Near Cancellation of Through Space and Through Bond Interaction in bicyclo[3.2.2]nona‐6,8‐diene

Abstract
The photoelectron spectra of bicyclo[3.2.2]nonane and its five dehydrogenated analogues are reported. Analysis of the π‐bands reveals that the unsymmetrical diene 5 retains the ‘natural order’ of the π‐orbitals present in the lower homologues, i. e. the in‐phase below the out‐of‐phase combination of the basis π‐orbitals πa and πc. The isomeric diene 4 is the first member of the symmetrical homologous series (I), which inverts this order, so that a1(π) (in phase!) lies above b2(π) (out‐of‐phase!).