Experiment 1 Synthesis of Acetaminophens

Topics: Aspirin, Carboxylic acid, Acetic acid Pages: 8 (1445 words) Published: March 5, 2015

Introduction:
Acetaminophen is a commonly used analgesic, which is essentially just a medicine that relieves pain (Prescott, 2000). Acetaminophen is created by synthesizing p-Aminophenol with Acetic anhydride. This reaction occurs when the amine group of the p-aminophenol is acetylated by the acetic anhydride. The resultant is an amide functional group (Ellis, 2002). However, the product that is obtained from this product is a crude solid which cannot be used as an analgesic and therefore the crude solid must be purified. This purified product is what is later put into the analgesic. In this experiment, the procedures that are important are vacuum filtration and recrystallization which are both used to obtain the Acetaminophen product. When collecting products, it is important to know how much product is left and what is lost through the experiment. To do this, the balanced equation will be looked at and then the theoretical yield will be calculated. In order to calculate the theoretical yield, two equations will be used:

Will be used for both reactants to determine which reactant is the limiting reagent. After the limiting reagent is used, then the theoretical yield will be calculated using:

This will give the mass of the Acetaminophen.
The actual yield will be available in the experimental data, and using this knowledge, this equation will be used to calculate the percentage yield:

Once the percentage yield is calculated then the quality of the apparatus and procedure can be determined to obtain better results and more product in the future. The purpose of this experiment, is essentially to determine the purity of the product that is collected and filtered and recrystallized. Experimental Procedure:

The experimental procedure used for this experiment was outlined in the CHEM 123L lab manual, Experiment #1. All steps were followed without deviation. Experimental Observations:
Table 1: Experimental Data Values obtained in the Experiment Observation
Value of Observation
Mass of P-Aminophenol
3.09g
Mass of Empty Erlenmeyer Flask
95.04g
Mass of Erlenmeyer Flask after collecting precipitate
98.62g
Mass of Crude Precipitate
3.58g
Volume of Water Used
35.80mL
Mass of empty Erlenmeyer flask after second filtration
72.96g
Mass of Erlenmeyer Flask after collecting second precipitate 75.44g
Mass of Purified Product
2.48g
Melting Point from Meltemp
161.5°C
Expected Acetominophen Melting Point (Aldrich Catalogue)
168°C-172°C

Table 2: Qualitative Observations obtained in the Experiment

First 5 Minutes
The liquid was a peach colour, the powder partially dissolved within it. After Adding Acetic Acid
The liquid was clear and was a greenish-yellow colour. The product dissolved almost immediately as the acetic acid was added. After Heating; room temperature
The precipitate started to form.
In the Ice Bath
The peach colour returned, a solid precipitate started to form. After 1st Vacuum Filtration
The powder was white and was clamped together in some places due to the slight dampness, but broke apart easily. Recrystallization
Whilst heating, crude product dissolved and there was a clear liquid. In the ice bath, crystal like structures started to form. As there was not enough precipitate, the bottom was scratched and precipitate started to settle at the bottom of the flask. After 2nd Vacuum Filtration

Crystal like powder was obtained. It was white and glitter like.

Results and Calculations:

Reaction Equation for the Synthesis of Acetaminophen
C6H7NO + C4H6O3  C8H9NO2 + C2H4O2
P-aminophenol + Acetic Anhydride  Acetaminophen + Acetic Acid

Determining the Theoretical Yield of Acetaminophen
1. Determine the Limiting Reagent

Daa = 1.082g/mL (Lide, 2000)
Therefore the limiting reagent is C6H7NO.
2. Determine the Theoretical Yield

Therefore the theoretical yield is 4.28g of C8H9NO2.
Determining the Percentage Yield

Therefore the percentage yield for this...
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