The Rules of the Diels-Alder Reaction are contained in the Chemistry StepsDiene.
In this post, we will discuss reactivity and details of the Diels-Alder reaction.The Diels-Alder reaction is a type of pericyclic reaction between a diene and a dienophile.
The diene is the first thing we should start with.The first thing to remember is that it can only react in the cis conformation.The traditional cis and trans isomerism of the alkenes is not being discussed.Conjugated dienes can be found in both cis and trans geometry.S-cis and s-trans are two double bonds that have a sigma bond that interconverts through a rotation.
The s-trans conformation is preferred by acyclic dienes.Since there is no free rotation about the sigma bond, cyclic dienes are locked.
The locked trans dienes do not react in the Diels-Alder, so they may react with themselves.
One molecule acts as the diene and the other is the dienophile in cyclopentadiene.Bridged bicyclic compounds are produced by cyclic dienes.
The electronic effect is the second factor.The reactivity of the diene is increased by electron-donating groups.
The interaction between HOMO-LUMO and Diels-Alder resulted in this.Even though it is a concerted mechanism, one can imagine the electron flow being initiated from the highest occupied molecular orbitals of the diene.This electron flow is supported by electron-donating groups on the diene increasing its reactivity, while electron drawing groups lower the LUMO energy level.
There are more points about the stereochemistry of the Diels-Alder reaction.
If there are two groups on the dienophile, the product will have them cis or trans exactly as they first appear.This shows that Diels-Alder is a stereospecific reaction.
Bicyclic compounds are formed if the diene is cyclic.The isomerism is the main concept here.In the exo isomer, the substituents of the dienophile are pointing away from the larger bridge.
The major product is formed when the electron-withdrawing groups of the dienophile are pointing towards the diene.You can read more about the transition state when acyclic dienes are reacted here.
If the diene is reacted with a mono-substituted dienophile, the product will have one stereogenic center and two enantiomers.
You need to consider the regiochemistry of the Diels-Alder if the diene is also unsymmetrical.You can check this post because it would be too much today.
Study materials for organic chemistry include sheet guides and practice problems.Just keep browsing.