The Diels-Alder Reaction By: Kayla Powers and Jakkrit Suriboot Introduction Diels-Alder reactions are used for synthesizing new carbon-carbon bonds and more specifically, six-membered cyclic compounds. In addition, this reaction synthesizes compounds that are otherwise difficult to obtain, such as bridged bicyclic compounds. A key characteristic of these reactions is their stereospecificity.
Two well-studied intramolecular pericyclic reactions are known as the Cope rearrangement. Notice that the both of these reactions require compounds in which two double bonds are separated by three single bonds. Pericyclic reactions are rare in biological chemistry, but here is one example: The study of pericyclic reactions is an area of physical organic chemistry that blossomed in the mids, due mainly to the work of R.
Woodward, Roald Hoffman, and Kenichi Fukui. The Woodward-Hoffman rules for pericyclic reactions and a simplified version introduced by Fukui use molecular orbital theory to explain why some pericyclic processes take place and others do not.
A full discussion is beyond the scope of this text, but if you go on to study organic chemistry at the advanced undergraduate or graduate level you are sure to be introduced to this fascinating area of inquiry.
Stereochemistry of the Diels-Alder reaction We noted earlier that addition reactions of alkenes often exhibited stereoselectivity, in that the reagent elements in some cases added syn and in other cases anti to the the plane of the double bond. Both reactants in the Diels-Alder reaction may demonstrate stereoisomerism, and when they do it is found that the relative configurations of the reactants are preserved in the product the adduct.
The following drawing illustrates this fact for the reaction of 1,3-butadiene with E -dicyanoethene. The trans relationship of the cyano groups in the dienophile is preserved in the six-membered ring of the adduct.
Likewise, if the terminal carbons of the diene bear substituents, their relative configuration will be retained in the adduct. Using the earlier terminology, we could say that bonding to both the diene and the dienophile is syn.
An alternative description, however, refers to the planar nature of both reactants and terms the bonding in each case to be suprafacial i.
This stereospecificity also confirms the synchronous nature of the 1,4-bonding that takes place. The essential characteristics of the Diels-Alder cycloaddition reaction may be summarized as follows: The reaction always creates a new six-membered ring. When intramolecular, another ring may also be formed.
The diene component must be able to assume a s-cis conformation. Electron withdrawing groups on the dienophile facilitate reaction. Electron donating groups on the diene facilitate reaction. Steric hindrance at the bonding sites may inhibit or prevent reaction.
The reaction is stereospecific with respect to substituent configuration in both the dienophile and the diene. These features are illustrated by the following eight examples, one of which does not give a Diels-Alder cycloaddition.Oct 25, · cyclopentadiene reacts much faster than 1,3-butadiene with Maleic Anhydride, but they both work.
I know cyclopentadiene is cyclic and the butadiene is not, but they both work for diels-alder, so why should the cyclic one go much faster?Status: Resolved.
The Diels-Alder reaction is a pericyclic reaction, in which a conjugated diene and an isolated alkene add together in a single step without intermediates by a cyclic redistribution of bonding electrons. Start over and calculate the LUMO for Maleic Anhydride Time permiting, do the EXO and ENDO alignments of the HOMO of cyclopentadiene and LUMO of maleic anhydride as shown Compare and contrast the structure of the ENDO and EXO Diels-Alder cycloadducts.
PC Spartan Plus is a molecular modeling program which approximates the. A particularly rapid Diels-Alder reaction takes place between cyclopentadiene and maleic anhydride. We already know that cyclopentadiene is a good diene because of its inherent s-cis conformation. In this investigation I utilized the Diels-Alder Cycloaddition Reaction instrument to frame cisNorbornene g/mol.
and Kurt Alder. from Germany.2g of maleic anhydride was added in test tube of ethyl acetate with ml of cyclopentadiene was added to the test tube the mixture got warm and it had a precipitate and the its dissolved.0 ml of.
Why does 1,3-cyclopentadiene react more rapidly with maleic anhydride than with another molecule of itself? 4. Why is a mL rather than a mL round-bottom flask to be used for cracking dicyclopentadiene when only.