![reaction-diels-alder reaccion-diels-alder](/images/stories/organica-i/diels-alder/reaccion-diels-alder/reaccion-diels-alder-01.png)
1,3-Butadiene (diene) adds to ethene (dienophile) to form cyclohexene. Diels-Alder forms six-membered cycles, which is why it is known as a cycloaddition reaction. The transition state of the reaction is cyclic, belonging to the family of pericyclic reactions.
![reaction-diels-alder reaccion-diels-alder](/images/stories/organica-i/diels-alder/reaccion-diels-alder/reaccion-diels-alder-02.png)
The Diels-Alder reaction is favored when one of the components has groups that transfer charge and the other groups that steal it.
![reaction-diels-alder reaccion-diels-alder](/images/stories/organica-i/diels-alder/reaccion-diels-alder/reaccion-diels-alder-03.png)
The Diels-Alder product always has one more cycle than the starting reactants