recognize whether or not a provided compound would certainly behave actually as a reenergetic dienophile in a Diels-Alder reactivity. predict the stereosoimg.orgistry of the product obtained from the reactivity of a provided diene with a given dienophile. identify that in order to undergo a Diels-Alder reaction, a diene need to be able to assume ans-cis geometry, and also determine whether or not a given diene can assume this geomeattempt.

You are watching: Why is maleic anhydride a good dienophile


Key Terms

Make certain that you can define, and also usage in conmessage, the vital terms below.

dienophile dimerization
Study Notes

Make sure that you understand also that the s-cis and s-trans forms of a diene such as 1,3-butadiene are conformers, not isomers. Note that some textbooks have the right to confusage the issue even more by referring to a compound such as (2Z, 4Z)-hexadiene as cis, cis-2,4-hexadiene, and saying that the many secure form of this compound is its s-trans conformer!

In fulfilling Objective 2, over, you must recognize that the Diels-Alder reactivity is stereospecific.

Finally, note reaction B in the reading shows 1,3-cyclopentadiene reacting via another molecule of 1,3-cyclopentadiene. When the same compound acts as both diene and dienophile in a Diels-Alder reactivity to couple it is a dimerization.


The Dienophile


In basic, Diels-Alder reactions continue fastest with electron-withdrawing groups on the dienophile (diene lover).Ethylene reacts gradually while propenal, ethyl propenoate, and also various other molecules presented beloware very reactive in a Diels-Alder reactivity.

*

In much the very same manner as electron-withillustration substituents on a benzene ring, these are commonly a double or triple bond in conjugation with the double bond in the dienophile.A resonance create can be drawn which places a positive charge in the dienophile double bond.This results in the double bond being less electron affluent (higher electron densitydisplayed in Red/Orange) than ethylene.Electrostatic potential maps present that the electron-withillustration teams pull electron thickness amethod from the double bond.

*


Stereosoimg.orgisattempt of Diels-Alder (dienophile)

The Diels-Alder reactivity is enormously helpful for man-made organic soimg.orgists, not just bereason ring-creating reactions are valuable in basic but likewise bereason in many situations multiple brand-new stereocenters are formed, and the reactivity is inherently stereocertain.Throughout a Diels-Alder reactivity the stereosoimg.orgisattempt of the dienophile is preserved in the product.A cis dienophile will certainly generate a cyclohexene ring with cis (syn) substitution on the two carbons from the dienophile.Likewise a trans dienophile will geneprice a cyclohexene ring via trans (anti) substitution on these 2 carbon.

*
api/deki/files/396111/Example_1.png?revision=1&size=bestfit&width=500&height=360" />


The retention of stereosoimg.orgisattempt is because of the planar nature of both reactants and also that the creating process is suprafacial (i.e. to or from the same face of each plane). This stereospecificity likewise confirms the concerted nature of the Diels-Alder mechanism.The illustration below illustprices this truth for the reactivity of 1,3-butadiene via (E)-dicyanoethene. The trans relationship of the cyano groups in the dienophile is maintained in the six-membered ring of the adduct.

*

Anvarious other facet of the stereosoimg.orgical retention of the dienophile is that just the enexecute product, rather than the alternative exo product, is created. The words endo and also exo are supplied to show loved one stereosoimg.orgisattempt once referring to bicyclic structures like substituted norbornanes. The encarry out position on a bicyclic framework describes the place that is inside the concave shape of the larger (six-membered) ring.As you can predict, the exo position refers to the outside place. Diels-Alder reactions via cyclic dienes favor the development of bicyclic structures in which substituents are in the enexecute position.Precommendation of the encarry out position is additionally a facet of the suprafacial nature of the Diels-Alder reaction.The orbital overlap required for the reactivity is greaterwhen the dienophile lies directly underneath the diene.

*

Alkynes have the right to likewise serve as dienophiles in Diels-Alder reactions:

*
api/deki/files/3794/image237.png?revision=1&size=bestfit&width=197&height=115" />

For some dienes, excessive steric hindrance causes the s-cis conformation to be highly strained, and therefore such dienes execute not conveniently undergo Diels-Alder reactions.

See more: Watch Will Ferrell Ice Skating Jimmy Fallon, Will Ferrell Figure Skates To Downton Abbey Theme

*

Cyclic dienes, on the other hand, are ‘locked’ in the s-cis conformation, and also are especially reenergetic. The outcome of a Diels-Alder reaction entailing a cyclic diene is a bicyclic structure:

*
api/deki/files/396117/Example_2.png?revision=1&size=bestfit&width=446&height=348" />


Instances (PageIndex1)

*

-->