The molecular structure of gauche-1, 3-butadiene: Experimental proof of non-planarity Academic Article uri icon


  • Abstract The planarity of the second stable conformer of 1, 3-butadiene-the archetypal diene for the Diels-Alder reaction, in which a planar conjugated diene and a dienophile combine to form a ring-is not established. The most recent high level calculations predict the species to adopt a twisted, gauche structure due to steric interactions between the inner terminal hydrogens rather than a planar, cis structure favored by the conjugation of the doubled bonds. Here we unambiguously prove experimentally that the structure cis-1, 3-butadiene is indeed gauche with a substantial dihedral angle of 34, in excellent agreement with theory. Observation of two tunneling components indicates that the molecule undergoes facile interconversion between two equivalent enantiomeric forms. Comparison of experimentally determined structures for gauche-and trans-butadiene provides an opportunity to …

publication date

  • December 14, 2017