CATALYSIS IN NUCLEOPHILIC AROMATIC-SUBSTITUTION REACTIONS - A REINVESTIGATION OF THE REACTION BETWEEN 1-FLUORO-2,4-DINITROBENZENE AND NORMAL-BUTYLAMINE

The reaction between 1-fluoro-2,4-dinitrobenzene and n-butylamine in toluene shows a two-step plot of k(obs) values vs the initial values of the concentration of the amine. The usual base-catalysis mechanism for HF elimination from the zwitterionic intermediate hardly explains this kinetic behaviour and the kinetic effect of addition of salts (and of 2-hydroxypyridine) to the reaction mixtures at different initial values of the concentration of n-butylamine. In contrast, the kinetic behaviours are easily explained by the presence of substrate-amine (or catalyst) interactions on the pathway of the substitution reaction.