Panacetin Lab

Topics: Chemistry, Paracetamol, Experiment Pages: 8 (1862 words) Published: October 25, 2013

Separating the Components of “Panacetin”
Extraction and Evaporation
&

Identifying a Constituent
of “Panacetin”
Recrystallization& Melting-Point Measurement

Organic Chemistry Lab

Introduction:

Panacetin purportedly includes sucrose, aspirin, and acetaminophen. However, the accuracy of Panacetin’s contents has been called into question by the Association for Safe Pharmaceuticals. Therefore, the lab must discover the accuracy of the ingredients listed on Panacetin’s label.

The unknown in this experiment is presumed to be something similar to acetaminophen, such as acetanilide or phenacetin. Recrystallization and melting point temperature were used to help identify the unknown in Panacetin. Recrystallization removes impurities as a substance goes through physical transformations from a solid to a liquid and back to a solid. As the solid reforms as a crystalline structure, it does so without incorporate any impurities that may have been present in the initial substance. Pure substances have specific melting points that can assist in identification. However, if the substance is not pure, the melting point will be lower than expected. The substance will also have a wider melting point range.

To separate the sucrose the lab needed to use ~2.95 grams of Panacetin and 50 mL of dichloromethane. This mixture was then used extract the sucrose via gravity filtration. To separate the aspirin, the lab used two separate portions of sodium bicarbonate. Two different liquid layers formed, one with an aqueous solution and the other with the organic dichloromethane. The aqueous solution was then separated into one container and the dichloromethane solution into another. The lab then added HCl to the aqueous solution until it was acidic, reaching a pH ≤ 2. The aqueous solution was then cooled and the aspirin precipitate was separated. To isolate the unknown, the lab heated the dichloromethane solution to evaporate the solvent until only the unknown remained. It was then heated to remove moisture and weighed.

Chemical Reactions

Procedure:

The procedure in the lab text 1was followed. However, beakers were used instead of flasks in separating the dichloromethane mixture. Furthermore, the separation of aspirin needed to be done twice due to miscommunication in regard to the isolation process for separating the aqueous and organic layers.

Diagram 1: Overview of Procedures

Data:

Table 1: Masses & Percentages of Samples / Solubility Volume of H2O

Description / Label
Mass
Percentages
(of 2.95g initial sample)
Mass of Initial Mixture:
2.95g
100%
Mass of Sucrose:
0.39g
13.2%
Mass of Aspirin:
0.85g
28.8%
Mass of Unknown:
(Crude Experiment #2)
1.30g
44.1%
Mass of Unknown:
(Purified Experiment #3)
0.99g
33.6%
Volume of H2O
(Used to dissolve experimental unknown Experiment 3)
≈ 26.5mL

Table 2: Melting Point Ranges of Unknown and Mixtures

Description / Label
Temperature Ranges (Celsius)
Melting Point Range
(Purified Unknown)
≈ 107.5° – ≈ 115.5°
(Average of 2 trials)
Melting Point Range
(1:1 Mixture: Unknown / Acetanilide)
≈ 107.5° – ≈ 117.0°
(Average of 2 trials)
Melting Point Range
(1:1 Mixture: Unknown / Phenacetin)
≈ 95.5°C – ≈ 113.0°
(Average of 2 trials)

Calculations:
Note, see Table 3.1: Physical Properties in the lab text 1 for reference data.

1a) Volume of boiling H2O needed to dissolve unknown (if unknown is acetanilide):

1b) Volume of boiling H2O needed to dissolve unknown (if unknown is phenacetin):

2) Percentage of unknown recovered after crystallization procedure and drying:

4) Percent composition of sucrose in the mixture based on the mass recovered:

5) Percent composition of aspirin in the mixture based on the mass recovered:

6) Percent composition of crude unknown in the...
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