Ring Opening Dynamics of the Cyclopropyl Radical and Cation: The Transition State Nature of the Cyclopropyl Cation
Authors/Creators
- 1. Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva 841051, Israel
- 2. Center for Astrophysics — Harvard & Smithsonian, Cambridge, Massachusetts 02138, United States
- 3. Universit ́e Paris-Saclay, CNRS, Institut des Sciences Mol ́eculaires d'Orsay, 91405 Orsay, France
- 4. Universit ́e Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33400 Talence, France
- 5. Synchrotron Soleil, L'Orme des Merisiers, St. Aubin BP48, F-91192 Gif sur Yvette, France
- 6. Quantum Theory Project, Departments of Chemistry and Physics, University of Florida, Gainesville, Florida 32611 (USA)
- 7. Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
Description
We provide compelling experimental and theoretical evidence for the transition state nature of the cyclopropyl cation. Synchrotron photoionization spectroscopy employing coincidence techniques together with a novel simulation based on high accuracy ab initio calculations reveal that the cation is unstable via its allowed disrotatory ring opening path. The ring strains of the cation and the radical are similar, but both ring opening paths for the rad- ical are forbidden when the full electronic symmetries are considered. These findings are discussed in light of the early predictions by Longuet-Higgins alongside Woodward and Hoff- man; we also propose a simple phase space explanation for the appearance of the cyclopropyl photoionization spectrum. The results of this work allow the refinement of the cyclopropane C−H bond dissociation energy, in addition to the cyclopropyl radical and cation cyclization energies, via the Active Thermochemical Tables approach.