Reactions of the N-F class of fluorinating reagents with solvents

The transformations of various reagents of the N-F type in water, acetonitrile, alcohols and aqueous solutions of alkali hydroxides were investigated. First-order kinetics for 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2] octane bis(tetrafluoroborate) (F-TEDA) and 1-hydroxy-4-fluoro-1,4-diazoniabicyclo[2,2,2]octane bis(tetrafluoroborate) (NFTh) transformations were established: F-TEDA is less stable in water at 60 degrees C than NFTh, while N-fluorobis(phenylsulphonyl) amine (NFS) is very stable. The addition of acetonitrile to an aqueous solution of F-TEDA enhanced the transformation (k = 1.3 X 10(-5) s(-1)), while a reaction which was three-times faster was observed in water/methanol solution (k = 3.5 X 10(-5) s(-1) at 60 degrees C), The energy of activation for the transformation of F-TEDA in water was found to be 21.1 kcal mol(-1), 20.6 kcal mol(-1) in water/methanol solution and 13.8 kcal mol(-1) in a water/acetonitrile mixture.