Definition: What is the Diels-Alder Reaction?

The Diels-Alder reaction is an organic reaction that is used to convert a conjugated diene (a molecule with two alternating double bonds) and a dienophile (an alkene) to a cyclic olefin. This process is concerted, where bonds form and break at the same time, and the entire reaction takes place in one step in the presence of heat. The class of reactions to which Diels-Alder belong is termed as cycloaddition. The electrons are transferred cyclically between the diene and the alkene to form a cyclic adduct. Diels-Alder reactions are stereospecific. The substituents attached to both the diene and the dienophile and retain their stereochemistry throughout the reaction. Electron withdrawing groups on the dienophile and electron-donating group on the diene facilitate reaction ^[1-3].

Examples of Diels-Alder Reaction ^[4,5]

Mechanism of Diels-Alder Reaction ^[6-10]

Applications of Diels-Alder Reaction

The Diels-Alder reaction is used in the synthesis of natural products like rubber and plastic. It also finds its application in pharmaceuticals and biomedical engineering. It is used to make synthetic steroids, such as cortisone and Vitamin D ^[2].

Retro Diels-Alder Reaction

The retro Diels-Alder reaction is the exact reverse of the Diels-Alder. It passes through the same transition state when the heat is applied. For example, cyclohexene breaks down into butadiene and ethylene at a temperature of 800 °C ^[11-13].

References
1. Definition – Name-reaction.com
2. Definition – Chem.libretexts.org
3. Definition – Study.com
4. Anthracene – Chem.qc.cuny.edu
5. Cyclopentadiene – Chemtube3d.com
6. Mechanism – Byjus.com
7. Mechanism – Masterorganicchemistry.com
8. Mechanism – Chem.wisc.edu
9. Mechanism  – Chemhelper.com
10. Mechanism – Chem.ucalgary.ca
11. Retro reaction – Chem.libretexts.org
12. Retro reaction – Organicreactions.org
13. Retro reaction – Masterorganicchemistry.com