Intermediates in nucleophilic aromatic substitution. Part XIV. Interaction of lyate ions with polynitronaphthalenes

Abstract

Interaction of hydroxide ion with 1,3-dinitronaphthalene, 1,3,8- and 1,4,5-trinitronaphthalenes, and 1,3,6,8-1,4,5,8-, and 1,3,5,8-tetranitronaphthalenes in aqueous dimethyl sulphoxide, aqueous dioxan, and water results in the equilibrium formation of the hydroxy Meisenheimer complexes of the appropriate polynitronaphthalenes. Similarly addition of methoxide ions to 1,5-dinitronaphthalene (in DMSO–MeOH 90:10 v/v), 1,3-dinitronaphthalene, 1,4,5- and 1,3,8-trinitronaphthalene, and 1,3,6,8-, 1,4,5,8-, and 1,3,5,8-tetranitronaphthalene (in methanol) results in the equilibrium formation of their methoxy Meisenheimer complexes. Rate constants for the formation and decomposition of these complexes and hence the equilibrium constants have been determined at 25°. Equilibrium constants have also been obtained from spectral data. Many Meisenheimer complexes liberate nitrite ions in a somewhat slower process. Rate constants for this process have also been determined by following either the rate of the decomposition of the complex, product formation, or nitrite ion liberation. Structures of the Meisenheimer complexes are substantiated by ¹H n.m.r. investigations and their stabilities are discussed comparatively.