A Nuclear Magnetic Resonance Study of some 4-X-Substituted-2,6-Dinitroanisoles and Related Meisenheimer 1,3- and 1,1-Complexes
The structures of transient 1,3-complexes 2 and stable 1,1-complexes 3 formed by the reaction of methoxide ion with various 4-X-2,6-dinitroanisoles in DMSO-d6 are confirmed by n.m.r. spectroscopy. 13C satellites in the proton spectra of anisoles and 1,1-complexes have been used to obtain [Formula: see text] as well as 4JH–H in these symmetrical compounds.The chemical shifts of the ring protons in 1,3- and 1,1-complexes give some information concerning the influence of the substituent X on the delocalization of the negative charge. In anisoles and 1,1-complexes, [Formula: see text] of the ring protons are mainly dependent on the inductive effect of X. Furthermore, a linear relationship is observed in anisoles between the chemical shift as well as [Formula: see text] of the methoxyl protons and the Hammett σP constant of X, thus suggesting an identical geometry of these molecules at C-2,-1, and -6.