UV Absorption in Linear Polyenes

butatdiene orbitals



Click on the graph to display the various bonding and antibonding molecular orbitals and energies. Use Surfaces from the Jmol popup menu to display other molecular orbitals for each polyene.

  • All the molecular orbitals for ethylene(ethene), 1,3-butadiene, 1,3,5-hexatriene, and 1,3,5,7-octatetraene are available.
  • Note the increasing number of nodes as the conjugated chain increases
  • Addition of successive conjugated double bonds progressively narrows the gap between HOMO and LUMO
  • Thus longer wavelength (lower energy) radiation required for the chromophore transition