Experiment a Diels-Alder reaction

Purpose:

In this experiment a Diels-Alder reaction was used to form the products. Cyclopentadiene and maleic anhydride were reacted together to form cis-Norbornene-5,6-endo-dicarboxylic anhydride. 7-oxabicyclo{2.2.1}hept-5-ene-2,3-dicarboxylic anhydride was also produced through a Diels-Alder reaction with the combination of furan and maleic anhydride.

Equation:

Procedure:

Part 1

In a flask equipped with a septum side arm and topped with distillation heat and a thermometer add 2.5ml of mineral oil. Heat the oil. At the end of the distillation heat place an ice filled beaker.

When the oil reaches 250°C inject 0.6ml of dicyclpentadiene drop wise through septum. Make sure the temperature does not go above 45°C. The product is then weighed.

Part 2

In a reaction tube place 0.20g maleic anhydride and 1.0ml of ethyl acetate then add 1.0ml of hexane. Then add 0.20ml of cyclopentadiene. Cool the tube in an ice bath. Remove solvent from crystals using pipette. Wash crystals with hexanes then remove solvent again. Allow crystals to dry.

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Part 3

In a flask place 2.4g maleic anhydride and add 20ml of diethyl ether. Dissolve mixture using hot plate then let cool to room temperature. Add 1.8ml of furane to the flask. Wrap the flask with Parafilm after placing a stopper on top of flask. Place the flask under the hood for the next lab period. Upon the return of the next class period the formed crystals were scrapped from the flask. The crystals were then weighed and melting points were observed.

Discussion and Conclusion:

A Diels-Alder reaction was used to produce the products of this experiment.

The first reaction was cyclopentadiene with maleic anhydride to from the product of cis-Norbornene-5,6-endo-dicarboxylic anhydride. Before that could be produced, dicyclopentadiene had to be cracked to get cyclopentadiene for the starting material. Cyclopentadiene and maleic anhydride were mixed together and cooled to room temperature, which produced crystals. The solvent was pipette out of the tube to separate the crystals. The crystals were then scraped on the filter paper to get weight and melting points. The end product yielded 82.6%. The melting point was observed at 162-163°C. This indicated a close to pure substance with the actual melting point being 165°C. The second part of the experiment was the reaction of furan with maleic anhydride.

This reaction produced 7-oxabicyclo{2.2.1}hept-5-ene-2,3-dicarboxylic anhydride. Maleic anhydride was combined with diethyl either to dissolve the solid. Then furan was added and place under the hood for the next class period. During this time crystals were formed in the stopped flask. The melting point for the end product was observed at 113-114°C. This indicated that the product was exo. The percent yield was calculated at 5.98%. There were many sources of error that could have contributed to the results of these experiments.

The end product could have cooled a little longer to form more crystals. Also the crystals could have been dried more to produce better melting points. Separating the solvent from the test tube was not completely precise and may have lost some of the product in the extraction. Scraping the crystals out of the flask or test tube was not easy and some of the product was lost during this step. Overall the experiment was a success.

Reference:

Williamson, K.; Minard, R.; Masters, K. Macroscale and Microscale Organic Experiments, 2011. Pg 617-629.