned meaning to a decarbonylation at a zeolite catalyst.