The relative reactivity of fluoro- and chloro-2,4-dinitrobenzenes in their reactions with amines

Abstract

Francesco Pietra Istituto di Chimica Generale, Universita di Pisa, Pisa, Italy. (Received 1 February 1965) Although the leaving group ability of fluoride relative to other halide ions in nucleophilic activated aromatic substitution reactions has received considerable attention (1), there is still much controversy about the factors governing it. In the course of a kinetic investigation of the reactions of activated aryl halides with amines in non-polar aprotic solvents, a preliminary account of, which has already been given (2), data have been collected which appear to be relevant to the above mentioned problem. These concern the reactions of fluoro-2,4-dinitrobenzene (FDNB) or chloro-2,4dinitrobenzene (CDNB) with piperidine, 2-methylpiperidine and cis-2,6_dimethylpiperidine respectively in benzene at 25’. In Table I are listed the data for the reactions of the last two aminesr those for piperidine have already been reported (2). Examination of the results for the reactions of FDNB (Table Ia, Ib) shows that the second-order rate coefficients increase with increasing amine concentration. The rate data can be very satisfactorily expressed by equation [1]