Mechanism and reactivity in the Morita–Baylis–Hillman reaction: the challenge of accurate computations

, far smaller than the errors reported in Plata and Singleton's study. On the basis of exhaustive calculations reported here, we suggest that our proposed approaches for modeling electronic structure, solvation, and entropy should be able to provide accurate predictions for many more reactions. We also suggest that reactions like the MBH reaction, where solvation and entropy effects are particularly large, are among the hardest for computational mechanistic studies.