Catalysis by amine salts of the reactions of 1-chloro- and 1-fluoro-2,4-dinitrobenzene with N-methylaniline in acetonitrile

Abstract

The second-order rate constant k_A for the reaction of 1-chloro-2,4-dinitrobenzene with N-methylaniline increases slightly with the addition of quaternary ammonium salts according to the equation k_A=k′+k″[salt]. Values of k″/k′ of 8.9 for the chloride and 4.1 for the perchlorate are much less than the value of 240 obtained previously for the chloride when the nucleophile was aniline. Any acceleration produced by the hydrochlorides of N-methylaniline, trimethylamine, or triethylamine is less than those given by the quaternary ammonium perchlorate. The results agree with a recently proposed mechanism for the halide ion catalysis of the anilinodechlorination reaction in acetonitrile.

The reaction of 1-fluoro-2,4-dinitrobenzene with N-methylaniline has a curvilinear dependence on the concentrations of tetraethylammonium chloride and the hydrochlorides of N-methylaniline and trimethylamine; the accelerations observed are greater than that produced by tetraethylammonium perchlorate. The results are interpreted as due to base catalysis by chloride ion at the intermediate stage.