Explore
Home 
Literature 
Links 
Posts 
Molecules 
Blogs 
Zeitgeist 
Markup Help 
News 
Everything Papers Books
An unusual intramolecular kinetic isotope effect (KIE) in the reaction of dichloroketene with cis-2-butene does not fit with a simple asynchronous cycloaddition transition state, but it can be predicted from trajectory studies on a bifurcating energy surface. The origin of the KIE is related to a high propensity for transition state recrossing in this system, with heavier masses recrossing less. The KIE can also be predicted by a statistical model that treats the cycloaddition as a stepwise mechanism, the rate-limiting second step being associated with an entropic barrier for formation of the second carbon-carbon bond. The relevance of this stepwise mechanism to other asynchronous but seemingly concerted cycloadditions is suggested by examination of organocatalytic Diels-Alder reactions.

Posts

O. M. Gonzalez-James, E. E. Kwan, D. A. Singleton  Journal of the American Chemical Society 2011, 134, 1914 (Paywall)Contributed by Steven Bachrach.Reposted from Computational Organic Chemistry with permissionOnce again the Singleton...
Once again the Singleton group reports experiments and computations that require serious reconsideration of our notions of reaction mechanisms.1 In this paper they examine the reaction of dichloroketene with labeled cis-2-butene. With 13C at the 2 position...