Experiment 2: Synthesis Of Acetaminophen

Question 1

Procedure to synthesize acetaminophen (part 1)

Answer 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

Question 2

Procedure to synthesize acetaminophen (part 2)

Answer 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

Question 3

Crude solid meaning

Answer 3

Not pure solid, this crude solid is purified using recrystallization

Question 4

How is melting point determined

Answer 4

• 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

Question 5

What is indicated by a melting point value with a very small temperature range?

Answer 5

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.

Question 6

What does a lower than theoretical melting point indicate about the recovered product?

Answer 6

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

Question 7

What is the melting point of acetaminophen?

Answer 7

169-172.2 degrees Celsius

Question 8

Synthesis meaning

Answer 8

When two or more reactants combine to form a single product

Question 9

Balanced reaction equation for this synthesis

Answer 9

C6H7NO (s) + C4H6O3 (l) -> C8H9NO2 (s) + CH3COOH (aq)
P-aminophenol + acetic anhydride -> acetaminophen + acetic acid

Question 10

Isolation meaning

Answer 10

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

Question 11

Purification meaning

Answer 11

The removal of any impurities from the desired product
- the purification of this experiment involves recrystallization

Question 12

What is the most important factor to crystallization?

Answer 12

Saturation

Question 13

What part of the structure in the p-aminophenol molecule contributes to its low solubility in water?

Answer 13

The non-polar ring structure

Question 14

What are the guidelines for choosing a solvent volume for performing a reaction?

Answer 14

Use just enough solvent to fully dissolve the solid and produce a saturated solution

Question 15

Why isn’t the solution stirred as it cools in the ice bath?

Answer 15

Stirring will speed up the rate of crystallization, trapping impurities in the crystal lattice

Question 16

What two values are used to determine the mass of crude acetaminophen recovered

Answer 16

Mass of empty Erlenmeyer flask, mass of Erlenmeyer flask containing crude product

Question 17

What mistake can be made during the recrystallization step?

Answer 17

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

Question 18

What may happen to the solid acetaminophen if the mixture of solvent and crude acetaminophen is heated too strongly?

Answer 18

The acetaminophen may undergo thermal degradation or decomposition into various phenol compounds