The stabilities of Meisenheimer complexes. Part VII. Adducts from 4-methoxy-3,5-dinitrobenzaldehyde

Abstract

In methanol 4-methoxy-3,5-dinitrobenzaldehyde is in equilibrium with its hemiacetal formed by solvent addition to the carbonyl group. ¹H N.m.r. measurements give the value of the equilibrium constant, K_S, for hemiacetal formation as 8. In the presence of methoxide ions a Meisenheimer complex is formed by base addition to the parent aldehyde. Visible spectral measurements allow the determination of the value of 210 l mol^–1 for K₁, the thermodynamic equilibrium constant for Meisenheimer complex formation.