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38/40 lab report on dies alder reactions...

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Jesus Reynaldo Vilas Jr TA: Xuming Li Dies-Alder Reaction Between Anthracene and Maleic Anhydride

Introduction. A dies-alder reaction is a conjugated addition of a conjugated diene alongside a dienophile. This is typically an alkene, or an alkyne and the conjugation is typically done to induce a cyclohexene. A diene, in organic chemistry, is typically a covalent compound with two double bonds. For the purpose of a dies-alder reaction, the double bonds within the diene are conjugated and separated by a single bond. These types of dienes are more stable than others due to being resonant stabilized. A dienophile is any compound that has an electron withdrawing group that is then conjugated onto an alkene. However, in certain situations the dienophile can actually be paired with an electron donating group, but these situations are rare. In order for a dies-alder reaction to occur two key points must be reached: the diene must be conjugated, and the diene must also be in the s-cis conformation, without these two points the reaction will not occur. The endo product is usually the major product because of the kinetic control that the reaction undergoes. The most common use of a dies-alder reaction is the creation of complex and flexible polymers due to its simplicity, versatility and efficiency.

Mechanisms and Side Reactions.

In the mechanism above, the diene, shown as anthracene and the dienophile, being maleic acid, double bonds are highlighted by the red arrow showing the movement of electrons. The tail end of the arrow indicates where the electron initially began, and the head of the arrow shows where the electron ends up. The result of the arrow pushing mechanism results in bond formation between carbons 1-3 and carbons 2-6 as seen above. The double bond in the product is located on 4-5 and the rest of the bonds are moved accordingly to the new conformation.

The side reactions that can occur in the experiment are shown above. In the first reaction the end product of the original dies-alder reaction bonds with water causing the formation of hydrolyzed 9,10-dihydroanthraceno-9,10-endo- α, βsuccinic anhydride. Experiment. A reflux apparatus was put together with the water-cooled condenser placed in a sand bath. The condenser was then attached to a regulator and a drying tube filled with CaCl2. A magnetic stir bar was placed into a round bottom flask alongside 0.6 g of anthracene, 0.3 g of maleic anhydride and6.0 ml of Xylene. The sand bath was turned on and the regulator was set to 40. The apparatus then began to reflux and after some time an oily residue appeared in the round bottom flask. Once this occurred, the mixture was allowed to reflux for an additional 30 minutes. Afterwards, the mixture was allowed to cool to room temperature and was then

placed in an ice bath for 10 minutes. Once crystals formed, the mixture was poured into a Hirsch funnel and then the excess liquid was vacuumed out and washed with cold Xylene. A small portion of the crystal was then taken and used to determine both the melting point and the H1 NMR data.

Name of Chemical

Anthracene

Maleic Anhydride

IUPAC Name

Anthracene

Furan-2-5-dione

Formula

C14H10

C4H2O3

Molar Mass

178.23 g/mol

98.06 g/mol

Melting Point (C)

215.76

52.6

Boiling Point (C)

339.9

202

Density

1.25 g/cm3

31.48 g/cm3

Safety

Hazardous in cases of

Very hazardous if

skin/eye contact or

ingested

inhalation/ingestion Hazardous in cases of Combustible

skin/eye contact or inhalation Corrosive to eyes/skin Combustible

Chemical Structure

Results. Mass of the desired product = 0.778 g Melting point of the desired product = 260 °C The color of the crystal was a pale yellow almost white color after it had been washed and dried.

The percent yield of the reaction was

0.778 g of C 18 H 12 O 3 x 100 % = 91.5 % 0.85 g of C 18 H 12O 3

The overall speed of the reaction was fast since when the magnetic stir rod was activated, an oily substance began to form rapidly. Discussion and Conclusion The melting point of the product was identical to the ideal melting point which shows that the product was of top quality. The percent yield of the reaction was extremely high which validates the quality of the testing done on the experiment

and also the accuracy of the tools used. The H1 NMR of the desired product was slightly off since a fifth peak was shown on the graph while only four peaks are visible on the ppm. This signified that there was another outlier group affecting the overall data. This could be a side reaction product appearing in the system and thus offsetting the data. In spite of this outlier, the lab did accomplish its purpose of teaching how to properly conduct a dies-alder reaction and I learned how to properly analyze data as well as the uses and simplicity of a dies-alder reaction. References. Anthracene-maleic anhydride Diels-Alder adduct. (n.d.). Retrieved September 08, 2020, from https://webbook.nist.gov/cgi/cbook.cgi?ID=C5443163 Says:, D., Says:, C., Says:, W., Says:, C., Says:, C., Says:, J., . . . Says:, S. (2020, February 24). The Diels-Alder Reaction. Retrieved September 08, 2020, from https://www.masterorganicchemistry.com/2017/08/30/the-diels-alder-reaction/...