Pyrrole studies. II. The structure of 2-pyrrolylmethyleneimines

Abstract

2-Pyrrolylmethyleneimines (III) are shown to exist as such and not in the alternative tautomeric form (IV). The graph obtained on plotting the long wave- length ultraviolet band of the aryl compounds (III: R = aryl) against their Hammett σ value is non-linear. This is explained in terms of the relative energies of the ground and excited states of the compounds and is also due to the overall electron-donating effect of the pyrrole ring.