Diels Alder Reaction Lab

The purpose of this lab is to use the Diels-Alder reaction to combine anthracene and maleic anhydride. Named after its two founders the Diels-Alder reaction is the addition of a conjugated diene (electron rich compound) with a dienophile (electron poor compound). (1) These compounds will be combined using [4+2] cycloaddition, where the numbers 4 and 2 come from the number of π electrons that are used in each compound to synthesize the product. (2) This experiment comes at the cost of losing two π bonds to form two new sigma (σ) bonds in the cyclic compound. (2)

Since the driving force of this reaction is the electron rich diene bonding to the electron poor dienophile as seen in Figure1 it is important to realize the effects that an electron withdrawing group would have on each compound. If an electron withdrawing group such as nitro- (NO2) is bonded to the diene it affects the electron density in a way that the diene no longer acts like an electron rich group, voiding the overall reaction as

By observing Figure2 (b) the nitro groups are in a cis configuration on the dienophile. This cis configuration is the reason why both the nitro groups in the product appear in the same direction (cis substuents); in the case where the nitro groups are in a trans configuration the groups in the product would be trans substuents. (3) In this experiment anthracene (electron rich) will be bonded with maleic anhydride (electron poor) by using heat to synthesize 9, 10-dihydroanthracene-9,10-α, β-succinic anhydride. The formation of two products is not ideal but luckily easy to separate. In order to separate the major product from the minor product, the addition of cold xylene is used. The minor product and the reactants are soluble in cold xylene, but the major product is insoluble. Washing the product with cold xylene than will result in a rather pure product.