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- Title
A variational transition state theory description of periselectivity effects on cycloadditions of ketenes with cyclopentadiene.
- Authors
Ramírez-Anguita, Juan; Gelabert, Ricard; González-Lafont, Àngels; Moreno, Miquel; Lluch, José
- Abstract
The reaction of cycloaddition of ketene and cyclopentadiene presents experimentally a competing mechanism where the branching ratio between the Woodward-Hoffmann allowed [4+2] and forbidden [2+2] cycloaddition product is 4.56 at −20 °C, but because the minimum energy path misses the [2+2] product altogether, it has been claimed to lie beyond the scope of transition state theory. In this paper, a variational transition state theory study on this reaction is presented. It is found that the minimum energy path affording the [4+2] product travels through a potential energy plateau very close to the minimum energy path that describes the interconversion between both cycloaddition products, allowing the transfer between both and the direct formation of the forbidden [2+2] product, in this way acting as a means to circumvent the Woodward-Hooffmann rules. Within the domain of the competitive canonical unified statistical theory, a value for the branching ratio in very good agreement with experiment is computed.
- Subjects
VARIATIONAL principles; PHASE transitions; RING formation (Chemistry); KETENES; CYCLOPENTADIENE; REACTION mechanisms (Chemistry); BRANCHING ratios; FORCE &; energy
- Publication
Theoretical Chemistry Accounts: Theory, Computation, & Modeling, 2011, Vol 128, Issue 4-6, p569
- ISSN
1432-881X
- Publication type
Article
- DOI
10.1007/s00214-010-0792-9