We will be performing the Diels Alder reaction with a very popular dieneophile – maleic anhydride. The diene we will be using is anthracene - a polycylic aromatic hydrocarbon (PAH) that can be found in coal, petroleum, and charcoal grilled hamburgers. The interesting aspect of anthracene is that it offers several different diene sites for the Diels Alder addition of maleic anhydride.
- Add 2 g of anthracene to a 100 or 250mL round bottom flask.
- Add 1 g of maleic anhydride to the round bottom. Despite its benign appearance, solid maleic anhydride is toxic and should not be handled with bare hands.
- Add 25 mL of xylene (dimethyl benzene) to the round bottom. Do not remove the xylene bottle from the fume hood. Do this operation in the hood!
- Add three boiling chips to the round bottom. Swirl the reactants to mix. The solids will not totally dissolve at this time.
- Attach the round bottom to a reflux condenser mounted on a ring stand. Attach water hoses as shown in the preceding diagram
- Use a thermwell mounted on an iron ring to heat the solution. Heat the mixture to boiling, and then adjust the heat input so that the boiling is maintained at a steady rate.
- Reflux for 25 minutes. Note any changes in the reaction mixture. Complement your “hood mate” on how nice he/she looks today.
- 8. Turn off the heat source. Carefully transferring the hot contents to a 50 or 150 mL beaker at this time will make to easier to remove the crystals that form.
- 9. Chill in an ice bath.
- 10. Vacuum filter the solid (crude) product in a vacuum (Buchner) funnel. You may wash it with a small amount of ice-cold xylene.
- 11. Remove boiling chips with a tweezers.
- 12. Admire and the crude product.
- B. Recrystallization
- Recrystallize your crude product with hexane.
|Weight of anthracene||1.000g|
|Weight of 9,10-dihydroanthracene-9,10-endo-α,β-succinic anhydride||1.255g|
|Chemical shift (d) in ppm||multiplicity|