Diels alder reaction of anthracene with maleic anhydride lab report

DIELS-ALDER

OBJECTIVES: To synthesize a bicyclic molecule, performing a Diels-Alder reaction, from anthracene and maleic anhydride. To characterize the product by NMR.

Background

The Diels-Alder reaction is a reaction, specifically a [4+2] cycloaddition, between a diene and dienophile. The word “dienophile” literally means “that has affinity for the diene”. The dienophile is an alkene and the diene is a conjugated diene.

The Diels-Alder reaction begins with the overlapping of the π system of the diene and dienophile. The Diels- Alder reaction requires the s-cis form of the diene, when there is no possibility of the s-cis form the Diels-Alder reaction cannot occur.

Diels-Alder are often used to synthesize bicyclic compounds. In this case we can have two possible products: endo and exo. If the substituent on the alkene point toward the newly formed double bond we have endo, if it points away from it we have an exo product. The endo product is usually favored.

In this experiment we will synthesize a bicyclic compound from anthracene and maleic acid

Experimental

1. Place 0.20 g of anthracene and 0.11g of maleic anhydride in 2.5 mL of xylene in the 10 mL flask from your micro-scale kit.

2. Attach the condenser to the flask and add a wooden boiling stick (don't use a stir bar, it will be hard to remove later).

3. Heat the solution to reflux on the sand bath, continue to reflux for 30 min.

4. Allow the solution to cool completely, then filter and collect the crystals on your Hirsch funnel, washing once with cold xylene. Air dry, with suction, for about 5 min.

5. Weigh the crystals, take a melting point (should be 260˚ C with decomposition). Analyze for purity by TLC (in 1:6 ethylacetate: hexane). Compare final product with starting material, anthracene. Take a 1H-NMR of the product.

6. On the next page, you are provided with 1H-NMR spectra of the two starting materials. Print off that page and turn in with your report: assign each spectrum (starting material 1 or starting material 2) as either anthracene or maleic anhydride.

Real life example of Diels Alder reaction

In this paper researchers describe a new strategy for the optimization of the synthesis of antibody−drug conjugate (ADC). The ability to couple biomolecules with drugs, reporter molecules, polymers, surfaces, and other biologically active compound is extremely important in biochemistry and in the biomolecular field. In this paper the authors report that a Diels Alder reaction (DA) is particularly efficient for this purpose.

References:

A. H.; St. Amant et al.; Bioconjugate Chem. 2018, 29, 2406−2414.

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POST LAB

1) Write the introduction for the Diels Alder experiment in not more than 5 sentences

2) Write the abstract using not more than 4 sentences

3) Write a short discussion (include the mechanism of the reaction)

4) Write the experimental section

5) Write the conclusions section