Complex formation between derivatives of 1‐nitroazulene and methoxide ion in methanol

Certain 3‐substituted 1‐nitroazulenes in methanol with sodium methoxide form complexes with methoxide ion. Complex formation occurs mainly when the substituent at position 3 is meta‐directing with respect to electrophilic aromatic substitution; the electron withdrawing capacity of the substituent appears to be the main factor determining the extent of complex formation According to the electronic absorption spectra and the nuclear magnetic resonance spectra 1,3‐dinitroazulene gives a complex in which the methoxide ion is attached to carbon atom 6. The complex formed from 1‐nitro‐3‐trifluoroacetylazulene has the methoxy group at the carbon atom of the carbonyl group. The complexes are in equilibrium with the uncomplexed nitroazulenes and do not give rise to substitution products.