Thermal Rearrangements

The effect of conjugation with double bonds and (in cyclopropane) the effect of ring strain on the cleavage of carbon‐carbon bonds during thermal rearrangements is discussed. In particular, the Cope rearrangement and the geometry of its transition state are described. The structurally degenerate Cope rearrangement of bicyclo[5. 1. 0]octa‐2,5‐diene is discussed, and this compound is used to illustrate the concept of “fluctional structure”, which finds its extreme expression in the hypothetical compound, tricyclo[3. 3. 2. 04,6]‐deca‐2,7,9‐triene.