The Proton Resonance Spectra of Some Substituted Furans and Pyrroles

The proton magnetic resonance spectra of some substituted furans and pyrroles have been analyzed for spin coupling constants and chemical shifts.The relative insensitivity of the spin coupling constants to the nature of the substituent makes it possible to estimate their values in the parent molecules furan and pyrrole. The magnitude of the spin coupling constants is correlated with the angles made by the CH bonds with the CC bonds of the ring.The chemical shifts are interpreted in terms of an effect due to the electronegativity of the substituent together with the effect due to conjugation with the ring.