Follow-Up:
The following two activities can be used on Day 2 or shortly after completion of this lab. They can also be used as extension activities:

1. Students can compare the quality of the synthesized aspirin with salicylic acid, commercial aspirin, and lab grade acetylsalicylic acid. To three separate test tubes, add a few crystals of the three substances and 1 drop of 1% Iron III Chloride. Observe color: pure aspirin should show no color, salicylic acid or traces of it in the aspirin will show a purple color.

2. Students can recrystallize the impure aspirin. The recrystallization is performed by scraping the crude aspirin from the filter paper to a large, clean test tube. Add about 7 mL of ethanol. Place the test tube in a 250 mL beaker of water and heat until the aspirin dissolves. Add 15 mL of warm water to the test tube. Keep warming the beaker until all the solid is dissolved. Cool the test tube and put a stopper on after it is cooled. Label and allow the tube to stand 24 hours. The pure crystals will begin to form about 2 hours after cooling. When the crystallization process is complete, filter off the crystals and wash with about 10 mL cool water. Dry overnight.

Lead a class discussion about the various symptoms aspirin is used to treat, along with its comparison to ibuprofen and acetaminophen. Aspirin acts as an analgesic against mild pain, such as headache, but is not effective against intense pain, such as severe burns. It lowers body temperature and reduces inflammation. Over long terms, evidence shows that aspirin taken in small amounts can be effective in helping prevent strokes and heart attacks. If used for long term therapy, aspirin may cause a person to bruise or bleed more easily. Persons who are anemic or have clotting defects, and mothers in the last trimester of pregnancy should not take aspirin. Children with flu or chicken pox can experience a rare and deadly liver disease, Reye's syndrome, if they take aspirin.

Ibuprofen (Advil and Motrin) does keep platelets from clotting if the dosage in the blood is kept at a consistent level. High doses of ibuprofen can lead to negative side effects, such as gastrointestinal distress and kidney problems. Acetaminophen (Tylenol) is an analgesic, but is not anti-inflammatory and does not prohibit platelets from clotting; in high doses it may produce liver damage.

Have students compare the structural formulas of these three common pain relievers and compare them, relating the chemical structure of each to its mode of action and side effects. (see "Chemical Structures of Pain Relievers" in the Supplemental Materials of the lesson How Aspirin Works.)

In addition to the GI distress caused by the acidic nature of the acetylsalicylic molecule, aspirin also causes stomach irritation due to the inhibition of the production of prostaglandins, a hormone responsible for slowing gastric acid production.

To follow up this activity with a demonstration of how aspirin affects an indicator organism, see the lesson How Aspirin Works.

Answers to Student Questions:

1. Describe the aspirin crystals. Sketch them below. Individual answers will vary, but include white small grained crystals with repeating units.

2. What are the functional groups found in salicylic acid? What do these groups tell you about the substance and how it might react in the body? Salicylic acid has a -OH group that indicates it is an alcohol and a carboxyl group (-COOH), indicating it is an organic acid. The acid in the molecule is one of the factors that causes irritation in the stomach.

3. What happened to the -OH group in the salicylic acid when acetic acid was introduced to the experiment? How does this affect the end product? The -OH group from the salicylic acid combined with the acetic acid, producing water and an ester group. This reduced the strength of the acid and made the aspirin easier to ingest.

4. Why did the aspirin need to be washed with the distilled water? How does this affect the end product? Washing the aspirin removes unreacted salicylic acid or acetic anhydride to yield a purer product.

5. How do different temperatures affect the solubility of the aspirin? Explain why the procedure called for placing the aspirin solution in a hot water bath and then an ice slurry. At higher temperatures, there is more kinetic energy, so molecules move faster and collide more frequently to interact with the water molecules. The hot water bath provided energy that increased the solubility of aspirin. The ice water cooled the solution, allowing the aspirin to "fall out" of solution and speed up the crystallization process.

6. What was the purpose of the fume hood? Fume hoods prevent gaseous substances from escaping into the entire lab and entering the nasal passages and lungs of people and possibly harming their tissues.

• Extract salicin from willow bark, willow leaves, or spiraea.

• Research botanical sources of some modern medicines, such as Taxol.

• Research homeopathic medicine, as well as the claims of some herbal treatments. Compare and contrast the claims and proven medicinal value.

• Compare the melting points of commercial aspirin, salicylic acid, and the synthesized aspirin.

• Use a spectrophotometer and determine the appropriate wavelength. Create a standard curve and test the students' product to the standard curve.

CHEMISTRY

Chemical properties: Use this activity to show the effect of temperature on the solubility of a substance.

Chemical structure: Use this activity to show orderly arrangement of atoms in crystalline structure of aspirin.

Chemical equations: Use this activity to practice writing and balancing equations.

Catalysts: Use this activity to show the effect of sulfuric acid, a catalyst, on the rate of reaction.

Organic chemistry: Use this activity to show the position of functional groups such as carboxyl, ester, and alcohol groups on participating molecules of reactants and products in reaction.

Organic chemistry: Use this activity to demonstrate dehydration synthesis.

Synthesis reaction: Use this activity to show a synthesis reaction and to determine percent yield.

Botany: Use this activity to demonstrate medicinal value of plants.

Ancient History: Use this activity to demonstrate the impact of Ancient Greek medicine on modern medicine.