Knowledge Bank

As part of a study of nonpolar molecules that exhibit surprising energy relationships among isomers, a C-type band in the infrared spectrum of the EE (trans-trans) isomer of 1,4-difluorobutadiene is being investigated. This band, centered at $934cm-1$, is due to CH out-of-plane flapping. Although the band structure contains evidence of substantial perturbations, the rotational structure at $0.002cm-1$ resolution appears to be fully assignable. Preliminary rotational constants for the ground state are $A=1.0507499(14),B=0.0389603(47)$, and $C=0.0375881(40)cm-1$ for this near-prolate symmetric top with $\kappa =-0.99729$. A synthetic method has been found to make the deuterated isotopomers needed for the complete structural analysis of the isomers of 1,4-difluorobutadiene.