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Descriptive Title of Experiment
Preparation of aspirin
Purpose
To prepare aspirin through the reaction of salicylic acid with acetic anhydride.
Brief Experimental Procedure
A 600ml beaker was filled to 450mL mark with water and placed on a hot plate. The 125mL Erlenmeyer flask was removed from the apparatus clamp and set aside. Next, the water was heated to 90 degrees Celsius. The temperatures were maintained by adjusting the hot plate setting—a 2g of salicylic acid, which had been pre-weighed in the test-tube. Then the Erlenmeyer flask was added to the setup again. Under the fume-Hood, a 2ml of Acetic Anhydride was poured into a graduated cylinder. Slowly and carefully, the Acetic Anhydride was added to the flask that contained Salicylic Acid. Ten drops of concentrated sulfuric acid were added to the flask, and gently the contents were swirled.
Next, the flask was placed in a hot water bath and secured with the apparatus clamp. It was then heated for 6 minutes at 90 degrees Celsius. While waiting for an ice bath, a 400mL beaker was filled with two parts of the ice and another one with water. Next, the flask was removed from the water bath. Slowly, 20 mL of iced distilled water was added to the flask as it helped to decompose the unreacted Acetic Anhydride hence converting it to Acetic Acid. It waited till the flask in the ice bath had completely crystallized. The inside of the flask was then scratched using a glass rod to initiate crystallization. In the flask, 25mL of distilled water was added. The Buchner on the front desk was attached to the vacuum filtration. The vacuum was turned on and then filtered paper made wet with distilled water from the washing bottle. Aspirin mixture from the Erlenmeyer flask was poured into the funnel. Next, the flask was rinsed by using a stream of distilled water from the wash bottle, and the rinsing poured into the funnel. Aspirin crystals were washed by adding 15ml of distilled water to the funnel. After the water had passed into the filter flask, the vacuum was left on for another more minute. Next, the vacuum was turned off and then filter paper removed with the aspirin crystals placed on a watch glass. The aspirin crystals were transferred from the filter paper into the glass vial, labeled, and the vial capped. Next, the experimental product was saved to determine the molecular weight of the aspirin in the next lab period. The filtrate was emptied into a non-hazardous waste bottle in the common hood, and the filter flask washed. Lastly, the filter flask was then attached to the apparatus clamp and then tightened.
Questions
- What is the objective of this experiment?
To prepare aspirin through the reaction of salicylic acid with acetic anhydride.
- What is a catalyst? What is the purpose of adding sulfuric acid?
Catalyst is a substance when added to a reaction; it increases the reaction rate without getting consumed. Sulfuric acid allows the carbonyl carbon of acetic anhydride to be more electrophilic.
- What are buffers?
A buffer is simply an aqueous solution that consists of a mixture of a week acid and its conjugate base or vice versa.
- What buffers are used in buffered aspirins?
calcium carbonate, aluminum hydroxide, or magnesium oxide
- If you had a job making aspirin for a pharmaceutical company, you might make some changes in the procedure used in CHM 107 laboratory to save time and/or money. Describe one practical improvement in lab technique that you could make and how it would increase aspirin production efficiency.
In the preparation of aspirin, to use an efficient procedure that eliminates the heating step initiated giving ferric-negative product, pure as there would be no purple color with alcoholic ferric chloride solution hence increasing the efficiency of aspirin production.
Post lab questions
- What is the objective of the experiment?
To prepare aspirin through the reaction of salicylic acid with acetic anhydride.
- What are prostaglandins, and what roles do they play in the human body?
Prostaglandins are those lipid autacoids and derived from the arachidonic acid. Prostaglandins control the processes of blood flow in the human body, blood clots formation, control inflammation, and control labor induction.
- How does aspirin function, and what interactions does it have with prostaglandins?
Aspirin is irreversibly as well as non-selective which inhibits both of the forms. It acetylates the hydroxyl of a series residue; hence the COX generates prostaglandins, which are thromboxane and pro-inflammatory, promoting clotting.
- Why is acetylsalicylic acid used now instead of salicylic acid, which was once commonly used?
The use of acetylsalicylic acid is advantageous when aspirin is produced because salicylic acid has an irritating effect on the human stomach. Acetylsalicylic acid passes through the stomach when largely is uncharged.
- What is the primary difference between salicylic acid & acetylsalicylic acid in terms of their chemical structure?
The difference between salicylic acid & acetylsalicylic acid the salicylic acid structure has a carboxyl group and a hydroxyl group attached to the benzene ring. On the other hand, the acetylsalicylic acid structure has a carbonyl group and an ester group attached to the benzene ring.
- What catalyst is used in this reaction, and what compound is produced as a byproduct of this reaction?
Phosphoric acid is a small amount as a catalyst, while acetic acid is produced as a byproduct.
- How do different brands of USP aspirin differ? Is there a benefit to purchasing buffered preparations?
Brands of USP aspirin differ in quantitative variation, always existing among the drugs. It is very beneficial to purchase buffered aspirin because the aspirin would minimize the acid’s side effects. It reduces heartburn as well as an upset stomach, which is caused by aspirin.
- What is the purpose of adding cold distilled water to the reaction mixture after heating in a hot water bath?
The reason is that aspirin is less soluble in cold water. It helps from dissolving too much to have a better yield product. It is washed to help in removing the impurities that dissolve in water.
- What is the purpose of vacuum filtration and washing the compound with distilled water?
The filters trap the solid and the liquid drawn through a funnel into a flask by the vacuum. Vacuum filtration helps to collect solid aspirin. The compound is washed with distilled water to remove impurities that do dissolve in water.
- How does FeCl3allow one to determine the purity of their product?
FeCl3 is added to an aspirin sample when the color changes to violet; it means that there are impurities within the acetylsalicylic acid.