The Diels-Alder reaction is a member of a class of reactions called cycloadditions. The reaction involves three π bonds, two from the diene and one from the dienophile in a concerted reaction to form a six-membered ring. Since the reaction involves four π electrons in the diene and two π electrons from the dienophile, it is sometimes referred to as a 4 + 2 cycloaddition.
Normal Diels-Alder reactions are favored by electron donating groups on the diene and electron withdrawing groups on the dienophile. The diene must be capable of achieving an s-cis conformation to generate the cis double bond in the cyclohexene product. Acyclic dienes may rotate around a single bond, but dienes locked in the s-trans conformation do not react.
The purpose of this experiment is to form 9,10-dihydroanthracene-9,10-α,β-succinic anhydride by way of a Diels Alder reaction between anthracene and maleic anhydride, as shown in the reaction below. Anthracene acts as the diene and maleic anhydride functions as the dienophile. Xylene (dimethylbenzene) is used as a high boiling temperature solvent so that the reaction will proceed quickly. Melting temperature analysis will be used to characterize the product.
In this experiment, you will
- Synthesize 9,10-dihydroanthracene-9,10-α,β-succinic anhydride.
- Isolate the product.
- Measure the melting temperature of your product.
- Characterize the starting material and product via UV absorption and fluorescence.