Experiment 2: Synthesis Of Acetaminophen Flashcards
Procedure to synthesize acetaminophen (part 1)
- heat p-aminophenol and DI water in a hot water bath to help dissolve p-aminophenol
- some of the p-aminophenol will dissolve but to help, add acetic anhydride
- once solid forms, place flask in ice water bath (DO NOT STIR) because the solid product should precipitate from solution
Procedure to synthesize acetaminophen (part 2)
- if no precipitation forms, scratch the bottom of flask to induce precipitation
- collect crude product through vacuum filtration and purify using recrystallization
- recover pure product and obtain a sample of purified product for melting point determination
Crude solid meaning
Not pure solid, this crude solid is purified using recrystallization
How is melting point determined
- Insert crude and purified products into their own melting point tubes
- insert the tubes and thermometer into the MelTemp and note the temperature at the first sign of liquid and when the solid completely melts
What is indicated by a melting point value with a very small temperature range?
When a melting point value has a very small temperature range, it is indicated that the substance is purified because the purification of substances removes the impurities of the crude product.
What does a lower than theoretical melting point indicate about the recovered product?
A lower than theoretical melting point indicated that there may be impurities because the recovered purified product should be exact/close to the theoretical melting point
What is the melting point of acetaminophen?
169-172.2 degrees Celsius
Synthesis meaning
When two or more reactants combine to form a single product
Balanced reaction equation for this synthesis
C6H7NO (s) + C4H6O3 (l) -> C8H9NO2 (s) + CH3COOH (aq)
P-aminophenol + acetic anhydride -> acetaminophen + acetic acid
Isolation meaning
Isolation simply means to remove or separate the desired product from whatever mixture or solvent it may be in
- vacuum filtration is used in this experiment
Purification meaning
The removal of any impurities from the desired product
- the purification of this experiment involves recrystallization
What is the most important factor to crystallization?
Saturation
What part of the structure in the p-aminophenol molecule contributes to its low solubility in water?
The non-polar ring structure
What are the guidelines for choosing a solvent volume for performing a reaction?
Use just enough solvent to fully dissolve the solid and produce a saturated solution
Why isn’t the solution stirred as it cools in the ice bath?
Stirring will speed up the rate of crystallization, trapping impurities in the crystal lattice
What two values are used to determine the mass of crude acetaminophen recovered
Mass of empty Erlenmeyer flask, mass of Erlenmeyer flask containing crude product
What mistake can be made during the recrystallization step?
If an extra 5 mL of solvent was added, the yield of acetaminophen product will be lower as the solution is not saturated and fewer crystals will precipitate
What may happen to the solid acetaminophen if the mixture of solvent and crude acetaminophen is heated too strongly?
The acetaminophen may undergo thermal degradation or decomposition into various phenol compounds
