Class Summary 12/01/04
12/01 Cope Rearrangment
What is the mechanism of the Cope Rearrangement?
NOT IONIC
Proposed intermediate is a six-membered transition state
Structure can be either a cyclohexyl-like system, or a biallyl system
Analysis of the products suggest that the intermediate is a chair-like cyclohexyl species (Doering, 1962)
Substituents play an important role in the nature of the Cope transition state
(Kinetics, energetics, product analysis were used to divine details)
What is the nature of the Cope transition state?
Variable transition state for Cope (varies between biradical cyclohexyl and diallyl system)
Gajewski used deuterated species and studied kinetics of bond-breaking and bond-making.
RELEVANT REFERENCES
Cope, A.C. and Hardy, E.M.
The Introduction of Substituted Vinyl Groups. V.
A Rearrangement Involving the Migration of an Allyl
Group in a Three-Carbon System J. Am. Chem. Soc.
(1940) 62, 441-444.
Levy, H. and Cope, A.C. The Rearrangement of Allyl Groups in Three-carbon Systems. IV.
Hydrocarbons J.
Am. Chem. Soc. (1944) 66,
1684-1688.
Doering, W. von E. and Roth , W.R.
The overlap of two allyl radicals or a
four-centered transition state in the cope rearrangement Tetrahedron (1962) 18, 67-74.
Gajewski, J.J. and