Acetylsalicylic Acid Lab

Acetylsalicylic Acid

September 15, 2005

September 23, 2005

OBJECTIVES

The objective of this lab experiment is to prepare aspirin (acetylsalicylic acid) by reacting salicylic acid and acetic anhydride.

INTRODUCTION

This purpose of this lab was to prepare aspirin using its basic components: salicylic acid and acetic anhydride. Salicylic acid and acetic anhydride, along with an acid catalyst, react to form acetylsalicylic acid (aspirin) and acetic acid. In this reaction, the hydroxyl group on the benzene ring in salicylic acid reacts with acetic anhydride to form an ester functional group. The acetylsalicylic acid crystallizes as the solution cools and begins to come out of the solution. The acetylsalicylic acid is further purified through recrystallization with ethyl acetate.

MATERIALS USED:

Test Tubes Pasteur Pipette

Salicylic acid acetic anhydride

Sulfuric acid 125 mL Erlenmeyer flask

Scale Water Hot water bath

Ice Bath Buchner FÑŒnnel

1% Ferric Chloride

Ethyl acetate Glass Rod

Iodine Aspirin Tablet

Commercial Aspirin tablet

METHODS

Part A

1. 2.0 g of salicylic acid was placed in a 125 mL Erlenmeyer flask.

2. 5.0 mL of acetic anhydride was added to the flask and five drops of concentrated sulfuric acid was also added.

3. The flask was swirled to dissolve the salicylic acid.

4. The flask was placed in a hot water bath for ten minutes.

5. The flask had to be placed in an ice bath briefly and the sides were scratched with a glass rod until crystallization occurred.

6. 50 mL of water was added and the flask was returned to the ice bath for another five minutes. This allowed for more crystallization to occur.

7. The solution was placed in vacuum filtration using a bÑŒchner funnel for five minutes. Distilled water was added to the flask to flush solution off the sides of the flask to be poured into funnel for filtration.

8. The remaining product was allowed to air dry and was weighed. The product weight was 2.88 g.

9. The percentage yield of the product was 11.02 percent.

Part B

This experiment was performed to determine if their was any salicylic acid left in the product.

1. Three test tubes were filed with .5 mL of water.

2. Small portions of the product were added to two test tubes, while the third was filled with water to act as the control.

3. One drop of Ferric Chloride solution was added to each tube.

4. The test tubes containing product turned into a tan/peach color while the control remained yellow. The concluded that the product had little to no salicylic acid present.

Part C

1. 3 mL of hot ethyl acetate was added to a small Erlenmeyer flask.

2. Product from the previous experiments was added to the flask.

3. The solution was placed in a hot water bath until dissolved and then placed in an ice bath and scraped with a glass rod until crystallized.

4. The solution was vacuum filtered until dry.

5. The ferric chloride purity test was performed on the new product. The same results from Part B occurred, further proving that the previous solution had little to no salicylic acid.

6. The melting point was determined by using a "melting point apparatus"(?) The melting point of the product was 131oC.

Part D

1. The purified product, ј an aspirin tablet, and ј a commercial aspirin tablet were each placed in separated test tubes.

2. 2 mL of water was added to each tube and each tube was boiled in a hot water bath.

3. A drop of iodine solution was added to each test tube to test the presence of starch. Starch was only present in the regular aspirin tablet, which turned into a violet blue color after having the iodine added to it.

DATE, RESULTS, AND CALCULATIONS

Part A

* 2.0g Salicylic acid(s) + 5.0 mL acetic anhydride(aq) + 5 drops sulfuric acid  2.88g acetylsalicylic acid + acetic acid Percentage yield= 11.02%

Part B

Test Tubes w/ ferric chloride Product Added? Result

Tube #1 Yes Solution turned tan/peach color (pure)

Tube #2 Yes Solution turned tan/peach color (pure)

Tube #3 (Control) No Solution turned yellow

Part C

Recrystallization was performed using ethyl acetate

* The melting point of the product was 131oC.

* Ferric chloride purity test results were also the same.

Part D

Product + water After Iodine is added.

Acetylsalicylic acid No color change

ј aspirin Violet blue color change

ј commercial aspirin No color change

DISCUSSION

In Part A, aspirin was prepared by the reaction between salicylic