Examination of the Infrare and Raman spectra ofcis,cis-dipropenyl ether (which was produced by isomerization of diallyl ether) has produced evidence for strong vibrational coupling between the two double-bonds. This ether has strong bands it 1655 cm−1in the infrared and at 1691 cm−1in the Raman. The 1658 cm−1band in the Raman is about 10 fold less intense than the strong polarised band. Thus it appears reasonable to associate the strong IR and Raman bands with the asymmetric and symmetric vibrations shown.