Viola, A. and MacMillan, J.H..
The Vapor Phase Acetylenic oxy-Cope Reaction of 5-Hexen-1-yn-3-ol, The Chemistry of an Allenol Intermediate", , J. Am. Chem. Soc., 92, 2404 (1970).
The vapor phase thermolysis of 5-hexen-1-yn-3-ol affords 2- and 3-cyclopentenecarboxaldehydes, trans-2,5-hexadienal, and sorbaldehyde in varying amounts, dependent upon temperature and contact time. Since the beta-hydroxyolefin cleavage, which normally competes with the oxy-Cope processes, is completely absent, kinetic parameters could be determined. The Arrhenius energy of 30+/- 2 kcal/mole and activation entropy of -14 eu are indicative of a concerted mechanism and suggest that the participation of triple bonds in electrocyclic reactions leads to increased rates in comparison with the corresponding olefinic structures. The kinetic data obtained the effects of temp. and contact time on product distribution, and the results of a deuterium tracer study indicate the intermediacy of the primary oxy-Cope product in the formation of all observed products. The latter, therefore, represent various reactions of the allenol, 1-hydroxy-1,2,5-hexatriene.