Experiment 1: Mechanism of Nitrile Oxide and Alkene Cycloaddition

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Experiment 1: Mechanism of Nitrile Oxide and Alkene Cycloaddition 1. Purpose: to clarify the mechanism for the cycloaddition reaction between benzonitrile oxide and an alkene, and to test the regiochemistry of the reaction between benzonitrile oxide and styrene. 2. Plan: Each student in a group of three will work to create a reaction with the Benzonitrile Oxide with, cis-stilbene, trans-stilbene, or styrene in an Erlenmyer flask. With this Reaction solution thin layer chromatography will be performed using each reaction solution. The different reactions will then be compared by running co-spot TLC’s. An NMR of the crude products from each reaction will be taken.

3. References:

* Chemistry 173Q Organic Chemistry Lab: Laboratory Manual Notes * Mohrig, Jerry R., Christina Noring Hammond, and Paul F. Schatz. Techniques in Organic Chemistry. 3rd ed. N.p.: n.p., 2010. Print. 4. Balanced Equations:

Sytrene + Benzaldehyde Oxime

Cis-Stilbene + Benzaldehyde Oxime

Trans-Stilbene + Benzaldehyde Oxime

5. Reagents and Quantities:
Reactant| MW (g/mol)| Grams| Moles| Molarity| Density (g/mL)| Volume (mL)| Cis-Stilbene| 180.25| 0.6| 0.6/180.25 = 0.003| 0.33 M| 1.011| 9.1| Trans-Stilbene| 180.25| 0.3| 0.3/180.25=0.002| 0.33 M| 0.9707| 5.2| Styrene| 104.15| 0.227| 0.227/104.15 = 0.002| 0.33 M| 0.909| 6.6| 5.25 wt% NaOCl| 74.44| Trans-S Rx:| | ---| 1.06| Trans-S Rx: 6.0 / 2 min| | | Cis-S Rx:| | | | Cis-S Rx:12.0 /4 min|

| | Styrene Rx:| | | | Styrene Rx:5.0|
CH2Cl2| 84.93| | | ---| 1.33| |
2.3 M Benzaldehyde Oxime| 121.13| Trans-S Rx:| 0.001 L x 2.3 mol/L = 0.0023| 2.3 M| ----| Trans-S Rx:1.0| | | Cis-S Rx:| 0.002 L x 2.3 mol/L = 0.0046| | | Cis-S Rx:2.0| | | Styrene Rx:| 0.001 L x 2.3 mol/L = 0.0023 | | | Styrene Rx:1.0 / 4 min| Pre-Lab 1

Set Up: 2:00 – 2:10
Clean Up: 4:45 – 5:00
In an Erlenmyer Flask, a solution of methylene chloride (CH2Cl2), 2.3 M benzaldehyde oxime, triethylamine, sodium hypochlorite and either Cis-Stilbene, Trans-Stilbene, or Styrene will be mixed together to create a reaction. Before the NaOCl is added, however, the solution will be cooled in an ice-water bath and spotted on a TLC plate. The Cis-Stilbene, Trans-Stilbene, or Styrene solution and the benzaldehyde oxime solution will also be spotted on the same TLC plate. The fourth spot on the TLC plate will be the solution from the Common Workup to be used as a cospot. This TLC plate will be developed using 10:1 hexanes: ethyl acetate solution. A 5.25 wt% sodium hypochlorite solution will then be added to the cooled solution with vigorous stirring (stir bar) and the organic layer will be spotted on a new TLC plate. After more 5.25 wt% sodium hypochlorite is added to the mixture, the solution will be spotted again on the same TLC plate. Then, the flask will be removed from the bath and allowed to warm to room temperature (while being stirred vigorously). After 5 minutes, the Cis-Stilbene, Trans-Stilbene, or Styrene solution, and benzaldehyde oxime will be spotted on the same TLC plate. (2:10 – 3:00) The Common Workup Procedure – From the reaction solution in the Erlenmyer Flask, the CH2Cl2 layer should be removed using a disposable pipette and this solution should be placed into a disposable test tube. After removing the stir bar from the Erlenmyer Flask, add ~5 mL of CH2Cl2 into the Flask. Cap the flask and shake it to mix the layers (make sure to vent the flask). Again, remove the CH2Cl2 layer. Dry the CH2Cl2 over anhydrous MgSO4 for ~10 min and filter the solution through vacuum filtration. Place the solution into a round bottom flask – this solution can be used for the cospot in the TLC. Remove the solvent by using the rotary evaporator. [Clean up while Rotovap is running] Transfer the crude product to a vial. (3:00 – 4:00) (4:00 – 4:10) Clean up from TLC

NMR – Place small amount of crude sample...
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