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A Mechanistic Study on the Photoisomerizations of Spiro[2,4]hept-1-ene, Vinylidenecyclopentane, and Vinylidenecyclobutane Hydrocarbons
journal contributionposted on 2008-06-19, 00:00 authored by Ming-Der Su
The mechanisms of photochemical isomerization reactions were investigated theoretically using the following model systems: spiro[2,4]hept-1-ene, 1-vinylcyclopentene, and vinylidenecyclobutane with the CASSCF/6-311G(d) (six-electron/six-orbital active space) and the MP2-CAS/6-311G(d,p)/CASSCF/6-311G(d) methods. The structures of the conical intersections, which play a central role in such photorearrangements, were obtained. The intermediates and transition structures of the ground states were also calculated to assist in providing a qualitative explanation of the reaction pathways. Our model investigations strongly indicate that a vinylcarbene-like intermediate can serve as a basis for discussion and rationalization of the results of the above photoisomerizations. Besides this, our theoretical findings suggest that the conical intersection mechanism found in this work gives a good explanation and supports the experimental observations. Also, all the relative final product yields predicted in the present work are in good agreement with the available experimental findings.
Spiromodel systemsmodel investigationsconical intersectionsphotorearrangementproduct yieldsvinylidenecyclobutanespirointermediateisomerization reactionsPhotoisomerizationMechanistic StudymethodMProlevinylcyclopentenefindingreaction pathwaysbasisphotoisomerizationVinylidenecyclopentanetransition structuresground statesconical intersection mechanismVinylidenecyclobutane HydrocarbonsThe mechanismsrationalizationCASSCF