Question

How can the NMP oxalate salt be converted back to NMP?

Here is the procedure:

PROCEDURES

Part A: Synthesis of (±)-N,N-dimethyl-3-phenyl-3-(4-trifluoromethylphenoxy)propanamine

1. To the 250-mL round-bottom flask (RBF) containing (±)-3-(dimethylamino)-1-phenylpropanol (product from Lab 6) and a magnetic stir bar, add 4 mL of 4-chlorobenzotrifluoride and 30 mL of dimethylacetamide (DMA).
2. With stirring, add to this mixture 30 mL of 1.0 M potassium tert-butoxide (caustic alkali!) in tert-butyl alcohol using a syringe.
3. Using a simple distillation apparatus, distill the mixture slowly, with stirring, over a 15–20 minute period until the temperature of the refluxing solvent mixture reaches 125–150 ºC
4. Remove the heating mantle, and disconnect the RBF from the distillation apparatus. Cool the RBF by briefly immersing it in a cold water bath or a stream of running water.
   1. RBF will be hot, so use a towel!
5. Add 40 mL water and 30 mL ether to the flask, swirl to dissolve, remove the stir bar, and pour the contents of the flask into a 125-mL separatory funnel.
6. Shake well, allow the layers to separate, and drain the lower aqueous layer into a 100-mL beaker.
7. Transfer the upper ether layer into a separate 100-mL beaker.
8. Return the water layer to the separatory funnel, add 10 mL fresh ether, then shake and separate. Remove the lower layer, and combine the ether layer with the previous 30 mL extract.
9. Return the water layer to the separatory funnel and extract it a third time with 10 mL of fresh ether. Discard the aqueous layer.
10. Pour the ether extracts back into the separatory funnel, and add 25 mL of water. Shake well, allow the layers to settle, and discard the lower aqueous layer. Add a final 25 mL of water to the separatory funnel, and again shake well, allow the layers to settle, and discard the lower aqueous layer. If the aqueous washings are still cloudy at this point, add 25 mL water to the ether solution in the separatory funnel, and once again shake well, allow the layers to settle, and discard the lower aqueous layer. Repeat this process until the lower aqueous layer is completely clear.
11. Dry the combined ether extracts with anhydrous Na₂SO₄, and decant the ether solution to a separatory funnel.

Part B: Synthesis of the Oxalate Salt of NMP

1. Dissolve 0.85 g of anhydrous oxalic acid in 15 mL of absolute ethanol in a 100-mL beaker. Place a magnetic stir bar in the solution, and put the beaker on a stir plate beneath the separatory funnel.
2. With good stirring, allow the ether solution of NMP to drop into the acid solution in the beaker until the first permanent insoluble precipitate forms. Stop the addition of NMP at this point and stir the contents of the beaker for a few minutes. The precipitate will slowly grow in bulk; when formation of new precipitate has stopped, continue adding the NMP-ether solution from the separatory funnel with stirring. If necessary, add additional 5-mL aliquots of absolute alcohol to the beaker. When all the NMP solution has been added, remove the stir bar from the beaker, and place the beaker in an ice bath for 5 minutes.
3. Collect the crystals by vacuum filtration using a Büchner funnel. Wash them with ether and allow them to air dry until the next laboratory period. Report the mass and the melting point.

Answer 1

NMP oxalate salt can be treated with 5 % NaHCO3 / H2O solution to produce NMP and oxalic acid. Cholo nao LOH 5% NaHCO, OH (= = = = HO NH нсіз CH3 CH3 NMP oxalate salt