Acetylsalicylic Acid
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Acetylsalicylic Acid
Experiment #8
Pg: 9-12
PURPOSE
The purpose of this experiment was to show that aspirin, otherwise known as acetylsalicylic acid, can be prepared by the reaction between salicylic acid and acetic anhydride. Through the process of crystallization, we should be able to extract acetylsalicylic acid.
REACTION EQUATION
C7H6O3 + C4H6O3 C9H8O4 + C2H4O2
Salicylic Acid + Acetic Anhydride Acetylsalicylic Acid (Aspirin) + Acetic Acid
TABLE OF PHYSICAL CONSTANTS
Physical
Constant
Molecular Weight
Melting Point/ Boiling Point
Density
Hazards
Acetylsalicylic Acid
180.2 g/mol
135˚C / 140˚C
1.40 g/cm³
Acetic Anhydride
102.9 g/mol
-73.1˚C / 140˚C
1.08 g/cm³
Salicylic Acid
138.1 g/mol
159˚C / 211˚C
1.44 g/cm³
Phosphoric Acid
98.00 g/mol
42.4˚C / 158˚C
1.88 g/cm³
Highly Corrosive
Water
18.01 g/mol
0.00˚C / 100˚C
1000 kg/m³
THEORETICAL YIELD
Acetic Anhydride (102.9 g/mol)
0.480 mL = .000480 L
.00480 L * 1.08 g/cm³ = .00518 mol
Salicylic Acid (138.1 g/mol)
0.210 g / 138.1 g/mol = .00152 mol
(Limiting Reagent)
.00152 mol * 1000 = 1.52 mmol
.210 g * 1000 = 210 mg
PROCEDURE
Set up 100 mL of water in a hot bath and set to 50˚C.
Weigh 0.210 g of salicylic acid and place in dry 5-mL conical vial.
Add 0.480 mL acetic anhydride followed by one drop of concentrated phosphoric acid.
Thoroughly mix solution using spin vane until salicylic acid dissolves.
Continue heating for 8-10 minutes after the solid completely dissolves.
Allow vial to cool to room temperate, during which the acetic acid begins crystallization.
After crystallization completes, add 3.0 mL water and stir thoroughly.
Vacuum filtrate using Hirsch funnel and 1 mL cold water to rinse product.
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