On the Relationship Between Electronic Absorption and Molecular Geometry: Carbonyl Chromophore n-π. Transition Enhancement and Crystal Structures of Bicyclo[2,2,2]octenones and Bicyclo[2,2,2]octadienones

Abstract

Spectroscopic studies on a series of methoxycarbonyl-substituted β,γ-unsaturated bicyclic ketones show a decrease in n-π* transition enhancement in the bicyclo[2,2,2]octadienone derivative relative to that observed in the correspondingly substituted bicyclo [2,2,2] octenone. Crystallographic studies on the related derivatives have been carried out in an attempt to ascertain the influence of ground- state molecular geometry. The results show the detectable difference in geometry to be small and suggest the change in enhancement to be, more likely, a spectral repercussion of homodiene conjugation.