Experiment 7_ Dihydration Using Oxone (1)

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1 11/1/21 Experiment 7: Dehydration Using Oxone Using LLE to isolate the desired product and TLC to determine its purity. Reaction Scheme : Hypothesis : If oxone is added to cyclohexene, the product will be a mixture of cis and trans diols because the 1,2-cyclohexandiol has two similar stereocenters, meaning there are many possible orientations of the molecule.

2 Reagent Table : Compound Molecular Weight (g/mol) Density (g/mL) Used Safety Oxone/dimethyldioxirane (C H O ) (KHSO and C H O) ₃ ₆ ₂ ₅ ₃ ₆ 74.08 1.10 Dissolve 800 mg in 4 mL water Irritant Cyclohexene (C H ) ₆ ₁₀ 82.14 0.81 100 μL Flammable, acute toxic, irritant, health hazard, environmental hazard Acetone (C H O) ₃ ₆ 58.08 0.79 4 mL Flammable, irritant Hydrochloric Acid (HCl) 36.46 1.18 A few drops Corrosive, causes severe skin burns and eye damage, toxic if inhaled Hexane (C H ) ₆ ₁₄ 86.18 0.659 DS #1: 1mL DS #2: 1mL Irritant, flammable

3 Ethyl Acetate ( C 4 H 8 O 2 ) 88.11 0.902 DS #1: 3mL DS #2: 3mL Irritant, flammable Magnesium sulfate (MgSO ) ₄ 120.37 2.66 A few scoops Irritant Cis-cyclohexane-1,2-diol (C H O ) ₆ ₁₂ ₂ Trans- cyclohexane-1,2-diol 116.16 1.2 TLC spotting Irritant P-anisaldehyde (C H O ) ₈ ₈ ₂ 136.15 1.12 TLC stain Irritant Diethyl ether (C H O) ₄ ₁₀ 74.12 0.71 20 mL Flammable, irritant Procedure :

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4 Characterize the compounds in their pure state for comparison: 1. As a class, determine which groups should prepare standards of the cis and trans cyclohexanediol standards. Make sure you get the compounds dissolved so that you can spot the plates. 2. Different groups should test different developing solvents. Calculate the Rfs and compare them with the rest of the class. DS: 25% hexane, 75% ethyl acetate Rfs: Rf (Cyclohexene) = 5.0/5.2 = 0.96 Rf (Cis-cyclohexane-1,2-diol) = 2.2/ 5.2 = 0.42 Rf (Trans-cyclohexane-1,2-diol) = 2.0/5.2 = 0.39 Visualization: p-anisaldehyde Best DS: 25% hexane, 75% ethyl acetate ‘ Oxone Reaction (done individually) :

5 1. Dissolve 800 mg Oxone in 4 mL water by shaking vigorously in a capped 20 mL vial. Make sure that the vial is well sealed. 2. In another 20 mL capped reaction vial, add 100 μL of cyclohexene (approximately 5 drops using a polypipet) to 4 mL of acetone and add a stir bar. 3. Cool the cyclohexene solution in an ice-water bath, then add the Oxone solution dropwise over 5 min with stirring. 4. Remove the vial from the ice bath and stir at room temperature for 30 min. 5. After 30 min, add a few drops of 1 M HCl to the reaction while stirring (the solution may become more clear). 6. Let the reaction stir for about 10 min. 7. Spot a sample of the reaction on a TLC plate. On the same TLC plate, spot samples of commercially purchased cis-cyclohexane-1,2-diol and trans-cyclohexane-1,2-diol. 8. Run the TLC plate in the EtOAc/hexane developing solvent mixture that your class decided would work well. 9. Visualize the TLC plate by dipping it in p-anisaldehyde stain, dabbing on a paper towel to remove excess stain, and then heating on a hot plate provided in the fume hood. 10. Circle all spots in pencil on your stained TLC plate. Store all developed TLC plates in the hood. DS: 25% hexane, 75% ethyl acetate Visualization: p-anisaldehyde A - reaction sample B - cis-cyclohexane-1,2-diol C - trans-cyclohexane-1,2-diol Rf (A1) = 0 Rf (A2) = 1.6/5.2 = 0.31 Rf (A3) = 5.1/5.2 = 0.98 Rf (B) = 2.3/5.2 = 0.44 Rf (C) = 1.7/5.2 = 0.33 Work-up : Only trans is present cyclohexene

6 1. Pour the reaction mixture into 20 mL water in a 50 mL beaker then transfer to a separatory funnel. 2. LLE: Add 10 mL diethyl ether and mix well. 3. Drain the aqueous layer and transfer the organic layer to a separate Erlenmeyer flask. 4. Return the aqueous layer to the sep funnel and extract with an additional 10 mL of diethyl ether. Then drain the aqueous layer. 5. Add the organic layer to the organic layer from before. 6. Check to see if your LLE was successful by running a TLC of your LLE layers. On the same TLC plate, spot samples of commercially purchased cis-cyclohexane-1,2-diol or transcyclohexane-1,2-diol. Circle all spots and take a picture of your stained TLC plate. DS: 25% hexane, 75% ethyl acetate Visualization: p-anisaldehyde AQ - aqueous layer O - organic layer C - cis-cyclohexane-1,2-diol D - trans -cyclohexane-1,2-diol Rf (AQ 1) = 0 Rf (AQ 2) = 1.3/5.0 = 0.26 Rf (O1) = 0 Rf (O2) = 1.5/5.0 = 0.30 Rf (O3) = 4.5/5.0 = 0.90 Rf (C1) = 0 Rf (C2) = 2.0/5.0 = 0.40 Rf (D1) = 0 Rf (D2) = 1.7/5.0 = 0.34 Rf (D3) = 4.7/5.0 = 0.94 7. Dry the combined organic layers over anhydrous magnesium sulfate. Trans is present cyclohexene

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7 8. Pre-weigh a clean, dry 50 mL beaker. Record the weight in your notebook. 9. Pour the liquid only into the pre-weighed beaker and evaporate diethyl ether using forced air to obtain the solid product(s). 10. Keep the beaker in a room temperature water bath throughout the evaporation. 11. Weigh the beaker with solid product when it is completely dry. Data : Weight (g) Pre-weighed empty vial 182.38 Vial + dried product 182.41 Product weight 0.03 Theoretical yield 0.1147 Database NMR:

8 Lab NMR (From another group) 1.95 ppm A=3.91 ppm B=3.33 ppm C=1.95 ppm D=1.69 ppm E=1-1.56 ppm

9 Analysis : TLC plates : Oxone reaction plate : The first TLC reaction plate (after DS characterization) created cyclohexane-1,2-diol. The high Rf value for the cyclohexene demonstrates that it is the most non-polar as it travels the highest up the plate. While this is true, the spot barely appeared on the top of the plate meaning that perhaps not all of the cyclohexene was converted into cyclohexane-1,2-diol. Perhaps if the reaction was held for a longer amount of time, this conversion would have been more evident, resulting in a more pigmented cyclohexene spot. The reaction sample demonstrated a lower Rf value which shows that the reaction progressed to near completion as the least amount of cyclohexene is present. Also, by examining the reaction sample spot, the Rf value lines the closest with the trans diol rather than the cis diol. This demonstrates that only the trans diol is present in the reaction sample and is the most preferred product in this reaction. LLE plate : This second TLC reaction plate was performed after the aqueous and organic layers were separated from LLE. The cyclohexene spot appearing in the organic layer again demonstrates a high Rf from it being relatively nonpolar. Furthermore, we can conclude that the organic layer is the trans diol because the Rf for the trans diol on the TLC plate was very similar to the one for the organic layer. Theoretical yield/percent yield : The calculated theoretical yield demonstrates the amount of cyclohexane-1,2-diol produced. When compared to the extracted amount of product, I received slightly lower results with a percent yield of 26.16%. This could have been due to drying the material with nitrogen rather than air, which perhaps could have overdried the material. Also, human error could have been a big factor in increasing the percent error and uncertainty. Human error is inevitable from the manual separation of LLE and timing the reaction using a standard stopwatch, just to name a few. NMR : 3.75 ppm 1.69 ppm

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10 Three of the peaks of the trans diol from the database NMR match up the three peaks from the lab NMR. It is important to note that the OH peak on the database (3.91 ppm) matched the lab OH peak (3.75 ppm) demonstrating that these are both the same molecule. While there are two peaks missing from the lab NMR, this could have been due to human error when taking the NMR and/or the extraction itself. Also, this lab NMR that I am basing off on was produced by a different group; them having different data. Conclusion : Based on this lab, my hypothesis was incorrect. From the TLC plates and the NMR, it is evident that trans-1,2-cyclohexanediol is the cyclohexene that was produced in this reaction. Examining Newman’s projections alone will not provide sufficient evidence to determine which one is produced more, rather extracting the reaction into organic and aqueous layers and conducting an NMR to determine purity demonstrates that the trans diol is synthesized the most.