Bijal Patel, 20467049
Partner: Poojan Parikh
T.A.’s: Long Pu
CHEM 123L, Section: 006, Rm: ESC 149
Tuesday February 4, 2013, 2:30pm-5:20pm
Experiment Done: Tuesday January 22, 2013
Acetaminophen was first introduced in 1955 (Richman, 2004). It is an over-the-counter drug that relieves pain and reduced fevers. Acetaminophen is considered an alternate to aspirin since it does not irritate the stomach (Richman, 2004). It also has very low toxicity is it is used properly. Acetaminophen is cheap and easily obtainable from any pharmacy. Acetaminophen is created when the amine group of p-aminophenol is acetylated by acetic anhydride. This creates an amide functional group and the by-product of this reaction is acetic acid. The crude acetaminophen will form as a white solid after the acetylated reaction. To turn this crude acetaminophen into a purified form, the recrystallization technique will be used. The recrystallization technique is when the solid is dissolved and forced to precipitate as a crystal solid later on. The crude solid is dissolved through heating with a small amount of solvent, in this case, deionized water. The solution is then cooled to room temperature and later put into an ice bath which is when the crystals form. These crystals obtained are more pure since the impurities are dissolved in the cold solution. When cooling, the solution should remain undisturbed. The purpose of this experiment is to determine the melting points of the crude and purified form of acetaminophen using a MelTemp melting point apparatus. Using capillary tubes, samples of the crude and purified solid will be tested. If the experiment is done properly, the crude solid should dissolve faster than the purified solid of acetaminophen. One must wear goggles and gloves at all times while working with acetic anhydride as it is corrosive. http://de.academic.ru/pictures/dewiki/83/Synthesis_of_paracetamol.png http://de.academic.ru/pictures/dewiki/83/Synthesis_of_paracetamol.png
The experimental procedure used for this experiment was outlined in the CHEM 123L lab manual, Experiment #1, Synthesis of Acetaminophen, pages 12-15. A slight change was made to the one material that was used. Instead of a 100mL round bottom flask a 50mL round bottom flask was used. Other than that, all steps were followed accordingly.
* Initial p-aminophenol: 3.00g
* 36mL of deionized water was added to the Erlenmeyer flask for the recrystallization technique.
Table 1: Outcomes of Crude and Purified Solids
Erlenmeyer Flask| Total Mass| Mass of Solid| Erlenmeyer Flask| Total Mass| Mass of Solid| 92.68g| 96.28g| 3.60g| 92.82g| 95.66g| 2.84g|
Melting Point: 162 °C| Melting Point: 164 °C|
*This table shows how much of the solid was obtained after the reaction along with their boiling points. This table can be used to see the difference between crude and purified solids.
Results and Calculations
p-Aminophenol + Acetic Anhydride Acetaminophen + Acetic Acid C6H7NO(S) + C4H6O3(l) C8H9NO2(s) + C2H4O2(aq)
The objective of this experiment was to find the melting points of the crude and purified solid. After conducting the experiment, it was found that the crude solid melted faster than the purified solid. Our values showed that our samples melted at a slightly lower temperature than what the Merck Index had stated. The Merck Index said that the melting point varies from 169°C -170°C. The melting points we had observed were from 162°C -164°C. This might be due to the fact that this experiment was not done under perfect conditions. Also, what we found in terms of how much acetaminophen was obtained, was that the crude product was obtained in larger amounts than purified. From the initial amount of p-aminophenol, which was 3.00g, we achieved 3.60g of crude...