Experiment Written by Vijay In this experiment, cyclopentadiene and maleic anhydride were reacted in solution to produce a single organic product in crystal form. Percent yield observed during the first week of experimentation was For the second week of experimentation, the percent yields observed were Sample A was purified by vacuum filtration but otherwise prepared under the same procedure as the sample from Week 1.
The Diels-Alder reaction combines a diene a molecule with two alternating double bonds and a dienophile an alkene to make rings and bicyclic compounds. The three double bonds in the two starting materials are converted into two new single bonds and one new double bond.
Since this reaction forms two new carbon-carbon bonds in a single step, it is a very useful and powerful reaction one which earned Otto Diels and Kurt Alder a Nobel prize in chemistry for discovering it.
Conformational requirements of the diene One quirk of the Diels-Alder reaction is that the diene is required to be in the s-cis conformation in order for the Diels-Alder reaction to work. The s-cis conformation has both of the double bonds pointing on the same side of the carbon-carbon single bond that connects them.
In solution, the carbon-carbon single bond in the diene that connects the two alkenes is constantly rotating, so at equilibrium there is usually some mixture of dienes in the s-trans conformation and some in the s-cis conformation. The ones that are at that moment in the s-trans conformation do not react, while the ones in the s-cis conformation can go on to react.
Because of the Diels-Alder's requirement for having the diene in a s-cis conformation, dienes in rings react particularly rapidly because they are "locked" in the s-cis conformation. Unlike dienes in open chains in which there is usually some proportion of the diene in the unreactive s-trans conformation, dienes in rings are held in the reactive conformation at all times by the constraints of the ring, making them react faster.
If your dienophile is disubstituted substituted twicethere is the possibility for stereochemistry in the product.
In the Diels-Alder reaction, you end up with the stereochemistry that you started with. In other words, if the substituents started cis on the same side on the dienophile, they end up cis in the product.
If they started trans opposite sides on the dienophile, they end up trans in the product. Formation of bicyclo products. When the diene is in a ring, the product of the Diels-Alder reaction is a bicyclo ring system which can be somewhat intimidating to draw at first.
A bicyclo ring system is a compound in which two rings share more than two carbons. There are two main bicyclo ring systems that you typically have to deal with, and these are the ones that come from the diene being in a five-membered ring system and the diene being in a six-membered ring system.
The nomenclature of bicyclic alkanes can be found elsewhere. When you make bicyclic products that is, when the diene is in a ringand you have a dienophile that is substituted, there are two possible products that you can form from the Diels-Alder reaction--the endo product, in which the substituent points down from the top of the bicyclic molecule, and the exo product, where the substituent points towards the top of the bicyclic molecule.
In general, you form the endo product preferentially over the exo product in the Diels-Alder reaction. Example of the Diels-Alder reaction In this example, since the diene is in a six-membered ring, you make a bicyclo product. Since the dienophile is cis disubstituted, you get the endo stereochemistry with the two cyano CN substituents pointing away from the top of the bicyclo compound.The Diels-Alder reaction is a concerted reaction (a reaction were multiple bonds are broken and formed in one step), and the stereochemical outcome of this reaction supports that conclusion.
The Diels–Alder reaction is an organic chemical reaction (specifically, a [4+2] cycloaddition) between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. SYNT The Diels-Alder ReaCtion of Anthracene with Maleic Anhydride (diene (diene (Eq.1) adduct (Eq.
2) adduct reactants and the symmetry of . The Diels Alder reaction between anthracene and maleic anhydride to form 9, dihydroanthracene-9,α, β-succinic anhydride was successful and occurred via the Diels Alder mechanism (see Reaction and its Mechanism section for details).
Pre-lab Questions: 1. Draw a full mechanism for the reaction of dibenzyl ketone with benzil to form the structures of the diene and dienophile in the Diels-Alder reaction in Part B, As part of your Post-lab report, interpret both IR’s, and the ‘HNMR’s provided for each.
Report your crude yield for each step, and your overall yield. The original method of Diels and Alder for the reaction of cyclopentadiene with maleic anhydride is modified for use in the elementary organic laboratory.