Diels Alder Experiment Reaction

Theoretical Background / Context

• The Diels-Alder reaction is one of the most important reactions of organic chemistry since they are used in synthesizing six-membered ringed cyclic organic compounds.
• It is also considered as a [4+2]-cycloaddition reaction because it involves an additional reaction between a conjugated diene molecule and a substituted alkene (dienophile) in order to produce a substituted cyclohexene system.
• Specifically, 4 π-electrons from the conjugated diene and 2 π-electrons from the dienophile are involved in the reaction.
• Therefore, it is counted as an electrocyclic reaction whose driving force is the formation of new σ-bonds as they are energetically more stable than the π-bonds.
• Furthermore, the Diels-Alder reaction is known as a non-polar reaction since no charged intermediates are formed during the reaction.
• In addition, no unpaired electrons are involved in the addition reaction.
• It is considered a concerted reaction since several bonds are formed and broken simultaneously during the transition state.

Figure 1. Schematic diagram for Diels Alder Reaction

Principle of Work

• An example of Diels Alder reaction is the cycloaddition of anthracene (conjugated diene) and maleic anhydride (dienophile) to form 9,10-dihydroanthracene-9,10-endo-a3-succinic anhydride as the Diels Alder product.
• Xylene is used as the reaction solvent due to its high-boiling that could accommodate the high temperature needed for running the chemical reaction in this Diels Alder experiment.
• Maleic anhydride is known as a highly reactive dienophile owing to the presence of two electron withdrawing carbonyl substituents within its chemical structure.
• On the other hand, anthracene is not a highly reactive diene because of both its steric hindrance in addition to its high stability due to aromaticity.