Title

Equilibrium structures for butadiene and ethylene: Compelling evidence for π-electron delocalization in butadiene

Abstract

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.

Publisher

American Chemical Society

Publication Date

1-1-2006

Publication Title

Journal of Physical Chemistry A

Department

Chemistry and Biochemistry

Document Type

Article

DOI

10.1021/jp060695b

Language

English

Format

text

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