Fluctuating Double‐Bond Localization and Charge Migration in π Systems

In π systems with localized double bonds, the switch from one localization pattern to another symmetry‐equivalent one, and the corresponding changes in electron distribution are often considered to proceed via a delocalized transition state of higher symmetry. We present a different mechanism, according to which the double‐bond localization and the concomitant charge distributions can fluctuate without change in energy and without passing through a delocalized, higher‐symmetry transition state. This result is obtained within a simple, independent‐electron (HMO‐type) treatment.