When it comes to organic chemistry and the synthesis of specific products there is an abundant amount of routes that can be taken and still get you the same result. For the following experiment, the main focus is the use of a cycloaddition reaction, also known as Diels-Alder. According to the lab manual, this reaction consists of the addition of a diene and a dienophile and that the Diels-Alder reaction builds stereospecific ring compounds with ease (Weldegirma 80).
The reaction takes place between the two pi electrons from the dienophile and the 4 pi electrons from the diene; what happens is the bonds react together in order to form new single bonds because they are more stable, in terms of energetics (Diels-Alder Reaction). In order for the reaction to take place it prefers if the dienophile has electron-withdrawing groups and if the diene has electron-donating groups (Weldegirma 81). The purpose of this also relates to energy, such that it lowers it and makes it more stable. When the reaction takes place, like many other reactions, there is both a major product and a minor product.
In the case of the Diels-Alder reaction one product is referred to as endo and the other as exo, both of which refer to the stereochemistry of the product. The reaction favors the product that has the most orbital overlap (Weldegirma 81). This is determined by looking at the outside groups. For example, “the endo product is the one where the outside groups on the diene are on the same side of the 6-membered ring as the electron withdrawing group,” and the exo product is “the one where the outside groups are on the opposite side of the ring as the 6membered ring” (James).
Overall, when it comes to the synthesis of a stereospecific 6-membered ring one of the more favored ways is the Diels-Alder reaction. To begin, the first step of the experiment was to crack down dicyclopentadiene into the form of cyclopentadiene, which was done using the process of fractional distillation. Five milliliters of dicyclopentadiene was utilized in the distillation at the temperature of 40°C for approximately 20 minutes. Next 0. 20g of maleic anhydride was dissolve in 2mL of ethyl acetate.
Then it was mixed with two drops of the cyclopentadiene. Lastly, the solution was then heated using a sand bath and then cooled in ice, which led to the forming of crystals that were weighed in order to calculate percent yield. Using the data from the results section, one can determine that the melting point f the final product was not collected. However, if it were it would have been compared to the literature value of 165°C. The purpose of this is to reveal how pure the final product is compared to the actual compound.
If the tested melting point were to be close to the literature that means the product is pure but if there is a significant difference that indicate that there may be other compounds or contaminates present. Then there is the percent yield, which reveals how much of the product was obtained versus how much could have been obtained based off the calculated value. For the following experiment, 45% of the product was obtained and this isn’t necessarily bad just because it isn’t 100%.
The only way to determine if 45% is bad would be to compare it to a literature experiment and see how much product was collected, but that value was not located. So based on the information that was collected it can be said that the desired product was collected and that it was done so efficiently. Then there is the possible side reaction that could have skewed the results. That is the dimerization of the cyclopentadiene, which happens when it is at room temperature.
If this were to occur it would lead to the synthesis of cis-norbornene-5, 6-exo-dicarboxylic anhydride instead of cisnorbornene-5, 6-endo-dicarboxylic anhydride. In order to avoid this diclyclopentadiene has to be cracked down through the process of fractional distillation to form cyclopentadiene. Overall, the wanted final product was collected. Conclusion This experiment helped utilize the cyloaddition reaction known as Diels-Alder in order to synthesize cis-norbornene-5, 6-endodicarboxylic anhydride using cyclopentadiene and maleic anhydride.
Reveling that the Diels-Alder reaction is very useful in the formation of stereospecific 6-membered rings. So the DielsAlder reaction can be used for many other situations like they synthesis of pharmaceutical drugs, aromas and more. Overall, one can say that this experiment was a success and accomplished what it was set out to do, which was perform a Diels-Alder reaction and synthesize cis-norbornene-5, 6-endodicarboxylic anhydride.
