Alex Wilson 9/11/12 Experiment #2 Separating the Components of Panacetin: Introduction: Of the three components likely to be present in your sample of Panacetin (aspirin, acetanilide, and starch), only starch is insoluble in the organic solvent dichloromethane (or methylene chloride), CH2 Cl2. If a sample of Panacetin is dissolved as completely as possible in dichloromethane, the insoluble starch can be filtered out, leaving acetanilide and aspirin in solution. The purpose of this experiment is to extract the components of Panacetin.
Although the acetanilide and aspirin are both quite insoluble in water at room temperature, the sodium salt of aspirin is very soluble in water but insoluble in dichloromethane. Because aspirin is a reasonably strong acid, it can be converted to the salt, sodium acetylsalicylate, by reaction with the basic sodium hydroxide. While the two layers are thoroughly mixed, the aspirin will react with the sodium hydroxide in the bottom layer, which then migrates to the aqueous layer and can be easily separated in a separatory funnel.
Adding some dilute hydrochloric acid to the aqueous solution restores free aspirin as an insoluble white solid; evaporating the solvent from the bottom layer leaves the acetanilide behind. Experimental: For the separation of sucrose, we weighed out 3. 048g of Panacetin onto a filter, and 50 mL of dichloromethane in a graduated cylinder. Then we transferred both the panacetin and dichloromethane into an Erlenmeyer flask and stirred it until the panacetin was dissolved. We let it dry by gravity and set it aside to dry. The filter paper weighed about 1. 320g and sucrose weighed out at 1. 028g.
Sucrose also ended up on the outside rim of the filter paper. We then proceed to separate the aspirin. We measured 30mL of NaHCO3 and mixed it with 7mL of 6M HCl. We drained the organic layer into a pre-weighed Erlenmeyer flask and save it for recovery of acetanilide. We took the combined aqueous extracts in an Erlenmeyer flask, and acidify the aqueous solution by slow addition, with stirring, of 20 mL of 6M HCl. We made sure the solution is strongly acidic by testing it with litmus paper getting a pH of 2. We then cooled the mixture to room temperature swirling the flask occasionally in an ice bath.
We collected the aspirin by vacuum filtration and washed the aspirin on the filter with cold distilled water. We let it air dry for 30-35 minutes and then weighed the aspirin. It weighed out at 0. 513g. The unknown component was calculated and weighed at 0. 738g. Results: When we were mixing the filtration and letting it vent periodically, we lost some of it. So our percent recovery is as follows: The unknown component weighed 0. 738g. And our percent composition is as follows: Discussion: Sucrose is insoluble in the organic solvent dichloromethane (CH2 Cl2).
Aspirin, acetanilide, and phenacetin are soluble in dichloromethane but relatively soluble in water. Aspirin reacts with bases such as sodium bicarbonate to form a salt, sodium acetylsalicylate, which is insoluble in water. Acetanilide and phenacetin are not converted into salts by sodium bicarbonate. The Reciprocal (Interconversion) of Aspirin and it’s Sodium Salt Conclusion: The breakdown of Panacetin: Mix panacetin with CH2 Cl2 and you will get a solid which is sucrose and you’ll get a filtrate of aspirin and an unknown substance. Then you will extract the aspirin with NaHCO3 to get an organic layer and a water layer.
The bottom layer for us was the organic layer, while the top layer was the water layer. After figuring out the organic layer you mix the unknown with CH2 Cl2, and then you will evaporate to leave just the unknown substance. When you figure out which layer was the water layer, you’ll mix sodium salicylate and H2O. You will then add HCl until the pH level of the solution reaches 2. After the pH reaces2, you have aspirin; which proves that as long as you follow the directions in this lab, you will have indeed separated the aspirin from the panacetin.
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