This lab is about synthesizing aspirin using a hotplate to heat the reaction. It involved vacuum filtration, recrystallization, and comparing the properties of aspirin with salicylic aspirin. The first thing we did in this lab was make a hot-water bath by putting a beaker with water on a hot plate. After measuring out 2. 1 grams of salicylic acid and 3 ml of acetic anhydride, we mixed the two together, along with 3 drops of sulfuric acid. We then put the flask containing the mixture into the hot-water bath, and heated it for 10 minutes. After removing the flask from the hot water, we added 2 mL of distilled water.
The next step was to add 10 grams of crushed ice to the flask and swirl. We were to cool the flask in an ice/water bath for 5-10 minutes with occasional stirring. The next step involved using a vacuum filtration. After we used it, there were about 2 grams of product. The third step of the experiment involved purifying the aspirin by recrystallization. We saved a small amount of crude aspirin product, which was used later in this lab. The rest of it was placed into a flask along with 6 mL of ethanol. The flask was put on the hot plate so all the solid would dissolve.
10 mL of distilled water was then added to the flask and it was reheated so al the solid would again dissolve. As soon as it dissolved, we let it cool to near room temperature, and crystals formed during cooling. The flask was then put in the ice/water bath for 5 minutes. We then collected the product by suction filtration. The fourth step involved measuring the melting temperatures of salicylic acid, commercial aspirin, purified aspirin, and crude aspirin. This lab required us to find various things. In step 1, we observed the physical characteristics of the crude aspirin and the purified aspirin.
The final step required us to find the melting temperatures of salicylic acid, commercial aspirin, purified aspirin, and crude aspirin. One source of error could have been the flask not being dry when we weighed the 2. 1 grams of salicylic acid. Any traces of water would have interfered with the synthesis. Another error could have been in step 3. When the flask was cooling in the ice/water bath, it could have tipped over. This would have affected the product. Data Sheet: On back Post-Lab Questions 1. Draw the structures of salicylic acid and aspirin.
Circle and identify the functional groups present in each compound. On back 2. The equation for the synthesis reaction is given in the Introduction. Copy this equation and indicate on the structures which bonds are broken in the reaction and how the resulting broken pieces pair up to give the products. On back 3. What impurities do you think are present in your crude aspirin product? Where do those impurities go in the recrystallization process? Salicylic acid is an impurity that would be present. Recrystallization involves dissolving the crude mixture in a suitable warm solvent.
The solution is cooled to a point at which one of the components of the mixture crystallizes out of the solution while the more soluble one remains dissolved. 4. What safety, environmental, and economic considerations would be important to a company manufacturing 1 million pounds of aspirin each year by this procedure? Which ones do you think are most important? Why? For safety reasons, a company would want to ensure that they take out anything that could be potentially harmful to people. In terms of the environmental aspect, they would have to consider the amount of materials used.
Economically, this process may be expensive to them, in order to meet all the requirements for properly manufacturing aspirin. I think the safety aspect is the most important because you have to ensure that people are not harmed by your product. 5. The aspirin synthesized in this experiment should never be taken home for medicinal use. Why not? It would still contain things that could be potentially harmful to a person and make them sick. 6. It should be noted that the conventional reaction will not take place if a catalyst is not added to the reaction mixture. Yet, good yields can be obtained in the microwave without a catalyst.
Speculate why. The difference in the methods would be the energy that is involved. 7. Look at the Principles of Green Chemistry in the inside cover of your book. Which principles does the conventional synthesis follow well? Which does the microwave synthesis follow? Which synthesis do you think is “greener”? Provide support for your argument. When comparing the two, I would say that the microwave synthesis would be considered “greener”. Concerning the principle of minimizing the amount of materials used, the conventional synthesis required more materials than the microwave synthesis.
In terms of toxic materials, some substances in this lab could be toxic. The concept of this lab was to synthesize aspirin. We combined salicylic acid, acetic anhydride, and sulfuric acid, and then heated them in a water bath. We collected the crude products by vacuum filtration. The products were purified by recrystallization. We then compared the properties of aspirin with salicylic acid. Truthfully, this was probably my least favorite experiment we have done in Lab. I did not have a clear understanding of some of the concepts involved with the experiment and post-lab questions.