Claisen Rearrangement Definition:

The definition of Claisen rearrangement is a [3,3] sigma-tropic rearrangement that is observed for allylic vinylic ethers.

Claisen Rearrangement Explained:

Because reactions tend to favor more thermodynamically stable conformations, we observe a shift of equilibrium towards products that contain C=O, rather than the C=C bond. Thermodynamically stable means that the molecules have lower energy.