Potentially bifunctional reactants. The kinetics of aromatic nucleo-philic substitution by benzamidine and n-butylamine

Abstract

Halogen substitution of 1-chloro-2,4-dinitrobenzene in chlorobenzene by n-butylamine proceeds more rapidly than substitution by benzamidine, neither reactions requiring a catalyst. Halogen substitution of 4-fluoro-1,6-dinitronaphthalene in chlorobenzene is of the second order in n-butylamine and of the first order in benzamidine. This indicates that the amidine may react bifunctionally when catalysis is required, as no enhanced rate for the reaction of the amidine, with respect to the corresponding reaction of an amine of similar basicity, results when no catalysis is required. In the case of 1-fluoro-2,4-dinitrobenzene an intramolecularly catalysed pathway is available to reactions with either benzamidine or n-butylamine, so that the former is not particularly favoured with respect to the latter. The relevance of these results to the studies of model reactions for enzyme action is discussed.