INTERACTION OF WALSH- AND π-ORBITALS——PHOTOELECTRON SPECTRA OF CYCLOPROPYL SUBSTITUTED BENZENES

In this paper the photoelectron spectra of a series of cyclopropyl substituted benzenes arerecorded and discussed. Although their interpretation is made difficult by conformational pro-blems, with the possible exception of hexacyclopropyl benzene (12), it is confirmed that theWalsh orbitals of the cyclopropyl group interact appreciably with the π-system to which theyare attached in both the bisected and perpendicular conformation. The ratio of the cross-terms is B(eA, 2p)/B(es,2p)≈1.4 rather than a much larger number suggested by thetraditional diagrams for the Walsh orbitals. It is shown that a representation, in terms ofof localized bond orbitals derived from an STO-3G model, is more appropriate and heuristi-cally useful.