Preparation of aspirin and oil of wintergreen

Topics: Carboxylic acid, Acetic acid, Ester Pages: 8 (1900 words) Published: October 22, 2013
 preparation of aspirin and oil of wintergreen

Organic compounds are those which contain carbon as well as a select other elements. An organic acid however, is an organic compound which contains acidic properties. An ester is an example of being a derivative of these organic acids. Esters can be prepared by the reaction of carboxylic acids and alcohols, with an inorganic acid used as a catalyst which is dubbed esterification. With o-hydrobenzoic acid, or salicylic acid, we are able to create acetylsalicylic acid otherwise known as aspirin as well as methyl salicylate, which is a component of oil of wintergreen. Both of which are used for pain relief/soreness. Salicylic acid is a member of the phenol class as their hydroxyl group (OH) is attached to a phenyl ring (benzene) and many phenols react with ferric chloride to cause a colour change. And so, in this investigation we are to prepare the two esters and compare their reactions with ferric chloride compared to the reaction between salicylic acid and the ferric chloride in order to identify phenolic properties.

Lab Equipment

125 ml Erlenmeyer flask
10 ml Graduated cylinder
Small watch glass
Filter paper
600 ml Beaker
Large test tubes
Hot plate


Acetic anhydride
1% Ferric Chloride Solution
Salicylic Acid
Methyl Alcohol
Concentrated Sulfuric Acid
Distilled Water

Synthesis of Aspirin

1. Place 3 grams of Salicylic acid in a Erlenmeyer flask and record the mass 2. Add 6 ml of Acetic anhydride to the flask of salicylic acid 3. Add 5 drops of concentrated sulfuric acid to the flask of salicylic acid 4. Swirl the flask in order to mix the reagents

5. Heat a beaker of water on the hot plate to 80-90 degrees Celsius, use the thermometer to check temperature 6. Place the flask of reagents into the beaker of heated water for 20 minutes 7. Remove the flask after 20 minutes and allow flask to cool to room temperature 8. Measure and add 40 ml of distilled water to the mixture in the Erlenmeyer flask and mix the contents 9. Place flask in an ice bath in order to complete crystallization 10. Prepare filtration process by placing filter paper in funnel 11. Filter crystals in funnel and wash slight by using ice cold water 12. Press crystals between paper towels and allow crystals to air dry Testing Crystals for Purity

13. Dissolve a few crystals of aspirin into 5 ml of water inside a test tube 14. Dissolve a few crystals of salicylic acid into 5 ml of water inside of a separate test tube 15. Add a drop of 1% ferric chloride and note the reaction

Purification by Recrystallization
16. Measure mass of aspirin
17. Calculate volume of ethanol needed provided 6g of aspirin dissolves in 20 ml of absolute ethanol 18. Prepare water bath in a beaker on top of a hot plate
19. Place Erlenmeyer flask containing aspirin and appropriate ethanol in the water bath 20. Add 50 ml of 50° C distilled water in the flask once aspirin has been dissolved 21. Place watch glass at mouth of flask and allow to slowly cool 22. Repeat filtration process in steps 10-12

23. Record mass of aspirin after it has completely dried

Synthesis of Methyl Salicylate

1. Place 1 g of salicylic acid and 5 ml of methyl alcohol in a test tube 2. Add 3 drops of sulfuric acid in the test tube
3. Prepare beaker of water to 70°c and then place test tube in beaker for 15 minutes 4. Waft the odour of the methyl salicylate
5. Add a drop of 1% ferric chloride solution into the test tube and note any change Results
Synthesis of Aspirin

Mass (g)
Molar weight
Moles used
Theoretical mass
Percent yield
Salicylic Acid
138 amu
1/46 mol (mass/molar weight)

=22.25% yield
Dry recrystallized aspirin
180 amu
1/46 mol
moles salicylic acid
X [Theoretical]
3.91 g (1/46 moles x 180amu/mole)

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