Equilibrium structures for butadiene and ethylene: Compelling evidence for π-electron delocalization in butadiene
Equilibrium structures have been determined for s-trans-1,3-butadiene and ethylene after adjusting the rotational constants obtained from rotational spectroscopy by vibration−rotation constants calculated from the results of quantum chemical calculations. For butadiene, the formal CC bond length is 1.338 Å, and the formal C−C bond length is 1.454 Å. For ethylene, the CC bond length is 1.3305 Å. These values appear to be good to 0.001 Å. It is shown for the first time that π-electron delocalization has the structural consequences of increasing the length of the formal double bond by 0.007 Å and decreasing the length of the formal single bond by 0.016 Å. Comparisons are made with structures computed with several quantum chemical models. The MP2/cc-pVTZ results agree best with the new re structure.
Craig, Norman C., Peter Groner, and Donald C. McKean. 2006. "Equilibrium structures for butadiene and ethylene: Compelling evidence for π-electron delocalization in butadiene." Journal of Physical Chemistry A 110(23): 7461-7469.
American Chemical Society
Journal of Physical Chemistry A
Chemistry and Biochemistry