Photoelectron spectra and electronic structure of some 4-substituted 2-allylanisoles

The electronic structures of 4-substituted 2-allyl anisoles (1-9) have been investigated by ultraviolet photoelectron spectroscopy and quantum chemical methods. The ionisation potentials corresponding to the π MOs π2 and π3 of the phenyl ring, and the nO orbital of the methoxy group as well as the allylic π(CC) orbital could be determined and assigned for 1-9. Linear regression analyses of the IPs related to these orbitals with different substituent constants indicated that Hammett σp values performed satisfactorily to fair for π2, π3 and nO but poor for allylic π(CC). Other substituent constants such as R and R− were fair only for π2 and π3, but poor for nO and π(CC).