Infrared carbonyl absorptions of 2-oxofurans: fermi resonance versus rotational isomerism as the cause of carbonyl band doubling in furan-2-carbaldehyde and related aldehydes

Abstract

43 2-Oxofurans have been examined at high resoultion in the i.r. CO region. The CO doublets observed for furan-2-carbaldehyde (and six related aldehydes) originate in Fermi resonance and not rotational isomerism: the CO stretching bands of the two rotational isomers in these systems must have almost exactly equal wave-numbers.