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Oxidation of Borneol to Camphor Lab Report, Lab Reports of Chemistry

Borneol is converted into camphor by oxidation process in the presence of NaOCl bleach and acetic acid, acetone which work as a catalyst

Typology: Lab Reports

2020/2021

Uploaded on 05/11/2021

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OXIDATION OF BORNEOL
INTRODUCTION
Borneol and camphor are both natural products found in many plants. Camphor can be isolated from the
wood of the camphor laurel tree. It has a distinct odor, and is used in Vicks Vaporub.
Borneol can be oxidized to camphor using many oxidizers. Historically, oxidations have often been done
by using toxic metal reagents like chromium(VI). Modern methods often aim to use more
environmentally friendly reagents, and in that same strain, the oxidant in our experiment will be
commercial bleach.
RELEVANT READING
Experimental Techniques:
1.3.K (pp. 58-62) Reflux Overview + Procedures
1.3.H (pp. 54) Sand Baths
1.2.B.5. (pp. 35) Volatile Liquids
4.5.E (pp. 228-229) Microscale Extraction
5.6 (pp. 300-305): Rotary Evaporator Overview + Procedures
Review Techniques:
1.3.B.3 (pp. 47) Stir-bar retriever
4.6.B.2 (pp. 233) Testing pH after sodium bicarbonate wash
4.6.C.2-3 (pp. 238-241) Drying agents
EXPERIMENT OVERVIEW
In the first lab session of this experiment, you will reflux the reagents for 30 minutes, then work up the
reaction with pipette extractions. Time permitted, you’ll also run a GC and IR of the product mixture.
The second lab session will be used for any unfinished parts of the lab.
OH
H
Borneol
NaOCl (bleach)
acetic acid, acetone
Camphor
O
pf3
pf4
pf5

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OXIDATION OF BORNEOL

INTRODUCTION

Borneol and camphor are both natural products found in many plants. Camphor can be isolated from the wood of the camphor laurel tree. It has a distinct odor, and is used in Vicks Vaporub. Borneol can be oxidized to camphor using many oxidizers. Historically, oxidations have often been done by using toxic metal reagents like chromium(VI). Modern methods often aim to use more environmentally friendly reagents, and in that same strain, the oxidant in our experiment will be commercial bleach. RELEVANT READING Experimental Techniques:

  • 1.3.K (pp. 58-62) Reflux Overview + Procedures
  • 1.3.H (pp. 54) Sand Baths
  • 1.2.B.5. (pp. 35) Volatile Liquids
  • 4.5.E (pp. 228-229) Microscale Extraction
  • 5.6 (pp. 300-305): Rotary Evaporator Overview + Procedures Review Techniques:
  • 1.3.B.3 (pp. 47) Stir-bar retriever
  • 4.6.B.2 (pp. 233) Testing pH after sodium bicarbonate wash
  • 4.6.C.2-3 (pp. 238-241) Drying agents EXPERIMENT OVERVIEW In the first lab session of this experiment, you will reflux the reagents for 30 minutes, then work up the reaction with pipette extractions. Time permitted, you’ll also run a GC and IR of the product mixture. The second lab session will be used for any unfinished parts of the lab. OH H Borneol NaOCl (bleach) acetic acid, acetone Camphor O

PROCEDURE

OXIDATION REACTION

  1. Pre-heat a sand bath to on a hotplate set to medium-high.
  2. Pre-weigh a 25 mL round-bottomed flask on the analytical balance, then add 0.40 g borneol (dispensed on the pan balance) and again obtain the mass on the analytical balance.
  3. Dissolve the borneol in 1.0 mL acetone (added via calibrated plastic pipette).
  4. In the fume hood, add 1.0 mL glacial acetic acid (via calibrated plastic pipette) a stir-bar, and 6.0 mL of household bleach ( 8 .25% NaOCl). A mild odor of chlorine gas might be apparent. While still in the fume hood, swirl the flask for ~ 2 minutes until the yellow color lessens- the flask can then be removed from the hood (it won’t smell so bad anymore).
  5. Place the round-bottomed flask into the sand bath and immediately attach a microscale reflux condenser, with water running through it.
  6. Heat the apparatus with stirring to reflux for 30 minutes, beginning the count when condensation (the “reflux ring”) is seen in the bottom of the condenser (ideally it would be a third of the way up the condenser). If condensation gets higher than halfway up the condenser, lower the heat somewhat.
  7. When the reflux period has finished, lift the flask out of the sand bath. The sand bath can be cooled atop a tile, or simply set aside.
  8. *Important : While still connected to the condenser, immerse the round-bottomed flask in a large beaker of tap water to cool the solution to near room temperature. Then remove the condenser. REACTION WORK-UP
  9. Use a “stir-bar retriever” to remove the stir bar. Pour the contents of the flask into a plastic 15 mL centrifuge tube, and rest it inside a beaker for stability.
  10. Into a second 15-mL centrifuge tube, add 3 mL water and 3 mL diethyl ether. Pour this liquid into the empty reaction flask (to rinse it), swirl the contents, and pour the mixture into the first centrifuge tube with the reaction mixture (this tube should contain ~ 14 mL liquid now).
  11. Cap and gently shake the tube to mix the layers. Set the tube aside and allow the layers to fully form.
  12. Transfer the bottom aqueous layer using a pipette into the other centrifuge tube. Label this tube as “aqueous.” Label the top layer remaining in the centrifuge tube as “organic.” Metal clamp to ring stand (no clip) sand bath on hotplate condenser Water in Water out Metal clamp
  1. Obtain the mass of the round-bottomed flask with solid. Before leaving for the day, place a stopper in the flask as the solid will sublime and smell up the lab. CLEAN-UP (DAY 1)
  • The aqueous layer from the extractions should be collected in a waste container.
  • The majority of the solid Na 2 SO 4 residue can be disposed of in the same waste container as the liquids, rinsing with water (it is not soluble in acetone). Small amounts of Na 2 SO 4 residue can be disposed of down the drain.
  • Throw away the plastic centrifuge tubes- they will not be reused.
  • Wipe down your lab bench with your sponge before leaving. GC ANALYSIS
  1. In the first or second lab session (depending on time): prepare a sample for GC by adding 2 “specks” of solid (each speck ~ 2 - 3 mm in diameter) to a GC vial, and dissolving the solid in 1.5 mL diethyl ether (note: different solvent than usual).
  2. Run the GC using the method “BORNEOL” (parameters: 45 ˚C hold for 2 min, 25 ˚C/min ramp to 175 ˚C, solvent delay 2.00 min).
  3. Print your GC spectrum and percent report. Attach these to your notebook.
  4. Summarize your GC data in your notebook using a table (retention time, percentage, compound). IR ANALYSIS
  5. An IR of the starting material borneol will be provided for you (obtained by either the instructor or one classmate). Attach this in your notebook.
  6. In the first or second lab session (depending on time), take an IR of your product (camphor).
    • Dissolve ~ 5 “specks” (each ~2-3 mm in diameter) into a GC or dram vial in about 1 mL dichloromethane (CH 2 Cl 2 ).
    • Use a pipette to deliver ~ 5 drops of this solution onto one IR salt plate. To prevent the pipette from dripping uncontrollably, withdraw and expunge the liquid several times before transferring.
    • Allow the solvent to evaporate on the plate (in the fume hood) to leave a thin film or residue. While evaporating, move the plate around to have it evaporate mostly in the middle of the plate.
    • Rest the salt plate in the black plastic holder in the IR instrument and take the IR spectrum. Clean the plate as usual.

BORNEOL OXIDATION (PRE-LAB)

Name: Lab: T/Th or W/F

  1. Complete the data table below. Show your calculations below the table, using dimensional analysis and significant figures. Copy the completed data table into your notebook along with the reaction scheme. FW mass volume mmol Other (d, M, mp) Borneol Glacial acetic acid 17.4 M NaOCl in bleach (8.25%) d = 1.09 g/mL Camphor Note: for a reminder of how to use mass %, see the General Chemistry Calculations exercise from week 1.
  2. Calculate the theoretical yield of camphor, using the quantities in the experiment. The reagents borneol, NaOCl, and acetic acid react in a 1:1:1 mole ratio.
  3. Give two differences between reflux and distillation. OH H Borneol NaOCl (bleach) acetic acid, acetone Camphor O
  1. Assign the peaks >1500 cm-^1 in the IR spectrum of your product to specific bonds and vibrations. One wavenumber per unique grouping is adequate. If your product is a mixture, specify which structure the signals come from. Wavenumber (cm-^1 ) Intensity (s, m, w) Assignment (ex. O-H stretch) Wavenumber (cm-^1 ) Intensity (s, m, w) Assignment (ex. O-H stretch)
  2. The active oxidizing agent in bleach, sodium hypochlorite (NaOCl), was present in this reaction in significant excess of the limiting reactant (consult the pre-lab table). Why would it be unwise to use exactly the same moles of bleach as moles of limiting reactant?
  3. Make an argument for what was probably the temperature inside the reaction flask during active reflux. There is more than one acceptable answer or approach to this question.
  4. Explain how a rotary evaporator allows for compounds to boil at lower temperatures than their normal boiling point.
  5. While designing this lab, Mrs. Nichols took TLC’s of the product mixture periodically to monitor the reaction. One TLC midway looked like the one below, with two spots for starting material and product. Identify which spot was borneol and which was camphor, and explain your logic. 1:1 hex:ethyl acetate Borneol or camphor? Borneol or camphor?