The stabilities of Meisenheimer complexes. Part 37. Kinetic and equilibrium studies of the reactions of 2,2′,4,4′,6,6′-hexanitrobibenzyl with aliphatic amines in dimethyl sulphoxide

Abstract

Kinetic and equilibrium data are reported for the reversible reactoins of 2,2′4,4′,6,6′-hexanitrobibenzyl (HNBB) with aliphatic amines in dimethyl sulphoxide, leading either to σ-adduct formation or to transfer of methylene protons to the base. The most rapid reaction observed with the primary amines n-butylamine and benzylamine and with the secondary amines piperidine and pyrrolidine is attack at the 3(3′)-positions of the substrate. With the primary, but not the secondary amines, this is followed by isomerisation to the thermodynamically preferred 1(1′)-adducts. Slow formation of the blue dianion (7) is observed with the primary and secondary amines and with DABCO. Analysis of the kinetic data indicates that two pathways for the production of (7) involve rate-determining attack of amine on the parent, or on the σ-adducts (2) or (4).