The Diels Alder reaction is a unique reaction of dienes with either alkenes or alkynes, which are referred to as dienophiles. It involves the conversion of two pi bonds to sigma bonds, which provides the energetic drive for the reaction. Available evidence indicates that the Diels Alder reaction is pericyclic, occuring in a single step with rearrangement of bonding electrons in a cyclic manner. The rate of the Diels Alder reaction is facilitated by having electron-releasing substituents on one reactant (usually the diene) and electron-withdrawing substituents on the other reactant (usually the dienophile).
| Electron-releasing Functional Groups | Electron-withdrowing Functional Groups |
|---|---|
| Alkyl Groups | Carbonyl Groups |
| Ethers | Nitro groups |
| Esters (Connected to reactant by oxygen) | Cyano (Nitrile) Groups |
Stereoselectivity is observed for the Diels Alder reaction. Reactions involving alkenes as the dienophile preserve the stereochemistry of the double bond in the product. Reactions using a cyclic diene react so that substituents on the dienophile are endo.
The Diels Alder reaction is a pericyclic reaction occuring in one step with cyclic electron movement. In order for this cyclic reorganization of electrons to occur, the reactants must have overlap of appropriate orbitals. This overlap is achieved when the planes of the diene and dienophile are oriented parallel and on top of each other. If this approximate orientation is not available for rotation below, obtain the Chime plug-in from the MDL Information Systems Website.
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