Lab #9: Synthesis and Analysis of Aspirin

Lab #9: Synthesis and Analysis of Aspirin Important Dates Lab Notebook Setup and Pre-Lab Assignment Due Dates for Lab Work

Post-Lab Quiz Lab Report and Notebook Pages Due

Daily Outline* 1

Synthesis of crude product

2

Vacuum filter crude product and prepare NaOH solution

3

Recrystallize crude product and vacuum filter purified product

4

Melting point tests on all aspirin products

5

Standardize NaOH solution and perform Fe3+ test

6

Titrate crude product

7

Titrate purified product

8

Wrap up any unfinished tests

*If you start falling behind, you need to come to lab during another period and get caught up!

Lab #9: Synthesis and Analysis of Aspirin Pre-Lab Discussion 1. In this lab, aspirin (acetylsalicylic acid) will be synthesized, crystallized, and recrystallized.

a. This reaction is classified as __________________________________. b. If 2.03 g of salicylic acid and 5.12 mL of acetic anhydride (density = 1.08 g/mL) are used, how many grams of acetylsalicylic acid could be produced? (i.e. What is the theoretical yield?)

The triangles represent impurities; the hexagons represent the desired product. A thermometer is to the right of each beaker. c. As crystallization occurs, the temperature of the sample _________________________. d. What is the purpose of crystallization?

e. Recrystallization is simply _____________________________________________________. f.

What effect should this have on the product?

Lab #9: Synthesis and Analysis of Aspirin 2. The purity of your aspirin will be assessed using three different techniques... a. What substances will be analyzed in each test tube? b. Qualitative or quantitative technique? Explain. c. What reagent will be used to react with the samples? d. What will you observe during this test? e. How will this be used to assess purity? f.

What is this set up used to test?

g. Qualitative or quantitative technique? Explain. h. How many samples will be tested? i.

How will this be used to assess purity?

j.

What is this set up used to test?

k. Qualitative or quantitative technique? Explain. l.

What substance and molarity is the titrant?

m. What substance is used to standardize the titrant? n. Why is the titrant standardized? o. What substances will be the analytes? p. How will this be used to assess purity?

Lab #9: Synthesis and Analysis of Aspirin 3. Melting point is used to assess purity… a. What is the literature value of the melting point of acetylsalicylic acid?

___________________

b. The following data is obtained from melting point analysis. Find the % difference for both samples. Sample Starting MP Ending MP Reagent 135.3 oC 136.7 oC o Crude 128.2 C 131.9 oC Pure 133.6 oC 135.2 oC

4. Acid-base titration is used to assess purity… a. What is the mole-to-mole ratio of sodium hydroxide to aspirin?

___________________

b. What indicator should be used for this titration?

___________________

c. How many grams of sodium hydroxide are needed to make 300.00 mL of a 0.150 M solution?

d. It requires 17.71 mL of NaOH from the question above to standardize 0.521 g of KHP. What is the molarity of the NaOH solution?

e. If 0.190 g of purified product is used for a titration, how many moles of acetylsalicylic acid are present, assuming the purified product is only acetylsalicylic acid?

f.

Only 6.78 mL of the sodium hydroxide solution (concentration calculated in question 4d) was required for neutralization. How many moles of acetylsalicylic acid are present according to the titration data?

g. What is the percent purity for the purified product based on this data? Show your work.

Lab #9: Synthesis and Analysis of Aspirin Introduction: In this experiment, aspirin will be synthesized using a reaction very similar to the way it is manufactured industrially. Salicylic acid is treated with acetic anhydride in an esterification reaction to produce an ester, acetylsalicylic acid (aspirin). The reaction is shown below. Your goal is to synthesize aspirin and compare the purity of the crude product to the purified product using three different techniques.

Materials: Salicylic acid (s) Acetic anhydride (l) Con. sulfuric acid, H2SO4 Iron(III) chloride, FeCl3, 0.02 M Ethanol/water solution, 50:50 KHP (s) NaOH (s) Phenolphthalein Erlenmeyer flask (125 mL)

Side arm flask with tubing Buchner funnel Filter paper Ring stand Utility clamp 3-prong clamp Hot plate (large) Assorted beakers Stirring rod & rubber policeman

Large test tubes (3) Sample jar (2) Graduated cylinder (50 mL) Watch glass Plastic pipet Melting point apparatus Clay triangle Buret Stir plate & stir bar

Procedure: 1. Synthesis of Aspirin – record observations a. Fill up a 400 mL beaker half-way with water. Place the beaker on a hot plate. Set the heat to 4 or 5. b. Measure ~4 g of salicylic acid into a clean, dry 125-mL Erlenmeyer flask. Record the actual mass. c. In the fume hood, add ~8 mL of acetic anhydride from the buret (found in the hood) to the flask. Record the actual volume. d. In the fume hood, add ~5 drops of concentrated sulfuric acid (catalyst) to the flask. e. Heat reaction mixture ~10 minutes. Stir occasionally, eventually the mixture should become clear. Do not allow the hot water bath to boil. If after 10 minutes there is still solid remaining or an oily liquid has formed, ~4 g salicylic acid tell Ms. Pluchino. f. Add ~50 mL of tap water to the reaction. Heat and stir the mixture until ~8 mL acetic anhydride it becomes clear. ~5 drops g. Label the Erlenmeyer flask with your name and store in the back of the sulfuric acid lab room. Crystallization will occur overnight as the solution slowly cools. 2. Vacuum Filtration of Crude Product a. Set up a Buchner funnel filtration and secure it to a ring stand. b. Chill a large test tube ½ filled with tap water in a small cold bath (150 mL beaker). c. Filter the solid aspirin product through a piece of moistened filter paper.

Lab #9: Synthesis and Analysis of Aspirin d. Rinse the crude aspirin product with small increments of the cold tap water. Do not rinse excessively as it may dissolve some of your product. e. Record the mass of a clean, dry sample jar. f. Transfer the crystals to the sample jar, label, and allow them to dry uncovered overnight. g. Record the mass of the crystals and the sample jar. This is the crude product.

3. Recrystallization a. Transfer about half of the crude product to a clean 125-mL Erlenmeyer flask. Record the exact mass. b. Add ~50 mL of tap water and reheat the flask directly on a hot plate set at 4 or 5. c. Once dissolved, remove the flask from heat and allow it to cool on the lab bench for 2-3 minutes. d. Set up a cold water bath (no ice cubes yet). e. Crystals should appear upon cooling. If not, add ice and scratch the inside of the flask as before. 4. Vacuum Filtration of Purified Product a. Set up the filtration apparatus, secured to a ring stand, with a new piece of moistened filter paper. b. Transfer the recrystallized product to the funnel and filter. c. Use a rubber policeman to transfer as much of the product as possible. d. Rinse the purified aspirin in the funnel with small increments of cold tap water. e. Record the mass of a clean, dry sample jar. f. Transfer the crystals to the sample jar, label, and allow them to dry uncovered overnight. g. Record the mass of the crystals and the sample jar. This is the purified product. 5. Quantitative Analysis: Melting Point a. Set up a melting point apparatus using a burner, ring stand, large ring clamp, and a clay triangle. Place the aluminum cylinder on top of the clay triangle, and place the digital thermometer into the cylinder. Must show data table in order to receive the digital thermometer! b. Using the tip of a scoopula, place a small amount of the crude product, the purified product, and the reagent grade acetylsalicylic acid on the cylinder. Draw a diagram in your notes and labeled each of the samples. c. Light the burner under the cylinder and heat the samples. When the temperature is close to the literature melting point of acetylsalicylic acid, heat gently. d. Record the temperatures when each sample begins (and ends) melting.

Lab #9: Synthesis and Analysis of Aspirin 6. Qualitative Analysis: Fe3+ Complex Formation a. Obtain 3 large test tubes. Must show data table in order to receive the test tubes! b. Crush a commercial aspirin tablet using a mortar and pestle. c. Use a microspatula to transfer a small amount of the aspirin to a large test tube. d. Add ~5 mL of 50:50 ethanol/water solution, stopper, and shake to dissolve the aspirin completely. e. Add 5-6 drops of 0.02 M FeCl3 solution to the test tube. f. Record your observations. g. Repeat steps c-f with the crude and purified products. 7. Quantitative Analysis: Titration a. Make 250 mL of ~0.1 M NaOH solution. Must show a reasonable data table for each set of titrations in order to receive the NaOH! b. Standardize your NaOH solution with KHP in triplicate. Remember, you want to use at least 15.00 mL of the NaOH solution during the titration. Calculate the mass of KHP required. c. Use this standardized NaOH solution to titrate your purified aspirin product in triplicate using ~0.4 g of the purified product dissolved in ~40 mL of 50:50 ethanol/water for each trial. Record the exact mass of the purified aspirin used for each titration. If you do not have enough purified product, divide your sample evenly for testing. d. Determine the actual number of moles of aspirin present based on the titration data. e. Determine the theoretical moles of aspirin present based on the mass of purified product used. f.

Determine the percent purity =

actual moles of aspirin × theoretircal moles of apsirin

sample. g. Repeat this titration with the crude product.

100 of the

Lab #9: Synthesis and Analysis of Aspirin

Notebook Pages – HANDWRITTEN

Lab #9 Rubric – 70 points Section

Description

Heading

Fill out heading completely on first notebook page of the lab. Name is filled out on subsequent pages.

1

0

The goal of the lab is clearly and accurately stated.

1

0

Goal

Points Earned

Data is recorded to the correct number of significant figures and includes appropriate units. Data for calculation of % yield of crude and % recovery of purified. 4 2 0

Data & Theoretical Calculations

Neatness Heading

Lab Report – TYPED

Calculations Table

Conclusion

Format

Data for melting point of crude, purified and reagent grade aspirin.

4

2

0

Observations for qualitative analysis of all three aspirin products.

2

1

0

Theoretical calculation for preparation of NaOH solution.

2

1

0

Theoretical calculation for mass of KHP needed for standardization.

2

1

0

Standardization of NaOH – includes at least 3 trials.

4

2

0

Neutralization of crude – includes at least 3 trials.

4

2

0

Neutralization of purified – includes at least 3 trials.

4

2

0

Legible, nearly laid out, dark enough to read, etc.

2

1

0

Include your name, lab partner’s name, title of lab, and due date of 1 0 lab report. Show formula (where applicable), substitute with units, answer with correct sig figs and units. Theoretical yield of crude aspirin synthesis.

4

2

0

Percent yield of crude aspirin synthesis.

2

1

0

Percent recovery of purified aspirin synthesis.

2

1

0

Percent difference of melting point – both crude and purified.

4

2

0

Molarity of NaOH based on standardization titrations.

4

2

0

Percent purity of crude aspirin based on titration data.

4

2

0

Percent purity of purified aspirin based on titration data.

4

2

0

State the percent yield of the crude product.

3

2

1

0

State the percent recovery of the purified product.

3

2

1

0

Assessment of the purity of your products based on the Fe3+ test.

2

1

0

Assessment of the purity of your products based on melting point.

2

1

0

Assessment of the purity of your products based on titration data.

2

1

0

Statement regarding the overall successfulness of the recrystallization based on the results of the purity tests.

2

1

0

Consistent font, neat layout, only one piece of paper, 0.75” margins, 1.5x spaced, use section headings, etc.

1

Total Score

0

/70