Unsymmetrically, Chemically Activated 1,2-Dicyclopropylacetylene: An Example of Restricted Energy Flow?

Article abstract of DOI:10.1021/ja00243a024

The Doering-Gilbert-Leermakers strategy for revealing chemical reaction possibly more rapid than internal flow of energy is applied to 1,2-dicyclopropylacetylene by examining addition of dideuteriomethylene to 1-cyclopropyl-2-vinylacetylene and of methylene to 1-(2,2-dideuteriocyclopropyl)-2-vinylacetylene in the gas phase.This reduction to practice of the general strategy has three advantages: one of the three isomers of allylcyclopropylacetylene, itself the key product of chemically activated rearrangement, bears internal witness to the achievement of structural symmetry prior to its generation; the long, linear acetylenic linkage precludes internal energy flow by a mechanism of intramolecular collision; and the activation energy of the cyclopropane-propene rearrangement is lowered significantly.Analysis of the experimental results reveals a small amount of rearrangement at high pressures occurring prior to complete symmetrization of structure and/or energy.If this observation can be ascribed to incomplete symmetrization of energy, the basic premise of the Rice-Ramsperger-Kassel-Marcus theory-that internal energy flow be so much faster than chemical reaction that a structureless statistical treatment is justified-may require reconsideration.