Mercer County Community College s2

CHE106: C h e m i c a l S c i e n c e C o n c e p t s

Aspirin Preparation Name

Partner

Objectives o To perform an aspirin synthesis reaction o To isolate the product by vacuum filtration o To interpret chemical tests for purity assessment

Introduction: Aspirin - the Wonder Drug

Aspirin was patented in 1899 by the Bayer company. Described as the “wonder drug”, it is the most widely used nonprescription drug in the world. It is in the class of compounds known as salicylates and is a non-steroidal anti- inflammatory drug. In the 5th century B.C., Hippocrates described a white powder from willow bark helped relieve pain and reduce fevers. Later this substance was identified as salicin , a natural salicylate which is similar to aspirin. The most common use of Aspirin is to relieve pain, reduce fevers and swelling. It has been found to be effective in the treatment of heart disease, strokes and recent studies have shown Aspirin may reduce enlarged prostate glands and prevent certain types of esophageal and skin cancers.

The active ingredient is actually salicyclic acid however this phenol is too abrasive to the stomach and promotes stomach bleeding and ulcers. Aspirin is converted to salicylic acid in the body where it suppresses the production of prostaglandins (a hormone that relays pain information to the brain).

The reaction: O

CO2H CO2H C O O O H3PO4 CH OH 3 + CH3CO2H

Acetic Phosphoric Salicylic Acetic Anhydride acid Aspirin acid acid

1 CHE106: C h e m i c a l S c i e n c e C o n c e p t s

Part I: Preparation of Aspirin

GOGGLES MUST BE WORN WHILE PERFORMING THS EXPERIMENT

Equipment: Reagents:

125 mL dry erlenmeyer flask salicylic acid 400 mL beaker with 3 boileezers acetic anhydride 10 mL graduated cylinder phosphoric acid hotplate distilled water stirring rod

Filtration apparatus (Figure 1, p5): two 250 mL filter flasks, funnel, filter paper, filter-vac 2 clamps, 1 long and 1 short piece of rubber tubing, vacuum adapter

EXPERIMENTAL Add 200 mL of tap water and 3 boileezers to a 400 ml beaker then heat the contents to boiling using a hotplate.

Place 2.0 grams of salicylic acid in the 125 mL Erlenmeyer flask, add 5.0 ml of acetic anhydride and swirl the flask (Caution! very irritating) then add

5 drops of 85% phosphoric acid (H3PO4.) to the mixture. Heat the flask in the boiling water bath for 8 minutes, remove from the hot water and (still wearing goggles) cautiously add 2 ml of distilled water to the hot mixture. This decomposes the excess acetic anhydride. Heat is given off; spattering may occur.

After decomposition is complete, add 40 ml of distilled water and stir the solution until crystals begin to form. Only then, cool the mixture in an ice bath in an 800-ml beaker to complete the crystallization. Allow 10 minutes for crystals to form. While the product is crystallizing set up the filtration apparatus.

Collect the product (aspirin) by suction filtration using a Büchner funnel. See diagram 1 on page 5. Place a piece of filter paper of the correct size in the funnel and moisten it with water to hold it down. Turn on the suction and press the funnel down to make a good seal. Swirl the solution and quickly pour your aspirin mixture into the funnel. Add small amounts of cold water to the crystals remaining in the beaker, and swirl and dump to transfer most of them to the funnel. The air passing through the crystals dries them to some extent, so after a few minutes remove the funnel from the filter flask and invert it over paper towels to dry them further. Throw the filter paper in the garbage can. Show the product to your instructor.

Instructor’s initials:

3 CHE106: C h e m i c a l S c i e n c e C o n c e p t s Aspirin analysis:

The most common contaminant found from the synthesis of aspirin is unreacted starting material, salicylic acid and acetic acid from the hydrolysis of acetic anhydride. The functional groups present in salicylic acid are a carboxylic acid and a phenol. Phenol compounds are corrosive to the mouth, esophagus and stomach lining. Phenols react with 1% iron (III) nitrate, Fe(NO 3)3 to produce a violet color. The intensity of the color is proportional to the amount of phenol present in the sample. Perform the iron (III) nitrate test on your compound, commercial aspirin and salicylic acid and compare the color intensity of each of the tests.

Equipment: Reagents: 3 test tubes commercial aspirin test tube rack salicylic acid 10 mL graduated cylinder distilled water stirring rod 1% Fe(NO3)3

EXPERIMENTAL Using a red crayon pencil label the test tubes: test tube 1 = SA for salicylic acid, test tube 2 = ST for student preparation test tube 3 = ASP For commercial aspirin

Crush 1 aspirin tablet using a mortar and pestle and place a spatula tip amount into the test tube labeled ASP. Add approximately the same sized sample of salicylic acid to the SA test tube and your compound to the ST test tube. Add 5 mL of distilled water to each test tube and stir with a stirring rod, wiping it clean for use in each test tube. Add 5 drops of 1% Fe(NO3)3 to each test tube.

Describe and compare the color of the solution of each test.

Which sample has the most phenol?

Which sample has the least phenol?

Would your compound be safe to take for a headache? Explain

4 CHE106: C h e m i c a l S c i e n c e C o n c e p t s Questions

1. Aspirin is a widely used drug because it is an analgesic, antipyretic and NSAID. Explain what these terms mean.

Analgesic

Antipyretic

2. Phosphoric acid is a catalyst for the aspirin synthesis reaction. Explain what a catalyst is.

3.Tylenol® contains acetaminophen, structure given below. Would acetaminophen produce a purple color if it was tested with 1% Fe(NO 3)3 solution? EXPLAIN.

HO CH3

Acetaminophen

4. Old aspirin often smells like vinegar. Suggest a reason for the formation of the odor?