The stabilities of Meisenheimer complexes. Part VIII. Equilibrium and kinetic data for spiro-complex formation in water

Abstract

Equilibrium and rate constants for the formation in water of spiro-complexes from four ring-activated aromatic glycol ethers are reported. Values of the rate constants K_–1 for opening of the dioxolan ring of these complexes are much higher than those for the expulsion of base from non-cyclic analogues. This may indicate ring strain in the spiro-complexes.

In moderately concentrated (>0·1_M) sodium hydroxide solutions complexes are formed by addition of hydroxide ions at unsubstituted ring positions in the spiro-complexes. Addition of hydroxide ions at two ring positions to the spiro-complex from the glycol ether of 2,4,6-trinitrobenzene gives an adduct (XIII) which may be regarded as a 1 : 3 σ-complex.