Process for preparing fluorobenzonitriles

Claim 1

A process for replacement, with fluorine, of at least one chlorine atom of a compound of the formula (4) ##STR4## in which a is a number from 1 to 5 and b is a number from 0 to 3, said process comprising reacting said compound of formula (4) with an alkali metal fluoride at a reaction temperature in the range of from 80 to 220° C. in the presence of: (1) 0 to 30% by weight aprotic or 0 to 5% by weight of a protic solvent, based on the weight of said compound of formula (4), (2) from 1 to 35% by weight, based on the weight of the compound of formula (4), of a catalyst, said catalyst comprising at least 5% by weight, based on the total catalyst, of a quaternary ammonium compound of the formula (1) ##STR5## in which R 4 is a linear or branched alkoxypolyoxyalkyl radical of the formula (C m H 2m O) p R 5 , in which R 5 is a hydrogen or a linear or branched alkyl radical having from 1 to 16 carbon atoms, m is a number from 1 to 10, and p is a number from 1 to 15; R 1 , R 2 , and R 3 are the same or different and are: a linear or branched alkoxypolyoxyalkyl radical of the formula (C m H 2m O) p R 5 , in which R 5 , m, and p are as previously defined; a linear or branched alkyl radical having from 1 to 30 carbon atoms; or a phenyl or naphthyl radical which is unsubstituted or substituted by halogen, C 1 -C 4 -alkyl, C 1 -C 4 -alkoxy, nitro, or cyano; X.sup.(-) is an inorganic anion.