Evaluation of L – Proline as a Catalyst for an Asymmetric Aldol Reaction
Abstract
This reaction is divided into two parts. In the first part acetone, L – proline and 4 – nitrobenzaldehyde are reacted to give (R)-4-hydroxy-4-(4-nitrophenyl)butan-2-one as the major product along with (S)-4-hydroxy-4-(4-nitrophenyl)butan-2-one. The identity of the product is confirmed by IR spectra of the product which gives peaks at 1073.94 cm-1, 1330 cm-1, 1515.05, 1600.13 cm-1, 1708.25 cm-1, 2930.82 cm-1and broad peak at 3418.10 cm-1. The mass of the product is 0.013 grams which gives a percentage yield of 29.81%. The melting point of the product is not taken due to minimal product.
In the second part of the reaction excess reagents are used and the…show more content… Product Characterization 6. Record the mass of the product obtained. Obtain 1H NMR, 13C NMR and IR verification of product identity and purity, and compute the percentage yield.
Mosher Analysis
Reaction
7. Dissolve 75 mg of Aldol product in 4.5 mL anhydrous CH2Cl2 in a flame dried vial. 8. Add 7.5 mg of DMAP followed by 0.075 mL pyridine and 0.125 mL (-)-MTPA-Cl. Allow the mixture to react under nitrogen with SureSeal overnight or until TLC shows complete consumption of starting materials.
Product Isolation 9. Wash crude reaction mixture with 0.1 M HCl (2.5 mL), saturated bicarbonate solution (2.5 mL) and brine (2.5 mL).
Product Characterization
10. Determine the ratio of diastereomers by 1H NMR and from the ratio calculate the enantiomeric excess of the Aldol reaction
Results
Mass Table | Watch glass & Product | Watch glass | Product | 41.902 grams | 41.770 grams | 0.013 grams |
Product Name (major) | (R)-4-hydroxy-4-(4-nitrophenyl)butan-2-one | Product Molecular Mass | 209.20 grams/mol | Limiting reagent | L – Proline (0.000208 mmol) | Theoretical Yield | 209.20 gramsmol × 0.000208 mol = 0.0436 grams | Percentage Yield | 0.0130.0436 gramsgrams × 100 = 29.81 % | Melting Point | Not determined due to very little product |
Significant IR peaks (cm-1) | (R)-4-hydroxy-4-(4-nitrophenyl)butan-2-one | 1073.94, 1330, 1515.05 & 1600.13, 1708.25, 3418.10 |
Mosher Analysis
The melting point and mass of the Mosher
