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 pi MOs pi(2) and pi(3) of the phenyl ring, and the n(O) orbital of the methoxy group as well as the allylic pi(C=C) 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 sigma(p) values performed satisfactorily to fair for pi(2), pi(3) and n(O) but poor for allylic pi(C=C). Other substituent constants such as R and R(-) were fair only for pi(2) and pi(3), but poor for n(O) and pi(C=C).